Thread: Goodell Pratt bench grinder

Here is one with just a nut and washer


But I think you will find this is what the original probably was.

Originally Posted by DSEL74

Here is one with just a nut and washer


But I think you will find this is what the original probably was.

Thanks for the pics and the add. The big question now will be if I strip and repaint the little grinder so it looks new like the one in the photo?

Cheers stew

Stew, I've blanked out the parts, but yet to do the screw cutting. I've been off work crook today so they won't get finished until the weekend unfortunately.

DSEL74, it's useful to see those pictures, but this is a curious design. Both the backing flange and the nut are left hand threaded. The only way this makes any sense is if the backing flange is tightened hard against the small shoulder on the shaft, but the shaft doesn't appear to have been designed for that. Only Stew will be able to tell when he re-assembles it. And even then it's strange that they went to the trouble of making everything left hand threaded given that there are two tool rests on opposite sides of the wheel.

But whatever, I'm making up a nut and a turned flange, and these parts will get Stew out of trouble. I'll post pictures when it's done.

Graham.

Not sure if I'm following you. On my other grinders the flange and the nut are one piece.

The is a flange on rack side of the emery wheel, only the outside one has spanner flats. There is usually a brass bush that sits inside the wheel to size the hole down to the thread bore.

Originally Posted by Oldbikerider

Stew, I've blanked out the parts, but yet to do the screw cutting. I've been off work crook today so they won't get finished until the weekend unfortunately.

DSEL74, it's useful to see those pictures, but this is a curious design. Both the backing flange and the nut are left hand threaded. The only way this makes any sense is if the backing flange is tightened hard against the small shoulder on the shaft, but the shaft doesn't appear to have been designed for that. Only Stew will be able to tell when he re-assembles it. And even then it's strange that they went to the trouble of making everything left hand threaded given that there are two tool rests on opposite sides of the wheel.

But whatever, I'm making up a nut and a turned flange, and these parts will get Stew out of trouble. I'll post pictures when it's done.

Graham.

Graham

I really do appreciate your help and your proposed nut and turned flange sounds excellent !

Cheers stew

Originally Posted by DSEL74

Not sure if I'm following you. On my other grinders the flange and the nut are one piece.


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Dsel74

The grinder is made for both right and left handers. Ie it turns in both directions with a tool rest on each side.

Interestingly enough, they are different tool rests on each side. The collection of photos of other examples confirm mine are original.

Graham

I suspect it's a left hand thread due to most people being right handed?

Cheers
Stewart

I wonder if the rear rest is in fact there to act as a form of guard perhaps?

Running it in reverse for say lefties will undo the nut.


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Originally Posted by DSEL74

I wonder if the rear rest is in fact there to act as a form of guard perhaps?

Running it in reverse for say lefties will undo the nut.


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The advertisement you posted says it's for left and right hand work......

So it does.


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Originally Posted by DSEL74

Not sure if I'm following you. On my other grinders the flange and the nut are one piece.

The is a flange on rack side of the emery wheel, only the outside one has spanner flats. There is usually a brass bush that sits inside the wheel to size the hole down to the thread bore.

I'm saying that there is no point in having both threaded parts, the one on the front and the one on the back of the grinding wheel, with left handed threads. A left handed nut would only self tighten on the wheel (and only for one rotation direction) if the threaded part on the opposite side of the wheel was either right handed or fixed against a step in the shaft or by other means.

On Stew's shaft there is a step that the inner flange could lock against, but it doesn't look large enough that it was designed for this. I'm not sure if the way the shaft assembles in the grinder frame allows for the inner flange to even push up against this step. I guess Stew will find out when he puts it back together.

Graham.

I follow you now.

I agree about the inner nut if the grinder is running forward. Would the inner nut tighten if it ran in reverse? So the self tightening action of one nut in either direction provides enough force to keep the wheel in place? Just an idea that popped in my head, might be flawed with more thought lol.

Hi Stew,

These parts should work for you. I've made three parts, a thin nut and a flat washer that will go on the outside of the grinding wheel, and a second thicker nut.

The inner flange, the one that came with the grinder, does not run very true. I suspect it's not actually the original, because it doesn't have any flats machined into it and because the thread is not true to the flange face. So I've also made up the thicker nut, which you could use in place of the inner flange if you wanted to. The machined washer has an undercut at it's centre, leaving an outer rim to support the wheel, just as the inner flange does.

I've confident that some combination of these parts will get your grinder up and running. It was fun to make these parts, it's a while since I've needed to do any turning, and this was a nice break from other work. I'll mail the parts back to you tomorrow.

Graham.

IMG_8675.jpgIMG_8673.jpgIMG_8674.jpgIMG_8671.jpgIMG_8672.jpg

Originally Posted by DSEL74

I follow you now.

I agree about the inner nut if the grinder is running forward. Would the inner nut tighten if it ran in reverse? So the self tightening action of one nut in either direction provides enough force to keep the wheel in place? Just an idea that popped in my head, might be flawed with more thought lol.

DSEL74, no I don't think it would. You need opposing threads, or a thread on one side and a hard stop on the other, for the self tightening action to work. And even then it only works for one direction of rotation.

Graham.

Originally Posted by Oldbikerider

Hi Stew,

These parts should work for you. I've made three parts, a thin nut and a flat washer that will go on the outside of the grinding wheel, and a second thicker nut.

The inner flange, the one that came with the grinder, does not run very true. I suspect it's not actually the original, because it doesn't have any flats machined into it and because the thread is not true to the flange face. So I've also made up the thicker nut, which you could use in place of the inner flange if you wanted to. The machined washer has an undercut at it's centre, leaving an outer rim to support the wheel, just as the inner flange does.

I've confident that some combination of these parts will get your grinder up and running. It was fun to make these parts, it's a while since I've needed to do any turning, and this was a nice break from other work. I'll mail the parts back to you tomorrow.

Graham.

IMG_8675.jpgIMG_8673.jpgIMG_8674.jpgIMG_8671.jpgIMG_8672.jpg

Graham

That looks beautiful, thank you! I must say it's beyond expectation!

Cheers stew