8. Technological process of drilling

Drilling of a blind hole:

1. Scribing and prick-punching

2. Clamping of the drill

3. Clamping of the workpiece in the machine vice and placing the point of the drill right above the punch mark;

Clamping the machine vice on the machine table

4. Setting the rotational speed at the machine

5. Spot-drilling of the workpiece (the point of the drill completely penetrates into the workpiece)

6. Setting the drilling depth at the machine which is switched off during this operation

7. Drilling up to the dog of the feed handle and/or depth indicator (feeding of cooling agent and permanent control of the flow of chips)

8. Cleaning and deburring

9. Checking of the diameter and of the depth of the bore hole with the help of a vernier caliper and depth gauge

If the bore hole is not true to size, i.e. if it is too large, this can have the following reasons:

Cause of the fault	Correction of the fault
Wrong drill point	Regrinding of the drill
The drill runs out when the spindle is running	Cleaning of the cylindrical shank of the drill as well as of the sleeve and reclamping of the drill. If the shank is severely damaged by ridges it can no longer be used and has to be replaced
The workpiece is not fixed	Clamp the workpiece on the table more firmly or secure it against displacement at least.