British Columbia Carpenter Apprenticeship Program Test 1.. ..... 17 Learning Task 2: Use Portable...

British Columbia Carpenter Apprenticeship Program

Level 3 Line C

7960003570

Use Portable Power ToolsCompetency C-2

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BC CARPENTER APPRENTICESHIP PROGRAM—LEVEL 3 1

Competency C-2Use Portable Power Tools

ContentsObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Learning Task 1: Use Portable Routers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Self Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Learning Task 2: Use Portable Sanders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Self Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Learning Task 3: Use Portable Mitre Saws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Self Test 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Learning Task 4: Use Portable Power Planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Self Test 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Learning Task 5: Use Portable Biscuit (Plate) Joiners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Self Test 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Learning Task 6: Use Bench Grinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Self Test 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

2 BC CARPENTER APPRENTICESHIP PROGRAM—LEVEL 3

Competency C-2Use Portable Power Tools

To install mouldings and trim accurately, a carpenter must be able to use many portable power tools. Portable power tools used for finish woodwork must be maintained carefully to ensure their accuracy.

This Competency covers portable routers, sanders, compound mitre saws, power planes, and biscuit joiners.

ObjectivesWhen you have completed the Learning Tasks in this Competency, you will be able to:

• describe the use and maintenance of portable power tools for finish work

• use and maintain portable power tools for finish work

Competencies Written: “Use and maintain portable power tools for finish woodwork”

You will be tested on your knowledge of the use and maintenance of the following portable power tools: routers, sanders, compound mitre saws, power planes, and biscuit joiners.

Practical: You will be required to demonstrate proper use of these portable power tools while completing one or more finishing projects.


Notes

COMPETENCy C-2 LEARNING TASk 1

Learning Task 1Use Portable Routers

Portable routers are very versatile tools. They can be used to round and shape the edges of wooden components. Using templates, jigs, and patterns, a router can make multiples of irregularly shaped components.

On a construction site, routers are becoming a common tool for trimming wall sheathing and cutting out window and door openings. They’re also used for creating cutouts for electrical boxes.

This Learning Task describes the safe use and maintenance of portable electric routers.

Types of RoutersA router is a high-speed motor with handles (Figure 1).

Figure 1. Standard router

The motor runs at 20 000 – 30 000 rpm. This is approximately seven times faster than a table saw. The high rate of speed is needed because router bits usually only have two cutting edges.

Even with its high rpm, a router must be moved slowly along the work to produce an even cut. If the router is moved too quickly, “tool marks” will be left on the wood.

There are two basic types of woodworking routers: the standard router (Figure 1) and a plunge router. A plunge router has its motor spring-mounted over the base. The plunge router is useful when the bit is “plunged” into the centre of a piece of wood.

Notes


LEARNING TASk 1 COMPETENCy C-2

For specific uses, plunge routers are very efficient but they are usually too bulky and delicate for construction work. Standard routers are more durable and compact. They’re useful for finishing carpentry work as well as framing.

A third type of router is a light-weight laminate trimmer. It’s used to flush trim the overhanging edge of plastic laminate when making counter tops. Although a standard ¼" shank router bit will fit in a laminate trimmer, most laminate trimmers aren’t heavy-duty enough to be used as a woodworking router without damaging the motor.

SizeThere are two factors that determine the size of a router: the horsepower of the motor and the maximum shank diameter of the bit.

Routers that are used on construction sites are usually “heavy-duty” and have at least a ¾ hp motor. When making finish cuts, or when cutting through thick material, bits with a ½" diameter shank are needed. These bits vibrate less, producing a smoother cut, and are strong enough to make deep cuts in hard woods.

ColletsRouter bits are attached to the arbor of the motor using a “collet”. The collet is a tapered metal piece that is split (Figure 2).

Figure 2. Split collets

Collet NutThe collet holds the bit securely in the router. When the collet nut is tightened (turned clockwise), the collet is forced into a matching tapered orifice.

The router bit is slid as far as possible into the collet. If the shank of the bit bottoms out, lift the bit out of the collet slightly (�⁄� in.).


Notes


Some routers have two collet nuts (Figure 3). The nut furthest from the bit is held stationary with one wrench, while the nut closest to the bit is tightened. Other routers have only one nut and use a finger activated locking system to hold the shaft from spinning while the nut is being tightened.

Figure 3. Collet nut

Router BitsThere are hundreds of profiles, sizes, and shapes of router bits. Most router bits are carbide tipped. Some are solid carbide. Tool steel bits are available but are not suitable for production work as they become dull quickly.

Some bits have a guide tip or bearing guide that follows the edge of the material being routed (Figure 4). Others rely on a steady hand, template, fence, or other method to guide the router.

Figure 4 shows the key terms used in discussing router bits.

Relief angleHook angle

Shank

Cutting edge

Top view of cutterSide view of cutter

Shank

Bearing

Shear angle

Cutting edgeor �ute

Figure 4. Router bit terms

Notes



Figure 5 shows how to measure router bits to determine their dimensions.

D = Cutting Diameter H = Cutting Depth R = Radius S = Shank Diameter I = Cutting Length

S S

R

H

D

I I

D

Figure 5. Router bit measurements

Guide BearingsMany router bits are equipped with guide bearings. These bearings support the router bit a fixed distance from the work.

The router bit and bearing are spinning at over 20 000 rpm. The bearing will burn the work if it is even slightly tight.

Test the guide bearings on router bits before using the bit. If the surface that the bearing rubs against is a finished surface, apply a piece of masking tape to the finished surface for protection.

Guide bearing

Figure 6. Guide bearing


Notes


Guide bearings used in combination with a fence attached to the router make a clean cut with less chance of damaging the finished surface.

Shank DiameterRouter bits come with either a ¼" or ½" diameter shank and require a collet of the same size (Figure 7).

Figure 7. ¼" and ½" collets with matching bits

Types of Router Bits

Straight Flute BitStraight flute bits, without guide bearings (Figure 8), cut a plough or dado in a board.

Figure 8. Straight flute bit

When fitted with a guide bearing, these bits are useful for trimming laminate and wood edging.

Laminate BitLaminate bits are used to trim the finished edge of a plastic laminate counter top (Figure 9).

Figure 9. 22.5° laminate bit

Notes



The usual angle for finishing plastic laminate is 22.5°. Other angles are available for laminate bits. They can be used in woodworking routers or laminate trimmers.

Chamfer BitA chamfer bit puts a 45° bevel on the edge of a board (Figure 10).

Figure 10. Chamfer bit

Bullnose BitBullbandsaw bits, or round-over bits, are used to round the edge of boards and trim (Figure 11). If these bits are set deep enough, they’ll cut a vertical edge at the end of the round over.

