# (Newbie) Holding 7" diameter stock in a 1030V? Possible?



## PrettyHateMachining (Dec 11, 2017)

So I have a need to turn some 7" diameter 8620 in my PM-1030V. Obviously this is significantly too large for the supplied 3 and 4 jaw chucks.

The workpiece is just a small sliver, 5/8"-3/4" thick. I'm pretty sure the lathe will be just fine but I need to hold the part and face off the ends so I need full access to both sides. I don't care about turning the outside diameter, it should be fine as-is.

I was thinking of using the factory-supplied faceplate and drilling/tapping 4 holes in the stock and bolting it to the faceplate, then reversing it so I can face off the other side. Advisable? How do you center the piece on the faceplate though, just lots of trial-and-error? Does it even matter that much if I'm only facing off the ends?

Alternatively, I was thinking a 6" 4jaw might be able to grab it on the outside diameter with outside jaws. But I don't see any way of getting a 6" chuck on this machine, has anyone done it and would it be worthwhile for this endeavor? I'm assuming trying to use outside jaws on a 5" chuck for 7" material would be...ill-advised? Maybe, maybe not?

Any other options that I'm not thinking of?

TIA!


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## JimDawson (Dec 11, 2017)

Bolting the workpiece to the faceplate sounds like your best alternative, but it might be a bit tricky to face around the bolts.    You could use countersunk cap screws and countersink them over deep so you can cut right over the top of them.  Centering is done just like on the 4 jaw, except you are using a soft hammer to tap the workpiece into position after you snug up the screws a bit.

You might see how well the workpiece would fit in your 5 inch 4-jaw.  You might have enough thread engagement left on the adjusting screws to be safe if you're careful.  You would also have to be sure that the chuck jaws are not going to hit the ways when they are over extended like that.


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## PrettyHateMachining (Dec 11, 2017)

JimDawson said:


> Bolting the workpiece to the faceplate sounds like your best alternative, but it might be a bit tricky to face around the bolts.    You could use countersunk cap screws and countersink them over deep so you can cut right over the top of them.  Centering is done just like on the 4 jaw, except you are using a soft hammer to tap the workpiece into position after you snug up the screws a bit.
> 
> You might see how well the workpiece would fit in your 5 inch 4-jaw.  You might have enough thread engagement left on the adjusting screws to be safe if you're careful.  You would also have to be sure that the chuck jaws are not going to hit the ways when they are over extended like that.



Thanks for your reply. I had planned on doing your idea (countersunk bolts about 1/8" under the surface) or I was going to drill the holes through the workpiece, tap them, and then bolt from the backside of the faceplate (bolt heads on the backside) and cut off the protruding bolts flush (or just beneath) the surface to be faced. The holes don't matter, this piece will get plug-welded to something else so it actually NEEDS holes drilled in it eventually. I guess one way requires a countersink and one way requires some tapping so they're both extra work.

As far as using the 5" 4jaw, I was considering that but I really have no reference as far as what is acceptable - how far out I can get the jaws safely. There will be basically no workpiece sticking out of the jaws (maybe 1/8" of it will so I can face it off easily) so I doubt clamping pressure has to be crazy. I guess I was worried about possibly damaging the chuck by having such little thread engagement? Is there a rule of thumb here? I've literally never even used my 4jaw, that's how newbie I am so I don't know what the guidelines are for what can fit in it and what can't.


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## JimDawson (Dec 11, 2017)

PrettyHateMachining said:


> I guess I was worried about possibly damaging the chuck by having such little thread engagement?



That is a good concern.  If you don't get crazy with tightening, 3 or more threads should be OK, it really depends on how snug the jaws fit in the chuck.  If they are pretty tight you can get away with a bit less thread engagement.  If they are sloppy then more engagement would be better.  I can't advise you on an absolute limit, but just excersize due caution.


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## Dabbler (Dec 11, 2017)

+1 on 3 threads.  Use very light cuts.


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## markba633csi (Dec 11, 2017)

You could get by on 2 threads but you are really out on a limb when you do that. But I've done it and lived to tell the tale.
Ever seen chuck jaws with broken threads? That's how it happens when you tighten too much. 
Mark


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## PrettyHateMachining (Dec 11, 2017)

I grabbed the 5" 4jaw and tried it out - no go. I can't even get it to grip the 7" stock with ANY threads at all. It grips 6" stock with 5-6 threads engaged so that will be fine, guess it's the faceplate for the 7" unless anyone has an idea about mounting a 6" 4jaw to this 1030V? I know you can get the backing plates from PM but I'd have no idea how to get it to mate to a 6" 4jaw. Unless anyone wants to hold my hand (I don't have a mill).


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## markba633csi (Dec 11, 2017)

I'd go with the faceplate method, using tapped holes like you had mentioned.  It'll work fine.
Mark


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## woodchucker (Dec 11, 2017)

you could always turn between centers. Do you have a half dead center? Use a center finding square to find the center, drill it, load it, and friction turn it, or make a dog out of some scrap metal and set a bolt in your dog plate.

You could also mount a plug to the back of the piece using a centered tapped hole. And one offset. That way you could grab it in the jaws. You would only need to worry about the center to align it.  But then you would need a steady rest to hold the free end.


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## Larry42 (Jan 18, 2018)

That is a perfect job for your face plate. I'd be inclined to drill & tap and bolt through from the back side. You can shim it between the work and face plate if the work is pretty crooked. Find the center with any means you have. Drill a small hole to use your live center in and push the work against the face plate. Mark, drill/tap, attach.


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