http://woodgears.ca/pantorouter/tenon_setup.html

Making tenon templates for the pantorouterI previously wrote about how to work out tenon templates in my large mortise and tenon article. To those skilled in math, the easiest way to express the calculations is with an algebraic equation, but it appears that many people find that confusing. So I'll take another shot at explaining it, this time, without equations. I will even use inches (because my router bits are all inches) And if you prefer not to read, just watch the video :)

Making tenon templates for the pantorouterI previously wrote about how to work out tenon templates in my large mortise and tenon article. To those skilled in math, the easiest way to express the calculations is with an algebraic equation, but it appears that many people find that confusing. So I'll take another shot at explaining it, this time, without equations. I will even use inches (because my router bits are all inches) And if you prefer not to read, just watch the video :)

The pantorouter cuts a tenon by tracing around the shape of it with a router bit. Large router bits work best.

To get a tenon shape that is rounded on each end, the router bit needs to trace a semicircle at each end.

The path the router bit takes needs to be offset by half the router bit's diameter on all sides. That makes the total size of the path that the router follows one router-bit-size wider than the desired tenon. 0.5" + 0.625" = 1.125".

The pantograph has a 2x reduction built in, so the template needs to be

twice that size. So the path that the guide bearing must take on the template is twice as big. 1.125" x 2 = 2.25"

To get the correct path, the template needs to be smaller by half the bearing size on each side. Subtracting half the bearing size twice, the thickness of the tenon template now needs to be reduced by the bearing size. 2.25" - 1" = 1.25"

And that's all there is to it.

So, in summary, we add the router bit size and tenon thickness together, double that, then subtract the bearing size to get the template thickness. For the width of the template (and tenon) the calculations follow the exact same steps.

If the guide bearing is twice the diameter of the router bit, the template ends up exactly twice the size of the tenon, which makes things even easier.

Having worked out how wide the tenon template needs to be, I cut a strip of wood that width on the table saw.

Next, I use a compass, set it to half the width of the strip of wood and mark the rounds on the ends. I run the point of the compass along the edges and end of the workpiece to mark where the center of the semicircle needs to be.

Next, cutting the rounded end on the bandsaw.

A disk sander is great for getting right up to the line, but I just graze the edge with the side of the bandsaw blade to

finish up (that works better with a bandsaw blade where the edge of the teeth have beenstoned)

I then screw the plywood template onto another piece of plywood to mount it on the pantograph. That way, I can take it off again if I need to tweak it.

Template mounted.

Here, I'm screwing on the appropriate size guide bearing. The first tenon I cut ended up just 3/8" in size, not the 1/2" it was supposed to be. Then I realized I still had the 3/4" guide

bearing on, not the 1" one that my template is designed for. Oops!

To line up where the tenon goes, I line the bit up to be vertically centered with the workpiece, then make sure that the guide bearing is at the same height as the center of

the template.

It's definitely a bit more work to set up than a tenon jig, but once set up, it produces tenons that have the shoulders perfectly cut, with a round on both ends, all in one step. And if you cut around it

clockwise (from the view in this photo) the bit will always cut into the wood on all sides, so there is no tearout.

The pantorouter is also capable of cutting mortises, but because I also have a slot mortising machine, I just use that to cut the

corresponding mortises.

If you use the same size bit for the mortise and the tenons, it may make sense to mount the mortise template right next to the tenon template, so you don't have to worry about realigning the templates when switching between mortising and tenoning.

To calculate the track length for a mortise template, take the width of the tenon, subtract the router bit size, then double that, and add the guide bearing size.

A nice fit!

I made this tenon template to cut the shelf supports for someshelves for my brother's basement

How the pantorouter worksThe "Pantorouter" is a template guided router for cutting shapes in wood. The template is mounted on the frame above the router. A ball bearing on the pantograph mechanism is used to follow the template.

For those not familiar with pantographs, the lattice pictured at left should help explain. The six pieces of wood are connected with pins at the corners.

The four areas inside this lattice each form a rhombus of equal dimensions.

