Thread: Mounting and centering lathe chuck on rotary table

Hi,
I tried exactly that, making a plug that was MT2 on one end and a nice fit in my 125mm Fuerda chuck's bore on the other. It gets the chuck close but not exact. The good thing about the plug is that it can be knocked out of the taper and through the chuck so you can put long things into the RT's bore.

If i was to do it again i think i would cut a disk of steel out and turn it to fit over the outside of the RT and into the register in the back of the chuck. The bottom line is though since i am getting a lathe with a D1-4 nose i will probably make D1-4 noses for both my RT and DH. That way you can take a job straight from the lathe and not lose any concentricity.

Ew

Originally Posted by Ueee

Hi,
I tried exactly that, making a plug that was MT2 on one end and a nice fit in my 125mm Fuerda chuck's bore on the other. It gets the chuck close but not exact. The good thing about the plug is that it can be knocked out of the taper and through the chuck so you can put long things into the RT's bore.

If i was to do it again i think i would cut a disk of steel out and turn it to fit over the outside of the RT and into the register in the back of the chuck. The bottom line is though since i am getting a lathe with a D1-4 nose i will probably make D1-4 noses for both my RT and DH. That way you can take a job straight from the lathe and not lose any concentricity.

Ew

Ew, thanks for the note. I was thinking of making a once piece arbor, although I went the easy route and purchased an MT3 blank arbor and will bush it. I also have a D1-4 cam lock on the lathe and it certainly crossed my mind about the transferring from the lathe to the RT. Would be really nice to have, but too much work at this point.

With regards to the MT2 plug and Fuerda chuck, how much was it out by?

Have a look at this thread by Stuart,

https://www.woodworkforums.com/showth...t=rotary+table
This has got to be the best adapter project I have seen. Not sure if you planned on going to as much trouble /effort but worth a look if you truly want repeatable results with mounting your chuck on the RT

Simon

Two suggestions: Use a 4 jaw, so you don't have to be fussy about centering the chuck on the table because you centre the work in the chuck. Or mount the work in your 3 jaw then dial the work to the RT, so the chuck is again irrelevant. (Or is that what you meant you've been doing?) Sorry, I'm not answering your question.

If you do use the MT bore, I suggest a short stub instead of a full taper. Getting the fit right so it locates in the taper snugly without jamming and still allows the chuck to seat on the table is a challenge. Especially since you need to keep both features perfectly concentric. So you can't really remove the part from the lathe to test it. I went down this road and gave up. But I'm easily distracted and you may succeed where I failed.

Originally Posted by Bryan

Two suggestions: Use a 4 jaw, so you don't have to be fussy about centering the chuck on the table because you centre the work in the chuck. Or mount the work in your 3 jaw then dial the work to the RT, so the chuck is again irrelevant. (Or is that what you meant you've been doing?) Sorry, I'm not answering your question.

If you do use the MT bore, I suggest a short stub instead of a full taper. Getting the fit right so it locates in the taper snugly without jamming and still allows the chuck to seat on the table is a challenge. Especially since you need to keep both features perfectly concentric. So you can't really remove the part from the lathe to test it. I went down this road and gave up. But I'm easily distracted and you may succeed where I failed.

Bryan, I do not have a 4 jaw for the RT. I am using a 3 jaw. I chuck the work up, center off the work then tighten. Watch it get pulled off center as I tighten and rinse and repeat. I figure if I had an arbor that could get me close enough, it would suffice for most of what I am doing at the moment. Then I could do a quick once over with the DTI and confirm the work is out by 0.01 and be done with it.

As far as the arbor, I had watched a bunch of videos and had in my head how to cut the MT3 taper. I was going to set an existing MT3 arbor between centers, spin the compound, set the DTI and zero it all in. I ended up chickening out at the last minute and purchased a "soft" machinable MT3 arbor with a 1" x 1" head on it. Partly because I lack an MT5 dead center (assumed on its way from the US on a Pigeons back by the time it is taking) to do the centering. Whilst the MT3 arbor would be a good project, I am trying to get another project done, so I bit the bullet and purchased the arbor. I am thinking I will make either a brass or steel bush to fit the MT3 arbor plug and that may get me close. How close is the $50 question..

PS; Thanks Simon. I will check out Stuarts project in some detail. At first glace the engineering is a little more serious than a simple "close enough" plug.

Hi Variant,
could you extend the MT3 arbor up into the jaws of the 3 jaw chuck and nip the jaws onto the arbor then tighten the chuck to the rotary table.

