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2 X 48 Belt Grinder (again)

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rwm

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#1
I started on my belt grinder!
I built this motor from scratch from scrap bin parts. I think it looks OK, although the capacitors are a little big. (Yes I know it reminds you of your ex but please refrain from commenting.)

HS-jwUCnQ3PeeLaJ8A1fiNECvdAtq2YZ-3s35knBOrnz8Cd5J2YGnBDrRjJ8pSR3hDwvFe4I5OtPkIpGs=w1902-h1075-no.jpg

26144839324_9b3bc57e27_h.jpg
Specs are 3/4 HP @ 3450 RPM. Already blows 15 amp circuits.
It's a start.
Robert
 

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rwm

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#2
Just some crude ideas while waiting for material.

26751150935_be74e1ba56_b.jpg

Not sure how to make the platten yet. Perhaps just like the table although it really doesn't need to be adjustable. What material?
How much spring tension?
Need to find appliance feet.
I'm torn about using a lever arm or an eccentric axle (like Mark did) for the tracking wheel. How much do these belts stretch over time?
I am thinking of crowning the top pulley only, not the drive pulley. Any ideas on that?
R
 

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#3
Just some crude ideas while waiting foNot sure how to make the platten yet. Perhaps just like the table although it really doesn't need to be adjustable. What material?
How much spring tension?
Need to find appliance feet.
I'm torn about using a lever arm or an eccentric axle (like Mark did) for the tracking wheel. How much do these belts stretch over time?
I am thinking of crowning the top pulley only, not the drive pulley. Any ideas on that?
R
I have been told you can crown either pulley but not both. I don't know if that is true so I chose to crown the drive pulley ( because my store bought 4 inch was that way). I have a set of plans for one that uses a lever instead of the eccentric shaft. I chose the eccentric shaft because it did not require welding.
Also, I have never had any belts stretch.
As far as material, I used aluminum because I had it but the frame needs to be at least 1/2 " thick to prevent flexing. Steel can be thinner, like 1/4". ( learned that the hard way)
 
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rwm

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#4
Thanks Mark! Very helpful info.
R
 

strantor

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#5
This won't directly answer any of your questions, but it will illustrate how a belt grinder can be made in a total vacuum of science and attention to detail. It's a belt grinder I made a few years back out of scrap. I didn't crown any pulleys or machine any eccentric axles or measure any spring tension. I used an old bent rusty ruler to adjust tracking, bungee cords to adjust tension, and a plastic golf back wheel to drive it (roller skate wheels for idlers). It works just fine, gets the job done.

https://www.google.com/url?sa=t&sou...IIGzAA&usg=AFQjCNF8y99YcykjxoY_QdNRtJjJeQE3nA

I admit it is the epitome of a kludge and it's on my list to do over. Now that I have machine tools in my arsenal I can do a much better, professional job. But it's just hard to find time to reinvent something that already works just fine.

Point is, don't over think it.
 

rwm

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#6
"...but it will illustrate how a belt grinder can be made in a total vacuum of science and attention to detail." I love the way you said that! That is a remarkable grinder! I think there is more science built into your design than you are giving yourself credit for. Still, I get your meaning.
I like the design process as much as building a tool and I hate that feeling that I could have done better. I am an optimizer! I like the collaboration here and always appreciate everyone's ideas even if I don't use them.
I hoping my grinder will be fairly heavy duty so I can hog away steel.
Pulley stock. (also Ice Press stock)
26146975953_836820f82a_b.jpg
This will give me a 4" drive pulley and a 2.5" crowned tracking pulley.

R
 

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Chipper5783

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#7
It looks like you are going with direct drive? That will yield a belt speed of about 3700 fpm. Have you considered a belt drive, so as to increase the belt speed (with the added benefit of getting the motor bump out of your way)? It will be interesting to see what comments you get on target belt speeds for different applications.

My recollection is that to really hog the metal off, you should push the belt speed to about 6000 fpm.
 

rwm

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#8
Yes, about 3700 SFPM. I thought that would be adequate but you may be correct. I considered the belt drive but dropped it in favor of the 3450 rpm motor. Hmmm...maybe too slow. A 5" wheel will get me up to 4500 SPFM which seems better. Couldn't you have told me this before I ordered the stock? ;)
R
 
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#9
You should be fine with the 4" pulley. I run a 1750 rpm motor which gives about 1850 sfm. that speed works great. I found running the belts too fast shortens their life dramatically. I checked with a manufacturer and they said the best speed was around 2500 sfm for best belt life. That is my opinion and findings. I'm sure there are many different opinions out there.
 

rwm

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#10
I made some progress...then disaster.