Figure 11. Bullnose bit

The size of the bit is the radius of the round over.

Ogee BitAn ogee bit is used to put an ogee shape on the edge of a board. The ogee shape curves one way and then the other (Figure 12).


Notes


Figure 12. Ogee bit

A variation of the ogee bit is the Roman ogee bit.

Dovetail BitUsing a jig, dovetail bits can make a decorative and strong dovetail joint. Dovetail joints are often used to hold the drawer front to the sides of a drawer.

Cove BitCove bits are used to put a cove (inside curve) shape on the edge of a board (Figure 14).

Figure 14. Cove bit

Cove bits are sized by the radius of the inside curve.

Figure 13. Dovetail bit

Notes



Changing Bits

1. Disconnect the router from its power source and remove the base plate.

2. Using the two wrenches supplied with the router, undo the collet nut. Remember that it has a right-hand thread.

3. If the collet sticks, continue to undo the nut until it comes free.

4. Clean the collet and insert the new bit. Tighten the collet nut with a firm, but not excessive, pressure.

5. Re-install the base plate.

Figure 15. Removing the collet nut

Setting the Depth of CutTo set the depth of cut, release the locking clamp and twist the base of the router around the router itself (Figure 16). The graduated ring is used to change the depth of the router bit by specific amounts.


Notes


Figure 16. Adjusting the depth of the router bit

After setting the depth, always make a test cut to determine that the setting is correct.

PlungingPlunging is simple when using a plunge router (Figure 17). With the depth clamp released, start the router and push it down into the work to the desired depth. Lock the depth clamp and route the shape.

Plunging with a standard router requires a little more technique. Start the router and place the edge of the base at an angle on the surface to be routed. Slowly lower the router with a twisting motion. Keep the base in contact with the work. As the router bit enters the wood there’s a tendency for the router to move. Hold the router firmly and lower the router into the work. Route the shape required.

Notes



Trigger (on/o�)

Depth stop

Base

Chip guard

Motor

Figure 17. Components of a plunge router

Router Bit SpeedThe cutting edge of a small diameter bit will be moving much slower than the cutting edge of a large diameter bit at any given rpm. The speed at the cutting edge can be found by multiplying the bit’s circumference by the rpm.

e.g., The cutting edge of a 6 mm (�⁄�") straight flute bit at 21 000 rpm is traveling at 25 km/hr, whereas a 25 mm diameter bit would be travelling at about 100 km/hr.

When using routers equipped with speed control, the router speed should be slowed down for use with large diameter bits (See Table 1).

Router Bit Diameter Maximum Router Speedup to 25 mm (1") 24 000 rpm

25 – 32 mm (1 – 1.25") 18 000 rpm

32 – 57 mm (1.25 – 2.25") 16 000 rpm

57 – 89 mm (2.25 – 3.5") 12 000 rpm

Table 1. Router speed settings


Notes


Templates and Guides

Templates and guides are used with routers to form specific shapes. Dovetail drawer joints are made using a dovetail jig and a dovetail bit. The hinge gains for door hinges are made using a router jig and a straight flute bit.

TemplatesA template can be as simple as a cutout in a piece of plywood. The plywood is clamped to the stock that is to be routered and the plywood cutout restricts the travel of the router.

Templates can be factory made for various purposes including the routing of numbers and letters for making signs.

As mentioned above, router templates are used for cutting hinge gains (Figure 18). This allows for fast production and good quality control.

Figure 18. Hinge butt template kit from Porter-Cable

Notes



Guide BushingsWith jigs and templates, the router is normally equipped with a “guide bushing” (Figure 19).

Figure 19. Guide bushings

When using a guide bushing, the gap between the router bit and the outside edge of the bushing must be considered when making the template.

Safe Operation of Routers• Workers near the operation of a router must wear hearing protection.

• Due to the speed of the bit, splinters can fly like small spears. Wearing a face shield is recommended when using a router.

• Take shallow cuts and do not allow the rpm of the router to slow when making a cut.

• Use two hands. A router has its unguarded cutter exposed from the underside of the tool. This makes it very dangerous. Keep both hands on the handles of the router while the router is running. This will require the work to be firmly held in place.

• Move against cutter rotation. Move the router so that the cutter is rotating against the direction of cut. Moving with the direction of cut will cause the router to run, or move erratically.

WorkSafeBC’s Occupational Health and Safety Regulation requires eye protection to be worn when there is a danger of materials entering the eyes. This means that all workers on all construction sites must always be wearing eye protection when work is underway.

Router TablesA router can be mounted upside down in a specially designed table (Figure 20). This allows it to be used much like a shaper and is convenient when many pieces of long stock need to be routered.


Notes


A single fence can be used to rabbet, dado, or rip lumber.

The table can be used with an in-feed and out-feed fence for jointing a board edge.

Tables can be used without a fence if the bit has a guide tip or guide bearing.

With a router table and a good assortment of bits, many woodworking projects can be built using almost no other power tool.

A vacuum or dust collector is often be attached to the router and table, usually on the back side of the fence, in order to collect the chips and dust at the source.

Figure 20. Router table

MaintenanceIf a damaged tool is found, tag the tool as defective and have it repaired. Do not continue to use the tool, or leave it for others to use.

Routers should not be used in a wet environment. If they become damp, move them to a warm location to dry.

Periodically check the inside of the collet for sawdust build-up.

Check the brushes after 50 hours of continuous use, or as directed by the manufacturer (Figure 21).

Notes



Brush access plug

Figure 21. Brush access plug

Now complete Self Test 1 and check your answers.



Self Test 1

1. List seven different router bits and draw the profile they cut.

2. When using a guide bushing and a template, what allowance must be made?

3. How often should the brushes be checked?

4. For safe operation, how should the router be moved in relation to the wood?

5. How is a standard router plunged into the work?

6. How does a collet work?

7. What tasks might you use a router for when framing?



8. Why would you use an in-feed and out-feed fence on a router table?

9. What is the maximum speed you would use with a 2" router bit?

10. How do you measure the cutting depth of a bit?


Notes


Learning Task 2Use Portable Sanders

Portable sanders are used by carpenters to create a smooth finish for woodwork and for fitting and trimming purposes.

Basic types of portable sanders include: belt sanders, disk sanders, orbital, and random sanders. A relatively new tool called a Multimaster is also used for sanding purposes.

Belt SanderBelt sanders are used to smooth and shape wooden pieces. The size of the sander is determined by the maximum width of sanding belt that will fit the sander. Common belt sanders use either 3- or 4-inch wide belts.

A belt sander is very useful for fitting pre-formed countertops. These tops have a scribe edge at the back. The top is scribed to the shape of the wall and then trimmed with a belt sander. To reduce chipping, always hold the belt sander so that the belt is cutting against the good side of the material, so that the plastic laminate is sanded toward the substrate.