Phil

Originally Posted by variant22

Bryan, I do not have a 4 jaw for the RT. I am using a 3 jaw. I chuck the work up, center off the work then tighten. Watch it get pulled off center as I tighten and rinse and repeat. I figure if I had an arbor that could get me close enough, it would suffice for most of what I am doing at the moment. Then I could do a quick once over with the DTI and confirm the work is out by 0.01 and be done with it.
<snip>
I am thinking I will make either a brass or steel bush to fit the MT3 arbor plug and that may get me close. How close is the $50 question..

I think .01mm is ambitious. If your spud is a nice fit in the bore of the chuck it should get you close enough for a 3 jaw. Like maybe .05. One way to establish the concentricity of the chuck bore would be to clamp a centre drilled bar in the chuck, then remove the chuck and mount the bar between centres with the back of the chuck facing out and clock the bore with a DTI. You can then true it if you want. Obviously everything you do is subject to the vagaries of scroll chucks. And I think it will still move when you tighten it on the table.

Disregard what I said about seating on the table. I remember now it wasn't a chuck I was trying to fit but something different. The concentricity part still applies but if you turn your adaptor between centres that should be ok.

PS: What Phil said.

Originally Posted by variant22

Bryan, I do not have a 4 jaw for the RT.

Buy one. What you are doing is stacking tolerances and that rarely leads to a good end.

I've got an 8" 4 jaw on my RT, no way I'd bother with a 3 jaw.

Ewan, I've got a genuine Emco D1-4 mount for a RT. I'm not interested in selling it but if you were wanting to make one I'd consider lending it to you for a while. Assuming I can remember where I put it.

PDW

Originally Posted by Steamwhisperer

Hi Variant,
could you extend the MT3 arbor up into the jaws of the 3 jaw chuck and nip the jaws onto the arbor then tighten the chuck to the rotary table.
Phil

Phil, thanks for the good idea. I will give this a try as I can see it giving me the true center more so than the chuck bore. I actually have an MT3 test bar on the way which would be perfect (straight section is 230mm long), except (and there always is one) I think it will be too long for the RT bore. I will not be cutting it up as it will be my center to center alignment bar. That said, if things go pear shaped with my bushing, I may get another test bar and cut it down.

Originally Posted by Bryan

I think .01mm is ambitious. If your spud is a nice fit in the bore of the chuck it should get you close enough for a 3 jaw. Like maybe .05. One way to establish the concentricity of the chuck bore would be to clamp a centre drilled bar in the chuck, then remove the chuck and mount the bar between centres with the back of the chuck facing out and clock the bore with a DTI. You can then true it if you want. Obviously everything you do is subject to the vagaries of scroll chucks. And I think it will still move when you tighten it on the table.
PS: What Phil said.

Interesting suggestion about removing the chuck with test bar in situ to test the concentricity. It may however be going to far given it is a 3 jaw and will possibly clamp differently the second time I insert the test bar.

I am hoping Ew will chime back in with the run out using his plug. 0.5 might be a bit hard to swallow..

Originally Posted by PDW

Buy one. What you are doing is stacking tolerances and that rarely leads to a good end.
PDW

Peter, I would consider purchasing one if I could find a source. I have not found one that will fit a Fuerda chuck to a Vertex HV-8 RT. The test bar might well be the best "purchasable" option.

Originally Posted by variant22

0.5 might be a bit hard to swallow..

I should think so. I said .05mm - coupla thou.

I have not found one that will fit a Fuerda chuck to a Vertex HV-8 RT.

No you will need an adaptor plate. If you go that way I can show you the one I made for my Fuerda 6" 4 jaw / HV8.

Originally Posted by variant22

Peter, I would consider purchasing one if I could find a source. I have not found one that will fit a Fuerda chuck to a Vertex HV-8 RT. The test bar might well be the best "purchasable" option.

You're not going to find a mount - you have to make one. It's an easy turning job. Mine is made out of 12mm aluminium plate. With a 4 jaw there's no need for great precision as you set up the workpiece and there's no way a RT is going to be spun fast enough to have to worry about imbalance.

I have a plain back P-B 8" 4 jaw chuck mounted on a 10" RT. With a 8" RT I think a 6" is the simplest to mount as this allows you the rim of an 8" disk to bolt to the RT, the chuck bolts to the disk. You can make a plate for an 8" chuck, just need to countersink the screws holding the plate to the RT.

As I said, dead easy job. Only took me 3 years to finish mine but - I didn't really need it until I NEEDED it.

PDW