Lathe question for the machinist

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triw51

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Feb 14, 2012
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I recently acquired a used lathe and on the controls is a switch for long deceleration and short deceleration. I understand the difference in how fast the work slows down but would like to know the advantages and/or disadvantages of each. Can anyone enlighten me please?
Thanks William
 
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randyrls

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William; I've never had a lathe with this feature. Is this lathe a Variable Frequency Drive (VFD)? Metal lathe?

If turning / threading up to a shoulder, you want the lathe to stop RIGHT NOW. This is quite likely when making kit-less threaded pen sections. The common way around this is to turn as close as you can to the shoulder, then use a parting tool to plunge in and clean up the corner. This doesn't work for threads though.

However if your lathe has a threaded spindle nose on it, short decel may cause the chuck to unscrew. Some chucks will have set screws in the base of the chuck to prevent this.

The only likely reason for long deceleration would be if the work piece is fragile or has a very thin cross section at some point.

An intriguing question. I'll be interested in others comments.
 

Curly

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It is explained in the manuals. https://oneway.ca/manuals
Basically it is to protect the VFD. A heavy object stopped quickly heats up the braking resistors in the VFD. Slow deceleration keeps the braking resistor from getting too hot and shutting down the VFD. At least that is the conclusion I came to.
 

Curly

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You’re welcome. All machines with electronic speed control will have a VFD and a 3 phase motor. The exception to that are the small lathes with DC motors. I am envious of your toy.
 
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