3. Preparation of centring, drilling and counterboring/countersinking

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,
3 workpiece

- Height gauge (for scribe-marking of parts).

- Coolant (to cool the cutting edges and increase the tool life).

Figure 19 Height gauge

1 stand,
2 slide,
3 scriber

What rotational speed will be necessary for drilling a part with a special drill (dia. 25, SS - high-speed steel) (V = 30 m/min)?

Formula:
given:
required:
Calculation:
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