New here. Belt grinder questions/suggestions

How big is too big? Haha. Have another motor lying around at work off of an old compressor that’s 5hp. 1740 rpm (assuming that makes it a 4pole?) once again, it has a 1 1/8” shaft, too.

Assuming it is actually 4 pole, theoretically the high hp shouldn’t matter with a vfd, right? I could just run it as low as needed.
 
I believe you would have to buy a vfd large enough to run a 5 hp motor which will make it more expensive.

Motor RPM formula: RPM=(Hertz*60*2)/ # of poles

(60*60*2)/4=1800 RPM.

So yes that should be a 4 pole motor
 
The question is really: is it a 3 phase motor?
If yes then yeah having a 5hp motor will work great, buy a cheap Chinese vfd off of Amazon or whatever and wedge that thing on your grinder and go to town!

If it's not 3 phase, motor you might use it as a temporary motor till you can get a 3 phase. You REALLY want variable speeds.
 
A.McPherson said:
The question is really: is it a 3 phase motor?
If yes then yeah having a 5hp motor will work great, buy a cheap Chinese vfd off of Amazon or whatever and wedge that thing on your grinder and go to town!

If it's not 3 phase, motor you might use it as a temporary motor till you can get a 3 phase. You REALLY want variable speeds.
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Yes it’s three phase. We have a couple of single phase low hp motors on some old tools we don’t use anymore. But I’ve just been writing anything off that wasn’t 3 phase or at least 1.5 hp.

The Chinese vfd I was looking at from Amazon like $85 ( the one house made used in his video) seems to only be 2-3hp max. If I specifically search 5hp vfd the price seems to jump to $300. I’ll keep searching though.

I can buy a brand new 56c tefc motor and vfd for like $330
 
Dcbruton said:
I can buy a brand new 56c tefc motor and vfd for like $330
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Yes, that is probably true, but the difference in performance between a 1.5 or 2hp and 5hp would be huge. You would not be able to bog down that 5hp, even using a large drive wheel.

Personally if I was going to spend that 300$, i'd go with the 5hp all day. But that's me, talking about spending your money... Lol!
 
Dcbruton said:
Motor is not a 56c face. But I was planning on mounting it to base of machine instead of face mounting it. I’ve found some 7” 1 1/8” shaft drive wheels on eBay. But it has also been pointed out that, that motor is a 6 pole and will not work with a vfd. So I’m in search of plan B motor as we speak.
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Mounting the motor to the base plate and using a shaft-mounted wheel is fraught with alignment issues. when running at high RPM alignment is a big issue.
While I understand your desire to use something that you have around you will do yourself a big favor to get a 56C face motor in the 1.5HP range. If you use a motor without a 56-C face, use a pulley system to connect the motor to the drive wheel.

BTW, I checked the motor stash in the shop and don't have a 1-1.5HP 3-phase one there. I have a bunch in the storage building that I will check today. I have been giving them away for a while and may have used up all the grinder size motors.

Save that big 5HP motor for a hydraulic press build someday.

General Comment to Readers:
I will reiterate my frequent comment that the latest trend for bigger grinder motors is 99% "Mine is bigger than yours" macho thinking. If you are a hobby or small production maker, it is unlikely you will ever need more than 1HP on your grinder. A 1.5 motor is plenty large enough for most every knifemaker to have all the power he/she needs. 2HP is the max I can see any need for mechanically. Remember, we are only contacting an area of a few square inches of steel against an abrasive surface.
A commercial Burr King machine shop grinder only comes with a 1HP motor. Their knifemaker model has a 1.5HP. The KMG and TW-90 ubergrinders now have gone up to a 2HP motor (KMG offers a 3HP option), which is more than needed, IMHO. Has anyone scrapped their old 1.5HP Bader, TW-90, or KMG classic because it was underpowered?
I have used many grinders with 1HP and 1.5HP motors in DC, single phase, and three phase and have never stalled the motor no matter how hard I was hogging. I have turned the steel blade cherry red from friction, but never noticeably slowed down the belt.
If you install a 5HP motor the grinder will be unstoppable, but is that a concern? Is it even desirable? What is a concern is the power supply wiring needed and the VFD size. Another big concern is mounting a large motor to the grinder. You will have to modify the plans a good bit to accommodate the much larger motor size and face or mounting needs. A 56C face motor that works with available grinder plans and drive wheels will make your build simpler and more likely to succeed.
 
