# Motor for Old Belt Sander?



## GoodNuf (2 mo ago)

I recently bought an old 6 x 48 inch belt sander. It’s a craftsman from probably early 70s. It’s like a bench top tool that’s cast iron and on a stand. It is usable as is but looks pretty rough. It has the original stand and half horsepower motor. I would like to replace the motor. I want to use 110 volt outlet. Should I use a motor with 3450 RPMs or 1725? Is 1 hp/ 12 amp pretty strong or would 1.5 hp/ ~15 amp be significantly more useful? I only spent $50 for sander. I’m a hobbyist at best.


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## JCamp (Nov 22, 2016)

If the motor works ok I’d suggest keeping it. Seems like the old motors were under rated whereas the new ones are over rated.


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## Phil32 (Aug 31, 2018)

I have a very similar machine (Delta) and have no problems as set up. I recommend no changes until (and if) you have a problem.

Added: The Delta motor is 1/2 hp at 1450 rpm. Drive pully 5"dia - driven pulley 4"dia.


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## jwoodcraft (7 mo ago)

As above, if it ain't broke...
Lots of hp not needed. I you do replace, 1725 is preferable, but just adjust the pulley sizes to get the right belt speed with whichever motor rpm.

I was just using one of those (but older) 20 minutes ago.


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## GoodNuf (2 mo ago)

JCamp said:


> If the motor works ok I’d suggest keeping it. Seems like the old motors were under rated whereas the new ones are over rated.


I have virtually no experience with one. It doesn’t seem to take much to stall it out, but for all I know, this may be normal and to be expected and thus acceptable. If not acceptable, I’ve wondered if some sort of adjustment would help.


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## jwoodcraft (7 mo ago)

Phil32 said:


> I have a very similar machine (Delta) and have no problems as set up. I recommend no changes until (and if) you have a problem.
> 
> Added: The Delta motor is 1/2 hp at 1450 rpm. Drive pully 5"dia - driven pulley 4"dia.



I have that machine as well, but maybe not a fair comparison between a monster R/I motor, and a newer capacitor start one.

My Craftsman machine has 3/4 hp 3450 rpm, & both pulleys are 4".

If the machine bogs down, check that the various bearings are OK, that nothing is binding, & that the belt is not slipping.


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## GoodNuf (2 mo ago)

jwoodcraft said:


> I have that machine as well, but maybe not a fair comparison between a monster R/I motor, and a newer capacitor start one.
> 
> My Craftsman machine has 3/4 hp 3450 rpm, & both pulleys are 4".
> 
> If the machine bogs down, check that the various bearings are OK, that nothing is binding, & that the belt is not slipping.


R/I motor?


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## jwoodcraft (7 mo ago)

GoodNuf said:


> R/I motor?


Repulsion induction- found on old Delta (& other) tools. They tend to be strong beyond the rated HP.


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## GoodNuf (2 mo ago)

jwoodcraft said:


> As above, if it ain't broke...
> Lots of hp not needed. I you do replace, 1725 is preferable, but just adjust the pulley sizes to get the right belt speed with whichever motor rpm.
> 
> I was just using one of those (but older) 20 minutes ago.


Is there a calculator online for choosing pulley size to achieve desired rpm?


jwoodcraft said:


> As above, if it ain't broke...
> Lots of hp not needed. I you do replace, 1725 is preferable, but just adjust the pulley sizes to get the right belt speed with whichever motor rpm.
> 
> I was just using one of those (but older) 20 minutes ago.


Do you prefer the slower 1725 rpm simply to more easily/ precisely control how much material is removed? Or does it affect torque at all?


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## GoodNuf (2 mo ago)

jwoodcraft said:


> Repulsion induction- found on old Delta (& other) tools. They tend to be strong beyond the rated HP.


I’ve heard the term “induction motor”. Is that short for repulsion induction motor? (I have mostly old delta tools)


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## jwoodcraft (7 mo ago)

GoodNuf said:


> Is there a calculator online for choosing pulley size to achieve desired rpm?
> 
> Do you prefer the slower 1725 rpm simply to more easily/ precisely control how much material is removed? Or does it affect torque at all?



The belt runs at a fairly slow speed, so the slower rpm motor is a good fit. Might have more torque, but that is just beyond my pay grade, as is the question is 'induction' short for 'repulsion/induction'.

I have not experienced any bogging down on either of my machines, but it might happen if I tried for that.

Did you check that the rollers and the motor itself turn freely?


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