Belt tracking adjustment knob

Figure 1. Portable belt sander

Notes



When installing a lap-joined sanding belt on a belt sander, put the belt on with the direction arrow pointing in the direction of the travel of the belt. Butt-joined belts can be installed in either direction. Always unplug the sander when installing a new belt. Check the underside of the platen to ensure no chips of wood are trapped. These will cause uneven sanding or grooves in the material.

Once a new belt has been fitted over the rollers, activate the tensioning device. Make sure the switch is not locked on before plugging the sander into an electrical outlet. Turn the sander upside down, run and center the location of the belt by turning the tracking adjustment knob.

As the belt gets broken in and heats up, tracking may need adjustment. If a belt won’t maintain tracking for very long, it has probably stretched too much to be used any longer.

When using a new belt sander, practice on scrap wood to get a proper feel for the tool. Belt sanders equipped with a coarse belt can cut deep into a wooden surface.

Keep the sander parallel to the grain of the wood. Belt sanders should have moderate pressure applied and be moved across the stock in a pattern that resembles a narrow elongated oval. Take care not to let either roller or the edge of the belt dig into the wood.

Most belt sanding will leave some sanding marks, requiring further sanding with another type of sander.

Never attempt to sand the face of veneer plywood with a belt sander. It can sand quickly through the veneer, ruining the surface. Sanding too deep on a tongue and groove project can also spoil the surface.

Floor Belt SanderSpecial belt and drum sanders are used to sand the surface of hardwood floors. These belt sanders are called floor sanders. They have a belt that is 8 – 12" wide and are equipped with a long handle that allows them to be used like a floor polisher.

Disk SandersDisk sanders are used for shaping curved surfaces and for sanding the edges of wood floors. They’re also used for removing old finish, paint, and varnish from siding, concrete, and other surfaces. Sizing is by the diameter of the largest sanding disk that will fit on the sander. The sanding disk is secured to a rubber backing pad using a lock nut.


Notes


Disk sanders should be used slightly tilted with enough pressure to just bend the disk. Use a long back and forth sweeping motion advancing across the entire surface. Always use both hands.

Finish sanding with a hand held disc sander is very difficult. The outer edge of the sanding disc has a tendency to leave a mark on the finished wood. Final finish sanding should be done with an orbital sander or by hand.

Floor Disk SanderA floor disk sander, sometimes referred to as an edger, is used for floor edges where a belt sander won’t reach. It takes disks in the range of 8 – 16" diameter. The sanding disks are fixed on with adhesives. The larger units have long handles similar to floor belt sanders.

Orbital SanderOrbital sanders are often called palm sanders or sheet sanders. They have a motor that moves the sanding pad at high speed in a tight circular motion. Most models orbit at around 14 000 rpm.

The main advantage of this type of sander is that specialty sandpaper is not required. Most orbital sanders use quarter or half sheets of standard 9" × 11" sandpaper.

Orbital sanders should be moved parallel to the grain when sanding. Light to firm pressure can be applied.

Be careful not to use the sander after the paper has torn or developed a hole, as the sanding pad could become damaged or worn.

Orbital sanders can be used for final sanding, although random orbital sanders are less likely to leave sanding marks (see below).

Figure 2. Orbital palm sheet sander

Notes



Random Orbital SandersRandom orbital sanders are also called dual action sanders. Most have a circular sanding surface that rotates slowly while it vibrates. This produces a random orbit. The random orbit ensures that no part of the abrasive material travels the same path twice. This action reduces the swirl marks common with orbital sanders. Following the direction of the grain is less important so a random orbital sander is ideal for sanding two pieces of wood joined at right angles.

Random orbit sanders combine the speed of an orbital sander (7000 – 12 000 rpm) and the aggressiveness of a belt sander to produce a finer finish.

Most random orbit sanders use sandpaper disks. They are held on by pressure sensitive adhesive or with a hook and loop system (similar to Velcro).

Figure 3. Random orbital palm sander

MultimasterThe Fein Multimaster tool and similar multi-tools from Bosch, Porter-Cable, Rockwell, and other well-known portable power tool companies are starting to become popular for sanding detailed areas.

They use a triangular sanding pad that oscillates back and forth at over 20 000 rpm. Most multi-tools can also be fitted with round sanding pads. These will not spin, but only oscillate using a very small stroke.


Notes


Figure 4. Multimaster with triangle sanding attachment

The advantage of this type of sander is that it is very safe to use, and it can reach into tight corners and other places without bouncing off or marring adjacent surfaces.

It’s important not to tilt the sanding pad when using it. If the corner of a triangular pad is being used in a tilted position, it will heat up quickly. This will melt the rubber pad and ruin it. Heat can build up quickly even when using the tool correctly. Because of this, it’s recommended to sand at lower speeds unless the sander is being moved quickly over a large surface.

SandpaperSandpaper is used for shaping and final surface finishing. There are many grades and types. See C–1 Learning Task 4 – Use Smoothing Tools for information on grits, abrasive types, paper types, and bonding.

Although sandpaper is available in many grits, normally only three different grits need to be used when sanding wood. The first sanding is done with a coarse grit (36 – 50), a second sanding with a medium grit (60 – 100), and a final sanding with a fine grit (120 – 180). When finished wood will be stained, oiled or varnished, a superior finish can be achieved by sanding with 220 grit and then 300 – 600 between coats.

Many sanders, such as the belt, disk, orbital, and Multimaster-types use specific sandpaper made to fit these types of sanders.

For sanders equipped with a vacuum dust collection, sandpaper with specially placed holes is used to facilitate dust collection. In addition to removing dust, the sandpaper will last longer since it will clog less rapidly.

Notes



Operating Portable SandersAlthough sanders are fairly safe to use, the following precautions should be followed:

• Unplug the sander from the electrical outlet when changing sandpaper. Check that the sander is turned off before plugging it back in.

• Wear eye and ear protection when operating power sanders.

• Wear respiratory protection. This is especially important when sanding painted or varnished material. The dust from some woods such as yew, redwood, and cedar can be toxic.

• Be sure to work in a room with adequate ventilation. Use appropriate dust collection systems. Many sanders come with a vacuum hose attachment, or a dust collection bag of their own.

• Do not wear loose clothing or jewelry. Long hair must be covered or controlled.

• Never force a sander by pushing down too hard. Forcing can cause overheating, kickback, stalling, or burning. It can also result in injury.

• Use a vise, clamp, or stop to secure the work piece before using a portable electric sander. This will keep you safe and keep your piece from being damaged.

• If finishing both sides of a board, use a pad, such as a carpet scrap on the underside of the board. This keeps the underside from becoming marred while the top side is being sanded.