Stacy E. Apelt - Bladesmith said:
Mounting the motor to the base plate and using a shaft-mounted wheel is fraught with alignment issues. when running at high RPM alignment is a big issue.
While I understand your desire to use something that you have around you will do yourself a big favor to get a 56C face motor in the 1.5HP range. If you use a motor without a 56-C face, use a pulley system to connect the motor to the drive wheel.

BTW, I checked the motor stash in the shop and don't have a 1-1.5HP 3-phase one there. I have a bunch in the storage building that I will check today. I have been giving them away for a while and may have used up all the grinder size motors.

Save that big 5HP motor for a hydraulic press build someday.

General Comment to Readers:
I will reiterate my frequent comment that the latest trend for bigger grinder motors is 99% "Mine is bigger than yours" macho thinking. If you are a hobby or small production maker, it is unlikely you will ever need more than 1HP on your grinder. A 1.5 motor is plenty large enough for most every knifemaker to have all the power he/she needs. 2HP is the max I can see any need for mechanically. Remember, we are only contacting an area of a few square inches of steel against an abrasive surface.
A commercial Burr King machine shop grinder only comes with a 1HP motor. Their knifemaker model has a 1.5HP. The KMG and TW-90 ubergrinders now have gone up to a 2HP motor (KMG offers a 3HP option), which is more than needed, IMHO. Has anyone scrapped their old 1.5HP Bader, TW-90, or KMG classic because it was underpowered?
I have used many grinders with 1HP and 1.5HP motors in DC, single phase, and three phase and have never stalled the motor no matter how hard I was hogging. I have turned the steel blade cherry red from friction, but never noticeably slowed down the belt.
If you install a 5HP motor the grinder will be unstoppable, but is that a concern? Is it even desirable? What is a concern is the power supply wiring needed and the VFD size. Another big concern is mounting a large motor to the grinder. You will have to modify the plans a good bit to accommodate the much larger motor size and face or mounting needs. A 56C face motor that works with available grinder plans and drive wheels will make your build simpler and more likely to succeed.
Click to expand...
Thanks for looking! In the meantime, I’ll keep an eye out for another 56c face that’ll work. If all else fails, I’ll order a new one in a few weeks. I’ve got my daughters bday party and some travel coming up. Wife may not be super thrilled if expensive grinder parts start showing up. Haha

Thanks for all the good info, fellas.
 
I found one 1HP 3Ph motor.
I'll get with you by email about it to see if you want it.
I also have two 1HP DC motors that are really large and heavy (one is in the big white box). Both are 56C face and will fit a grinder.

What I found was lots of 1/4HP to 3/4HP motors of good size with high torque. Some of the 1/4 and 1/3HP but are as big as a 1HP motor.
I didn't even try to move the 3HP DC motor (hint - it has a 2" lifting ring eye-bolt on it) or the 3HP 3Ph motor. Those can stay where they are for the time being. These are going in the shop stash in the shop upstairs already. They are a mix of 1.2 to 3/4 DC and HP motors single and 3Ph. I'll try and shoot a photo when I carry these up to their brothers. Boy, am I glad I overbuilt the joists for the upstairs floor with doubled 2X10s and a central 40-foot log 6X10 laminated support beam supported by 6X6 posts.

The 1/3 and 1/2HP motors make great light duty disc sanders. The 1/2 and 3/4 HP motors work great on drill presses and small metal cutting band saws.
Changing a one speed or belt-adjusted-speed tool to VS is a game changer. I picked up a nice benchtop drill press with a bad motor for $10. It is sitting with a 3/4HP DC motor and speed control to swap out the motor when I have time. I have the same changeover ready for my floor drill press. After that, I will change the big Ryobi bandsaw to 1HP VS.

Years back I bought motors nearly every week from an auction company for around $10-20 each. They would ship everything I bought in a two-week period in one box for around $20. They motors were all NIB or NOS. I also bought box lots of carbide tooling and drills for stupid cheap. They tossed them in the box along with the big stuff at no additional shipping charge.

(not in the photo) I purchased two 3-phase motor-VFD trainer/demo setups which are in aluminum Case-M type enclosures at an auction for $15 each. They sell for around $900 each (which is just plain crazy). They are low HP, but with the dials and meters you can program speed, torque, current, ramp speed, etc. I have one set up for stropping and fine polishing with a leather disc. I may turn the other into a lapidary/faceting/polishing machine. I'll take a photo of those later.

That funny looking thing in the front of the van trunk is a 3phase vibrator motor with 100Kg vibrating force. I have two of them. They will be used on a barrel type tumbler/deburring machine similar to a Mr. DeBurr. A VFD will allow fine tuning the tumbling rate for max action.

IMG_20230718_160327.jpgIMG_20230718_160615.jpg
 
Stacy E. Apelt - Bladesmith said:
I found one 1HP 3Ph motor.
I'll get with you by email about it to see if you want it.
I also have two 1HP DC motors that are really large and heavy (one is in the big white box). Both are 56C face and will fit a grinder.

What I found was lots of 1/4HP to 3/4HP motors of good size with high torque. Some of the 1/4 and 1/3HP but are as big as a 1HP motor.
I didn't even try to move the 3HP DC motor (hint - it has a 2" lifting ring eye-bolt on it) or the 3HP 3Ph motor. Those can stay where they are for the time being. These are going in the shop stash in the shop upstairs already. They are a mix of 1.2 to 3/4 DC and HP motors single and 3Ph. I'll try and shoot a photo when I carry these up to their brothers. Boy, am I glad I overbuilt the joists for the upstairs floor with doubled 2X10s and a central 40-foot log 6X10 laminated support beam supported by 6X6 posts.

The 1/3 and 1/2HP motors make great light duty disc sanders. The 1/2 and 3/4 HP motors work great on drill presses and small metal cutting band saws.
Changing a one speed or belt-adjusted-speed tool to VS is a game changer. I picked up a nice benchtop drill press with a bad motor for $10. It is sitting with a 3/4HP DC motor and speed control to swap out the motor when I have time. I have the same changeover ready for my floor drill press. After that, I will change the big Ryobi bandsaw to 1HP VS.

Years back I bought motors nearly every week from an auction company for around $10-20 each. They would ship everything I bought in a two-week period in one box for around $20. They motors were all NIB or NOS. I also bought box lots of carbide tooling and drills for stupid cheap. They tossed them in the box along with the big stuff at no additional shipping charge.

(not in the photo) I purchased two 3-phase motor-VFD trainer/demo setups which are in aluminum Case-M type enclosures at an auction for $15 each. They sell for around $900 each (which is just plain crazy). They are low HP, but with the dials and meters you can program speed, torque, current, ramp speed, etc. I have one set up for stropping and fine polishing with a leather disc. I may turn the other into a lapidary/faceting/polishing machine. I'll take a photo of those later.

That funny looking thing in the front of the van trunk is a 3phase vibrator motor with 100Kg vibrating force. I have two of them. They will be used on a barrel type tumbler/deburring machine similar to a Mr. DeBurr. A VFD will allow fine tuning the tumbling rate for max action.

View attachment 2257519View attachment 2257521
Click to expand...
Dang! You got all kinds of goodies! Haha. I’ve thought about building a disc grinder. Maybe out of that 6 pole motor I have? there are also some single phase motors at the shop I could prolly snag, but first things first, get this grinder built.

The motors you’re talking about for bandsaws, do people build bandsaws too? Or you just talking about swapping out the motors for something with more power/variable speeds?
 
Swapping out the motor for 3phae and a VFD. Instant VS bandsaw.
On some bandsaws, like the old Craftsman ones with a hanging motor and a V-belt, it is a piece of cake. On newer type it may take some drilling or making a C-face adapter. It also may take modifying or replacing the drive pulleys.
On drill presses, you usually need a motor with a foot plate. This is called a 145T-C frame. It has a 145T foot and a C-face.
 
Found a new old stock baldor 3/4hp 3 phase 3450rpm 56c near by on marketplace for $100.

Is that gonna be too under powered? I was hoping he’d negotiate price a bit more so I wouldn’t mind having an under powered motor to begin with then upgrade later. But the $100 is firm.

Still wouldn’t mind picking it up if it’ll get the project rolling, as long as I’m not just gonna hate the low power.
 
Dcbruton said:
Found a new old stock baldor 3/4hp 3 phase 3450rpm 56c near by on marketplace for $100.

Is that gonna be too under powered? I was hoping he’d negotiate price a bit more so I wouldn’t mind having an under powered motor to begin with then upgrade later. But the $100 is firm.

Still wouldn’t mind picking it up if it’ll get the project rolling, as long as I’m not just gonna hate the low power.
Click to expand...

Get it, make progress.

You can always use that motor other places if you upgrade.

Drill press, it's nice to have variable speed and instant reverse for tapping.
disc sander
 
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