With the rhombuses all the same size and shape, you can see that the distance between the point that I'm holding and the fixed point on the opposite corner will always be divided exactly in half.

The linkage shown previously doesn't actually need all those pieces to work. In a pantograph, the redundant links are not present. Scalings other than 2:1 are possible with most

pantographs, but for the sake of simplicity, my pantorouter has the reduction fixed at 2:1.

With a pair of markers in the pantograph, a shape drawn with the red marker will be drawn at half that size by the green marker.

On my pantorouter, I use a ball bearing to follow the template in place of the red marker, and mount my router where the green marker was. The router mount is an odd shape so that the router's

axis goes exactly where the marker was.

The pantorouter is basically the same linkage as this but built much sturdier to support the weight and cutting forces of the router.

When

I prototyped my machine, I found that pulling up on the handle against the

weight of the router was tiring over time. So I added some springs, string, and cams to counteract the weight of the router.

The cams are shaped such that the spring's tension profile is matched to the way that gravity exerts a larger moment on the router the further it is away from the pivot. There's one spring for each arm of the pantograph, one mounted behind, the other in front of the pantograph.

For routing internal cavities such as mortises, it's also necessary to plunge with the pantorouter. I added a plunge mechanism by making the whole back half of the machine

move back and forth on a sled. A lever attached to the side moves the plunge sled.

The sled moves back and forth on linear glides that I made from drawer slides

I also added some depth stops to the plunge mechanism. These allow me to limit how deep the router will plunge. The second stop on the left limits how far back the router can travel. This is

useful for locking the plunge position in place. It can also be used for setup. I'll often use the tip of my router as a stop for where to position the stock. I'll move the router all the way back, and slide the piece against the router until it hits the bit. Then I use the plunge mechanism to cut the desired depth.

I should add that this does not involve starting the router with the bit touching the stock. I can always move the router out of the way sideways.

Making large mortise and tenon joints with the pantorouterI wanted to explore making some really big mortise and tenon joints with the pantorouter. I didn't actually have a project that needed such joint, so I made some test joints just to demonstrate.

I decided to make a 25 x 75 mm (1" x 3") mortise and tenon. That would be a good sized joint if one was using 2 x 4 lumber to build a traditional workbench.

I bought a 1/2" (12.7 mm) router bit with a cutting length of 2" (51 mm) for the job. This was

actually not the longest router bit available, but I figured it should do. Fully inserted, the bit still stuck out of the collet quite a ways. So I cut off about 1.5 cm from the back of it. It was relatively easy to cut with a hacksaw.

I used a 26 mm guide bearing (couldn't find a 1" bearing). I measured the router bit's actual cutting diameter at 12.8 mm - slightly larger than specified. Plugging my tenon, bearing and bit size into

the formula:

Ttemplate = 2 * Ttenon + ( 2 * Dcutter - Dbearing)

Plugging in my numbers:

Ttemplate = 2 * 25 mm + ( 2 * 12.8 - 26)   =   50 - 0.4

The term in brackets in the right worked out to -0.4 mm. So basically, my template needs to be 0.4 mm smaller than twice the size of my tenon. Easy enough. I cut the tenon template on the table saw. I used a 1" washer to trace an arc on the corners. The actual radius I needed for the corners was twice the 12.8 of the bit, minus the 0.4 mm adjustment, or 25.2mm. I figured the 1" (25.4 mm) of the washer was close enough.

If you don't like equations click here for another explanation.

I glued the template onto a thin piece of plywood for mounting. I also glued a few strips of wood to another piece of wood for the mortise template. The mortise template is

much wider than the guide bearing so I can move all around the inside perimeter of it to cut a rounded rectangle shaped mortise.

The mortise template is twice the size of my desired mortise plus the 0.4 millimeters I worked out earlier. For inside templates, the adjustment factor goes the other way around.