Sander MaintenanceMost portable electric sanders require very little maintenance other than empting the dust bag. The sanding pad and the motor ventilation ports should be checked for sawdust buildup. An air compressor can be used for cleaning these areas.

The cord and plug should also be checked periodically for cuts, abrasions, kinks, and other damage.




Self Test 2

1. What type of sander is used for sanding the edge of a wood floor?

2. What type of sander is used to fit a pre-formed countertop?

3. How is a sanding belt installed on a belt sander?

4. List five different types of sanders.

5. How do you adjust the tracking when installing a new belt on a belt sander?

6. What motion should be used with a belt sander?

7. What is a sheet sander?



8. What are some advantages of the Multimaster sander?

9. How many different grits of sandpaper are usually required for finishing?

10. Name three wood species with toxic sanding dust.


Notes


Learning Task 3Use Portable Mitre Saws

The once-popular radial arm saw has been largely replaced by the portable power mitre saw. Although not as versatile as a radial arm saw, power mitres are safer, more accurate, and quicker to use.

Carpenters use portable mitre saws for both framing and finishing work. With the use of side tables to support lumber, or a specially designed stand, these saws can be used as a framing chop saw or to cut compound angles for crown mouldings.

Types of Mitre SawsThere are two basic types of mitre saws: those that have a sliding device and those that do not. The sliding device allows the motor and blade to slide along a track. This allows the saw to cut much wider boards.

Sliding compound mitre saws are able to cut a mitre and a bevel at the same time. Most modern compound mitre saws are able to bevel to the right and to the left.

Figure 1. Sliding compound mitre saw

Notes



Sizes of Mitre SawsThe size of a mitre saw is determined by the maximum diameter of the blade that it can use. Most mitre saws are 8-, 10-, or 12-inch saws. Twelve inch diameter blades are not as common and are substantially more expensive.

The power of the saw is determined by the size of the motor. The maximum power source for portable tools in Canada is 120 volts. This limits the power of the saw. 12" saws are usually under-powered and tend to slow when cutting wide or thick boards.

The width of the cut is another factor when choosing a power mitre saw. A 10" non-sliding mitre saw may only be able to cut boards up to 7" wide, whereas the 10" sliding mitre saw shown in Figure 1 is capable of a 13" cut.

Mitre Saw Use and SafetyRepetitive work can lead to a lack of attention. When cutting blocks or pieces of wood, use extra care to keep your hands away from the blade. Finger injuries are common when using a mitre saw without appropriate care. Don’t let carelessness or impatience result in a lifelong injury.

For all cutting, allow the saw to reach its maximum rpm before beginning the cut. When cutting wide or thick boards, cut slow enough to allow the motor to maintain its speed. If the blade is allowed to slow down, damage to the motor may occur and the quality of the cut will be jeopardized.

Use a sharp blade. If the blade is dull, the saw will slow when cutting and may produce smoke. Using a “thin rim” blade will reduce waste and reduce the load on the motor.

General Safety Rules• Use clamps to support the work piece whenever possible.

• When supporting the work piece by hand, keep both hands outside the “No Hand” area. (This will be marked with a symbol on the base of the saw.) Do not use a mitre saw to cut pieces that are too small to be securely clamped.

• Do not reach behind the saw blade or fence for any reason.

• Never cross your hand over the intended line of cutting. Do not support the work piece “cross handed”.

• Always disconnect the power cord from the power source before changing blades, making adjustments, or attaching accessories.


Notes


• Mitre saws are intended to cut wood or wood-like products—they cannot be used with abrasive cutoff wheels for cutting ferrous material such as bars, rods, studs, etc. However, when cutting materials such as aluminum or other non-ferrous metals, use saw blades specifically recommended for non-ferrous metal cutting.

• Inspect the work piece before cutting. If the work piece is bowed or warped, clamp it with the outside bowed face toward the fence. Always make certain that there is no gap between the work piece, fence, and table along the line of the cut. Bent or warped work pieces can twist or rock and may cause binding on the spinning saw blade while cutting. Make sure there are no nails or foreign objects in the work piece.

• Do not feed the work piece into the blade or cut “freehand” in any way. The work piece must be stationary and clamped, or braced with your hand. The saw must be fed through the work piece smoothly and at a rate which will not overload the saw’s motor.

• Cut only one work piece at a time. Multiple work pieces cannot be adequately clamped or braced and may bind on the blade or shift during cutting.

• Be certain the mitre saw is mounted or placed on a level, firm work surface before using.

• Plan your work. Provide adequate support accessories such as tables, saw horses, table extension, etc. for work pieces wider or longer than the table top.

• Do not use another person as a substitute for a table extension or as additional support for materials.

• Always use a clamp or a fixture designed to properly support round material such as dowel rods, or tubing.

• When cutting irregularly-shaped work pieces, plan your work so it will not slip and pinch the blade, and be torn from your hand. Moulding, for example, must lie flat or be held by a fixture or jig that will prevent it from twisting, rocking, or slipping.

• Let the blade reach full speed before contacting the work piece.

• If the work piece or blade becomes jammed or bogged down, turn the mitre saw “OFF” by releasing the switch. Wait for all moving parts to stop and unplug the mitre saw, then work to free the jammed material.

• Braking action of the saw causes the saw head to jerk downward. Be ready for this reaction when making an incomplete cut or when releasing the switch before the head is completely in the down position.

• After finishing the cut, release the switch, hold the saw arm down, and wait for the blade to stop before removing work or cutoff piece. Reaching under a coasting blade with your hand is dangerous!

Notes



• For slide action cutting, first pull the saw head assembly away from the fence, until the blade clears the work piece or to its maximum extension if the blade cannot clear the work piece. Make certain the clamp does not interfere with the guard and head assembly. Turn the saw “ON” and lower the saw to the table. Then push the saw through the work piece. Release the switch and wait for the blade to completely stop before raising the head assembly and removing the work piece.

• Never “pullcut” since the blade may climb the work piece causing kickback.

• For chop action cutting, slide the head assembly to the rear as far as it will go and tighten the slide lock knob. Then turn the saw “ON” and lower the head assembly to make the cut. Failure to tighten the slide lock knob can cause the blade to suddenly climb up on the top of the work piece and force itself toward you.

Think safety! Safety is a combination of operator’s common sense, knowledge of the safety and operating instructions, and alertness at all times. Do not allow familiarity gained from frequent use of your mitre saw to become commonplace. Remember that a careless fraction of a second is sufficient to inflict severe injury.

ControlsMost mitre saws have some variation in how the controls operate. The following control description is for a Bosch 4410L.

