Centring, Drilling and Counterboring / Countersinking - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training: Instruction example 3.1.: Shaft

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 3.1.: Shaft

This example serves to practise centring with the centre drill on rotationally symmetrical parts held in a chuck.

Figure

Material

GGL - 25 (GG = cast iron, L = flakes, GGL = grey cast iron, 25 = 250 MPa tensile strength)

Dimensions

dia. 60×250

Cutting and operating tools

Centre drill B 3.15; key

Measuring and testing tools

Vernier caliper

Accessories

Drill chuck, hard chuck jaws

Required previous knowledge

Reading of drawings, measuring and testing, scribing and prick-punching

Explanations to the working drawing

B 3.15:	B = centre hole type B
	3.15 = nominal size of the centre drill (d)

Surface finish: unmachined Rz 80, centre hole Rz 20

Sequence of operations	Remarks
1. Dimensional inspection
2. Clamping of workpiece	Type of clamping: "chucking" in hard chuck jaws. Clamp short. Consider spindle capacity. For longer parts use spindle support.
3. Clamping of tool	Chuck centre drill in drill chuck. If necessary, have drill chuck held in tailstock spindle using taper sleeves.
4. Setting of cutting values	Select speed rate as high as possible. Feed manually.
5. Positioning of tailstock	Move tailstock in working position and lock it.
6. Switching on lathe
7. Tool to take first cut	Ensure that tool is in central position when taking first cut. Adjust tailstock, if necessary.
8. Centring	Finish centring. Consider size specified.
9. Returning of tool carrier (tailstock)	Leave sufficient space for unloading.
10. Switch off machine
11. Measuring
12. Re-chucking	Turn part by 180° around its longitudinal axis and clamp it short.

For machining of the second side repeat operations 5. to 11. Operation 7. is not necessary since central position of the centring tool has already been aligned.

Figure