Aligning the template for a cut

I added a "setup bar" to reference from. This bar represents the level of the table on the template side of the pantograph. I worked out the position of that by

placing a 1/4" shaft in my router and a 1/2" guide bearing on the pantograph. With the shaft in the router on the table, the bottom edge of the bearing corresponds to that exact position on the template side. I made some pencil marks on the template frame for where the bar goes so next time I only need to line up the bar with the pencil marks. The setup bar can get in the way of the router, so I take it off after finishing the setup.

My stock for the tenon is 36 mm wide, and I want the tenon to be centered. So the center line of the tenon needs to be 18 mm from the edge. On the pantograph side, that dimension doubles, so the template's center line needs to be 36 mm above the setup bar.

Here's my cut tenon. The tenon is 6 cm long (2 3/8"), which is longer than the cutter length of the router bit. I started the cut with the plunge carriage pulled back, cut all the way around, and then plunged all

the way in to finish the cut. That way I can cut tenons longer than the actual cutter length of the bit. If I hadn't shortened my bit, I could have made a tenon about a centimeter longer. And if I had bought the longest bit available, I could have made a tenon 8 cm long!

The chips sure go flying while making the cut - there's quite a bit of material to be removed.

The router motor blows air out the front, which really spreads the

chips around. On the plus side, at least this gets the chips out of the way.

That previous shot is a still frame from the video I shot. I set up my camera a meter away, but it still got a fair bit of dust on it. It's of the reasons I try to use cheap cameras in the workshop. I

haven't had a camera die of dust exposure yet. But what can happen is that dust gets in between the lens groups inside the zoom lens. That dust is impossible to get out.

The finished tenon. I always make all the cuts around the edge with a "climb cut", basically with the cutter moving into, not out of the wood. This eliminates any sort of tearout.

I made some through mortises on much thinner stock to test the fit with. My initial fit was too tight, so I sanded the edge of the tenon template down just a bit. I also found my mortise a

little too wide, so I put a strip of 0.25 mm thick UHMW tape to one of the inside edges of the template.

This photo shows the fit after adjustments.

Now cutting the big mortise. Clearing out chips for a cut this deep is a challenge. But fortunately, with a mortise this wide there's plenty of room. For a mortise that's just the width of the bit, it

would be more of a problem. If I was making a lot of deep and narrow mortises, I'd probably invest in a spiral bit.

The finished mortise

The tenon fits quite nicely, with just a bit of friction going in. When I pull the tenon out rapidly, it actually makes a loud "plop" from the partial vacuum in the mortise because air

couldn't get past the tenon fast enough as I pulled it out (see end of video).

You know your mortise and tenon joint makes a good fit if it goes "plop" when you pull it out!

See also:

More about thePantorouter

Making a boxon the pantorouter

Making tenon templateswithout equations

Mortise and tenon joint accuracy

Multi slot mortising machine

You can buy  detailed plans for the slot mortising machine

I have always used a home-made slot mortising machine for my mortise and tenon joints. My previous slot mortising machine was made possible because of a lucky surplus sale find. But I had always wanted to be able to build a mortising machine from scratch using readily available materials. I have finally achieved building such a machine, and this article describes how it works.

Horizontal motion

mechanism  

Building thehorizontal sliders

mechanism  

Router mount and

vertical adjustment  

Joints thismachine can cut 

Building the router

mount and verticaladjustments  

Building a standfor the

slot mortiser  

Horizontal router table for the slot mortiser 

You can also see a Tony C's slot mortiserbased on the plans on on LumberJocks.Tony also has a lot ofphotos if it's construction on flickr. 

These articles are also available in German

Dave Tenney on making pantorouter templates

After building the

pantorouter I decided that it would be really sweet if I had templates pre-made to make a wide range of tenons and mortises. I like the way the template system works on the metal pantorouter, so this is the direction that I went in.

Rather than milling a slot in the template the way that Matthias did, I glued the template together. I had used this idea last year when I made a template for my tenoning jig and figured it would work well here.

All of my templates are made for using a 1/2" straight bit to cut the tenons. I just change the bearing on the follower to make 3/8” and 1/4” tenons.

The first thing to do is make up a batch of template stock. I am using 19mm birch plywood for mine; it’s fairly hard and very stable.

