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Spindle Speeds - Emco Compact 5 CNC


This lathe has six spindle speed ranges. The ranges are selected by various belt and pulley settings. Within each range, the spindle speed is infinitely variable by adjusting the knob on the machine's front panel.

As the spindle speed is varied by the panel knob, the torque available from the motor varies. The best balance of speed and torque is roughly in the second and third quarters of each speed range. The lathe manual explains this in some detail and it is summarised below. It is very important to take this into account when screw cutting. If, because of low torque, the spindle slows down during a threading cut, the thread pitch will be incorrect.

Belt and pulley setting BC1: best torque is in the speed range 117 to 244 rpm.
Belt and pulley setting BC2: best torque is in the speed range 180 to 370 rpm.
Belt and pulley setting BC3: best torque is in the speed range 280 to 590 rpm.
Belt and pulley setting AC1: best torque is in the speed range 517 to 1070 rpm.
Belt and pulley setting AC2: best torque is in the speed range 800 to 1670 rpm.
Belt and pulley setting BC3: best torque is in the speed range 1200 to 2500 rpm.

As a general rule, always use the lowest belt and pulley setting which will give the required spindle speed. This will ensure maximum torque is available.

On the lathe front panel there is a seven segment readout of the spindle speed. Ignore this and use the seven segment display on the PC screen. WELturn measures the spindle speed more accurately than the native Emco system.

Just before machining begins, WELturn checks to see that the spindle is rotating at the speed set in the NC code. WELturn allows a margin of error but, if the speed is too far out, it will give you the option of continuing with the incorrect speed or making an adjustment with the speed control knob or changing the belt and pulley configuration.

WELturn's ability to measure the spindle speed accurately is essential for screw cutting. Before beginning to cut a thread, WELturn automatically measures the speed and uses the result to calculate the feed rate which will give the required thread pitch.

Parting-off Feed Rate and Spindle Speed
Screw Cutting
Surface Finish - Feed Rate