|Centring, Drilling and Counterboring / Countersinking - Course: Techniques for machining of material. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 22 p.)|
|1. Purpose of centring, drilling and counterboring/countersinking|
|2. Types and application of centring, drilling and counterboring/ countersinking tools|
|3. Preparation of centring, drilling and counterboring/countersinking|
|4. Centring with the centre square, centre bell and height gauge|
|5. Centring with the centre drill|
|6. Centring with the turning tool|
|7. Drilling with the drill and boring with the boring tool (turning tool)|
|8. Counterboring/countersinking with counterbore/countersink and turning tool|
The manufacturing process is to be prepared so that all working tools and materials are readily accessable.
In this, the following rules should be observed:
- Check the tools for serviceability. Use serviceable tools only.
- Tools to be used must not be placed one above another.
- Store tools in clean condition.
- Store measuring and testing tools on adequate supports only.
- Select the necessary auxiliary tools and means according to the work order and place them at disposal on adequate supports.
Setting up of the lathe for centring, drilling or counterboring/ countersinking basically involves the following steps:
- Clamping/chucking of workpiece and tool.
- Setting of cutting values.
- Tool to take first cut and feed setting of tool.
- Intermediate inspection.
- Setting to final size.
- Dimensional and visual inspection.
Clamping/chucking tools and auxiliary tools/means to be used:
- Three-jaw chuck (to chuck the workpiece on the lathe).
- Chuck or collet (for firm gripping of the workpiece).
- Drill chuck (to chuck centring, drilling and counterboring/ countersinking tools with straight shank).
Figure 15 Drill chuck
- Taper sleeve (to hold tools with different tool taper).
- Drill block (for positive, automatic tool guide by means of the tool slide).
Figure 16 Drill block
- Centre square (for scribe-marking the centre of rotationally symmetrical parts).
Figure 17 Centre square
- Centre bell (for punch-marking rotationally symmetrical parts at the central position of their diameter).
Figure 18 Centre bell
1 centre punch,
2 centre bell,
- Height gauge (for scribe-marking of parts).
- Coolant (to cool the cutting edges and increase the tool life).
Figure 19 Height gauge
What rotational speed will be necessary for drilling a part with a special drill (dia. 25, SS - high-speed steel) (V = 30 m/min)?