Tightening CBN wheel on Rikon Bench Grinder

[Luis Reyes]

Ok, I feel really stupid asking this but I'm perplexed and I know the CBN wheel isn't tight so I'd rather be safe.

I recently got my first bench grinder (Rikon 1HP) with CBN wheels to sharpen my woodturning tools. I realize the nut on the left is left threaded and the one on the right is normal thread. But since I need to move both nuts in the same direction to tighten how do I get the shaft of the grinder to not rotate so I can properly get both nuts tight?

Thanks in advance!

[Neil Strong]

Neither nut needs to be wrench tight, just snugged up and they will tighten themselves with use. The inertia will do that.

Snug the nut up one side and handhold that wheel while snugging up the nut on the second wheel.
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[Brice Rogers]

If you kind of "snap" the wrench in the tightening direction, it'll allow you to snug it down. I have a mill and I do that to tighten the collet. I suppose that in that case I could put a strap wrench on the collet end to have something to tighten against, but I haven't found that necessary.

[Reed Gray]

The grinding wheels are not supposed to be 'tight'. This was from the old friable wheels which could and would crack if you tightened them down too much. About finger tight is all you need. They ain't going no where.

robo hippy

[Luis Reyes]

Thanks for the responses so far. When I start the grinder and then stop it, the left wheel keeps spinning after the shaft stops. I'm assuming that's too loose? I've done it as finger tight as I can but worried about the fact that it'll keep spinning even though the shaft stops

[Neil Strong]

When I start the grinder and then stop it, the left wheel keeps spinning after the shaft stops. I'm assuming that's too loose? I've done it as finger tight as I can but worried about the fact that it'll keep spinning even though the shaft stops

Not had that happen on any of the CBN/diamond wheels on my bench grinders, even the ones that slide onto the shaft easily, so I'm just guessing what the problem might be. A few thoughts...

Do you have aluminium or steel hubs on your CBN wheels? Steel is much heavier of the two and has more momentum when the grinder is turned off.

Have you done any grinding with the wheels yet? If the nuts are snugged up grinding with the wheels should further tighten them up on the shaft.

As your grinder is new it should be good out of the box, but is there an issue with the bearings? Take all of the wheels off the grinder and run naked (the grinder, not you) to see how long it takes to come to a stop after turning off. If abrupt then the issue might be the bearings, but unlikely on a new grinder. I'm not familiar with Rikon grinders and whether they have motor braking, but if so it could be cutting in too soon or aggressively. Others that have Rikon grinders may be able to answer that.

How loose are the CBN wheels + bushings on the shaft? Are they a firm sliding fit or do they float on? An overly loose fit may give you some slight runout but should still snug up square for a friction hold onto the shoulder of the shaft with the machined surfaces.

If I was still having wheel overrun concerns I would consider adding a second retainer nut (left and right) if there is enough exposed thread on the shaft. This would only work if the inner nut was secure against the bush before locking in place with the second nut.

[Reed Gray]

I have the Rikon 1 hp grinders also. The wheels spin for a long time after I turn the grinder off, like a couple of minutes. I would expect that this is what is happening rather than the motor turning off and the wheel free spins around the shaft.

robo hippy

[Bill Howatt]

If only 1 wheel spins then I'd say it is loose. I have never put a wheel on just "finger tight", always tightened with wrench obviously with care with the "stones". It should tighten with use and a I can say from experience that if it spins the wrong way it will indeed loosen. Should be able to determine just how loose by hand turning when holding the other side's wheel stationery.
Given how normally easy the armature rotates on the bearings, the wheel must be pretty loose to not spin the shaft.

[Steve Demuth]

If the wheel is spinning and the shaft isn't, then it is indeed too loose. As others have said, you don't want the nuts over tightened, but they have to grip the wheel enough to make it move with the shaft. In my experience, that requires a modest wrench tightening.



So, to answer your original question: if you are having trouble holding the shaft, start with both wheels off. Put one side on and then wrap a stout cord (like clothesline) around the threads on the other end. Twist the cord ends together tightly so the cord tightens firmly on the threads of the shaft. That'll give you enough leverage to wrench tighten the other end. Then take the cord off and put the second wheel on. The tight wheel on the first side will be more than enough to hold the shaft for tightening the second.

A lot of people will tell you they've never had to do such a thing, and no doubt that's right. Doesn't mean there is anything wrong with a little help holding the shaft.

On a metal wheel like your CBNs, if the wheel is highly polished, it can also be helpful to rough up the area on the wheel where the flang sits a bit. Just hit it with a little 220 grit sandpaper. Gives the flang something to grip.

[roger wiegand]

I don't remember the details on this, but some grinders have a smooth shaft threaded on the end and if the wheels are slightly thin or the washers aren't thick enough the wheel won't hold firmly even with the nut cranked all the way down. You might try adding a thicker washer.

[Neil Strong]

I don't remember the details on this, but some grinders have a smooth shaft threaded on the end and if the wheels are slightly thin or the washers aren't thick enough the wheel won't hold firmly even with the nut cranked all the way down. You might try adding a thicker washer.

Good point Roger. With the small hubs on the CBN wheels i have done away with the flanges that come with the grinder and that can leave you short on thread length on the shaft. If using pressed washers to pack out they can give you some lateral runout, in which case machined washers may be needed.

[tom lucas]

You might need something like this:
https://woodturnerswonders.com/colle...hined-aluminum

You want a good machined spacer to keep things running true.