SlidingBase

MiterAngle

Workpiece

Quick-ActionClamp

Bevel AngleScale

Figure 2. Controls and parts of the Bosch 4410L mitre saw


Notes


Rough CuttingSet up a table for the saw with extensions to support the lumber when cutting framing materials. Use a marker for making multiple cuts or use a stop block. (Care must be employed when using a stop block as this will result in a cut piece lying between the spinning blade and the stop block. Unless held firmly, the blade can catch this piece and launch it violently.)

Move the saw slowly through the wood when cutting through thick or heavy stock.

Keep the mitre saw out of the rain and always use the appropriate blade type and size.

To accurately cut finish moulding to size, the mitre saw must be able to make precise cuts. Mitre saws used for finish work should not be used for rough cutting.

Finish CuttingBefore making the first cut, check that the saw is cutting square and plumb when both the horizontal and vertical angles are set to zero. If the saw is out of adjustment, refer to the operator’s manual and adjust the saw.

Always test cut a piece of moulding and check the angles before cutting the finish materials.

Use a sharp blade that is appropriate for the cut being made. Special cut-off blades are available for use when finish cutting.

Hopper CutsHeavy crown mouldings are cut with their back laid on the bed of the saw. A hopper cut (compound mitre) is used to mitre heavy crown mouldings. The mitre angle and the tilt angle used for the hopper cuts are dependent on the angle of the moulding and the angle of the mitre.

There are three standard angles for crown mouldings: 38°, 45°, and 55° (Figure 3).

Notes



38º45º 55º

38º Crown moulding 45º Crown moulding 55º Crown moulding

Figure 3. Types of crown mouldings

The bevel and mitre angle for the three standard crown mouldings are shown below

38° MouldingsType of Cut Bevel Angle (tilt of blade) Mitre Angle (swing of table)

90° corner 33.9° 31.6°

135° corner 17° 14.5°

45° MouldingsType of Cut Bevel Angle (tilt of blade) Mitre Angle (swing of table)

90° corner 30° 35.3°135° corner 16° 17°

55° Mouldings

Type of Cut Bevel Angle (tilt of blade) Mitre Angle (swing of table)90° corner 23° 39.5°

The angle formed by the walls is not always 90° or 45°. If other angles of walls are being finished, the saw settings will have to be determined by test fitting. Calculating the angles is possible but usually not practical.

Always test fit the mouldings before cutting multiple members. Keep a sample of the moulding and record the mitre and bevel angles used.

Table and Trigonometric Formulas for Compound AnglesThe following table and trigonometric formulas may be used to find mitre and bevel angles.

BC CARPEnTER APPREnTICESHIP PRogRAM—LEvEL 3 33

Notes

CoMPETEnCy C-2 LEARnIng TASk 3

Four-sided Butt Four-sided Mitre Six-sided Mitre Eight-sided MitreTilt of Work

Bevel Degrees

Mitre Degrees

Bevel Degrees

Mitre Degrees

Bevel Degrees

Mitre Degrees

Bevel Degrees

Mitre Degrees

5° �⁄� 5 44 �⁄� 5 29 �⁄� 2 �⁄� 22 �⁄� 2

10° 1 �⁄� 9 �⁄� 44 �⁄� 9 �⁄� 29 �⁄� 5 �⁄� 22 4

15° 3 �⁄� 14 �⁄� 43 �⁄� 14 �⁄� 29 8 �⁄� 21 �⁄� 6

20° 6 �⁄� 18 �⁄� 41 �⁄� 18 �⁄� 28 �⁄� 11 21 8

25° 10 23 40 23 27 �⁄� 13 �⁄� 20 �⁄� 10

30° 14 �⁄� 26 �⁄� 37 �⁄� 26 �⁄� 26 16 19 �⁄� 11 �⁄�35° 19 �⁄� 29 �⁄� 35 �⁄� 29 �⁄� 24 �⁄� 18 �⁄� 18 �⁄� 13 �⁄�40° 24 �⁄� 32 �⁄� 32 �⁄� 32 �⁄� 22 �⁄� 20 �⁄� 17 15

45° 30 35 �⁄� 30 35 �⁄� 21 22 �⁄� 15 �⁄� 16 �⁄�50° 36 37 �⁄� 27 37 �⁄� 19 23 �⁄� 14 �⁄� 17 �⁄�55° 42 39 �⁄� 24 39 �⁄� 16 �⁄� 25 �⁄� 12 �⁄� 18 �⁄�60° 48 41 21 41 14 �⁄� 26 �⁄� 11 19 �⁄�

Note: Tilt of work refers to angle off plumb

Four-sided Compound Cuts

Mitre Angle

Bevel Angle

=

=

tan

sin

–

–

1

1

runLPUR

rriseLPUR2 ×

Five-to-Ten sided Compound Cuts

Mitre Angleunit run=

× ÷

tan

tan ( )–1

2LPUR angle

= × ÷Bevel Angleunit rise cos (angle 2)

sin–1

LPUR

Note: angle refers to angle between walls

135º 0’ 0”120º 0’ 0”

Notes

34 BC CARPEnTER APPREnTICESHIP PRogRAM—LEvEL 3

LEARnIng TASk 3 CoMPETEnCy C-2

Most buildings are rectangular with some octagons and hexagons. The compound mitres tables below provide the angles for these typical situations with typical 35°, 45°, and 55° mouldings.

Four-sided Butt Four-sided Mitre Six-sided Mitre Eight-sided MitreTilt of Work

Bevel Degrees

Mitre Degrees

Bevel Degrees

Mitre Degrees

Bevel Degrees

Mitre Degrees

Bevel Degrees

Mitre Degrees

5° �⁄� 5 44 �⁄� 5 29 �⁄� 2 �⁄� 22 �⁄� 2

10° 1 �⁄� 9 �⁄� 44 �⁄� 9 �⁄� 29 �⁄� 5 �⁄� 22 4

15° 3 �⁄� 14 �⁄� 43 �⁄� 14 �⁄� 29 8 �⁄� 21 �⁄� 6

20° 6 �⁄� 18 �⁄� 41 �⁄� 18 �⁄� 28 �⁄� 11 21 8

25° 10 23 40 23 27 �⁄� 13 �⁄� 20 �⁄� 10

30° 14 �⁄� 26 �⁄� 37 �⁄� 26 �⁄� 26 16 19 �⁄� 11 �⁄�35° 19 �⁄� 29 �⁄� 35 �⁄� 29 �⁄� 24 �⁄� 18 �⁄� 18 �⁄� 13 �⁄�40° 24 �⁄� 32 �⁄� 32 �⁄� 32 �⁄� 22 �⁄� 20 �⁄� 17 15

