Page 50 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

Skill Sequence

Drilling blind holes

Objectives: At the end of this exercise you shall be able to
• drill blind holes to the required depth using the depth stops.

Method of controlling depth of blind holes
While drilling blind holes, it is necessary to control the feed of the drill. Most machines are provided with a depth
stop arrangement by which the downward movement of the spindle can be controlled. (Fig 1)

Fig 1

Most depth stop arrangements will have graduations by which the advancement of the spindle can be observed.
Generally the blind hole depth tolerances are given up to 0.5 mm accuracy.

Setting for drilling blind holes
For blind hole - depth setting, first the work is held on the machine and the hole is located correctly.
The drill is started, and it drills until the full diameter is formed. Note down the initial reading at this point. (Fig 2)

Fig 2

Add the initial reading to the depth of the blind hole to be drilled.
Initial reading + Depth of hole = Setting.

Adust the stop next to the required setting, using the scale.
Tighten the lock nut to prevent the setting from being disturbed.

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CITS : C G & M - Fitter - Exercise 62