Metric Mini Lathe Leadscrew

[Rick Kirkland 1Participant @rickkirkland1]

Well that's a bit more information David so I'll assume it's 1/4" diameter with a two start. the next question is what is the lead of the screw required? This has a major bearing on how much core diameter remains once the threads with their associated root clearances have been machined in. Also it means that for a decent core diameter to remain the thread pitch needs to be relatively fine on small diameter screws. If you're using form tool inserts you may be able to purchase one small enough for your purpose but if you're grinding your own form tool from HSS toolsteel You'll need loads of patience, a decent grinding jig, a good magnifier a little bit of luck and remember also, if the nuts need screwcutting you will need an internal tool to the same form , which will be pretty small after all is said and done. An Acme tap may be a better solution the only problem being the availability of 1/4" Acme form taps with two starts. I'm willing to bet THAT is a non start! My next question is does it absolutely HAVE to be Acme form in that particular diameter and application.? I'm not saying it's not possible but it's a bit of an involved process.

[David Watson 3Participant @davidwatson3]

This is part of an on going problem with my Clayton. The steering shaft is tapped 1/4 Whit as per drawings. This is ok but means a lot of free play and a lot of turns of the steering wheel to move the steering much. A suggestion is to use a 1/4" Acme two start thread.

The shaft was available from Blackgates ready machined with nut to match. Sadly no more and a shaft ready machined is rather costly. As you said taps and dies are not available for that size and of course two start makes things more difficult.

I havnt tried screw cutting yet but it might be worth a try if I can sort out the confusion about the gearing on this Mini Lathe.

[David Watson 3Participant @davidwatson3]

I am getting things in order and gathering information about screw cutting on the mini lathe. I have a copy of the gear layouts for the end cover, imperial threads. If any one out there could copy me the lead screw dial indicator information from the front cover it would help.

[Neil WyattModerator @neilwyatt]

http://www.arceurotrade.co.uk/Catalogue/Machine-Spares/C3-Mini-Lathe-Spares/C3-55-Thread-Cutting-Charts

http://www.arceurotrade.co.uk/Catalogue/Machine-Spares/C3-Mini-Lathe-Spares/C3-120-Front-Cover-Label

[David Watson 3Participant @davidwatson3]

Thanks Neil, I have ordered the imperial chart from them for the change wheels. The chart for the lead screw on the front of the cover is different on the Warco. I have asked Warco if it still available.

Warco say my lathe is imperial if it has a 16TPI label on the lead screw dial bracket. This dosnt ad up with the invoice etc. Maybe my father fitted an imperial lead screw kit from Warco?.

[Howard LewisParticipant @howardlewis46836]

Just to add to the confusion, my Chester Conquest Super C3 seems to have a 1.5mm pitch Leadscrew, with 20 tpi Leadscrews for Cross and Top Slides, with a label on the Thread Indicator Dial saying "16T"

The exact pitch of the Cross and Top Slide leadscrews is less vital on this machine, since the DROs provide for Imperial or Metric readout. (Just hope that they are accurate in both units)

The only advice that I can offer is CHECK carefully.

Howard

[David Watson 3Participant @davidwatson3]

I can see the mini lathes limit points already. If I want to make a two start thread as planned, the gear charts smallest set up is for 12TPI. It may be simpler to stick to a single start thread. I am going to exsperiment with different screw threads this weekend.

[Neil WyattModerator @neilwyatt]

You can go to much coarser pitches than 12tpi.

The largest pitch for a standard imperial mini lathe is 1 tpi, but for pitches corarser than about 16tpi you need to make a leadscrew handle and drive from the leadscrew (and possibly use thread milling). With 100T gears you could theoretically cut 1.5625 inch pitch (0.64tpi).

Neil

[David Watson 3Participant @davidwatson3]

My old Myford ML4 had a huge stack of gears with it but I never got as far as screw cutting. The mini lathe gear lay out for 12 TPII must be in line with the standard set of gears. I think wasting a couple of bits of off cut round bar is my first move. Its not a problem if this proves more than me or the lathe can cope with. The shaft that is fitted works of a fashion.

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