45° 30 35 �⁄� 30 35 �⁄� 21 22 �⁄� 15 �⁄� 16 �⁄�50° 36 37 �⁄� 27 37 �⁄� 19 23 �⁄� 14 �⁄� 17 �⁄�55° 42 39 �⁄� 24 39 �⁄� 16 �⁄� 25 �⁄� 12 �⁄� 18 �⁄�60° 48 41 21 41 14 �⁄� 26 �⁄� 11 19 �⁄�

In unusual situations or custom construction, such as battered wall formwork or odd angled walls, use the formulas shown previously to calculate the mitre and bevel angles. For example, the calculations for the bevel and mitre angles for a seven sided structure with a tilt of work of 15°, are as follows:

The angle between the walls are based on 360° / 7 = 51.429°; 180° - 51.429° = 128.571° between walls

LPUR (length per unit of run) is the hypotenuse of a triangle with a 15° angle (tilt of work) and a short side unit of run, any number, say 10. Therefore, sin 15° = 10/LPUR; LPUR = 38.637. The unit of rise for this triangle is the adjacent side; tan 15°=10/adj. adj = 37.321

Mitre angle = tan–1 (10 / 38.637 x (tan 128.571°/2) = 7.105° = 7°

Bevel angle = sin–1 (37.321 x cos (128.571° / 2))/ 38.637 = 24.778°


Notes


LPUR

10

Unit rise

15º

Figure 4. LPUR

MaintenanceMaintaining a mitre saw is similar to maintaining most portable power tools. The blade should be replaced when it becomes dull, and all electrical cords and connections must be kept in good condition.

Mitre saws are moved to and from the job on a daily basis. This continual relocation can result in loose screws or bolts. Regularly tighten all bolts and screws. Replace any parts that may have come loose or been lost.

Before using any mitre saw, check that the guard is moving freely and protects the blade fully. Never use a saw with a disabled or non-functioning guard.

Clean the saw regularly—remove all sawdust and pitch.

Under normal use, a mitre saw will not require lubrication with the exception of the slide bearing.

Always check the manufacturer’s operating manual regarding maintenance.

Adjusting the FenceWhether doing finishing work or rough work, the fence must be properly aligned to produce accurate cuts. Follow the manufacturer’s instructions when making adjustments to the saw. The following is a typical procedure for adjusting mitre saws:

Notes



Mitre AdjustmentOn most saws, aligning the fence to the blade makes the mitre adjustment.

1. Set the mitre adjustment to zero.

2. Loosen the fence bolts.

3. Use a framing square that has been checked for squareness to align the fence to the blade.

4. Tighten the bolts.

5. Reset the 0° indicator if necessary.

Bevel AdjustmentTo adjust the bevel, the bevel angle indicator (pointer) is adjusted.

1. Set the bevel adjustment to any angle.

2. Cut a block and test the cut using a sliding T bevel and a protractor.

3. If not exactly the angle shown on the indicator, adjust the pointer to show the correct angle.

The 45° bevel setting usually has a stop to allow a quick setting. This stop is adjustable.

1. Set the bevel adjustment to 45°.

2. Cut two test blocks and test the combined cut using a 90° square.

3. If not square, adjust the stop to make the cut exactly 45°.

Hopper BoxThe hopper box simplifies the cutting of compound mitres required for crown and cornice mouldings. It is a shop-made accessory that is fastened to the mitre saw. It combines a fence and table, typically made from plywood, glued together at a right angle. The largest size of the moulding that can be cut in a hopper box is based on the maximum depth of cut of the mitre saw. Mouldings larger than this require compound mitres and use of the tables above.

As shown in Figure 5, the moulding is placed on the mitre saw upside down to how it will be installed. It is as if the table is the ceiling and the fence is the wall. A strip is fastened to the table to hold the moulding at the correct. The typical angles are 38°, 45°, or 55°. In this position, the saw can be set to the normal plan view mitre angle.


Notes


Figure 5. Hopper box

For example, to install the moulding at a 90° outside corner, the long point of the moulding will be at the top against the ceiling. On the hopper box, with the work piece upside down, the long point will be on the table. The saw is set to a 45° mitre and the cut made. Another example is for moulding in an octagonal room. To fit the 45° inside corner, with the long point on the wall, place the top (ceiling side) of the moulding on the table and the bottom (wall side) against the fence, and cut with the saw set to 22.5°.

Used this way, the hopper box eliminates the need to set both mitre and bevel angles on the saw. It takes a couple of cuts to get used to placing the moulding upside down, but once you get it, the results (both in quality and speed) are worth it.

Avoid cutting right through the table of the hopper box!




Self Test 3

1. What type of cut is made when fitting a wide crown moulding at corners?

2. How is the mitre angle setting adjusted?

3. What type of blade will reduce waste?

4. What limits the power of 12" mitre saws?

5. What does the term “freehanding” mean?

6. What are the bevel and mitre angles when cutting 55° crown moulding for a 90° corner?


Notes


Learning Task 4Use Portable Power Planes

The portable power plane is very useful for fitting doors and other edge planing (Figure 1). The rotary cutting action is very similar to a jointer used in a woodworking shop.

Depth adjustment knob

Fence lock

Trigger (on/o�)

Front baseRear base

Figure 1. Portable power planer

Parts and ControlsMost power planes have an adjustable infeed table for setting the depth of cut. They have a stationary outfeed table. Most power planes have an adjustable fence as an accessory.

Size of the planes is based on the width of the blades, 3.25" is common for many power planes.

The length of the shoe (tables) is also important. Just like manual hand planes, the longer the plane, the straighter the edge it leaves. Shorter planes work better for shaping and contouring. Most power planes are about 12" long.

ShoeThe infeed and outfeed tables are also called the shoe, sole, foot, or base. The infeed table is used to guide the plane into the work. The difference in height between the infeed and the outfeed tables creates the depth of cut.

The sole of the plane must be held firmly and evenly against the work.

Notes



Depth Adjustment knobThe depth adjustment knob raises and lowers the infeed table to set the depth of cut. The range of adjustment is usually 0 – �⁄��".

Using the PlaneIt’s helpful to scribe a pencil line at the total depth of cut on the material being planed.

1. Set the depth of cut using the adjustment knob. To avoid overtaxing the motor, use shallow cuts when planning with the full width of the blades.

2. Hold the plane with one hand on the switch handle and the other on the adjustment knob.

3. Place the plane’s infeed table in the correct starting location, making sure the blades are not in contact with the surface. Attempt to plane with the grain of the wood (Figure 2).

4. Start the plane and allow it to reach full speed before beginning the cut.

5. Push down firmly so that the infeed part of the shoe is flat on the surface.

6. Move the plane slowly into the work and maintain a firm downward pressure.

7. Be especially careful to keep the plane flat at the beginning and end of each cut.

8. Do not set the plane down until the blades have stopped spinning. Be careful not to set the plane on a surface that might dull a blade.

