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colin hamilton22/02/2022 10:17:12
140 forum posts
61 photos

I'm looking to convert and old freestanding pedestal grinder into a buffing machine. Would it be possible to make one of these shafts on my manual lathe. Is if possible to cut a tapered thread?

Thanks Colin

screenshot_20220222-100536_ebay.jpg

Gary Wooding22/02/2022 10:26:14
983 forum posts
254 photos

I wouldn't bother making one, they're readily available and not very expensive. Don't forget that right-hand ones have a left-handed thread. **LINK**

Tony Pratt 122/02/2022 10:40:21
1961 forum posts
12 photos

In the dim & distant past I did make one on a Myford super 7, I used a taper turning attachment to cut the tapered thread. I can't see how you would do it without the attachment?

Tony

Hopper22/02/2022 10:46:07
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6392 forum posts
334 photos

Yes you can do it. And without a taper turning attachment. This maestro from Indonesia shows how at about the 5:20 mark.

 
His method is basically, turn the tapered section first. Then set up the lathe to screw cut the coarse "thread" that forms the spiral, with a suitably shaped form toolbit instead of a thread cutting tool. Then there is the interesting bit. As he screwcuts along the job, he uses the cross slide to manually make the toolbit follow the path of the taper. Quite a trick.
Note, he uses an inverted tool bit and runs the lathe in reverse so he cuts away from the chuck. You would have to make sure which direction you wanted your spiral to run and adjust lathe set up accordingly . I think those grinder mop mounts are "handed" so the mop always tries to screw on in use.
 
There is more of this guys' antics on the thread on here called "A Great Machinist". I have learned a lot of great little tricks from him and a bunch of others like him in Indo, Vietnam and Pakistan. Necessity is the mother of invention over there where you can't just buy a solution to every problem.

Edited By Hopper on 22/02/2022 10:51:10

Tony Pratt 122/02/2022 11:04:26
1961 forum posts
12 photos

Yes worth a go, I would imagine scrap rate would be high.wink

Tony

Martin Kyte22/02/2022 11:28:24
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2751 forum posts
48 photos

Clockmakers have been cutting fusees for many years by removing the leadscrew from the cross slide, enguaging the screw cutting feed and applying pressure to the cross slide by hand in order to produce the groove for the clock line. I've done a few and have never produced a scrapper.

regards Martin

Baz22/02/2022 11:31:42
723 forum posts
2 photos

Made one a couple of weeks ago for my daughter, she has an Axminster polishing machine that takes 6 inch mops but they are held like grinding wheels with flanges and a nut. She wanted to be able to use smaller mops and so we decided she needed a pigtail. Axminster sell them but they are clamped on by grubscrews, I don’t like the idea if the shaft getting graunched up by the screws or one becoming loose and hitting her in the face so my version screws on the end of the spindle. I used taper turn attachment set at about 10 degrees and 12 tpi, the coarsest thread the lathe will cut. I used a screw cutting style tool but at about 40 degree angle, and for depth, cut it until it looks right. Took about an afternoon to do.

Hopper22/02/2022 11:41:04
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6392 forum posts
334 photos
Posted by Tony Pratt 1 on 22/02/2022 11:04:26:

Yes worth a go, I would imagine scrap rate would be high.wink

Tony

Yes, I imagine a few "practice" pieces would be in order.

I would say the trick is to start at the large end and screwcut toward the small end, as he does in the video. That way if you hesitate, the tool simply goes off into empty space and you can go back and start again, no worries. But trying to do it the other way, starting at the small end, would mean any hesitation on the cross slide would result in a major dig in of biblical proportions!

colin hamilton22/02/2022 11:57:41
140 forum posts
61 photos

This forum is awsome.

I was going to buy but my pedestal spindles are chunky so not sure if I could buy. Also I've spent shed loads on the machines so it seems odd not to spend more on materials than buying and having a go!!!

Sounds like manual control of depth on the course setting making use of a home ground tool is the way to go. What could possibly go wrong!!!

Cutting from thick to thin makes a lot of sensesmiley

Dave Wootton22/02/2022 12:02:40
304 forum posts
65 photos

I can remember at the firm I trained at there was a polishing and plating shop, the tapered ends for the polishing machines were re threaded regularly when they wore. I never tried it ,the job was left to one of the old hands, a superb craftsman, he rethreaded them by manipulating the cross slide with the leadscrew engaged, I'm sure that he did as Hopper suggests started at the large end.

The polishing machines were very scary , with something like 3hp motors,I used to sneak in and use them to polish bits of motorcycle until I managed to fire a primary chaincase across the shop as it was caught by the wheel. another telling off and banishment from the polishing shop!