We need some 1/4” stock for the slot spacer.

Then we need some slightly oversized 3/8" stock with a 5 degree bevel on one side. My stock measures about .405 (I need better calipers!) which is .030 over on the fat end.

Now we need to lay out the size of mortise and tenon we want to make. Our slot length is double the intended mortise size minus 3/4”. In this example I am making a 3/4” mortise.

So doubling that would be 1 1/2” and taking away 3/4” would leave a slot size on 3/4”. For another example, if I wanted to make a 3 1/4” mortise my slot would be 5 3/4”.

Next we will glue in the spacers. Make sure the bevels are on the outside.

Once the glue has dried we can lay out the ends of the template. I am laying mine out on the back so the radius of my circle is

going to be .655 or so. I made a pattern for this that you can see above the template. I use the caliper to check that the distance from the slot to the outside of the arc is about .405

After cutting it out on the bandsaw and sanding it to the line I glued it onto a piece of Luan as a backer board.

So how does it work? Perfect fit on the first try! Of course it helps that I had already made a couple of test templates working out all these

dimension…

And of course, if you’re going to make one you might as well make a tree full.

The Pantorouter

I call this machine the "pantorouter" because it's essentially a big pantograph mechanism with a router in it. It's used to route shapes from 2x sized templates. I originally designed it for cutting tenons, but the machine is very versatile and can be used for all kinds of wood joints.

This version is optimized for use with routers with cylindrical bodies only. My larger Pantorouter XL is designed to accomodate plunge routers. 

Using the pantorouterto make joints

How it works

Coming up withthe design

Cutting throughdovetail joints

Tenon templatesfor the pantorouter

How to align templates

Cutting a large joint.

Dave Tenney onmaking tenon templates

Making plantationshutters

Making a finger joint

Cube in a cube in a cube

Pantorouter plans

You can also buy aPre-built all-metal pantorouter

Construction of the machine:

Building thepantorouter

Router mountfor a palm router

Linear glidesfrom drawer slides

Holddown clamp

Improved pantorotuer followers

Specifications

Buy plans for the pantorouter

More projects where I used the pantorouter:

Coat hooks

Paper towel holder

Wooden hings

Scaffold build

Building a largemirror stand

Quickie workbench

Ukulele neck mortise

Rolling under bedstorage drawer

Scarf splice joint tofix broken chair legs

Needlessly complicatedaxe handle repair

Half-blind dovetail joints

Clever 3-way joint(Kawai Tsugite)

Double tenon with the metal pantorouter

Making pantorouter followersWhen I did

my pantorouter comparison with the all-metal version thatKuldeep builds, I mentioned that I liked how Kuldeep made the followers with a bearing on a shaft, but didn't have a way to attach a bearing myself, so I'm keeping with the old system of mounting follower bearings on my wooden pantorouter.

I received many suggestions, such as using Locktite to mount the bearing on the shaft. But my real problem is actually that shaft size and bearing holes in the bearings I have don't match. But with so many suggestions, I started thinking about how to make round followers on shafts for my pantorouter.

If I cut a thread on the end of the shaft, I could then mount various nuts on it, like this knock down nut with a nice wide circular flange, so it already forms a round follower. You can buy nuts like that at The Home Depot.

Or I could put a hex nut on the end of the shaft and grind that round on my bench grinder. With a bit of sanding and polishing, that makes for a fairly easily sliding round follower, and it turned out quite precise too.

1/2" bearings have smaller holes in them, but using the same technique on the bench grinder I was able to grind the shaft down so it fit in the bearing, though not tightly. But some shims, cut from aluminium cans, made for a tight fit.

Whenever I take something apart, I always keep the washers and other small hardware that might be useful. So I have a whole drawer full of round bushings and spacers,

and I started to dig through those to see what might work.

I found some bushings that fit snugly on the 6 mm shafts I was using. I used 6 mm to make it compatible with Kuldeep's. I used one bushing as a follower directly and ground another one down a little (again on the bench grinder) to fit the hole of a 26 mm bearing I had. Again, with a shim from an aluminium can to make it fit snug. I also found one bushing that fit perfectly between the 6 mm shaft and the 8 mm hole for another bearing.

You could also make your followers out of 1/4" bolts, which already have threads on them. Combined with a nut

with integral washer, as shown, all you would have to do is glue the nut on and cut off the bolt head to make a follower.

Going through my junk, I made quite a lot of followers of different sizes.

But one size I didn't have was 1" (25.4 mm),

so I decided to make one that size out of wood.

I started by cutting a slightly larger circle from Baltic birch plywood on the bandsaw. The hole I drilled is a bit undersized for the shaft. I roughened up the end of the shaft and used some Gorilla glue in the hole and shaft, then drove the shaft in with a hammer.

After that, I spun the disk in a hand drill, held up to my disk sander to make it perfectly round.

I'm guiding the shaft with a piece of wood, near the end to make sure it's steady. I ended up sanding that one down to just under 1", then applied some UHMW tape to it to bring it back up to size and make it slide easier.

UHMW tape is also useful for up-sizing metal followers. Each turn of UHMW tape adds 0.3 mm to the diameter of the follower. Just be sure to have a whole number of turns on the follower so the tape is the same thickness all around.

I ended up making a lot of followers, mostly from random bushings and round plastic parts. I have no more than 1 mm of size difference between

most of them.

I made a mounting block to clamp the 6 mm shaft on my

pantorouter. I didn't have a 6 mm drill, but a 15/64" drill made for a hole that fit the 6 mm shaft just snugly. The only change I had to make to my wooden pantorouter was to drill a 17/64" (6.7 mm) hole all the way

through the operating lever, then mount the new holder. The orange knob on the holder clamps the block together to lock the 6 mm shaft in it. That knob came from a broken Ryobi circular saw.

Making tapered and slotted tenon templatesHaving figured out how to make followers like on the all metal

pantorouter, the next challenge was to make the clever templates with the slot in the middle and tapered edges around the outside. The tapered edges of the tenon template allow fine adjustments in tenon size to be made.

I set my table saw to four degrees, then cut a bevel on a piece of 18 mm thick Baltic birch plywood. 18 mm is perhaps a bit thick, but I figured more thickness is better, and the next thinnest Baltic birch plywood I had was 11 mm.

With the wide side of the plywood facing up, I set my compass to half the width, then use it with

the point on either edge to check the center of the mark, and draw an arc from there.

I tilted the bandsaw to four degrees, checking it with a speed square, because

my homemade bandsaw doesn't have any angle scale.

Cutting out the

semicircles. I cut within half a millimeter to the line...

...so that I don't have to sand away very much material finishing it up.

For my first tapered template, I drew the semicircles

on the front (the narrow side), but then realized the disk sander table doesn't tilt towards the disk. Oops! That's why I drew the semicircles on the back this time. I was however able to tilt the strip sander table towards the belt a bit, but the disk sander is better for this job.

I cut the slot in the template on my pantorouter, just using a straight piece of wood to roll the follower bearing along to get the straight line.

Despite being very careful, I got the line about 1 mm off center and, worse yet, about 0.2 mm higher on one side. Arrgh! Sliding the template on a router table to cut the slot could be iffy, but would avoid the possibility of getting the angle wrong. I ended up "fixing" it by doing a plunge cut on the table saw (with the template held down against the fence), then finishing it with a chisel.

Gluing the template on a backer board, being very careful to keep the template exactly flush along the bottom edge to make sure it's

straight.

So I hope this gives you some ideas for how to make followers and tapered templates for a wooden pantorouter.

But if you haven't built a pantorouter yet, I'd recommend starting out with just a bearing on a block and leave these fancy followers for a later upgrade. You probalby want to start using your pantorouter as soon as possible, and mounting a bearing on a block is much easier.

Also, if you attach the follower bearing on the block with a countersink screw, if you back out the screw just a bit, the bearing can slide the same amount in all directions. So even with the "old" method of making the followers, you can still effectively adjust the fit, making the tenon slightly smaller by loosening the bearing mounting screw.