Barrel threading, how to do it?

[RobF]

Hi Rob,


Yes I guess you could use a lathe with a very short headstock (know you of such a beast?) ...but you would still need to support the unequal mass of a HW breechblock that would be sticking out the back of the headstock (I think this is what a lathe spider would be used for?) otherwise, as it is spinning, the centrifugal force would try to throw the breechblock out/away from the centreline of the lathe spindle with disastrous results.


A HW80 breechblock is roughly 35mm x 18mm in cross sectional area, with an approximate bias of 24mm towards the bottom edge of the block (the bit that houses the barrel plunger and the cocking link) so to keep the barrel turning true to the centre of rotation along it's entire length, you would need a lathe with a spindle bore diameter of at least 48mm to accommodate the breechblock inside the lathe spindle.


I hope that doesn't sound too much like gobbledygook?...but I suspect it does...

No that all makes sense. I just saw some short headstock lathes on a gun smithing page on Facebook so wondered.

[DCL_dave]

No that all makes sense. I just saw some short headstock lathes on a gun smithing page on Facebook so wondered.

I suspect such a lathe would be a very specialised and expensive bit of kit?

I don't do facebook, but if it can be viewed without having to log in?...any chance of a link, please?

[RobF]

I suspect such a lathe would be a very specialised and expensive bit of kit?

I don't do facebook, but if it can be viewed without having to log in?...any chance of a link, please?

I'll see if i can find them. The problem with Facebook is stuff gets buried and lost and is pretty hard to search. It's not really concerned with longevity.

[hmangphilly]

I suspect such a lathe would be a very specialised and expensive bit of kit?

I don't do facebook, but if it can be viewed without having to log in?...any chance of a link, please?

Dave
Google Grizzly gunsmith lathe

It's only a short headstock lathe with a built in spider at the back .

I haven't been stuck for much on a normal lathe . I just have to pretend I'm a proper engineer and use the noggin.

Like you said , all that breech block flapping around unsupported and off centre prob ain't good .

[DCL_dave]

I'll see if i can find them. The problem with Facebook is stuff gets buried and lost and is pretty hard to search. It's not really concerned with longevity.

Thanks Rob.

Dave
Google Grizzly gunsmith lathe

It's only a short headstock lathe with a built in spider at the back .

I haven't been stuck for much on a normal lathe . I just have to pretend I'm a proper engineer and use the noggin.

Like you said , all that breech block flapping around unsupported and off centre prob ain't good .

Thanks Phil, I shall go a looking

[RobF]

Thanks Rob.



Thanks Phil, I shall go a looking

I think that's what I found. I remember it having a bit of an American name and it was on a US site.

[Rich]

If you take it steady and slow then the out of balance forces won't be too serious. Anyway, it wouldn't be too difficult to mount a balance weight opposing the breech block, much as one might add a balance weight if turning a component fixed to the faceplate.

[DCL_dave]

If you take it steady and slow then the out of balance forces won't be too serious. Anyway, it wouldn't be too difficult to mount a balance weight opposing the breech block, much as one might add a balance weight if turning a component fixed to the faceplate.

Slow and steady is fine for screwcutting, but what about turning down to size and crowning, etc,? Btw, slow and steady is all my treadle lathe does!

How would you calculate the weight needed to counterbalance? (it's a bit like a pound of flesh type calculation, surely?)

3 jaw chuck and shims or 4 jaw chuck (which I don't have) is easiest, surely?...it holds the breechblock securely so that the offset mass of breechblock makes very little difference.

[johnbaz]

Could the barrel not be held between two centres and a faceplate with a dog to hold it- Weights can be added to the faceplate to make the balance right?


Like this but the centre in the dead end would be better if it was a ground type to allow access for the cutting tool..



One of these but with less material removed so that it fits the bore squarely..






John