Tool & Cutter grinder options…

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

An ordinary lathe plus toolpost grinder and a few simple DIY bits and pieces will perform all the normal tasks of a T&C grinder perfectly well .

Tearable paper covering over slides is quite adequate protection against dust .

MikeW

[Chris HeapyParticipant @chrisheapy71135]

The diamond cup wheel turned up this morning so I was able to finish this job and try it out. Are these diamond wheels – the aluminium mounting part – supposed to be finish-turned by the user? I first noted the bore was not even circular so I chuck it up in the lathe (by the inside using external jaws) only to find hardly anything was concentric – the rear face, the external surface, as well as the bore. Anyway, I sorted all that out and made a couple of flanges and it now runs as it is supposed to do.

I made a small T-slot table to mount the tool holder on:

And here's my first try at sharpening something with it (a boring tool – and the shield has been swung back for the photo):

It works as expected. Next I'll get on with working my way through a box of blunt endmills. I may be some time

[Mark P.Participant @markp]

Does anyone have any gen on this?

Mark P.

[Chris HeapyParticipant @chrisheapy71135]

What do you want to know? It is a cheap Chinese copy of a design that has been around for years. Yuasa make one (better quality) but the best type of this device uses air bearings. I have not seen an example of the Chinese version, maybe if someone on here has one they can pass comment on how it performs.

[Chris HeapyParticipant @chrisheapy71135]

I was about to start on connecting a vaccum hose up to the cover on this grinding head, then I thought – what if it sucks sparks into the cleaner? Suddenly it didn't sound like such a great idea. Whilst trying the grinder out on a carbide boring tool and also a piece of round HSS I have to admit there weren't many sparks, but there were some. Any comments?

[Ian PParticipant @ianp]

I doubt the sparks will still be sparks once they get drawn past the mouth of the nozzle.

Whilst each glowing particle might be at quite a high temperature it does not contain much total energy so as long as the nozzle is not made of tissue paper or highly flamable plastic you should be OK.

Ian P

[Neil GreenawayParticipant @neilgreenaway71611]

How about passing the vacuum extract through a cyclone to eject any sparks into a separate containerinstead of a vacuum cleaner that could contain other combustable workshop dusts?

Neil

[Chris HeapyParticipant @chrisheapy71135]

Yes that is the worry – my 'shop cleaner ends up with all sorts of potentially inflammable rubbish inside. I don't want to walk away from it and have it slowly smouldering inside!

Neil: yes, perhaps a separate container (like a 3ltr milk carton) would work. The hose from the grinder could reach into the bottom of the carton, the outlet for the hose to the vacuum near the top.

[Chris HeapyParticipant @chrisheapy71135]

I found another use for this grinding setup – a poor man's surface grinder

To digress: I bought an old Griptru chuck – something of a mistake because when I tested the chuck the inside jaws were completely useless. The outside jaws (and therefore the rest of the chuck) appear to be fine and hold true, but the inside jaws were so worn they weren't even gripping at the tips and you could see daylight at the ends

OK, accepting the jaws were toast (I will have to look out for a replacement set) I set about trying to figure a way of re-grinding them, and my thoughts turned to the diamond cupwheel mounted on the mill. I checked the squareness of the wheel off against the mill table and as far as I could tell it was nicely orthogonal – although it's difficult to be certain because the face of the diamond wheel is not a smooth machined surface. Nevertheless an 8" square placed against the front edge revealed no errors. Good enough for an experiment then.

I clamped the 3 jaws together and used a parallel to hold them in line, and two clamps to hold the lot down onto the mill table. The 8" square was used again to align them all with the rear edge of the table and overhanging a little.

I could only comfortably take 1/2 thou off each pass – the cup wheels are a bit fragile and I didn't want to break it. Grinding continued until the front of the jaws all looked the same, but by then I realised something wasn't right…

I expected more material to be taken off the bottom edge of the jaws than the top (in the photo above) simply because it was clear that is the way they had worn. However, with grinding complete I expected to see a nice even ground surface but what I got was a definite taper. Oops. It was as if the base (the teeth) of the jaws were not square to the front gripping surfaces. Not what I expected at all. I now realise what I should have done was mount the jaws upside-down onto the parallel because that surface definitely would be square with the inner gripping edge. So I'll have to do it all again.

I've lost nothing though because those jaws really were useless as they stood. I don't know if the jaws are hardened right through or a deep case, if the latter I may well run out of hard steel in the grinding process.

Chris

[Clive HartlandParticipant @clivehartland94829]

I have noticed the gripping face of the jaws of my chuck are hollow ground and I believe the method is to clamp a ring and using a small dia. stone travel through the clamped jaws.

Any other methods known? I feel that a flat surface on the gripping part of the jaws is not right.

Clive

[Chris HeapyParticipant @chrisheapy71135]

Posted by Clive Hartland on 06/06/2013 07:43:21:

I have noticed the gripping face of the jaws of my chuck are hollow ground and I believe the method is to clamp a ring and using a small dia. stone travel through the clamped jaws.

