contact wheel problem (Help!!)

B

beochie

Joined
Jan 21, 2009
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Well I just made a great write up and it was deleted after I installed ispell. so here is the short version.

After what seems like an eternity building my grinder I finally broke down and bought a 10" grizzly wheel, had bearings put in at at a local machine shop (Huge headache, I hate that shop now). The bearings looked just a tad off center. I got it home, mounted it, tried to grind on it and it was jerky/bouncy and very hard to make a good line. I put my dial indicator on it and it varies .010 or 10 on this indicator.

222yfq.jpg

http://img687.imageshack.us/i/222yfq.jpg/

Is this why it was jerky?

Also the shop made some horizontal lines in the rubber when they put it in the lathe. Is this going to be a problem?

Also the rubber on the left side of the wheel seems higher than the rest of it.
221yfq.jpg

http://img687.imageshack.us/i/222yfq.jpg/

I'm thinking about taking a 1/4 inch belt tracking it all the way to one side, putting a chisel on my tool rest and trying to make this thing round, ridge and bump free... What do you think?
 
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Rubber is pretty grabby. Without a very secure setup, that sounds pretty risky. You might try that with a sharp file?
 
Hi Beochie
There are probably many ways of truing it up but from a tool room prospective this is the way I would recommend. Mounted on it's bearings in a lath and a tool post grinder to skim cut it true. That is how I have done it in the past.
 
The way you described truing the wheel is exactly how Rob at Beaumont Metalworks does it to true up his wheels on the KMG grinders. Be very careful to keep the chisel pointed down a bit from 90 degrees to the rubber wheel....more like scraping than cutting. I trued up my 14" wheel and it works well. Just easy does it and when you run the small belt to the other side take it easy on the blending of the two sides...as you can easily create a hump or a dip. Try to have your tool rest right next to wheel and ease the chisel into it........verrrrry slowly. Bevel down on the wood chisel and make the chisel very sharp.
 
loussharp1 said:
Hi Beochie
There are probably many ways of truing it up but from a tool room prospective this is the way I would recommend. Mounted on it's bearings in a lathe and a tool post grinder to skim cut it true. That is how I have done it in the past.
Click to expand...

This is what I had in mind too.
You can grind rubber.

But that will only make the outside of the rubber round.


It looks like they chucked it by grabbing on the outside of the rubber wheel.

At the least I would have gripped it at the shoulder with the jaws pushing out rather than in on the rubber.

The ideal would have been to mount it on an independent 4 jaw, or faceplate like that, indicating on the existing bore to be sure it was centred.
Doing it that way, you can then bore the bore and straighten the outside all in one setup so they are true to each other.

You can see what I mean here
http://www.youtube.com/watch?v=klzHjz1_G78


If they drilled into the aluminum off centre, the whole wheel may need to rebalanced after the wheel is trued round.

If you can find a GOOD auto racing engine rebuilder, who "blueprints" they may have a better understanding of straight, true, and balanced at 3,000 rpm than some job shops who aren't really interested in your job.

You may find that after paying for the wheel and the labour, you could have bought a Sunray poly wheel from Tracy Mickley at USAKnifemaker. Thtat's true on the 8" at least, on the 10" they are more $, you still have some room
 
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As I remember from grizzly's pic on their website, that wheel lacks a square flange at the rim or one on the hub. Holding it in a lathe takes some doing and would not be a simple chuck and bore. Now that the hole is off center, trueing the rubber is not likely to address all the problems that will come with the off center bore, you also have a balance issue.
The shop that messed it up might be willing to fix it if you raise enough of a stink. Otherwise you need to find a better machinist that is willing to deal with such a PITA on a onesy basis.
I been wanting one of those grizzly wheels for sometime and if you decide to bail on it make me an offer. I might try to fix it for myself. I just don't feel confident enough in my tooling or skills to risk your part or money, I'm used to wasting mine. LOL
That being said, up front and honest, I'll tell you how I might have done it with a fresh bore And how I think I might fix it. My hope is that after reading it you might have some idea what you are asking the next guy to do and be able to get a feel for wheither or not you want to give him the job.
Starting from a fresh bore, I'd mount the appropriate size shaft in the lathe chuck with a live center on the free end and indicate it in to be true on the length and run out. Then mount the wheel and turn the hub and/or flange square, on both sides. Once this is done the wheel can be removed from the shaft and mounted in the chuck. At this point the wheel should be indicated in again. Just because the chuck was true at 3/4 inch does not mean it will even be close at 1 1/4 inch. Now the hole can be bored out to the target dimension.
This next part is what I think will have to be done to fix the existing problem, it is also worth mentioning that it would have also worked for the virgin peice.
Measure the wheel across fresh areas well away from the deformaties caused by previous machining. Set up an x-y fence on the mill table. This is done by setting up a fence bar left to right (x) and another front to back (y) on the mill table and indicating them in to be true to the travel of the mill in the appropriate directions. After finding the edges of the fences move the mill to the mathematical center of the wheel based on the previous measurements. Mount the wheel to the table snuggly against the fences with the previously mentioned un-deformed surfaces touching the fences. With a boring head or end mill you can now punch out the bore on center. I would not use a drill bit as they like to follow an existing hole.
You have a couple of options. You can bore it to suit the next size up bearing or bore a bit over and plug it with fresh material and start over going for the original bearing size.
As for truing the rubber coating I defer to the others methods as I know just enough to know that rubber is a pain to machine and my results are seldom what I hope for. The rubber may relax some and not be much of a problem in use, I honestly don't know.
 
Wear a mask if you try to true it. You'll still be blowing black boogers for days. I just did mine a couple of weeks ago.
 
It sounds like your "machinist" sucks. They should fix it, I agree. I've used a large bastard mill file to tune up my 12 and 8 contact wheels with success. But you should get that thing re-bored for sure. +1 to what they said, I suppose.
 
I agree they suck. I'm thinking of it like a tatoo. Why would I take it back to the same turds that messed it up in the first place. If they couldnt do it right in the first why would I even consider them fixing an existing problem.

I'll try the chisle trick tonight and report back.
 
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