Dave

Hopper22/02/2022 12:09:42
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6392 forum posts
334 photos

Haha. Dave I had to laugh. My Dad worked at the Chrysler factory so my first motorbike, an old WW2 Harley, ended up very well chromed thanks to the bumper plating shop. Later as an apprentice at the same place, I used to see those guys polishing bumpers and those were some scary antics. WHS would have a fit today. Let alone the open plating baths with acid and heavy metals discreetly run down the city drain on night shift.

Dave Wootton22/02/2022 13:45:48
304 forum posts
65 photos

Looking back I do wonder how we survived, letting 16 year old idiots loose on powerful barely guarded machinery, I don't remember many people wearing safety glasses unless grinding, and then not many. The plating shop resembled something out of a Hammer horror film, foul smelling vats of who knows what bubbling menacingly. As for the heat treatment shop I was told " careful with this it's cyanide, the antidote is up there but it's worse than the cyanide!" Basil the chap in charge used to sit near the tratment ovens to eat his sandwiches in the winter months. All this at a firm that boasted of being state of the art and at the forefront of Harold Wilsons white heat of technology.

Very handy for motorcycle mad teenagers though, I had a very shiny Triton, not sure how I survived that either.

Happy Days

Dave

Edited By Dave Wootton on 22/02/2022 13:46:10

Edited By Dave Wootton on 22/02/2022 13:48:15

Andrew Johnston22/02/2022 13:52:17
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6601 forum posts
701 photos

The OP really needs one of these...... teeth 2

....set up to screwcut RH 19tpi BSPT threads:

screwcutting_copy_unit.jpg

the resultant 3/8" BSPT blowdown plugs, and a couple of embryo fusible plugs:

blowdown_plugs_finished.jpg

Andrew

MikeK22/02/2022 14:15:03
226 forum posts
17 photos

Haven't done this, but if I had to do it I think I would try it by setting over the tailstock to cut the taper *and* the thread. Does that not work?

old mart22/02/2022 15:34:47
3771 forum posts
233 photos

Offsetting the tailstock might not be able to produce a steep enough taper, these adaptors are cheap as chips on ebay.

Pete Rimmer22/02/2022 15:47:00
1233 forum posts
65 photos

I don't use a tail for my buffing wheel. I just have a straight shank arbor that passes through the hole in the mop with a large washer either side. It runs nicely and doesn't vibrate as much as when I used the tail.

If you're only planning to use one mop most of the time it's an easy option.

larry phelan 122/02/2022 17:17:24
1180 forum posts
15 photos

Dave, your post brought back "Happy Memories" of being put to operating a pressbrake, with a "guard" which did not work at the tender age of 16.. This thing would suck you in and blow you out in bubbles, I wonder what the H&S shower would make of it these days !

We also had degreesing baths using something called Tricoetheleane [excuse the spelling, 50 years on ], this stuff would send you on a trip, no bother !

And yet, we are still around ! Who needs guards, ear defenders. facemasks ect ? These things are for wimps !

So what if you end up with being half deaf, half blind, with rotten lungs and minus a few fingers ?

Do you think the "Company" cared ? Did they hell !

Been there ,done that ect,ect.

Looking back, I ask, how did they ever get away with it ?

These days, it,s gone the other way, you can,t switch on a machine unless you have a "Cert"

Excuse me while I go and pour a strong drink, I need one !

noel shelley22/02/2022 17:45:42
1339 forum posts
21 photos

Drill and tapped one for a friend recently. I would not bother to try and make one, even though I have a taper turning attachment. At about £10 from the polishing shop I seem to think. It is vital that it is true to the axis of the machine it is being used on ! If you have a screw on chuck be careful running a lathe in reverse. Noel.

mechman4822/02/2022 17:53:23
avatar
2947 forum posts
468 photos

see ..

https://w**LINK**

Cheap enough for a set to convert your grinder.

George.

Sam Longley 122/02/2022 18:33:39
942 forum posts
34 photos

I know that this sounds like a bodge but would it be possible to do the following.

Turn a taper.

Wind a copper wire around the taper, using a very thin wire between to keep equal spacing.once a pitch has been established

Solder the wire in place

Using a tool like a wood turners scraper with a "V" point ground in it just run it along the resulting grooves to form Vs

Or perhaps do the same with a triangular file

The thread does not have to be particularly accurate to carry the pad & just needs some form of LH screw.

Would that work. Or is it a rubbish idea?

Edited By Sam Longley 1 on 22/02/2022 18:36:17

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