Crown on roller wheel

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trg-s338

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I am machining some aluminum roller wheels for a belt sander. How does one machine a subtle crown on 2 inch wide wheel of several diameters on a lathe that would help keep the sanding belt centered on the wheel when running? A form tool?
 
I really dont know the 'real' answer -- I think theres a formula in Machinerys Handbook.

Strictly 'for what its worth' - your mileage may differ - I never slept at a Holiday Inn, etc, etc, this was my experience...

I had done several in 3x2" & 6x2" carefully trimming away with cross feed and carriage from a central point, trying to keep a 'rounded' profile - mounting it on the sander only to watch the belt wander (which happens when there is too much crown) or, the belt not track (uneven crown) - even scrapping a couple wheels when I got to much crown. Having heard several comments about how little crown is actually needed to get tracking and needing a 2x1" wheel, I just grabbed a coarse file, and drawing a magic marker line for center, started filing to the edges, eyeballing it. About the second time I tried the belt it tracked nicely. I have since done another 6" and a 3" using just a file and eyeballing - it really doesnt need much.
 
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I used a form tool, made from an old file, to make a new crowned pulley for my Themac tool post grinder. Now, it was only about 1" wide, so I didn't have a problem with chatter. If I were doing 2" wide ones, I'd make two form tools, and do the radius in right- and left-hand passes. You could make one tool and use it appropriate angles to achieve the contour, but two tools in separate holders would make the job go quicker for multiple parts.


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My lathe is pretty rigid for 11" swing, so you could have chatter trouble on lighter gear.

Here's the full write-up, including making the tool: http://www.frets.com/HomeShopTech/Tooling/FileLatheTool/filelathetool.html
 
If you wanted to get crafty, take a nice piece of hardwood and dish it on the table saw (you do know how to do that, right? ;) ) and set some 80 grit cloth in the dish, and after roughing it in, finish with the abrasive stick.
 
I usually cut a 1 degree taper both sides of center and hit with a file o round off.
 
Looks like some element of each of your responses will have to come into play here. I will try some filing first but if I have trouble with symmetry, I will go the form tool way. Filing, sandpaper form tool are a creative idea. I do like the file form tool from file idea though. I'll have to see what works for me. I am going to need several of these rollers for the belt grinder I am building. Thanks all!
 
Flat belt pulleys at $66.85? I think I'll just continue with my learning curve. :=)
 
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