Feed direction

Figure 2. Feed the power plane with the grain of the wood

The feed direction is against the rotation of the cutter head. It’s not always possible to move with the grain when planing wood with mixed grain or end grain. Make shallow cuts to reduce chipping when working against the grain.


Notes


An adjustable fence can be used as a guide as well as to rabbet the edge of boards (Figure 3).

Figure 3. Using a fence

Changing and Setting the BladesThe knives of a power plane must be changed often. Follow the manufacturer’s instructions for removal of the knives. The knives may either be replaced, or sharpened by a professional. As knives become dull, they may be able to be dressed on a whetstone between sharpenings.

Follow the manufacturer’s instructions to install the sharpened knives. The depth adjustment knob should be set at zero and the infeed and the outfeed table should be in alignment. The finished position of the knives must just touch a straightedge when it rests evenly across both shoes of the plane as shown in Figure 4.

Front base Rear base

Straight edge

Figure 4. Cutter head at top-dead-centre position

Before operating the plane, check that all of the screws holding the knives in place are fully tightened.

Notes



Figure 5 shows the cause and effect of improperly setting the blades.

A B

A B

A B

Correct setting

Nicks in surface

Gouging at start

Gouging at end

Although this side view cannotshow it, the edges of the bladesrun perfectly parallel to the rearbase surface.

Cause: One or both blades fails tohave edge parallel to rear base line.

Cause: One or both blade edgesfails to protrude enough inrelation to rear base line.

Cause: One or both blade edgesprotrudes too far in relation to rear base line.

A—Front base (movable shoe)B—Rear base (stationary shoe)

Figure 5. Results of improper blade settings

The cutting knives are exposed at the bottom of the plane. Take extra care to keep both hands on the power plane’s handles. Do not guide the edge of the plane with your finger.




Self Test 4

1. How deep should the cut be when planing a board that is the full width of the plane blade?

2. What is the position of the cutting knife in relation to the plane’s shoe?

3. Describe how to plane wood with mixed grain.

4. How is the depth of cut adjusted?

5. Referring to Figure 5, what causes gouging at the end?

6. How wide a cut do most handheld power planes make?

7. Why would you want to use a pencil to mark the total depth of cut?


Notes


Learning Task 5Use Portable Biscuit (Plate) Joiners

Biscuit joiners are used when building cabinets, shelving, furniture, and other woodworking projects. The biscuit joint is similar to a dowel joint (Figure 1). Biscuit joiners are also known as plate joiners.

Biscuits Dowels

Figure 1. Biscuit vs. dowel joint

The biscuits are flat wafer-like wooden supports that fit into saw kerfs cut by the biscuit joining tool. The biscuits fit snugly into the saw kerf and, when glued in place, bond the two pieces of wood securely together.

The biscuits are designed to swell when glue is applied. This leads to a very tight fit, but can cause problems if the glue is applied too soon before joining the two pieces together.

Like dowels, the biscuits help to align the face of the boards being joined. However, unlike dowels, the biscuits will allow some movement longitudinally. This makes the layout of the biscuits less critical than the layout for dowels.

Controls and PartsThe biscuit cutter has a spring-loaded retracted blade. The adjustable fence sets the height, tilt, and depth of cut. The fence is placed against the material to be joined and lined up using a centering mark. Then, with the blade turning, the biscuit joiner is pushed into the board to create a kerf cut. The cut becomes a pocket for half the biscuit. Normally, the pocket is made slightly longer and deeper than the actual size of the biscuit.

Notes



Trigger (on/o�)

Depth adjustment knob

Fence lockAdjustable fence

Figure 2. Parts and controls of a biscuit joiner

Biscuit Size AdjustmentBiscuits are available in various sizes. The curved radius is the same for all sizes of biscuits except for the #FF. This makes the kerf size adjustment simple. The depth of the saw kerf is reduced for the smaller biscuits and increased for the larger biscuits.

Depending upon how much lateral adjustment is needed, the depth can be made to fit the biscuit closely or deeper to allow more adjustment when lining up the joint.

½"(12.7 mm)

2 3⁄8"(60 mm)

2 3⁄16"(56 mm)

1 13⁄16"(46 mm)

3⁄8"(9.5 mm) 5⁄16"

(8 mm)

Figure 3. Biscuit sizes

Biscuits come in three standard sizes and one mini size. A 4" diameter blade is used for the standard sizes and a 2" diameter blade is used for the mini #FF biscuit (Table 1). Only some models of biscuit joiners will accept a 2" blade.


Notes


#FF 13 x 30 mm �⁄�" x 1 ��⁄��" FF = Face Frame for 1 �⁄�" width, and up

#0 16 x 47 mm �⁄�" x 1 ��⁄��"#10 20 x 52 mm �⁄�" x 2 �⁄��"#20 24 x 54 mm 1" x 2 �⁄�"

Table 1. Biscuit dimensions

Height AdjustmentThe location of the saw kerf in relation to the face of the board is set with the height adjustment.

Centering the biscuit to the board’s thickness is usually not desired. If the biscuit is centered, and the location of the biscuits along the joint is symmetrical, the boards can be flipped end-for-end and the biscuits will still line up. This is problematic as it can lead to confusion about which face is which.

If the height is adjusted so that the biscuits are slightly off-centre, there can be no confusion as to how the boards line up (Figure 4).

Figure 4. Set the biscuits slightly off centre

Notes



Shelf InstallationBiscuits can be used to support the ends of shelves. In this case, the location of the biscuit on the gable (cabinet side or vertical member supporting the end of the shelf) is very important. The centre of the saw kerf is indicated on the fence of the biscuit joiner. This centre mark is aligned to the centre of the biscuit location on the gable when cutting the saw kerf into the gable.

The kerf in the ends of the shelves is usually positioned at the centre of the shelf. If the kerf is slightly deeper than the biscuit, the edge of the shelf can be easily aligned with the edge of the gable.

Cabinet bottoms and tops can be joined to gables in the same manner.

Figure 5 illustrates types of joints that can be made using biscuits.

Edge to edge joint Corner joint O�set joint

45º Frame joint “T” joint Edge mitre joint

O�set

Figure 5. Various biscuit joints

Double BiscuitsDouble biscuit joints can be created when working with wood that is at least 1" thick. There should be at least �⁄��" material left above, between, and below the biscuits (Figure 6).


Notes


3⁄16" (5 mm) minimum

3⁄16" (5 mm) minimum

1" or greater stock thickness

Figure 6. Double biscuit spacing

Joining Multisided ProjectsFigure 7 gives the angle settings for joining 4-, 5-, 6-, and 8-sided projects. It’s important to locate and size the biscuit kerf depth so that it doesn’t penetrate the outside surface. The fence angle depends on whether an inside or outside registration is used. Inside registration is when the inside of the joint is aligned and outside registration is when the outside of the joint is aligned.

