Page 22 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

Fig 1

Note : Remove the reamer occasionally by turning it clockwise to clear of the chips from the flutes.
Never use a hand reamer under power.
Never turn the lathe spindle or reamer backward. This will damage the reamer blunting the cutting teeth
of the reamer, and will also result in developing scratches on the reamed surface of the hole.

Remove any burrs from the edge of the hole with a scraper.

Method of checking the bore with a plain cylindrical plug
gauge

Objectives:At the end of this exercise you shall be able to
• select the plug gauge according to the bore limits
• check the low limit of the bore with the ‘GO’ end of the gauge
• check the high limit of the bore with the ‘NO-GO’ end of the gauge.

Select a plug gauge of the correct size and tolerance for the hole being checked.
Clean both the ends of the gauge and the hole of the workpiece with a clean dry cloth.
Check both the ends of the gauge and the workpiece and ensure they are free from burrs in the bore.
Position the ‘Go’ end of the gauge squarely to the axis of the hole at the front and apply light pressure axially. (Fig 1)
Note : If the hole is within limit, the gauge will enter easily.

Allow the plug to enter for the full length of the bore.
Check for the play between the plug gauge and the borediameter.
Note: If the plug does not go throughout the bore, it indicates that the bore is tapered.
The plug should not forced inside unless the bore is rectified.

Excessive play or looseness in any one direction indicates that the hole is elliptical.
Check with the ‘No Go’ end of the gauge also, using the same procedure.
An entry of a ‘No-Go’ gauge into a hole beyond the chamfered length indicates an oversized hole, bell
mouthed or tapered hole.
Do not force or twist a plug gauge in the hole. Forcing or twisting will cause excessive wear.
While checking, the plug gauge and workpiece must have the same temperature.

7

CITS : C G & M - Fitter - Exercise 59