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Belt Grinder Blues


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Hi All,

I am at the end of my wits, fresh out of ideas, and seeking some advice. I was just out in the shop, putting what I thought to be the final touches on my "new" belt grinder when lo & behold I find that the belt will not track properly. I had the same issue with my $50 home-made grinder, so you can imagine how I feel since this one has cost me over ten times that amount. :(

Here is the scenario: when I rotate the belt forward in a normal grinding direction, the belt tracks inward toward the machine. when I rotate the belt in the opposite direction it tracks outward. I have tried just putting the belt over the drive wheel & front two platen wheels to see if it was the idler wheel, but the same thing happens. The idler wheel does not seem to have any effect at all. :confused: I am beginning to suspect it is one of two things: either the drive shaft is not aligned correctly (not sure how to check), or the drive wheel is not concentric. Anyone have any good ideas?

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well looking at your pictures one thing that dosent look good is the pulley with all the nuts(as spacers?) on the shaft... that right there can cause problems as it appears to be allthread... i dont think that is a good idea for a shaft for a few reasons... if the allthread is resting directly against bearings it will be sloppy... and allthread is usually a soft steel so will wear badly .. instead i would use a shaft of drill rod or a grade 8 bolt with a long sholdier so the bearings are resting on shaft instead of thread.also i agree that somewhere there needs to ba a bit of crowning to keep it tracking... dosent take much.. good luck!

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Are the belts that aren't tracking on this machine the same ones that didn't track on the other machine? Have you tried different belts? I have had batches that didn't track on anything that I had.

How much tension do you have on the belt?

If you take a precision square and check the sheels for perpendicularity to the surface, mainly the drive wheel and the platen wheels, are they square?

Otherwise I second the suggestions made so far.

Jamie

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Didn't think about tension, but YEAH! I agree with Jamie! I changed contact wheels on mine and had to tweek the tension. Had it way too loose at first. Not slack by any means but not tight enough and that belt went crazy!!!I would adjust the tracking slightly to the outside and off flew the belt! Slightly to the inside and the belt crashed into the frame! Increased the tension; problem solved! Seems if you have a slight crown to at least one of non-contact rollers and proper tension and a lot of other design flaws can be overlooked and even many even flawed belts may be forgiven (No guarantees YMMV. I have 2 crowned rollers and sometimes I wonder if they work against each other or in unison, but before I crowned them, I couldn't keep belts on at all.

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First make sure that the shaft driven by the motor is parrellel to the shaft on the front bottom wheel in both planes. If you take both wheels off you may be able to see this by eye on the horizontal plane. site from front to back and see if the line up. Then from the top you should determine if they are parellel. You will have to be creative to figure this out. Then do the same thing with the top front wheel and see if all is well with both the other shafts. Fix any problems you find. (From the looks of the machine and how it is built I suspect it is correct) The crown the drive wheel. I would chuck it it the lathe and take about an eighth inch off of eash edge the rcrown it to the center in a nice curve on each side. I wonder about the speed on the belt. Not sure what the motor speed is but your pulleys are set to increase the motor speed. The drive wheel is fairly small so you may be alright. My comercial grinder has a max speed of 6200 sfm. I have never used it at that speed. I ususally run about half speed or a bit more. Try good belts like 3M or Norton. I like the 3M 967 belts in 100 and 220 grits. If I were to buuild this machine I would ehave o ne of the wheels rubber covered. I think it helps provide belt traction if you push into the belt a bit and it helps with vibrations. You have done a great job and with a bit of tweaking it should be fine. Let us know what makes it work...

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that tracking wheel looks suspiciously cylindrical/flat to me. I think it has to be crowned as others have said. Mine is crowned and when I first put it together I had some "issues" and got a little nervous. One additional thing... Check the centerline of all your wheels. Shim/adjust as necessary to get them all aligned. Either crown the tracking wheel you got, or order one somewhere and I think your problems will go away. Good luck...

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Ok, tonight I removed the flange mounted bearing and scribed lines on the bearing support plates & bearing cases. Then I carefully reinstalled the bearings, making sure that the scribed marks lined-up. The drive shaft slid smoothly into place and did not bind. After doing that, I checked the bearing support plates were square; which they were. Then I put a new 3M belt on and hand fed the belt and the tracking issue still occured. At that point I almost got religious on the thing, but managed to keep my temper in check.

I believe that the drive pulley is aligned correctly, so I suspect that the two platen pulleys must be the culprits, because when I checked them with my square they seemed to be misaligned; the top one tilted forward and the bottom one tilted downward. I am guessing that the holes in the platen must not be tapped straight? This is very frustrating - I mean, how can some guys steal their kids roller blades, their wife's ironing board, along with some angle iron & baling wire and get a grinder that tracks true? I am completely mystified.

At any rate, I am not going to be able to fix any of this mess until I get my "new" lathe & "new" mill set up.

Good night & God Bless,

Chad

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I hate to type and run, as I'd like to chime in on this one a little more,. I've been running a BIII for the last ten years, and here lately the tracking has been giving me fits. I haven't had the time to delve into it completly to fix it, so I've had to resort to the perverbial quick fix of taking some masking or freezer tape and laying down a couple of rounds(layers) down the center of the idler wheel and it works like a charm in keeping the tracking acurate, It requires changing about once a week at the rate I use it anyway, and although it is temporary, it does do a good job for the time being. Wes

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