I've got the connections figured on an old 1/8hp, 1,435 rpm tumble dryer motor, and I can source a suitable grinding wheel from Axminster. But pls can anyone suggest a source of a suitable spindle (and a drive belt as well) onto which I can mount the wheel. No continuous use requirement.
I'd love a truly DIY solution to this instead of having to buy something - any chance that a bicycle wheel bearing could work?? (Apart from a drill press I have no other bench machinery suitable for metalwork, so pls no advice that requires any metal turning etc!)
While I applaud (and share) your diy spirit, sometimes cold logic comes into it. Given that you can buy a 6" 150W twin wheel grinder, complete with wheels, for £12-£15, is there really any sense in making one?
and, IMO more importantly, with suitable safety guards. Exploding wheels are impressive enough even with the guards. I wouldn't want to be in the same room as one that didn't have proper guards.
Would it really be powerful enough for a bench grinder? 1hp = 746 watts so 1/8hp is only 93.25 watts plus you would have losses in the belt and pulleys - bench grinders have the wheels mounted on the motor spindle so don't have those losses. Even a 150W bench grinder like Grunff mentioned isn't that powerful.
How true. When I was an apprentice back in the '70's someone did the classic of trying to use a surface grinder without turning on the magnetic table. One of the fragments of the exploding wheel passed straight through both sides of one of those modular offices and embedded itself in a masonry wall (about 20' from the machine). Ever keen to drum safety into us they had the apprentices in the wood shop make a nice wooden glass-fronted case which was fastened to the wall over the wheel fragment with label describing the dangers of grinding wheels. OK, this was an 8" wheel on a multi-horsepower 3000rpm machine but I still wouldn't want to be stood in front of a 6" wheel on a 150W bench grinder when it let go.
Point taken re safety, but for a start most bench grinders run at circa 3,000 rpm, so at most I'll be doing half that speed (comparable to the 1,425rpm of what Axminster calls a "Slow-running Grinder"). In fact, since I'll only be doing hand-tool sharpening where speed of metal removal is not the primary requirement, I'd probably want to run it even slower by using a larger diameter pulley wheel on the spindle. I'm sure that Tormeks run at something very low - 90rpm??
I concede that if there's a flaw in the stone then there is a likelihood of catastrophic failure, but under the usage scenario I have in mind: 1) low rpm and 2) very low stress imparted to the wheel from light grinding of chisels etc, I'd be content with a diy guard made from sturdy perspex.
As to the motor rating, I was surprised to see only "1/8 hp" on the T/D motor casing. Sometimes of course, comparative motor ratings can be deceptive (see multitudinous posts on any US woodworking discussion group about the dodgy practice whereby starting power rating is claimed by tool manufacturers as continuous power rating, eg for shop vacs). This T/D motor did spend 10 years turning a heavy drumn full of wet clothing, after all, so I'd expect it to cope with what seems like a fairly small load.
Yes, of course I could buy something ready made, but I personally like the DIY challenge of this project.
Any more views on how to get a low/no cost spindle?? I hope that I can run this setup with a wheel on only one side of the spindle, ie I don't need to counter-balance it with one on each side.
I have one comment: surely it would be much better to mount the wheel straight onto the motor shaft?
What does the shaft look like? What size hole is your grind wheel? You can do all the metal work you like on the motor shaft, it is its own lathe after all.
btw the speed is sufficient for the job. I once used an old one that did 360rpm, and it did the job.
Thinking more about this overnight, I suspect that you're right in that this would be simpler than using an indirect drive via a belt and a spindle. I haven't measured the motor shaft yet, but it looks to be circa 10mm dia, so I can bush it out to take either a 12.6mm or a 16mm bore wheel. The only problem will be cutting a thread to take a locking nut on the "outside" end of the shaft (I can epoxy on a nut on the "inside" end); yes, it is it's own lathe as you say, but I'll need a secure/ precise way of holding/ applying the tooling??
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