Top pulley finished. The bearings fit nicely. The large stock is for the drive pulley.
26478078210_46579ec8f7_h.jpg

26144899884_9189ef8919_h.jpg

So after facing and machining a boss I drilled the center hole enlarged it to 9/16 and tried to ream it to 5/8. Here is my setup for reaming.
26478081520_cfb84239af_h.jpg

The problem is that the reamer began to chatter (more like a vibration) immediately. I tried slower and faster with the same results. Now I may have messed up the bore of this pulley possibly beyond salvage.
26657469772_9dc7b9dd12_h.jpg

Someone please help! What am I doing wrong to cause this chatter. The reamer is securely fastened in the tailstock and I used plenty of cutting oil. The reamer itself is new. It is not damaged even after this anomaly. I was running at 500 and 750 rpm. I should have just used a darn drill or boring bar ! I want to understand why this didn't work?

R
 

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TOOLMASTER

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#11
go sloooooooooooowwwwwww

like 50
 

rwm

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#12
After the last post I decided to try the slowest speed possible. My lathe will only go down to 60 rpm. I used the same reamer to finish the deeper half of the bore at this speed. It didn't seem to make as much vibration but when I examined the bore I had the exact same chatter pattern. I have used reamers in the past and never had this issue. I realize I started too fast the first time but 60 rpm should be sufficiently slow. Could it be that once the bore has chatter marks it becomes impossible to overcome?
In any event, I took a light finishing pass with a boring bar and I have a reasonably snug fit on the shaft. I hope it will not loosen when the high spots wear down. I think this will be functional but this is not the kind of work I like to see leaving my shop. I may eventually re-make the whole darn pulley. But it was not a cheap slug of aluminum.
I invite further comment. Should I trash this reamer and buy a spiral cut?
Oh yeah, I cut a key way in this mess.
26750810885_18743409b0_h.jpg
Now I have to drill a hole and hit the keyway! Or should I avoid the keyway. I have seen it done both ways.
R
 

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Chipper5783

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#13
I feel your pain. How much material were you taking with the reamer? You really don't want to take too much, but you also don't want to take too little. I'm sure there are plenty of formula and tables. My guess is that aluminum would be pretty tolerant of light cuts with a reamer. On a critical hole, I'll drill quite a bit under size, then bore it to near size, then finish with the reamer.

With this being your driving wheel, make the axle between centers, then just secure the shaft with Loctite. You can then skim the wheel OD and it will be very concentric (should run nice and smooth, and the chatter in the bore will not be an issue - makes a nice surface for the Loctite to grab).
 

FOMOGO

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#14
I would agree with Chipper above, you need to be closer to your finish diameter before reaming. Work is looking good though. You can always bush it if it proves to be to big, but you'll probably be fine. Mike
 

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#15
I agree with both chipper and fomogo. I learned that 1/32" is about the most you want to remove with a reamer.


Sent from my iPhone using Tapatalk
 
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#16
I'll agree with less of a cut and lots of WD40 for lube. I usually ream at about 1/2 the speed you drilled the hole and feed the reamer aggressively. And retract often to clear the cuttings or you'll ream over sized.

Greg
 

rwm

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#17
Thanks for the tips guys. In summary it sounds like too fast a speed and too deep a cut. I should have bored it closer to final ID. FYI, this wheel will be direct drive off the motor so no loctite. I thought about sleeving it but that would end up being more work than re-making it correctly.
R
 

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#18
I thought about sleeving it but that would end up being more work than re-making it correctly.
R
Why do you say that? I've never actually done a sleeve but it seems to me like it would be a simple affair.
You could take a few light cuts and then press fit an 11/16 brass rod in there and then drill out the rod
 

rwm

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#19
True...well I wanted a keyway so I would need to bore the hole out even larger, say like 1" and then press in a brass rod. I was concerned about getting the right fit between the sleeve and the pulley. I will go that route if the pulley loosens in use. Thanks!
OK...next issue I need help with. The set screw path is 2.5" deep. My 1/4 x 20 tap is not long enough to reach the bottom. How do I deal with that? Can I make some kind of tap extension?
There's this from McMaster but they are pricey:
2583a14p1-a02cl.png
R
 

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chips&more

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#20
You cannot make this pulley in one operation on the lathe then set screw it and then mount it on the motors shaft and expect it to run true. The chances of it running true with this process are slim to none. If you want it to run true, you must finish the bore, leave the OD roughed out and put in the set-screw(s). Then return to the lathe with a turned shaft the diameter of the motors shaft in the chuck. Mount the unfinished pulley, probably using a ball bearing/dead center in the tail stock. And then finish the pulley. Hope this helps…Dave.
 

rwm

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#21
Thanks Dave. I had not considered that. I have finished the pulley but not run it yet to see how much vibration I get. If I have an issue I will move forward with your suggestion and rework the surface.
I was able to cut most of the threads with a standard tap. I had about 3 unfinished threads at the bottom of the hole so I made a poor mans tap out of a SS bolt. That easily cut the last few threads and the set screw goes in smoothly.

