Lathe chucking pistol barrel

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Leakingaz

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How can i chuck a non-tapered pistol barrel in a 4 jaw lathe chuck without marking the bluing or the barrel. I will be rechambering and the jaws will be fairly tight to maintain my index without moving?
thanks
mike
 
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Option 1 - Machine out some soft jaws to match the barrel contour.

Option 2 - Wrap the barrel to an equal thickness in something like one layer of thin shim stock and make sure you have as little runout as possible with a dial indicator (indicate the interior of the bore, of course). If you can find or make thin lead foil or sheet it'd be great for this.

Option 3 - Toolpost grind your hard jaws to exactly match the barrel's contour, and hope there's no slippage once clamped. Membership in a powerful church may aid this endeavour.

Option 4 - Wrap the barrel to a roughly equal thickness in something like heavy canvas, and hope the runout doesn't increase as you rechamber. Light cutting will be key here.

I'm sure there are other options, but it all depends on how much potential inaccuracy you're willing to accept re: bore alignment and runout.

-M
 
Also, if it's not tapered and you have perfectly trued hard jaws without burrs on them, you may get away without marking by just straight-up clamping the work and using discretion re: force.

-M
 
Some tough Leather works good.
Brass shims are also a good material
Paper and tape will tear and mar if it slips.

misread it.
 
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The mention from Sunray about a collet chuck must have woken up some part of my brain since it is common practice to chuck thin walled material in homemade collets.

Get a piece of non-ferrous barstock (brass, aluminum...) and make a collet from it. Turn down the o.d., chuck that in the 4 jaw (indicated) and bore to exact o.d. of the barrel. Hacksaw your compression cut and re-insert into the 4 jaw. Insert barrel and indicate. Lock her down and reindicate. I guarantee that you will get no slippage between the collet and barrel and no subsequent chuck rash as well as no crushed parts IF you make the collet thick enough. Wall thickness should be about .5" or 12.7mm.

Ripstop said:
Hacksaw your compression cut.
Click to expand...

You will have to make considerations for the front sight in the compression cut or you can cut the collet in two and assemble (and indicate) everything together while putting it in the chuck. What is very important is that you bore the collet to the diameter of your barrel. Too far out either way and it will not grip properly.

Good luck with your project.
 
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Um.... maybe I'm missing something here but why don't you avoid pissing around and the chance of f#cking up your bbl, clamp and cut the thing (I would put on a 3 jaw chuck if you can) and then just re-blue it after.....? I would think that would be a lot easier than screwing around with pads and runout.
 
Soft Jaws !!

Just use some alum soft jaws or some made of free machining steel , bore them out to the size you need , Deburr them well and you should not have a problem , I would shy away from the 4 jaw , a good three jaw will suffice , we use the same method to machine the i'd of small aircraft parts that have been anodized and or black oxided on the o/d and it does not mark them
** JUST BE SURE THE JAWS ARE FREE OF ANY BURRS **
:sniper:
 
Acceptable and extremely common in industry. Most smaller home lathes do not come with base jaws and interchangeable top jaws though. I wish mine did. The lathe I ran at work had three sets of hard jaws and sixty+ sets of soft jaws.
 
I am not a machinist but I thought the reason for using a four jaw chuck in an operation like this ( over a three jaw) was becase you need to get the bore aligned with the centerline of the lathe. Seems to me that with a three jaw chuck you are relying on the OD of the barrel to be concentric with the bore, with a four jaw you can make up for any mis alignment and have the bore perfectly centred by using a dial indicator and adjusting the chuck to minimize runout
 
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