Any other methods known? I feel that a flat surface on the gripping part of the jaws is not right.

Clive

I've tried those methods before without success – used a 1/2" diamond lap from the tailstock, and used a die grinder held in the toolpost. The problem I found is that you cannot tension the jaws in their normal gripping configuration AND grind them at the same time. The hollow-ground effect I think is just a by-product of the manufacturing process rather than a required feature. To be honest my feeling is that attempting to re-grind jaws is probably a waste of time because if you have wear in the gripping surfaces I suspect there is also wear in the side slots – which you can't compensate for. Still, it's an interesting exercise.

Chris

Edited By Chris Heapy on 06/06/2013 08:23:55

[Ian PParticipant @ianp]

Posted by Clive Hartland on 06/06/2013 07:43:21:

I have noticed the gripping face of the jaws of my chuck are hollow ground and I believe the method is to clamp a ring and using a small dia. stone travel through the clamped jaws.

Any other methods known? I feel that a flat surface on the gripping part of the jaws is not right.

Clive

A concave surface is a by-product of the internal grinding purpose. Generally it does not cause any problems but as it can only be the correct curvature at one jaw position I see no reason not to have the gripping face flat, or even convex.

Use a dial indicator, a bright light, a suitable ground test bar, and a hand held diamond file. Inspect the grip of each jaw against the light, mark with felt tip pen, remove jaw and stone the edge to suit. As a concave gripping edge is not ideal for letting the light pass I aim for a narrow flat. Once any gross errors or bellmouthing are corrected use the dial indicator to see which jaw/s need tweaking.

I have contemplated using the standard internal toolpost grinding technique but always shy off after trying to work out how to 'tension' the jaws whilst having the whole edge to grind.

Ian P

[Chris HeapyParticipant @chrisheapy71135]

Posted by Ian Phillips on 06/06/2013 09:01:50:

… I have contemplated using the standard internal toolpost grinding technique but always shy off after trying to work out how to 'tension' the jaws whilst having the whole edge to grind.

Ian P

The closest I got was to use a small copper coin placed against the first tooth of the jaws (i.e., not the gripping surface but just beyond it) and lightly tighten the jaws onto that. This configuration leaves the whole length free for grinding. Unfortunately, although it tensions the jaws correctly, with it being right at the back of the jaws it also causes the jaws to take up all clearances in one direction only – an unnatural bias, and if the slots are slightly worn you still end up with a slight bell-mouth.

Chris

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Clive ,

From an earlier posting :

Grinding out the jaws of any self centering chuck while the jaws are loose will give uncertain results at best since the jaws are not loaded and the clearances not biased in the same way as when gripping a workpiece .

Any self centering chuck can have jaws corrected simply by putting a round aluminium bar lap in the tailstock , covering it with grinding paste and working it back and forth through chuck jaws . Jaws are gently and progressively closed down onto the lap as work proceeds . All loads and clearances of jaws during lapping process are the same as when gripping so maximum accuracy is achieved .

For best results turn down most of the aluminium bar slightly leaving just about one inch long as the actual lap and in the final stages of lapping run the lap almost completely out of the jaws at both ends of stroke .

Takes about twenty minutes .

Michael Williams .

[Ian PParticipant @ianp]

Maybe its time for a re-think on chuck design?

If the scroll thread was trapezoidal instead of being square, the jaw would be driven away from the chuck body when it was tightened and take up any slop on the slots.

It might work.

Ian P

[Chris HeapyParticipant @chrisheapy71135]

A rather poor attempt to capture video of the grinding operation!

[Ian PParticipant @ianp]

Chris

The video is clear enough to show what you are doing OK, but grinding the jaws by referencing off the OD of the jaw is, as you discovered, not likely to be particularly accurate.

I suppose if you gripped a bar normally, then used a toolpost grinder to take off the very (OD) tips off the jaws you would create reference points that would relate to each particular jaw. Then you method might work.

Ian P

[BubbleParticipant @bubble]

Hello all

You need one of these to load the jaws in the proper direction against the scroll.

I used a stone just a little smaller in diameter than the jaw gripping diameter

Can't remember what I used as the grinding spindle, could have been the

spindle from my Taylor Hobson engraver and a lash-up drive.

I think the original idea was from "Duplex" in ME.

Jim

[Chris HeapyParticipant @chrisheapy71135]

Jim – great idea, I hadn't thought of that one

Ian, the reference point(s) were the first step not the tips of the jaws, those must surely be concentric otherwise these outside jaws couldn't work at all.

Chris

[Ian PParticipant @ianp]

Posted by Chris Heapy on 06/06/2013 14:48:32:

Jim – great idea, I hadn't thought of that one

Ian, the reference point(s) were the first step not the tips of the jaws, those must surely be concentric otherwise these outside jaws couldn't work at all.

Chris

Chris

Yes I saw they were referenced on the step, what I was suggesting was to tickle up the step to create new references with the jaws tensioned.

Ian P

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