Cover Image
close this bookCentring, Drilling and Counterboring / Countersinking - Course: Techniques for machining of material. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 22 p.)
View the document(introduction...)
View the document1. Purpose of centring, drilling and counterboring/countersinking
View the document2. Types and application of centring, drilling and counterboring/ countersinking tools
View the document3. Preparation of centring, drilling and counterboring/countersinking
View the document4. Centring with the centre square, centre bell and height gauge
View the document5. Centring with the centre drill
View the document6. Centring with the turning tool
View the document7. Drilling with the drill and boring with the boring tool (turning tool)
View the document8. Counterboring/countersinking with counterbore/countersink and turning tool

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)?