# Motor and VFD for Belt Grinder



## ddickey (Apr 3, 2017)

Was thinking a 2 horse and 1750 rpm with a vfd.
My question for those who have belt grinders, is 2 horse large enough or to large? 1750 or 3600 rpm motor?


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## Jonathans (Apr 3, 2017)

Are you talking about a 2x72 type grinder? For what purpose?


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## ddickey (Apr 3, 2017)

Yes, 2x72. General grinding, especially tool bits.


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## Silverbullet (Apr 4, 2017)

My preference for a belt grinder would be 1750. The 3600 May burn the belt and the platen  , of course ALOT depends on what you grind, tool bits high speed in my thinking will sharpen better at the slower speed the tool bit will heat up slower and and not change the temper. But you should dip them frequently anyway to keep them from changing color. I've watched people ruin tools by just burning them up grinding . Sharpening is not a two minute job. Takes time to be done right.


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## ddickey (Apr 4, 2017)

I'm leaning towards that also. With a VFD you should be able to run 3600 rpm with a 1750 motor.


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## tq60 (Apr 4, 2017)

Should means maybe...

Motor design may limit what it will Bo before failure and bearings with other limiting factors so consider total design starting at surface speed of the belt and if variable speed needed then the extremes of that.

There is likely some formula to calculate power requirements to maintain said speed per surface area too but for hobby use where it is more intermittent a storage system consisting of heavy pulleys or wheels act as flywheels.

Motor speed itself can be altered via pulley system to increase or decrease and relocate motor to out of the way as well.

If using on hand motor then more limited but if buying motor then vfd capable needs to be a data point.

Old swimming pool filters are often rated well and have mounting flanges in face so something to consider if looking for creative sourced parts

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


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## LifeIsAGrind (Apr 10, 2017)

Hi Ddickey,

I recently built my 2x72 and did a lot of research that's still relatively fresh in my brain.  To answer your question, I believe 2HP is just right and 1750 rpm is preferred, but it may depend on your setup.  I can give details on my setup if it helps.

My first piece of advice would be to contact support at Electric Motor Wholesale and/or KB Electronics if you plan to use one of the KB VFDs.  They are pretty standard drives on 2x72s (as you may know), and after doing a ton of research, I ended up with one as well.  (I guess there's a reason all the knife guys use them).  Both support lines were extremely helpful, and the EMW guy told me to call with questions even if I wasn't buying from them.  Wow!

I went with a Dayton 2HP, 3-phase, 1725 rpm motor I got off ebay, new old stock, for $110.  I used the KBAC-27D VFD and used the frequency doubling setting.  Support at KB explained that (with their VFDs anyway) this achieves the same speed as the ~3600 rpm motor, but provides much more torque up to 1725 rpm, and then tapers off torque at the top end, in the speeds where you'd more likely be doing finish work anyway.  And this VFD offers constant torque (pushes back against you), which is great for hogging.  It can also use 110v or 220v and converts to 3 phase for the motor.

In my research, I did not find anyone that said you would need more than a 2HP motor.  Note BTW, at 110v wiring, a 2HP motor will only be 1.5HP.  I have not wired mine for 220v yet, and haven't been able to bog my motor (so maybe I won't need to?).  Oh, if you get a KB, check on the factory installed RFI filter.  Mine whines through my shop speakers, but I didn't know about the option and you can't add it after the fact.

The 2x72s seem to be primarily used by knifemakers, but I find it to be a great general purpose grinder as well.  I got spoiled having access to them on a regular basis at a blacksmith/metal shop I hang out at.  Even though I have a myriad of grinding and sanding tools in my own shop, I felt increasingly put out by not having one on hand.

I still need to apply a Pyroceram ceramic glass plate to my flat platen for better wear and flatter grinding, and maybe make some more attachments, but what a great addition to my shop already!

Happy to share any other opinions or knowledge I gained in the process...

Greg


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## ddickey (Apr 10, 2017)

Thanks Greg


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## ddickey (Jun 6, 2017)

I finally got my belt grinder wired up last night. I bought a KBAC-27d VFD and a 2 horse Leeson. I bought these as a package on Ebay.
The motor hesitates, on/off at low frequencies up to about 20%. KBAC said I need to send the VFD in for software upgrades as the motor is an energy efficient one. I'm going to change some settings and see if i can get this thing to run smooth.

EDIT: I talked to another guy from KBAC and the problem was fixed. Has to do with boost on the energy efficient motors. They need more boost at startup.


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## brav65 (Jun 7, 2017)

I just bought a Northridege Tools 2x72 an it is a pice of art.  I was collecting all the pieces to build my own grinder and just could not help myself after looking at these grinders.


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## ddickey (Jun 7, 2017)

I think my Reeder is well made but could be refined some.


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## mikey (Jun 7, 2017)

brav65 said:


> View attachment 235009
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Hey Brooks, did you get the package as shown? If so, how do you like it? That is a very nice grinder!


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## ddickey (Jun 7, 2017)

I have a really nice Reeder for sale Mike. LOL


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## mikey (Jun 7, 2017)

My home improvement project is protecting me from you and from any other big purchases right now, Duane! Doesn't keep me from envy, though.


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## brav65 (Jun 7, 2017)

mikey said:


> Hey Brooks, did you get the package as shown? If so, how do you like it? That is a very nice grinder!


Hey Mike,  yes I did get the exact same machine.  I just got it at the end of last week and have it assembled but not hooked up to power yet.  I have to run a 20 Amp 220 circuit this weekend and build a stand for it.  I have been saving for a year to get this baby.


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## mikey (Jun 7, 2017)

Nice, Brooks. Congrats on what looks to be a well-built sander. So many on the market today and that one looks to be reasonably priced for what it is. Thanks for the heads up. Give us a review when she's up and running, please.


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