. parts of a telescopic gauge

. constructional features of telescopic gauges

. parts of a small hole gauge

Telescopic gauges are popular for fine work as they are very rigid and have a better 'feel'.

Uses

Used for measuring the sizes of holes, slots and recesses.

Construction


Telescopic gauges are 'T' shaped. They consist of a pair of telescopic legs or plungers connected to a handle. The plungers are spring loaded to force them apart. After inserting the gauge in a hole or slot, it can be locked in position by turning the knurled handle. It may then be withdraw from the hole and measured with a micrometer.


Telescopic gauges are available in a set of 5 nos, to measure holes from 12.7mm to 152.4mm.

No.1 12.7mm to 19mm

No.2 19.0mm to 31.7mm

No.3 31.7mm to 53.9mm

No.4 53.9mm to 88.9mm

No.5 88.9mm to 152.4mm

Small hole gauges

Telescopic gauges are not suitable for measuring holes below 12.7mm. For measuring smaller holes and slots, small hole gauges are used.

Construction

A small hole gauge consists of tube having holes on the opposit sides at one end where hardened balls are fixed. The other end of the tube has an external thread. A screwed thimble is fixed with a threaded ttube. A plunger with a tapered end, and spring loaded, is in serted in the tube and tightened with the screwed thimble. At the end of the thimble a knurled handle is fitted. While rotating the knurled handle in a clockwise direction the plunger moves forward up, and pushes the balls out to contact the surfaces


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A small hole gauge is an instrument used for indirect measurement, while a micrometers is usually used for measuring the sizes.

Small hole gauges are available in a set of 7 numbers to small hole gauges are available in a set of 7 numbers to measure holes from 3.2mm to 12.7mm.

No. 1 3.2mm to 3.8mm

No. 2 3.8mm to 4.5mm

No. 3 4.5mm to 5.1mm

No. 4 5.1mm to 6.4mm

No. 5 6.4mm to 8mm

No. 6 8mm to 9.6mm

No. 7 9.6mm to 12.7mm