6. Cylindrical turning and facing of shouldered cylindrical parts

Turning of shouldered cylindrical parts means turning of parts having one or more shoulders (diameters). This is also often called turning with trip stop control (or turning multiple diameters). The part is held in a chuck or between centres with or without counter-support. The cutting is done on the circumferential surface or end face of the part.

- In cylindrical turning the internal surface (using the internal turning tool, also called boring tool) or external surface of the part is machined (see Fig. 2).

- In batch production it is absolutely necessary to use the bed stop and length blocks.

- As counter-supports the tailstock with centre (Fig. 22) and steady rest are used.

Figure 22 Tailstock. sectional view

1 tailstock centre,
2 sleeve,
3 handle for lock nut,
4 hand-wheel,
5 look nut,
6 spindle,
7 spindle nut

- When turning longer parts using the tailstock or steady rest as counter-support, the cylindricity of the part must always be checked. Misalignment of the steady rest or centre offset of the tailstock may result in eccentricity. In that case the tailstock is to be aligned as per Fig. 23.

Figure 23 Aligning the tailstock

1 work spindle end,
2 tailstock end,
3 feed direction of the turning tool,
4 tailstock alignment in mm,
5 correction facilities

- Constant lubrication to the tailstock guideways is a must.

- When facing any shoulders (shoulder faces) the cutting tool is to be moved in opposite direction to the feed direction. This avoids faulty faces.

- Firm chucking of the part is of utmost importance

Existing safety facilities must not be made ineffective.

What are the reasons for eccentricity when machining parts with counter-supports?
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