Machining BSP taper threads

IIRC you thread cut in the normal way but use a taper turning attachment so you cut a tapered rather than straight thread. Never done it myself but it came up in machining class and that's what I recall the technique was.

What's the thread size?.

I wondered about that and came up with a similar conclusion - except that if yoy haven't got a taper turning attachment you could offset the tail stock and do it between centres.

Rusell

David and Russell

Thanks for the information, the size is 1" BSPT considering machining myself in SAE660 Phospher Bronze, thread length is 2 1/2". Will do a drawing of it so I can work out if I can offset my little lathe tailstock far enough.

Cheers

David

Seems quite long compared to the normal length of a 1" BSPT thread. Any particular reason?.

According to MH taper is 1 in 16 on diameter. If the part is 2.5" long then an offset of .078" If the part is actually longer then offset pro rata. Smug Bastard Mode ON As I have an ELS I would just enter the data and thread Smug bastard mode OFF

I am also not sure why you need that thread length.

Richard

It's a long time since I did any,but a thread length of 2 1/2 inches seems over long for a tapered pipe thread on 1" BSP.

Allan

Hi All

The item in question is a boiler washout plug, I believe they are effectively over length to allow a degree of recutting of the thread in the boiler over time. I have a drawing on the way to me to check it against.

Cheers

David

Usually a tapered thread is quite short (the length equal to about three quarters of the diameter). If the length is not too important have you thought about trying an old ships chandlers?