Buying a 4 jaw chuck

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TheSandman
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Buying a 4 jaw chuck

Post by TheSandman »

I'm trying to get set up for doing barrel chambering. I'm looking at chucks and they are listed at .003 runout. Isn't the runout zeroed during setup? Thanks
SteveM
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Re: Buying a 4 jaw chuck

Post by SteveM »

That could be the runout due to the chuck not being straight (wobble vs eccentric).

You should look into soft jaws. You bore them to the size needed. They will be on size and parallel to the bore every time. The also provide more gripping surface.

I bore them, chuck up the part and the needle on a tenths indicator barely moves.

Find a chuck on ebay that takes two piece jaws but is missing the top jaws. Hard top jaws cost a bloody fortune, so the demand for such chucks is low and the price is too (I got mine for $65).

You can get cheap steel and aluminum soft jaws from US Shop Tools.

If this is something you are going to use a lot, get a jaw holding fixture that holds them while boring, like this:
Image

Shameless plug: I have one of the best ones for sale. It fits an 8" to 13" chuck.
You can see it here:
https://www.chaski.org/homemachinist/vi ... 8&t=109814

What size chuck are you using?

Steve
TheSandman
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Re: Buying a 4 jaw chuck

Post by TheSandman »

Thanks SteveM, I'm looking for a six inch 2 1/4x8 tpi
SteveM
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Re: Buying a 4 jaw chuck

Post by SteveM »

TheSandman wrote: Wed Sep 30, 2020 11:43 am Thanks SteveM, I'm looking for a six inch 2 1/4x8 tpi
Also consider flat back chucks as you can get a backplate.

Keep your eyes out for backplates and pick them up when you can, especially for an odd thread. That way when a chuck comes along you can grab it knowing you already have the backplate.

Steve
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Harold_V
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Re: Buying a 4 jaw chuck

Post by Harold_V »

TheSandman wrote: Wed Sep 30, 2020 9:11 am I'm trying to get set up for doing barrel chambering. I'm looking at chucks and they are listed at .003 runout. Isn't the runout zeroed during setup?
To be clear, unless a universal chuck (the typical three jaw) is an adjustable type, no, they are not zeroed during setup, and, for the most part, they are not capable. As has been stated, an adjustable type is an exception, as is a four jaw independent chuck.

Even well built three jaw scroll (universal) chucks are subject to runout, which generally varies according to the opening required of the jaws. That's due to the minor error in the scroll bore and the helix machined on the face of the scroll, which is keyed to the chuck jaws. Any variation in concentricity or in the helix translates in to error in runout.

Soft jaws are the magic bullet of holding for lathe work. They may or may not be the solution for gripping a barrel, however. If the barrel is not dead round, or if the bore is not dead concentric with the exterior, it may not be an acceptable method for gripping a barrel. In such a case, assuming one is adept at centering properly, an independent chuck (four jaw) would be a better choice.

H
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GlennW
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Re: Buying a 4 jaw chuck

Post by GlennW »

It's a bit confusing, as your title states a four jaw chuck, but them you quote runout specs.

Are you looking at four jaw scroll chucks?

You should be looking for a four jaw independent chuck for chambering use, not a scroll chuck.

Pistol or rifle barrel?
Glenn

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TheSandman
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Re: Buying a 4 jaw chuck

Post by TheSandman »

Yes it is a 4 jaw independent. TIRO is listed as .003, it must be off ctr of spindle. I have a three jaw and it doesn't tighten up on 1" steel rod. Lathe is 70 years old. Chuck might be too. I'm learning alot reading this forum. I really appreciate how generous you-all are with your knowledge. Thanks
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BadDog
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Re: Buying a 4 jaw chuck

Post by BadDog »

When a chuck is too large to grip the work piece, you can make a split bushing to adapt. I've used an aluminum drop a few inches long, face and drill/bore to provide slip fit, mark Jaw 1 and orientation so you can put it back the same way, use bandsaw (etc) to make a slit down one side opposite jaw 1 (just between 2 jaws really), and place back in chuk oriented the same way. Insert workpiece in bushing and tighten. It's not going to be perfectly zeroed, but if carefully done, likely to be closer than a non-adjustable 3 could manage gripping directly. My work isn't usually terribly runout sensitive, but I've done this a few times with good results when I didn't want to be going back and forth between heavy chucks.
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10KPete
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Re: Buying a 4 jaw chuck

Post by 10KPete »

Having done a bunch of barrels in the last 30 years, and being associated with some really good 'smiths, I can say with certainty that a 4 jaw independent chuck is the only way to go. I use a 4 jaw more than a 3 jaw for most everything. The 3 jaw is used when I'm doing parts where the concentricity doen't need to be better than the 2 or 3 thou I get from either of my 3 jaw chucks. It only takes a few extra seconds to dial in a part in the 4 jaw when you are practiced with it.

You say your 4 jaw chuck runs our about 3 thou.. If you are measuring the body of the chuck you are wasting your time. Unless it's so far out it causes vibrations when running ( in which case send it back! ) just ignore the runout of the body.

Pete
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pete
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Re: Buying a 4 jaw chuck

Post by pete »

Reading between the lines, this is a new chuck your looking at from a dealer? A 4 jaw independent that's listed as having .003" run out? Do you have a link to what your looking at because as Glenn said something just isn't making sense with that specification. So it's either some kind of typo or it's not an independent chuck at all.
TheSandman
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Re: Buying a 4 jaw chuck

Post by TheSandman »

I just looked at some others(on ebay) and they are measuring at outside and face, both of which mean very little. All the ones I've looked at are cheap Chinese on ebay
pete
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Re: Buying a 4 jaw chuck

Post by pete »

Well as 10KPete mentioned the chucks O.D. run out unless it's bad enough to start causing vibration issues means little. However the chucks face run out is very important. It's a datum or reference surface for some work where your using it to help seat work square to the lathe ways. The work piece would still be cut true to those ways, but any wobble on the chuck face if it's used as that reference surface would result in a non perpendicular work piece face to it's length.

While your initial thought about indicating out any work piece run out is normal with any 4 jaw independent is correct, there's also a few more surfaces on these types of chucks that are highly important as well. The jaw slots in the chuck body need to be properly square to that chuck face and ideally they very closely fit the chucks jaw width so precision ground surfaces aren't optional. And having the jaw tips square to the lathe ways is also important. Although those could be re-trued once the chucks mounted to the lathe spindle. But it makes sense the factory would be using the chucks ground face as there reference when finish grinding those jaw slots after heat treatment. If that chuck face is poorly done then it can create further misalignment's as the rest of the chuck is being ground. For myself I'd be real leery about buying any 4 jaw that had allowable run outs of up to .003" on the chuck face.
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