8.4 FEEDS AND SPEEDS

---

If we consider the speed and feed of a lathe,

- Spindle Speed is in revolutions per minute

- Feed is in inches per revolution

The Feed Chart is used to select the speeds and feeds of the lathe, and is often attached to the lathe near the setting levers.

There are some simple (geometric) equations that can be listed,

Typical cutting speeds for a high speed steel tool are, [Krar]

Typical feeds when using a high speed steel tool are, [Krar]

8.4.1 The mrr for Turning

considering the parameters defined in the discussion of speeds and feeds, etc, the mrr is given below,

8.4.2 Process Planning for Turning

The general steps when process planning for turning external parts are,

1. Rough cuts all diameters to within 1/32" starting with the largest diameters first.

2. Rough cut all shoulders and steps to within 1/32"

3. Do special operations such as knurling and grooving

4. Cool the workpiece to get it close to the final dimension.

5. Finish turn the diameters, then the shoulders and steps

6. Deburr if necessary

If the part is to be mounted between centres, plan should precede by,

1. cut stock that is 1/8" larger than required.

2. Put the work in the lathe, in a chuck, and face and centre drill the end.

3. reverse the pice in the chuck and face the piece to size, and centre drill.

4. Mount the work between centres

For work to be mounted in a chuck, (implies internal features),

1. cut the stock 1/8" wider in diameter, and 1/2" longer.

2. Mount the work in the chuck with 5/16" to 3/8" inside.

3. Use a facing operation (lightly) to square the end.

4. Rough cut the external diameters, from the largest to the smallest.

5. Drill out the centre of the work using a drill chuck mounted in the tailstocks spindle. Start with a centre drill, and increase drill sizes to increase the hole.

6. Mount a boring tool to cut the internal diameter to close to the final diameter.

7. Cut any special feature now.

8. Do finish cuts on outside and inside.

9. Reverse the part in the chuck and face off the material to size. Protect the work by placing a piece of soft metal between it and the chuck.