CBN wheels and woodcraft grinder

[Stephen Massman]

I found several posts on this topic here on SMC. Yesterday after doing a little cleaning and organized after my recent project, I installed two new CBN wheels (80 and 180) on my woodcraft slow speed grinder. I sharpened around 10 turning tools and was ready to stop when I noticed a electronic type smoke smell. The grinder was also very hot to the touch, and had smoke coming out of each side of the motor housing. I sharpen with very little pressure and no stalling or slow down of motor. I was worried enough to put the grinder outside in case it caught on fire.

Today, I decided to try it again. I did give the wheels a hard tug to get them moving and then turned on the grinder. It was running for about 30 seconds and still didn't come up to full speed.

Does this sound like a dead or dying grinder or possible bad capacitor.

I have attached two pictures, one of capacitor and one of back side of grinder with wheels attached.

[Ralph Lindberg]

Generally a cap failure is noticed when the motor doesn't start moving, but if you switch the power on, with the wheel already moving it quickly comes up to speed.
My guess is a winding or brush issue.

[Ken Fitzgerald]

Out of curiosity, are the new wheels heavier than the old ones?

I find it curious that this appears to have started immediately after you changed the wheels.

The photo you show of the capacitor doesn't seem to show evidence the smoke was coming from the capacitor. I suspect the smoke is coming from the motor.

[Stephen Massman]

The CBN wheels are heavier than the AO wheels that were on it. I also find it strange that the problem didn't come up until after I swapped out to new CBN wheels.

[Michael Mason]

I have the same setup and have had no problems.

[Joe Kaufman]

Smoke out of the vent holes and high temperatures are generally a bad thing. Since the motor can't reach full speed, sounds like the capacitor and starting windings don't drop out of the circuit on start-up. Not sure if a relay is used but doubt it's is a mechanical / centrifugal switch. For safety sake, it would be advisable to do further testing using a GFI protected circuit. As of Saturday, I have the same setup. Had been using one CBN and one AO wheel for 3+ years. Just changed to the second CBN wheel and haven't notice any difference in the startup time. I always spin the wheels by hand to ease the stress of startup.

[Steve Peterson]

I always spin the wheels by hand to ease the stress of startup.

I have heard other people say they spin the CBN wheels by hand during startup. Some motors have a spec for the number of startup cycles allowed per hour. Heavier CBN wheels would take a higher startup current and make the problem worse. Undersized wiring or low house voltage would also take longer for the motor to come up to speed.

I typically measure 125-126V at my house, which is on the high side but still within spec. I also always use 12ga wiring with 20A breakers in the shop. I have one CBN and one AO wheel on the same Woodcraft grinder that has been running for a few years without issue.

Steve

[Thom Sturgill]

I recently added a second CBN wheel and its design is such that its heavier than the first wheel (Wooden Wonders new design with 1" plating on each side). I have had to start hand spinning the wheel to get it to start up. This is a Delta VS 8" grinder. I removed a 1 1/2" thick MDF wheel that I had loaded with honing compound.

[robert baccus]

Might try removing the 80 grit. Most guys seem to use the 180 grit for sharpening. Will remove some weight and sounds like no loss if it runs properly.

[Jebediah Eckert]

I have the same grinder and it stopped working. It wouldn't start and would trip breaker after a moment or two. I brought it in for repair. They told me between the wheel and the motor is a shield to protect something or other from Sparks. The wheels got too tight and crushed this shield giving too much resistance for the start up. Maybe the wheels are on too tight or somehow that guard got crushed in?

[Jeff Holoboski]

I know nothing about electrical but have the same Grinder/CBN wheel set-up.CBN wheels are heavier-I give the grinder a spin before turning it on.Installation seemed to be straight forward for me.Hope you get it worked out.

[Stephen Massman]

thanks for all the insight and comments. I am going to work on it this weekend and pull both wheels off and let it run and then add one back at a time. I may also replace the capacitor since it is easy and inexpensive.

Steve

[Cliff Hill]

Ken at Wood Turners Wonders is now making all of his CBN wheels from 6061 Aluminum so if the weight of steel wheels is a problem his wheels may be the solution.. I realize this won't help people like me that have steel wheels but it should be a consideration for those contemplating purchasing new CBN wheels.

Cliff

[allen thunem]

the fact of the matter is that these are cheap grinders. I have had three. first two I returned because the wheels wobbled terribly and I couldn't balance them. third one runs or ran great with two cbn wheels. used it without any problems until I ran across a better jet grinder. now the woodcraft grinder just sits.

[Stephen Massman]

I am considering just trashing the woodcraft and going with a new jet from CSUSA. The woodcraft is five years old and at the $110 I paid for it is has had a good life.

[Morey St. Denis]

Cliff, your information looks to be ahead of any formal product launch specifications. No mention of this variation could I find on the website... Will those bare turned aluminum wheels get hardcoat anodized? How is the CBN bonded to the substrate? Nickel electroplating, such as typically used with a steel disk, can be problematic over aluminum...

[Stephen Massman]

I did have some time last night to try the grinder with no wheels. It did take a couple seconds of churning sounds to actually get the shaft to rotate after flipping the ON switch. Once the shaft was spinning it was very quick to come to full speed. I don't know much about electronics and motors, but that sounds like a bad capacitor. I tried to take the left and right side motor housing off but couldn't get them to come off. After removing the four screws on each side, I was able to spin the side motor housings but could not get them to come loose enough to pull them off.

I did call Woodcraft yesterday and the tech support person made it sound like the grinder should be trashed. They did offer me a discount on the Rikon slow speed grinder, which I did take them up on and got a discount on shipping. I asked the tech if the Rikon would be able to handle the two CBN wheels and he said yes with no issues.

The Rikon grinder is on back order until middle of March, so it would be nice to possibly find a solution for my current woodcraft grinder. I can go to the local Grainger and see if they carry a capacitor and see if that helps. But the fact the smoke was coming out of the motor housing leads me to think it isn't capacitor related.

Any thoughts would be greatly appreciated.

Thanks
Steve