Bench grinder - adding a threaded tapered spindle adapter

[fishwatcher]

I recently got a 6” bench grinder. It’s a very typical MIC grinder, lots of products look like this.

It has a 1/2” arbor, with threaded ends. I bought a 1/2” threaded taper spindle adapter, to easily swap buffs.

It installs via a smooth bore and a set screw. Only the further out set screw fits and it’s screws right into the edge of the smooth and threaded section of the arbor.

Are there tapered spindle adapters where the bores are threaded and there is a flat section to use a wrench on? Seems like it would be a higher quality join between the arbor and the spindle adapter. If this exists.. please share any links. The one I got was $15 a pair (Left and right) from Amazon.

That little set screw doesn’t give me a lot of confidence.

Thanks!

 

[RaisedByWolves]

Without being able to touch it all I can say for sure is it sure looks sketchy as hell.

 

[Shiftless]

I suppose you could upgrade the mount by drilling and tapping another hole closer to the motor for a second set screw.

 

[PoorUB]

Is the bore deep enough to cut off the end of the adapter closer to the hole so both screws can get a bite?

I never used one of those adapters on a bench grinder. I used an old 3600 RPM motor I had.

 

[fishwatcher]

Is the bore deep enough to cut off the end of the adapter closer to the hole so both screws can get a bite?

I never used one of those adapters on a bench grinder. I used an old 3600 RPM motor I had.

That’s a possibility worth checking out. However.. that second grub screw would then be biting into the arbor thread.

I’m going to see how this works for now. Maybe just a dab of loc-tite will help with the single grub screw.

 

[Zeus36]

Drill and tap for a second set screw at 90 degrees to the factory screw. Same distance from the end of the adapter. If your still concerned, add three setscrews in addition to the factory one - giving you four points of contact at 12, 3, 6 and 9 clock positions. That will give you a balanced weight load. Doubt that would be much of an effect at 3450 RPM ... if it were me, I'd just do a second setscrew at 90 degrees.

 

[RoninB4]

-It's not just the ONE set screw that makes me question this. A buffing wheel at that extended distance and the amount of force needed to use the buffing wheel creates considerable deflection loading. That moment, combined with ONE puny 1/4-20 set screw holding it all in place, at speed, is highly cringe worthy. If/when that set screw backs off, even a little, the momentum can/will whip the whole assembly around as it walks off the shaft. It can either bend the shaft or launch the assembly into the operator or anything in the flight path. The fitment of shaft to collar can also contribute rotational problems (ellipse). The advice of a "second set screw" isn't really good advice either, a set screw shouldn't be the primary constraining factor on a rotating assembly like this. It may appear to work fine but how many sessions will it last until it gives a false sense of security? Don't use this unless it's altered to be a safe design (it currently isn't). Could this set up work safely? Yes it might but if you don't understand what needs to be done I'd recommend not using/attempting this.

 

[racecougar]

^^^^THIS.

 

[gregs]

I would try to shorten it so that as much of the grinder shaft fit inside to provide support.

 

[fishwatcher]

@RoninB4 et al, thank you! I will heed these warnings.

So does anybody have a lead on a product like this with a threaded (not smooth) bore? It seems like there’s a market for them, currently addressed with a handful of similarly built grub-screw options like the one I got.

 

[RPH]

McMaster - Carr has some screw on tapered buff arbors. Left and right side respectively. About $12 each.

 

[Shiftless]

McMaster - Carr has some screw on tapered buff arbors. Left and right side respectively. About $12 each.

This sounds like the best way to go by far! Better log on to MMCarr today.

 

[Zeke]

I paid $60 for a MIC buffer with extended arbor housings. It gets hot after a few minutes use but for clearance to the wheel you can't beat it. I use a wire wheel on it too. Has a weird mm size close to 7/8th" so that makes buying wheels tough. Cloth are fine.

 

[fishwatcher]

McMaster - Carr has some screw on tapered buff arbors. Left and right side respectively. About $12 each.

