Thread used on British Browning .303 jacket.

[Brit plumber]

Hi Chaps, I’m after some help identifying a thread on a barrel jacket from the Browning 303 Mk2. The thread appears to be that of a 32 tpi 55 deg Whitworth thread 5/32 bolt but the jacket is 1.562” in diameter. Would anyone have an idea? Perhaps carried over from the American ANM2 .30 cal?

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[Peter Laidler]

I would imagine that the thread would simply be a thread on a diameter BP. In this case, exactly as you say, a 55 degree (but I suspect it'll be 60 degree somehow...) 32TPI thread on the 1.56 dia.

If it was me I'd machine the thread onto a bar of mild steel and see how you go.

[Patrick Chadwick]

The 1.562" is a very odd diameter. But less odd if you think 1"17/32, which is 1.5625".
And 32 tpi threading gear? I have quite a bit. Admittedly not in that diameter, but 32 tpi Whitworth-form thread on various diameters is common enough for engineering piping applications that it does not surprise me. Just get yourself a Coventry die-head and the cutter inserts, and away you go!

[Brit plumber]

Thanks Peter, a 60 deg Metric thread pitch fits too but I assumed being vintage British that it was more likely Whitworth. And you know what they say about assumption.... I also need to learn how to cut threads on the lathe rather than using a die on the lathe and turning the chuck by hand (I have been watching Utube vids to get the idea)

Thanks for the reply too Patrick, I think 1.562" is 1 and 9/16 though. I'm assuming (again) that the diameter of the jacket originates from the US Colt ANM2 .30 that the .303 was based on, I can't be sure though as I don't know anyone who has one.

I can see me taking my part finished replacement to a more competent engineer than myself. At least I can take it and not sound a complete idiot when I ask them to cut a thread on it.

Thanks, Chaps.

[Patrick Chadwick]

Thanks for the reply too Patrick, I think 1.562" is 1 and 9/16 though.

Oops ! You're right

[Peter Laidler]

You shuld be able to cut that thread on a little Myford BP. Is yours a lever change gearbox or old cog-change gearbox? Either way, once you have done the simple maths/ratios it should be a simple matter. Just practice on a few offcuts from the fitter/turners shop. Especially easy if you are cutting an external thread

[bigduke6]

I also need to learn how to cut threads on the lathe rather than using a die on the lathe and turning the chuck by hand (I have been watching Utube vids to get the idea)

BP, I can give you a few pointers regarding threading on a lathe, one thing you need is the gauge below, cheap as chips and saves a lot of tears, used mainly for lining up the tool so its square to the job.

[Peter Laidler]

I've got a good idea BP and Big Duke......... Next time you're up in that neck of the woods BP, you both come from/live in that part of the world, maybe you could join forces with Big Boy for a few hours on his machine and just run through a few valuable pointers.

[Brit plumber]

Thanks guys, I may just have to have a go at this my self, the youtube vids make it look harder than I think it actually is. I have the kit, I just need to make sure that I can get the tube in the lathe bed. As its a slight cone, I don't think it will go in the chuck unless someone has another idea.

Big Duke, am I right in thinking your up Carlisle way?

[Patrick Chadwick]

As its a slight cone, I don't think it will go in the chuck unless someone has another idea.

Post a photo of the tube, marking where the thread should be cut, and I can advise you how to hold it and do the job.