Bump-i-ty Bench Grinder

[middle.road]

(can I post about bench grinders here?)
So I was dinking around with the 8" craftsman yesterday. I was trimming down some bolts for the
step-son's cycle, and there's an annoying problem. (probably operator error, loose nut at the end of the bolt...)
I have dressed both wheels but when the piece part is placed against the wheel it like bounces off.
Does that make sense? I put the bolt (~Ø6mm) in a 3/8" 'pin vise' and when I went to twirl it against the wheel it does a bumpity-bump-bump action.
I can't do it smoothly either free hand or on the tool rest.
First thing I'm thinking is that the wheels are badly out of round, and I'm not sure how to correct that.
Second thing, I got to looking at the design. I will have to redo the tools rests. The wheel housing mounted to the motor is stamped steel instead of the old time cast housing style.
Not enough mass and dampening effect perhaps. Looking at DanS's Baldor write up, that design has quite a bit more mass - heftier.

 

[Billh50]

I had an out of round wheel that did that once. I dressed it and it still did the same thing. So I took a black marker and colored the wheel and dressed it again. I ended up taking off almost an 1/8" before the black finally disappeared. All the while I kept thinking I had a bent or loose arbor.

 

[rgray]

Sounds like you need a diamond to true the wheel. I made up a diamond holder for my bench grinder years ago. It can be just a square piece of steel with a hole to hold the diamond truer with a threaded hole through so a bolt can be turned in to advance the diamond point into the wheel. Mill the bottom so it has a lip to guide it on the tool rest or bolt a plate to the backside that hangs down to use as a guide.
The diamond points come in lots of sizes. I used 3/8 and a 1/4" bolt to advance it.

 

[roadie33]

Sounds like you need a diamond to true the wheel. I made up a diamond holder for my bench grinder years ago. It can be just a square piece of steel with a hole to hold the diamond truer with a threaded hole through so a bolt can be turned in to advance the diamond point into the wheel. Mill the bottom so it has a lip to guide it on the tool rest or bolt a plate to the backside that hangs down to use as a guide.
The diamond points come in lots of sizes. I used 3/8 and a 1/4" bolt to advance it.

You have any pics of your setup rgray?
I wouldn't mind trying to copy your design for truing up some wheels.

 

[rgray]

Yes...Embarrassingly crude. I have 3 grinders with rests that it works on.
The hex shaft started life as an arctic cat drive shaft. When the bearing fails the shaft is cut off by the bearing race as you drive.
The top rounded area is whats left of where the bearing rode. The bolt is a hood hinge bolt from a 98 arctic cat.
Welded some wings on to guide it and milled the rear up to fit along my tool rests.
Front drilled and reamed for the diamond and the rear of course drilled and taped for the bolt.

 

[FOMOGO]

I'm sure you checked, but sometimes it's the obvious things you miss. Is it rotating toward the the tool post, they can be wired wrong. Mike

 

[turnitupper]

I have had good results by using an angle grinder with a cheap diamond tile/concrete disc for dressing badly gouged/imbedded/out of round wheels.
Attach a piece of flat stock to the tool rest to allow the grinder's guard to sit on it, turn both machines on and sweep the disc lightly across the wheel.
This works quickly and well. It also has the advantage of dressing the disc concentric to the grinder's spindle thereby giving MUCH smoother cuts and less chipping cutting tiles.
John.

 

[derf]

Dressing a wheel and truing a wheel are 2 different things. First thing I would do is remove the wheel from the arbor and check the fit. It may have a bushing missing to center it up. Once that is OK, I'd true it up with a diamond.

 

[middle.road]

In between battling the alligators today, I placed a piece of masking around the wheel and using a cheapo indicator,
checked the runout. It's around .010" total. Going to try making up a diamond dresser this weekend or might try
the angle grinder idea.

@FOMOGO, yes rotation is good. First thing I did when I got it home was to check that, and with it sitting out in the driveway just in case a wheel came apart... Standing well away from it.