Thanks for this. I double-checked and all of their products for 1/2” arbor are with unthreaded bores. https://www.mcmaster.com/products/~/for-use-with~bench-grinders?s=tapered


Update:

When I asked their sales support team for a threaded version via text, they said, “I'm sorry we do not carry the item you are looking for.”

 

[fishwatcher]

I paid $60 for a MIC buffer with extended arbor housings. It gets hot after a few minutes use but for clearance to the wheel you can't beat it. I use a wire wheel on it too. Has a weird mm size close to 7/8th" so that makes buying wheels tough. Cloth are fine.

Thanks @mic214. What is a MIC buffer? Link? Nevermind.. figured this out .

Ideally I want to get multiple uses out of my bench grinder that are easy to make change without fuss. The room I have for additional tools is very limited.

 

[alfadan]

I suppose at a minimum, file an angled spot on the shaft, in that when you tighten the setscrew (with loctite), it pulls the adaptor tighter on the shaft. Blue the shaft with a sharpie and use the set screw to mark it and file carefully with trial fits.

 

[fishwatcher]

I suppose at a minimum, file an angled spot on the shaft, in that when you tighten the setscrew (with loctite), it pulls the adaptor tighter on the shaft. Blue the shaft with a sharpie and use the set screw to mark it and file carefully with trial fits.

Like this a lot! Thx

 

[fishwatcher]

I think this might be the solution!

It says “threaded tapered”, has a hexagonal shaft (not round), and other products on their site actually mention set screws (this one does not). It also mentions 20 internal threads. l sent email into Tar Heel parts to confirm!

Threaded Tapered Spindle 1/2" Bore Right Hand Taper

Designed to be used with pinhole center wheels. No need for washers or nuts! Spiral thread allows wheel to spin up tapered shaft when motor is turned on. These are used on side grinders and end grinders. TAPER RH 1/2" X 20 INTERNAL THREADS Safety First - Always wear adequate & proper EYE, EAR...

tarheelparts.com

 

[jayemm]

I think this might be the solution!

It says “threaded tapered”, has a hexagonal shaft (not round), and other products on their site actually mention set screws (this one does not). It also mentions 20 internal threads. l sent email into Tar Heel parts to confirm!

Threaded Tapered Spindle 1/2" Bore Right Hand Taper

Designed to be used with pinhole center wheels. No need for washers or nuts! Spiral thread allows wheel to spin up tapered shaft when motor is turned on. These are used on side grinders and end grinders. TAPER RH 1/2" X 20 INTERNAL THREADS Safety First - Always wear adequate & proper EYE, EAR...

tarheelparts.com

Aren't the threads on a 1/2" bench grinder shaft a 1/2-12 thread instead of 1/2-20 as mentioned above?

 

[fishwatcher]

Aren't the threads on a 1/2" bench grinder shaft a 1/2-12 thread instead of 1/2-20 as mentioned above?

@jayemm I think you’re right, it’s not 20 threads per inch.

I see 9 threads in about 5/8”. So I guess that’ll end up being 12 in one inch. Shoot.

 

[jayemm]

@jayemm I think you’re right, it’s not 20 threads per inch.

I see 9 threads in about 5/8”. So I guess that’ll end up being 12 in one inch. Shoot.

Yep, I found that out when a 1/2-13 nut wouldn't fit. And don't forget, the threads on the left side of the grinder shaft are LEFT HAND threads.

 

[gregs]

I'm betting that if Tarheel sells a slip on/set screw adapter that it must work ok and not fly off and kill people. I think if you follow some of the suggestions above all will be well. If you plan on leaving it on permanently you could add sleeve retainer or JB Weld to the shaft for an additional layer of safety.

 

[fishwatcher]

I'm betting that if Tarheel sells a slip on/set screw adapter that it must work ok and not fly off and kill people. I think if you follow some of the suggestions above all will be well. If you plan on leaving it on permanently you could add sleeve retainer or JB Weld to the shaft for an additional layer of safety.

"sleeve retainer". Another new thing I've learned from GJ today, Thx @gregs!