# looking for 5 position drum switch info for 2 speed motors



## jer (Oct 23, 2017)

Hello all, I have a friend with a 1943 SB 16"x60", if I remember correctly, lathe he is completely restoring. He says it has a two speed motor. It is 3Ø and 3HP 240volts. He wants to replace the 3 position switch with a 5 position switch to use the 2 speed function. Anyone here able to help us? TIA.


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## Dave Paine (Oct 24, 2017)

I cannot help with the 5 position switch, but has your friend considered installing a VFD?  Many models available with 3 phase 240 V input.   This will provide a lot more speed control,  smooth start and stop, potential for adding a brake resistor if needing fast stopping e.g., for threading to a shoulder.


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## jer (Oct 24, 2017)

Thanks Dave, he has a 20HP VFD that he can use. I think he was wanting to also make use of the 2 speed motor.


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## Dave Paine (Oct 24, 2017)

There was a thread on using a big VFD to power a small motor some months ago.  I am not finding the thread, but the consensus was that it may not work, so your friends 20 HP VFD may be too large for the 3 HP motor.


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## jer (Oct 24, 2017)

He runs a 3 or 5 hp, each, lathe and mill presently on this VFD. So the SB lathe would be the 3rd machine. It is not uncommon for him/us to have 2 going at once.


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## mksj (Oct 24, 2017)

Not really a good setup to run a 2 speed motor off of a VFD, I just haven't had good success in the past, and this is even with setting the VFDs with the parameters set for each motor speed. If the motor was run at the 5 Hp setting on the VFD, there would be no need to use the second low speed. A 20Hp VFD might work, but usually they are bracketed within a specific operating range/size. The VFD would need to be in a V/Hz setting, if more than one machine is operating on the same machine than you have issues with overload/fusing. On a cost basis, it may be easier and maybe about the same cost to get an inexpensive 5 HP VFD, then try to find a 5 way drum switch and all the wiring complexity.  What I commonly see is to use a separate drum switch for setting the motor speeds and a separate spindle direction switch. This makes for a much less complex switch arrangement.


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## jer (Oct 24, 2017)

Thanks Mark, I was wrong on the VFD HP it is 15HP. I'll pass this info on to him.


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