Relation between Machining Process and Tolerance Grades

Designation of Standard Fits

Preferred Fits

Preferred Fits (ANSI)

Limit Gauges

What is the Limit Gauges?

After producing a part, it is necessary to ensure parts are within specified limits, so protecting the design intent, the type and method of inspector decided for every feature toleranced individually. One of the important tools used for inspection are limit gauges. Gauges are:

• Inspection tools of rigid design, • Without a scale.• serve to check the dimensions of manufactured parts.• Decreases the inspection cost and time

Gauges do not indicate the actual value of the inspected dimension on the work. They can only be used for determining as to whether the inspected parts are made within the specified limits.

Classification of Limit Gauges

According to their type:• Standard and limit gauges.• Limit gauges.

According to their purposes:• Workshop• Inspection

According to the form of the tested surface:• Plug gauges for checking holes.• Snap and ring gauges for checking shafts.

According to their design:• Single limit and double limit gauges,• Single ended and double ended gauges,• Fixed and adjustable gauges.

Plain Plug Gauges

'Go' and 'No Go' for sizes up to 10 mm, (solid type). 'Go' and 'No Go' for sizes over 10 and up to 30 mm (Taper Inserted type).

Go and No Go for sixes over 30 mm and up to 63 mm (Fastened type), Go and "No Go" for sizes over 63 mm and 100 mm (Fastened type).

Go and No Go for sizes over 100 mm and up to 250 mm (Flat type).

The plain gauges are marked with the following on their handles for their identification:• Nominal size• Class of tolerance. • The word 'Go' on the 'Go' side• The words 'No Go' on the 'No Go' side. • The actual values of tolerance.• Manufacturer's name or trade-mark.

Plain Ring Gauges

Snap Gauges

Plate Snap Gauges

'No Go' Snap gauge for dimension varying from 3 mm to 100 mm'No Go' Snap gauge for dimension varying from 100 mm to 250 mm

'No Go' Plate Snap gauge for dimension varying from 3 mm to 100 mm

'No Go' Plate Snap gauge for dimension varying from 100 mm to 250 mm

Combined Limit Gauges

Used for cylindrical holes, Combine, both the 'Go' and 'No Go' dimensions of a plug gauge. It is achieved by employing a spherically ended gauge of the same diameter as the lower limiting dimension of the hole. Towards the outer edge of the spherical member, a spherical projection S is provided. For checking the hole for 'Go' position, the gauge is inserted into the hole with the handle parallel to the axis of the hole. For checking the hole for 'No Go' limit, the gauge is tilted so that the spherical projection S is normal to hole. The gauge in this position should not enter the hole.

Position Gauges

The design of position gauges is based on the shape of the work. A different position gauge is required for each design of work. Their design can be based either on the principle of sighting the gauge and work, or on the method of feel.

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Checking the location of a recess in relation to a flat surface. Checking the location of a surface parallel to the reference surface is to be located

No light will pass with 'Go' side light will pass with 'No Go' side.