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Truing a grinding wheel - Printable Version

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Truing a grinding wheel - RichK - 11-19-2016

I picked up an old Grizzly slow-speed grinder at a barn sale.  The big wheel doesn't look damaged but it needs to be trued.  I used a cheap star dresser, a diamond dresser and a stick dresser.  The grinding wheel is still not concentric.  There is at least one low spot.   I mostly sharpen by hand, so this is just a side project.  My goal is just to get this one concentric.  Any ideas?

RE: Truing a grinding wheel - MichaelMouse - 11-19-2016

That cup washer looks like it's sloppy.  Make a effort to get a good center bushing and maybe one of those thin-kerf stabilizers to get a better grip than what looks an undersized cup washer.

RE: Truing a grinding wheel - RichK - 11-19-2016

I flattened the washer flanges when I first set it up, so I know they are flat.  It didn't occur to me that they may be undersized, so adding stabilizers is a good idea.  I'll also check the bushing.  It's a plastic reducer that fit snug into the wheel hole.  Maybe I should glue the bushing parts together to reduce any play on the inside.  Thanks.

RE: Truing a grinding wheel - iclark - 11-20-2016

The plastic bushings are a bad concept. Invest in a steel bushing and your life will be much easier.

With the plastic bushings, you are really just trying to get the wheel centered and then hold it by the sides.

RE: Truing a grinding wheel - wood2woodknot - 11-20-2016

Any suggestions on sourcing cup washers and bearings? I'm thinking of replacing the ones on my 5/8" arbor Ryobi.

RE: Truing a grinding wheel - Steve N - 11-24-2016

Was it low to begin with, and if so was it lower then, than it is now?

RE: Truing a grinding wheel - EricU - 11-25-2016

the earlier replies are assuming the wheel is moving, in which case you will never be done.  So you might want to see if they are right or not. I would draw with sharpie all over the cutting face and then true.  I would true for a while and then see about flat spots.  Mark where the flat spot is from the side, re-sharpie, and true some more.  If the flat spot moves, you'll know those previous responses were correct.

I've never trued a wheel by freehand, surface grinders have a truing mechanism that keeps the truing stick at a constant radius.  So that's what you have to try to do with the freehand truing.

I know how frustrating truing can be. Of course, I was confident that my wheel wasn't moving. But for some reason, diamond wheels are never true, almost always nicely heart shaped. And taking material off it a slow process. I guess machine shop owners would rather pay a guy machinist wages to true a wheel than get a true wheel from the manufacturer. Of course, some of them have cnc truing, so it's just machine time. But that can be a lot more than the machinist.

RE: Truing a grinding wheel - daddo - 11-25-2016

Turn the wheel until the surface of the wheel that is proud is in front of you. Take a scrap 1x piece of wood and set it on the proud part of the wheel and tap it with hammer. If the proud part changes any, the bushings are worn or not true.
Start with good bushings or you may never get it right.
A diamond can true it up, but the diamond must be held steady and not free handed. You can also use another old grinding wheel to grind it down some.

The large wheel turns slowly (60-80 rpms?). If you could increase the speed to about 300 or so (Check it's rated rpm's), it would help.

RE: Truing a grinding wheel - RichK - 12-01-2016

The bearings and spindle are ok.  Turns out the bushing is not a reducer.  I'm not sure what it's constructed from, but it's disintegrating.  I'm going to get a new wheel and new flanges.  That should solve all issues.
Thanks for all the comments and suggestions.

RE: Truing a grinding wheel - mike4244 - 12-04-2016

I have the same exact grinder. Since it only turns at 70 rpm's the wheel does not have to be perfect. Does the hollow go across the entire 2" width? How much more does the wheel need to be trued ? My wheel turns concentric but is not square to the side of the wheel. I have a slight bevel , about 1/16" or so . This from more pressure on one side.
Does not affect the honing process. If you can hone a tool with your not so perfect wheel, then forget about getting it perfect. If you feel that you must get the wheel concentric then keep truing up with the dressers. I use a  tungsten carbide stick type dresser on all my wheels. I recall only having to dress the stone once in 10 years. The small 4" wheel on the side has never been used , a waste of space as far as I am concerned.