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close this bookCentring, Drilling Counterboring and Countersinking, Reaming and Tapping on the Drilling Machines - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training
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View the documentIntroduction
View the documentInstruction example 1.1. Distance piece
View the documentInstruction example 1.2. Gib
View the documentInstruction example 1.3. Cylinder
View the documentInstruction example 1.4. Prismatic guideway
View the documentInstruction example 1.5. Stop

Instruction example 1.5. Stop

With this instruction example the drilling, countersinking and tapping of prismatic workpieces is practised. Centring or punch marking is presupposed.



100 Cr 6 (1 % carbon, 1.2 % chromium)


85 × 30 × 20 (premachined)


Twist drill of Ø 6.75 mm; 30° included angle countersink; M8 machine tap

Measuring and testing means

Vernier caliper, M8 thread limit plug gauge


Machine vice, drill chuck, tap chuck, taper sleeves, drill drift, parallel, coolant or lubricant

Required previous knowledge

Reading of drawings; measuring and testing; kinds and applications of tools, clamping and auxiliary equipment; kinds and shapes of thread

Explanations to the working drawing

M8: m - metric screw thread, 8 - nominal diameter

Sequence of operations


1. Measure rough dimensions.

In case of undersize reject workpiece.

2. Clamp workpiece.

Kind of clamping: loose vice clamping. Insert parallels, set up for size 30 mm.

3. Clamp tool.

Insert drill chuck, use taper sleeves.

4. Align.

Pay attention to centre position.

5. Drill first through hole of Ø 6.75 mm.

Spot-drill and check for centre, finish through hole as preparation for tapping, use coolant.

6. Align.

7. Drill second through hole of Ø 6.75 mm.

Finish hole according to working step 5.

8. Clamp tool.

Use taper sleeves.

9. Align.

10. Countersink first hole for Ø 6.75 mm.

Countersink for 8.5 mm, keep cutting values of the multiple-edge tool low (n = 30 r.p.m.)

11. Align.

12. Countersink second hole for Ø 6,75 mm.

Finish countersink according to working step 10.

13. Reset workpiece.

Clamp the workpiece for turnover (180°). Clean bearing surfaces before.

14. Countersink the side turned over.

Countersink holes for Ø 6.75 mm according to working steps 9 - 12.

15. Clamp tool.

Use tap chuck and taper sleeves.

16. Tap M8.

Make tapped holes. Align according to working step 4. Consider run-out time and switching phase from clockwise rotation to counter clockwise rotation (n = 60 r.p.m.).

17. Make dimensional inspection and visual check.

Make surface check.