cutting a 1mm pitch thread on Imperial lathe

I want to make a faceplate for my unimat 3

which the headstock is a 14mm x 1mm thread which is 25.4 tpi

would it be ok to cut the thread at 26tpi

Thanks in advance

Best Wishes Martin

Edited By Martin Walsh 1 on 15/09/2012 16:16:09

Martin,

What lathe are you ging to use to cut the thread ? there may be better alternatives depending on the gear train.

Hi John

Iam using a super 7 with Imperial gearbox

Best Wishes Martin

It may be worth getting a tap as you may want to make other equipment for your lathe. I don't think that 0.6mm error per inch is good enough for this application. Perhaps you could use a tap on the blank faceplate and turn the register after screwing the job onto your lathe spindle back -to- front with a spacer then turning as usual. Colin

You'll need someone to calculate it through the train, MLs have various setups

Usually a short thread is a doddle on an 8 tpi leadscrew

20 on the spindle and 63 on the leadscrew with a direct drive is sufficient

63/20 x 8 = 25.2

A tap isn't really concentric enough, it's best used to tidy things up

Edited By Ady1 on 15/09/2012 17:35:05

Have a look at this piece of free software: **LINK**

It allows you to put in the list of gears you have available and the leadscrew pitch or tpi and will then calculate the best combinations of gears. It will do metric pitches on an imperial lathe and v.v

Russell.

P.S.  It works in Windows and, under Wine, in Linux.

Edited By Russell Eberhardt on 15/09/2012 19:19:55

Download that programme NthreadsP from www.lathes.co.uk here **LINK**

I use it to calculate metric threads on my imperial Barker lathe

Once you've put your changewheel set in and saved it you can calculate any equivalent thread

Martin.

Two choices, if you replace the 24 driver gear with a 34 and select 36 tpi on the gearbox you will get an error on 1mm pitch of 0.05%

Another alternative is to change the 24 tooth to 30 tooth and select 32 tpi and this will give a pitch of 0.992mm

This way you only have to change one gear and not the whole imperial quadrant.

John S.

Another useful gear calc app here

thank you very much for the replys guys

and the downloads

Dont forget that you will have to keep the leadscrew nut engaged until the thread is finished.

You will not be able to pick up the thread with the leadscrew dial.

That is unless you have already made the Graham Meek screwcutting dog clutch, and this sort of job turns form being a real chore into a doddle.

(Another quick plug for Gray's design)

Phil

And another plug for Gray's brilliant interpretation of the design.

Just cut five 19 TPI gas thread fittings on an all metric lathe, 900 revs up to a shoulder - no problems.

John S.

hi the link for the useful gear calc app has a virus downloaded scanned the file it said it was ok then installed then all went tit's up it had a virus my PC is still trying to get rid of it

Caution with the program

Ty Kevin

Hi martin,

look here (at bottom of page 1) Metric conversion set 1481

www.usinages.com/.../confirmation-donnee-notice-boite-avance-myf...

or at quick change gearbox manual BA section (select 0-BA)

pierre

Hello Martin,

If you have a 70 tooth gear wheel, it might be worth using that as the 'Mandrel' gear driving the quadrant gearing set up for FINE pitch and the gearbox at 8TPI.

I did some calculatiuons on threading possibilities some time ago, mainly to see what one could get with the finer BA thread cutting, using the fine pitch arrangement to achieve the necessary reduction in gearing. I do suggest you check it out with some M6 threading [1mm pitch] in the chuck to be sure it follows before cutting your faceplate, and remember to keep the clasp nuts engaged until the thread is finished.

Good luck

Brian Wood