Could I have done this more efficiently…

[Robin GrahamParticipant @robingraham42208]

I had a request to perform minor surgery on this piece:

It's an insert for woodworking lathe chuck which adapts the M38 internal thread of the chuck to the M33 external thread of the spindle. The problem was that the 30mm diameter parallel part at the top of the pic needed to be bored out to 32mm to fit the register on the spindle nose. Simple enough eh?

But you've got b****er all to hold onto – just the parallel part on the right which mates with the chuck:

 

The best I could think of was to make a 30mm 'plug' to fit into the existing bore and index off the stub:

 

I glued that in place with shellac, then mounted in the 4-jaw on the parallel bit on the left, and after much rubber-malleting, key twisting and cursing got the thing aligned radially and axially to something better than a thou.

It seems to have worked, but I have have a nagging feeling that I might have made heavy weather of the job.

I'd be interested to hear how others would have approached it.

Robin

 

 

 

 

 

Edited By Robin Graham on 18/02/2021 00:00:56

Edited By Robin Graham on 18/02/2021 00:15:47

[Robin GrahamParticipant @robingraham42208]

[Grindstone CowboyParticipant @grindstonecowboy]

I'd have gone for making a threaded hole in a lump of something that the adaptor could be screwed into and then the whole thing could be clocked in a 4 jaw chuck. But there's probably a better way

Rob

Edit – looking at your second pic, I'm starting to think I've misunderstood what you are trying to do as I can't see how your setup helps at all as it's covering the part I thought you wanted to bore out?

Edited By Grindstone Cowboy on 18/02/2021 00:53:37

[Paul LousickParticipant @paullousick59116]

It is for woodwork and does not have to be as accurate as for metal but an option is to screw the insert into the woodwork chuck.

Then clamp a piece of round bar in its jaws and then use the round bar to mount everything in your metalwork lathe by the round bar. Everything then should be axially aligned.

I do a similar operation when I have to add a threaded hole in the end of a BSP plug to turn it into a reducing bush by screwing it into a pipe socket, held in the lathe chuck.

Paul.

PS. After looking at the photos again, I am a bit confused (easy to do at my age).

The top photo shows an internal thread of M33 and the 30mm dia register that has to be bored out to 32mm but the last photo has the plug fitted to this end. How did you bore out the hole. Was the plug removed first ??

 

Edited By Paul Lousick on 18/02/2021 01:11:43

[Grindstone CowboyParticipant @grindstonecowboy]

+1 for Paul's method – removes the need to make my threaded lump.

Rob

[Ian ParkinParticipant @ianparkin39383]

Surely you cant have a register smaller than 33mm?

[HopperParticipant @hopper]

Yes you could have done it more efficiently by holding the piece by the threaded section in the three jaw chuck with some shim of suitable thickness wrapped around it to protect the thread. Or a bit more fancy and turn a sleeve in the lathe to fit the OD of the threaded section, then mark the sleeve so you know which part goes next to which jaw, remove from chuck, slit lengthways with a hacksaw then put back in the chuck to hold the job.

Would it have been as accurate as the way you did it? Probably. Holding by that small turned section on the end is begging for it to move during machining. Sleeve as above would hold it solid.

[Ian ParkinParticipant @ianparkin39383]

Just because its for a woodwork machine does not negate the need for accuracy ..i make chuck adapters for woodworking lathes..a couple of woodturning supply shops keep me busy in between the day job…and if i send an adapter out that isn’t true to a thou the buyer complains

remember that woodlathes spin at 2-3000 rpm with spindle Work…and people want to machine parts in the chuck then turn it around and run true.

Robin i imagine that your insert is m30 x 3.5mm rather than m33 if your register was 30mm

[JasonBModerator @jasonb]

For those confused about the plug I suspect the use of Shellac was so that it could be easily removed once it had been used to clock the part thus allowing the boring to take place.

[old martParticipant @oldmart]

I think your method was very good and to a high standard. There are usually several ways to do any job, depending on what tools and materials are to hand at the time.

[Robin GrahamParticipant @robingraham42208]

Thanks for replies, and apologies for not being clear about the 'plug'. Jason's suspicion about the shellac was spot on – I glued the plug in so I could mount the work in a tailstock collet, offer it up to the 4-jaw to get somewhere near, take away the tailstock to index off the plug, then remove the plug and bore. As I am perhaps going to do now.

I'm slightly pleased with myself because I had considered almost all the solutions proffered – usually when I post my problems I get replies which make me think doh, I'd be better off taking up knitting as a hobby. Maybe I'm slowly getting better at this game!

What I didn't think of until too late was that I could have asked the chap to give me the chuck as well as the insert, then I could have bunged his chuck in the 4-jaw, indexed off the chuck body, screwed in the insert and bored – that would guarantee concentricity – essentially the same as Paul's method.

A difficulty for me was that I wasn't sure where to take a reference from. I had thought about Hopper's approach but I've not had much luck in the past using screw threads as a reference for this sort of work, so (perhaps wrongly) rejected the idea. I ended up thinking that if I made the new bore parallel and concentric with with the old I could hardly be criticised. Hence my method.

Ian – you are quite right. The insert is a Nova IQNS or Sorby equivalent, M30 internal thread – I mistyped. The difficulty was that it had to fit to the the nose of an Arundel J4 Senior lathe which has a 32mm register. I think that's unusual.

I bored out to to 32.02 – fitted like a glove, client satisfied. I think I got away with it!!

Robin.

 

 

 

Edited By Robin Graham on 19/02/2021 01:09:45

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