Knurling - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training: Instruction example 7.4.: Control knob

Knurling - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training

		(introduction...)
		Introduction
		Instruction example 7.1.: Locking screw
		Instruction example 7.2.: Ring thread gauge
		Instruction example 7.3.: Knurled screw
		Instruction example 7.4.: Control knob
		Instruction example 7.5.: Grip

Instruction example 7.4.: Control knob

This example serves to practise straight knurling of convex parts.

Figure

Material

St 34 (St = steel, 34 = tensile strength up to 340 MPa)

Dimensions

dia. 44 x 65 mm

Working tools

Right-offset side-cutting tool, radius turning tool, chuck key, hollow (concave) knurling tool

Measuring and testing tools

Vernier caliper, radius gauge

Accessories

Hard chuck jaws, supporting plates, coolant and lubricant

Required previous knowledge

Reading of drawings, measuring and testing, behaviour of material in chipless shaping, longitudinal turning and facing, use of coolants and lubricants

Explanations to the working drawing

M 16:	M = metric thread, 16 = nominal diameter
Straight knurling K 1.0:	K = hollow (concave) knurling wheel 1.0 = tooth pitch 1 mm

All surfaces finished.

Sequence of operations		Remarks

1.	Dimensional inspection

2.	Clamping of workpiece	Chucking in hard chuck jaws 40 mm deep.

3.	Clamping of tool to produce outside diameter	Right-offset side-cutting tool.

4.	Setting of cutting values

5.	Producing the outside diameter	t/2: d = 42 mm less 0.5 mm = 41.5 mm

6.	Tool change for producing the radius	Form turning tool to be selected according to radius of knurling tool.

7.	Setting of cutting values	Form turning tool is made of high-speed steel - v = 25 - 50 m/min. v = 25 m/min to be selected for form turning.

8.	Producing the radius	Radius turning tool to be in centre position.

9.	Tool change for producing knurling	Straight knurling tool to be clamped approx. 1 mm below centre and at right angle to workpiece axis.

10.	Setting of cutting values	v = 6 - 10 m/min, since concave knurling wheel v = 6 m/min to be selected.

11.	Straight knurling of diameter	To be cooled and lubricated with soluble oil or cutting oil. First knurling to be done with one feed setting, if possible. Tool to be positioned over full width - central position is essential Operation must not last longer than necessary since surface gets harder and more brittle because of pressure.

12.	Deburring of edges of knurled portion	Material is forced towards end faces forming burr.

13.	Unloading of workpiece

14.	Dimensional inspection	Dimensional and visual inspection (cleanliness of knurling grooves). Knurling wheel to be cleaned by wire brush.

Figure