Centring, Drilling and Counterboring / Countersinking - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training: Instruction example 3.4.: Draw-in bush

Centring, Drilling and Counterboring / Countersinking - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training

		(introduction...)
		Preface
		Instruction example 3.1.: Shaft
		Instruction example 3.2.: Die plate
		Instruction example 3.3.: Adapter
		Instruction example 3.4.: Draw-in bush

Instruction example 3.4.: Draw-in bush

This example serves to practise countersinking with the counter-sink and turning tool (boring tool) of hollow cylindrical parts.

Figure

Material

15 Cr 6 (15 = 0.15 % carbon. Cr 6 = 1.5 % chromium) case-hardening steel

Dimensions

dia. 52×82

(pre-machined dia. 50×80, hole dia. 20)

Cutting and operating tools

Countersink 60°, inside turning (boring) tool for corner work, chuck key

Measuring and testing tools

Depth gauge, protractor, dial gauge

Accessories

Chuck jaws which can be turned out, taper sleeves, supporting plates, coolant

Required previous knowledge

Reading of drawings, measuring and testing, scribing and prick-punching, drilling and counterboring/countersinking

Explanations to the working drawing

ø 20 H 7:	ø - diameter, 20 - nominal size,
	H - disposition of the tolerance zone
	7 - quality

0.02 - admissible true-running error 0.02 mm surface: finished Rz 20, Rz 6.3 fine-finished.

Sequence of operations	Remarks
1. Dimensional inspection
2. Clamping of workpiece	Type of clamping: "chucking" in stepped chuck jaws which can be turned out. Chuck on dia. 50 (surface and end face pre-machined as per sketch 1). Check for true running (Turn out chuck jaws, if necessary).
3. Clamping of tool	Locate tool in tailstock. Ensure firm fit of taper.
4. Countersinking 2×60°	Countersink 2×60° by means of manual sleeve adjustment. Select low cutting speed. Use coolant. Use sleeve scale. Visual inspection of size and surface finish.
5. Re-chucking	Type of clamping: "Chucking". Check for true running (radial and axial runout).
6. Clamping of tool	Clamp inside turning tool short on top slide. Ensure clearance angle. Swivel top slide by 45°.
7. Countersinking 10×45°	Set end stop. Take first cut on transition between inner surface and end face. Set cross slide to "0". Set feed. Finish turning with several chips by means of manual top slide adjustment. Use coolant for turning tool without carbide tip. Visual inspection of surface finish.
8. Dimensional and surface inspection.
9. Unloading.

Figure