Gear train to cut imperial threads on metric lathe (AL 340)

[19brendan81]

Hi Guys,

Im making some bigger diagrams for the thread and feed settings for my lathe because the ones printed on the machine are too small. There is a smudge in the diagram that explains the gear train for the cutting imperial threads on my metric machine.

For metric threads the gear train is: gear a (spindle) drives the 120 tooth gear which drives gear b (gearbox)

For imperial threads, do I just replace the 120 tooth gear with the 127 tooth gear? I cant tell from the diagram if this is all thats required, or if gear a drives 127 which is keyed to 120 which then drives gear b.

Of course gears a and b are difference sizes depending on the pitch selected. Any help would be appreciated.

Brendan

[Stustoys]

For imperial threads, do I just replace the 120 tooth gear with the 127 tooth gear? I cant tell from the diagram if this is all thats required, or if gear a drives 127 which is keyed to 100 which then drives gear b.

Hi Brendan,
I assume 100 is a typo?

I think you'll find gear a(spindle) drives the 120T which is keyed to the 127T which drives gear b(gearbox)

Either that or I've just put my foot in my mouth again

Stuart

[19brendan81]

Yeah Typo...will fix.

My diagram definately shows gear b being driven by the 127, so I reckon you could be right. Thanks.

[pipeclay]

The 120 will be driven by the Stud and the 127 will be driven by the Screw.

[Stinger.au]

Sorry partial thread hijack..

Is there any way to use the threading start dial with metric threads on an imperial leadscrew? I would assume the period where your leadscrew and spindle sync to the same point would be quite long (many multiples of turns of the threading dial)

[Dave J]

There is an in depth discussion about this a little while ago, I will see if I can chase it up for you. It worked out it was more hassle than it's worth.

Dave

[Stinger.au]

Ah, I will have a search for that next time I am on (little late atm). Yes I have not done any serious analysis, but from a bit of rough mental calculation you would need to wait a long time for the correct alignment of spindle and leadscrew. Probably need some sort of revolution counter on the threading dial as well.

[19brendan81]

Hey Stinger,

There is an interesting way of doing this explained at the bottom of this page.

Metric Threading

Its written for cutting metric threads on an imperial lathe but I assume it works in reverse.

Brendan

[Abratool]

Hey Stinger,

There is an interesting way of doing this explained at the bottom of this page.

Metric Threading

Its written for cutting metric threads on an imperial lathe but I assume it works in reverse.

Brendan

Great reading Brendan, A lot of excellent information.
I will have to practice using my imperial lathe to cut metric by disengaging the half nuts as outlined, To date I have always left them engaged.
regards
Bruce

[Bryan]

Wow, that's a great article. It's going in my Howto folder. Thanks Brendan and Mr Hoffman.

[19brendan81]

Its a good read hey. Someone else on the forum put up a link to another part of that guys site, on HSS sharpening. He has a lot of excellent articles up there. The home page for his metalworking stuff can be found here...

Home Machine Shop Area


P.S I may have given people a bum steer when I said in my first post the articles at the bottom of the page....its actually about half way down and is titled -

"You Have to Keep the Half Nuts Engaged for Metric Threading" - Not!"

[Stinger.au]

No worries, the entire page is good reading.