Tap:
26478093430_dd8883cc22_h.jpg

Finished pulleys (unless Dave is correct)
26683906171_77c426c76d_h.jpg 26683907061_d2760c1b0a_h.jpg

Robert
 

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f350ca

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#22
Maybe drill the hole to size for threading to the bore, then thread the top inch or so. Make a pin that fits inside the hole and use it as an extension to the set screw.

Greg

Oops, too late
 
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#23
You cannot make this pulley in one operation on the lathe then set screw it and then mount it on the motors shaft and expect it to run true. The chances of it running true with this process are slim to none. If you want it to run true, you must finish the bore, leave the OD roughed out and put in the set-screw(s). Then return to the lathe with a turned shaft the diameter of the motors shaft in the chuck. Mount the unfinished pulley, probably using a ball bearing/dead center in the tail stock. And then finish the pulley. Hope this helps…Dave.
I don't know why not. I made my direct drive pulley in one shot on the lathe, Bored it, cut the OD, took it off , drilled the set screw hole and it runs as true as it could possibly be.
Finished Drive Wheel 2.JPG Finished drive wheel.JPG
 
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rwm

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#24
That is a very elegant pulley Mark. I thought about removing some of the center material like you did to reduce the mass. Not sure it is necessary though.
I test ran my pulley last night. It runs very smoothly with almost no vibration. Better to be lucky than good!
3450 RPM and you can't tell it's moving in the video!

That is a very elegant pulley Mark. I thought about removing some of the center material like you did to reduce the mass. Not sure it is necessary though.
I made some progress on the tracking pulley design.
26657476272_7715d6bc35_h.jpg
26657474672_e1a21f1556_h.jpg

Is anyone but me worried about my tracking pulley turning at 8000 PRM?! Will the bearings hold up?
Is there any reason I would want tracking adjustment moving the pulley left and right (rotation in x,y plane) rather than tilting it up down (rotation in x,z plane.)?

R
 

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#25
Gunrunner you need to order a set of these for the Z axis hand crank. Bill did you just spit coffee on your monitor? :rofl:

View attachment 253356
 

rwm

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#26
Note the thin strip of metal connecting the pulley carrier to the upper arm. That is the "hinge." There will be a knurled thumb screw extending through the arm and contacting the base of the pulley carrier. That will deflect the pulley upwards. I am thinking about a single screw although I could do one screw in the front and one in the rear which might allow some adjustment in the other plane? Thoughts?
R
 
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#27
Note the thin strip of metal connecting the pulley carrier to the upper arm. That is the "hinge." There will be a knurled thumb screw extending through the arm and contacting the base of the pulley carrier. That will deflect the pulley upwards. I am thinking about a single screw although I could do one screw in the front and one in the rear which might allow some adjustment in the other plane? Thoughts?
R
Oh...... I see it now. One screw should suffice. The framework should keep everything parallel . you shouldn't have to worry about the other plane as long as the frame is sturdy and does not flex anywhere. That was an issue I had to address and it took a little reenforcement of the frame to correct it. You may have been better off to use some square tubing instead of the angle iron, then again, the angle may work just fine.
 

rwm

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#28
For Mark!

26683917441_5bc41c7070_h.jpg

I have sanding belts on order from MMC. Hopefully Tuesday on those.
I guess I need to start working out the table/rest. I have a nice piece of SS for that. I need it to tilt up to 45 deg and be able to move in and out from the belt appropriately.
R
 

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kvt

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#29
looking good, It almost looks like the angle iron sticks up just a bit to high or should it be on the other side so that it is not in the way of the belt, What are you using to tension the belt. I'm keeping an eye on this build for when I build one.
 
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#30
I'm posting some photos of my table. it may give you some ideas. it tilts to 45 and moves in and out to adjust the gap. mounts and adjusts with one bolt.


table 2.JPG table mock up (2).JPG table.JPG table3.JPG tension device.JPG
 
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