Introduction:

Gauges are inspection tool of rigid design, without a scale, which serves to check

the dimensions of manufacturing parts.

Gauge do not indicate the actual value of the inspected part of the component.

They are used to determine whether the part is made within the specified limit.

Made up from the High carbon and alloy steels. Chrome plating or cemented

carbides used as the surface material at certain wear points.

.

Classification:

Based on the standard and limit

(i) Standard gauges - made as an exact copy of mating parts

(ii) Limit gauges or “go” and “not go” gauges - Made to the limits of parts

Based on the Purpose

(i) Working gauges - To check the dimensions after manufacturing

(ii) Inspection gauges - To check the part before final acceptance

(iii) Reference or master gauges - To check the dimensions of gauges

Depending on form of tested surface

(i) Gauges for checking holes

(ii) Gauges for checking shafts

(iii) Gauges for checking tapers

(iv) Gauges for checking threads

According to Design

(i) single limit and double limit

(ii) single ended and double ended

(iii) fixed and adjustable

Cylindrical Pin Gauge

Adjustable Snap Gauge Plain Ring Gauge

Cylindrical Plug Gauge Adjustable Thread ring

gauge

Plug gauge

Thread plug

gauge

Limit Gauges:

Limit Gauges (Continued):

OR Gauge maker’s tolerance

Tolerance on gauge is 1/10 of work tolerance.

Wear allowance

Go gauges constantly rub against the surfaces of the parts in

inspection are subjected to wear and loose their initial size. No Go

gauge is less subjected to wear.

Wear allowance is given on Go gauge only.

wear allowance = 5% of work tolerance

This principle states that the Go gauge should always be so

designed that it will cover the maximum metal condition (MMC) of as

many dimensions as possible in same limit gauge, whereas Not Go

gauge to cover the minimum metal condition of one dimension only .

Taylor’s Principle of Gauge Design:

'go' limit is the one between the two size

limits which corresponds to the maximum

material limit (MML).

The upper limit of a shaft and the lower

limit of a hole.

„GO' gauge can check one feature of the

component in one pass.

'no go' limit is the one between the two

size limits which corresponds to the

minimum material condition.

The lower limit of a shaft and the

upper limit of a hole.

“GO” Limit:

“NO-GO” Limit:

Taylor’s Principle of Gauge Design:

“GO” Plug Gauge should have a full Circular

section.

Length should be equal to the length of the

hole.

“NO-GO” Plug Gauge should be in the form

of pin or bar.

Should check the upper limit of the hole.

“GO” Limit:

“NO-GO” Limit:

Taylor’s Principle of Gauge Design:

FIGURE : A go/no-go plug gage purchased to

check a particular hole size. Note that the go

member is longer than the no-go member.

FIGURE : A single-end progressive-type go/no-go

plug gage can more quickly check hole sizes.

Examples: GO/ NO-GO Plug gauge

Examples: Thread Plug gauge

FIGURE : (A) Prussian blue is applied to the part to

be checked. (B) The taper plug gage is then inserted

in the hole and twisted. (C) The even transfer of

Prussian blue to the gage indicates a proper fit and

accurate taper.

A

B

C

Examples: Taper Plug gauge

FIGURE : Go and no-go thread ring

gages. The no-go gage has a ring

around its circumference for

identification, just like a no-go plain

ring gage.

FIGURE : The go and no-go limit

can be shown by a step on a taper

ring gage. A tapered part passes

inspection when the end is between

the stepped surfaces.

Examples: Thread ring gauge

Taper ring gauge

FIGURE :Two styles of snap gages. The outer

anvils of the snap gages are set to the go limit

and should always pass over the part being

checked. If they do not pass, the part is too

large. The inner anvils are set to the no-go limit

and should not pass over the part. If they do,

the part is too small.

A

B

Examples: Snap gauges

FIGURE: A digital snap gage. A “0” point

can be set at any size and the digital

readout shows the amount of variation

from that size.

FIGURE: Some thread snap

gages used for checking external

thread dimensions. Note that

some have solid anvils and some

have rollers. The front gage is

only a go gage.

Examples: Snap gauges

Advantages of Limit gauges

•Limit gauges are conveniently used in mass production for

checking various dimensions to ensure interchangeability.

•Easily used by semi-skilled labour.

•These are economical.

Disadvantages of Limit gauges:

•They do not give exact size of component.

•It is uneconomical to manufacture gauge to measure work

tolerance finer than 0.013 mm. To measure this instruments are

used.

•Comparison of indicating instruments with limit gauges: