10000 + FPM belt speed grinder

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Natlek

Joined
Jun 9, 2015
Messages
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For normal grinder with 2800 RPM motor I will need to use very large drive wheel to reach that speed which is out of question , lot of trouble there.....Pulley take to much space so I think this is simplest way how I should make it . I would use double frame .What do you think ?

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Can you overdrive the motor with a VFD? At around 3800rpm you could use a 10" wheel with direct drive.

I can't really tell from the sketch how the tensioning mechanism is supposed to work. I think it might be easier to add a belt tensioner and just set the pulley tension separately.
 
Hubert S. said:
Can you overdrive the motor with a VFD? At around 3800rpm you could use a 10" wheel with direct drive.

I can't really tell from the sketch how the tensioning mechanism is supposed to work. I think it might be easier to add a belt tensioner and just set the pulley tension separately.
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10 inch wheel on 3800 rpm is not joke , I think ? I don t like that idea .........And motor is very loud on that speed .

I have simple solution for tensioning both belts at once .Off center bolt washers from both side of double frame ......
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Tracking is even more simple .

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Like always I build grinders backwards ..
Parts for work rest and platen for behind belts are ready :)
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what purpose does a 10000rpm machine serve?
 
Other than being just plain awesome?

Fast removal of lots of material at high pressure...
 
People have done that.

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But I vote for a VFD with a 8" wheel. Motor is not loud at double speeds. Everything else on the grinder is the loudness heard. Those small bearings in contact wheels will scream. I did it but decided to change the motor from 2 pole to 4 pole to get more torque on low speeds. When forced enough even on low speeds those grinds are large and material is taken of fast. Some even the size of rice when new belt is used. And a lot quieter. No one heard late night grindings.
 
JoeBusic said:
People have done that.

View attachment 2070852

But I vote for a VFD with a 8" wheel. Motor is not loud at double speeds. Everything else on the grinder is the loudness heard. Those small bearings in contact wheels will scream. I did it but decided to change the motor from 2 pole to 4 pole to get more torque on low speeds. When forced enough even on low speeds those grinds are large and material is taken of fast. Some even the size of rice when new belt is used. And a lot quieter. No one heard late night grindings.
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I make grinder like that some four years ago ,three speed 10-20 and 40 m/s and I still have it and use it .


My motors are all loud when I double speed , why ? 3 phase 2hp 2800 rpm motors ? I don t need more torque on low speed simple because I will not use low speed , that s why I don t want to use VFD on this one . I want to make simple and crazy fast grinder .And I think this one will be just that . I am not sure about bearings , I tested this one 30mm Dia and inner hole is 10mm /double row , Japan made / on 20 000 rpm and they are quiet and they stay cool enough .I will use two of them in one wheel .This days I will make all calculation to see what size/rpm of drive wheel I will need to get 60 m/s , ratio of pulley and size of other two wheels to reduce RPM as much as I can ......

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This bearing are almost same as this one but smaller .Dia 20mm and inner hole is 8mm and on that video they run on 29700 RPM :)
2hp , 2800 rpm and 22 cm. drive wheel and about 32 m/s belt speed as I remember
 
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Wild Bill 1 said:
please check your grinding belt speed rating. Be safe.
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Thanks for the note . I use grinding jig so there is no danger .And even if the belt breaks, it is not absolutely dangerous, it already happened to me once, my fault, not due to high speed.
Most belt manufacturer recommend 40-50 m/s belt speed for grinding hardened steel .
 
OK. It's easy then. 20cm wheel to 10cm wheel, back to 20cm drive wheel and you have 60m/s.
 
Ken H> said:
It's not a 10K "rpm", it's 10k "SFPM" belt speed.

I'd sure hate to bump a knuckle on 36 grit at 10K SFPM! It's be to the bone before you even felt it.
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thanks! I looked it up and found this calculator, so now I know something I didn't before! And I could've paid better attention to the op
 
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All I can think of is the few times I tried to use a grinding jig + 10k sfm when I come off the bevel. That would make for faceting issues for me. BUT… if you can control it and then abrasives hold out, let the big dog eat 😊
 
N Natlek Essentially as long you use 20cm drive wheel all you have to do is double the speed. So the small one has to be half the size of the big one. If you can get them of the shelf without going thru the trouble making them.
 
The calculator link posted by Lorien is for SFPM while the one posted by Natlek is for RPM.

Both are good calculators.
 
Lorien said:
what purpose does a 10000rpm machine serve?
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Are you familiar with lathe ? Suppose you have 60 degrees cutting tool ,which is common for some thread . You have steel in chuck and you want to remove material .IF lathe chuck turn very , very slow and you move cutting tool fast /say 0.5 mm depth of cut / what kind of finish you will get ? It would look like some stretched spiral , right ?Like you are trying to make some thread 🤣 IF you slow down speed of cutting tool /with same depth of cut/ that *Spiral* will become something like spring ? BUT in both case you will have deep deep grooves in steel . IF you slow cutting tool more that grove will start to be less and less deep and no more *spiral* .NOW , put the lathe chuck on the highest speed , slow down as much as possible cutting tool /with same depth of cut/ and you will get almost mirror finish , right ? So with same 60 degree cutting tool/read 36 grit ceramic belt / and same depth of cutting you can get totally different finish .
What purpose does a 10000rpm machine serve?
Let say I have 20 blade to grind bevels , all same shape and thickness and will have same bevels geometry .
I will need to do several adjustment on angle on my grinding jig to grind bevels on one side on first knife as I want it .Other side I will grind normally faster because angle on jig is already set .On next knife .......bevels a *done* on several passes .On next one .....................you will need to see it to believe it :)
Remember lathe ? More belt speed and slow movement of jig with *RIGHT* pressure /depth of cut/ can remove material extremely fast , and leave nice even finish with no deep groves/scratches .Repeat same with very light pressure and you will get even better finish .I don t think that anyone is capable to achieve that with *free hand grinding * on that kind of speed of belt .
Grinding Jig keep same grinding angle ,all you need to do is to push and pull it .HIGH belt speed make all that more easy . Jig also keep blade cool MUCH longer . ....
Also speed cools belt and grits ,even blade little and belt lasts longer.
 
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