# of Sides Joint AngleFence Angle Setting

Outside Registration Inside Registration

490º

4 90° 45°

581º

5 81° 54°

675º

6 75° 60°

867.5º

8 67.5° 67.5°

Figure 7. Fence settings

Notes



Safety PrecautionsClamp the piece to receive the saw kerfs securely in place before attempting to cut the kerf. Do not hold the piece with one hand and try to use the biscuit joiner with the other hand.

Use both hands to hold the biscuit joiner. In case of an accidental slip, this will ensure that there is no way for the saw blade to cut your hands.

Check that the blade is fully guarded when the tool is at rest. The spring-loaded sliding mechanism that allows the blade to move in and out must move freely. If not moving freely, apply light oil and wipe clean.

Follow the manufacturer’s instructions when changing blades.




Self Test 5

1. What fastening system is a biscuit joint similar to?

2. When edge joining, where should the biscuit be located?

3. How is the biscuit aligned when joining a shelf to a gable?

4. How is the biscuit joiner adjusted to accommodate different sizes of biscuits?

5. What size blade is needed for a mini #FF biscuit?

6. What is the size of a #10 biscuit?

7. What is the fence centre mark used for?

8. What angle should the fence be set to for a 5-sided project?


Notes


Learning Task 6Use Bench Grinders

Carpenters use bench grinders to grind plane irons (blades), chisels, hatchets, and knives. Grinders can be used for many other purposes, but it’s best to reserve one grinder wheel specifically for the sharpening of precision tools, such as plane irons and chisels.

Bench grinders commonly have two grinding wheels. Often one is fine grit and the other a coarse grit.

Figure 1. Standard bench grinder (guard hoods removed for clarity)

Wheel Types, Size, Hardness, Grit, and Grain Structure

Wheel Abrasive TypesThere are two main types of materials used to make the wheels: silicon carbide and aluminum oxide. The silicon carbide wheel is the standard grey colour while the aluminum oxide is white. Although not commonly used due to their expense, diamond wheels are available.

Notes



• Aluminum oxide wheels are economical, facture resistant, and far superior to silicon carbide. They cut faster and do not tend to heat as fast.

• Silicon carbide is used for non-ferrous materials, such as aluminum, copper, and brass, as these materials tend to plug up the pores in an aluminum oxide wheel.

• Diamond is one of the hardest abrasive materials. Commonly used in grinding and polishing ceramic, stone, and aluminum alloy.

SizeThe size of a bench grinder is determined by the maximum diameter grinding wheel that the bench grinder can accommodate.

Standard diameters are 5, 6, 7, 8, 10, 12, or 14 inches. Common widths are ½, ¾, 1, 1¼, 1½, and 2 inches. Wheel arbour holes are 1, 1¼, and 1½ inches. Bushings are used when wheels are being placed on �⁄� and ¾ inch shafts.

Wheel HardnessWheel hardness is measured on a scale ranging from A (very soft) to Z (very hard). The type and amount of bonding material determines the hardness rating. Most wheels range from the upper soft zone (I) to the lower hard zone (P).

GritWheel grit is similar to sandpaper grit and runs from 24 (coarse) to 150 (very fine). 80 grit is recommended for plane irons and chisels, and 120 grit for carving tools.

Grain StructureAlthough the grain structure can range from 0 (dense) to 16 (open), most are in the range of 5 or 6. Dense grain structures have grains that are close together and generate a consistent finish. Open grain structures have grains that are spaced apart for faster stock removal.

Specialty WheelsCool wheelsLee Valley Tools sell an aluminum oxide soft bond wheel (rated H) that comes in both 80 and 120 grit. They have an open structure for aggressive grinding. This wheel wears faster than a harder stone, but won’t burn tools as easily.


Notes


Felt wheelsWheels made from a dense felt are used with a blade honing compound to produce an edge sharper than a razor. They can also be used to give polished steel a chrome-like appearance.

Tool RestsPlane irons and chisels are held against a tool rest during grinding. The tool rest must be perfectly smooth. Even the slightest nick or groove will make it very difficult to move the chisel across the face of the grinding wheel.

The tool rest is adjustable and should be adjusted to produce an angle between 28 – 30° for most chisels and plane irons. Adjust the tool rest so that there is no more than a �⁄�" gap between it and the grinding wheel.

Safety PrecautionsAll grinders come equipped with wheel guards and hoods. Do not remove these.

The wheel guard hood is not sufficient protection for your eyes. Wear additional eye protection when using a grinder. A face shield with eye protection is preferred. A face shield is considered a secondary safeguard to protective eyewear—it should never be worn without safety glasses or goggles.

Never exceed the rated speed for the wheel. Compare the rated speed on the grinder’s rating plate with the wheel’s maximum allowable speed. The rating on the wheel must always be higher.

Notes



Figure 2. Rating plate

Never grind around flammable materials. Keep sparks directed away from yourself and others.

Grind slowly, do not force the blade or chisel into the wheel.

Ring TestInspect the grinding wheel for cracks or damage prior to use. A cracked or damaged wheel can fly into pieces while grinding. When installing a new wheel, or when in doubt about an existing wheel, conduct a ring test:

1. Remove the wheel and support it in the centre using a finger, dowel, or pin.

2. Strike the wheel using a non-metallic object, such as the resin-plastic handle of a screwdriver.

3. The wheel should be struck about an inch in from its circumference at the four 45° to the centerline locations.

4. The grinding wheel stone should have a consistent ring that isn’t dull.


Notes


MaintenanceThe direct drive motor requires little maintenance. Maintaining bench grinders consists of adjusting the tool rests and truing the grinding wheels.

Truing Grinding WheelsMost grinding wheels are designed to grind mild steel. If aluminum or other soft metals are ground, the wheel will quickly fill with metal particles. Grinding hardened steel or the corners of mild steel objects will leave grooves in the grinding wheel.

To reshape a grooved grinding wheel and to remove embedded metal, the wheel must be dressed. There are two types of wheel dressers: a Huntington wheel dresser and a diamond wheel dresser. Both are used in the same manner:

1. Set the tool rest back far enough from the surface of the wheel to allow the heel of the dressing tool to hook over the tool rest.

2. Turn the grinder on and work the dressing tool carefully across the face of the wheel. Always wear a face shield when dressing a grinding wheel. The dressing tool must rest on, and be guided by, the tool rest as you gently hold it against the wheel, moving it slowly back and forth across the face of the wheel.

3. Stop the grinder and check the condition of the heel. Continue as needed.

4. After the condition has been corrected, stop the grinder and readjust the tool rest.

Figure 3. Using a Huntington wheel dresser

Notes



Figure 4. Diamond wheel dresser


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