Die ing to know

Good evening

I have a chart that tells me what drill size i need to drill for tapping.

Was wondering if there was a chart that give what OD i need to turn on the lathe to cut treads with a die?

M10 1.25 is the thread i want to cut.

I do have the 20th edition engineers book and was looking through it today but there is that much information in it i got lost. Also i have to read it in the shed as the wife doesn't want it in the house because it stinks of must lol.

Thanks

Steve

Hello Steve,

O.D. is always the same as the thread size i.e. M10 is 10mm O.D.

You will find that after running a die along it, the O.D. will be slightly smaller

David

Edited By David Noble on 06/06/2020 17:50:40

Edited By David Noble on 06/06/2020 17:51:14

m10 is 10mm but there is a tolerance range Link

pgk

I tend to turn the OD slightly less than nominal, makes no difference to functionality but it cuts easier Just used a die for an M6, turned to 5.95 diameter but 5.9 would have been fine.

Tony

Turning the raw material slightly undersize before using a die results in a truncated thread.

Truncated threads are not unusual, and are intended to prevent root/crest interference.

Back in the late 50s there were formulae to calculate how much undersize the raw material should be, to truncate Unified threads.

In the same way that using a slightly oversize drill for tapping a hole, and reducing % engagement, does not reduce thread strength disastrously, neither does truncating a male thread.

Howard

I cannot cut an M10 with a die, either holding the work in a vice or lathe chuck. I would not entertain doing the job under power. I would use the die as a chaser after cutting most of the thread with a single point tool.

I finished a 7/16”BSF thread in brass this way two hours ago.

JA

You can always Tap or Die threads in the lathe, without being under power.

Make and use a Mandrel Handle.

1 ) You can feel how much torque is being applied, so hopefully, can stop before breaking anything, if there is a jam up.

2 ) If cutting a thread upto a shoulder, you can stop just before hitting the shoulder, avoiding broken tooling or a ruined thread.

Ideally, a Die should be held in a sliding Tailstock Die Holder.

This should hold the Die square to the work, avoiding drunken threads, also the risk of stripping the just cut thread by trying to drag the Tailstock along the lathe bed.

For the same reasons, it is worth making up a sliding Tap holder for the Tailstock. Mine uses ER 25 collets.

The Tap will slip in the holder rather than breaking, if anything gets even remotely tight.

Howard

Thanks for all the replies guys iv taken your advice onboard.

See link for the build

https://www.model-engineer.co.uk/forums/postings.asp?th=165635

Thanks

Steve