Spindle Speed
Using the correct spindle speed is important for getting safe and satisfactory results, as well as maximizing tool life.
To set the spindle speed for your operation, you will need to: 1) Determine the best spindle speed for the cutting task, and 2) configure the lathe controls to produce the required spindle speed.
Determining Spindle Speed
Many variables affect the optimum spindle speed to use for any given operation, but the two most important are the recommended cutting speed for the workpiece material and the diameter of the workpiece, as noted in the formula shown in Figure 70.
*Recommended |
| Spindle | ||
Cutting Speed (FPM) x 12 |
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= | Speed | |||
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Dia. of Cut (in inches) x 3.14 |
| (RPM) | ||
*Double if using carbide cutting tool
Figure 70. Spindle speed formula for lathes.
Cutting speed, typically defined in feet per minute (FPM), is the speed at which the edge of a tool moves across the material surface.
A recommended cutting speed is an ideal speed for cutting a type of material in order to produce the desired finish and optimize tool life.
The books Machinery’s Handbook or Machine Shop Practice, and some internet sites, pro- vide excellent recommendations for which cutting speeds to use when calculating the spindle speed. These sources also provide a wealth of additional information about the variables that affect cutting speed and they are a good educational resource.
Also, there are a large number of easy-to-use spindle speed calculators that can be found on the internet. These sources will help you take into account the applicable variables in order to deter- mine the best spindle speed for the operation.
Setting Spindle Speed
The spindle range lever and spindle speed lever, shown in Figure 71, are used to select one of the 15 spindle speeds.
Spindle |
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| Spindle | |
Range |
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| Speed | |
Lever |
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| Lever | |
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Figure 71. Spindle range and speed levers.
The spindle speed and range levers control the gear configuration in the headstock to produce the selected spindle speed.
To avoid damaging gears, ALWAYS make sure the spindle is completely stopped BEFORE moving the spindle speed levers.
The chart below shows the various combinations of lever positions for achieving a desired speed.
| Spindle | Spindle |
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| Range | Speed |
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| Lever | Lever |
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| A | B | C | D | E | |
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| 1600 | 545 | 240 | 105 | 45 | |
X | min | 1150 | 395 | 175 | 75 | 33 | |
845 | 290 | 130 | 55 | 24 | |||
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Figure 72. Spindle speed chart and applicable
spindle lever positions.
Model G0746/G0749 (Mfg. Since 3/13) |
