cutting left hand thread

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cutting left hand thread

This topic has 9 replies, 5 voices, and was last updated 8 February 2017 at 08:37 by mick70.

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7 February 2017 at 07:47 #282812
mick70
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@mick70
how do you cut left hand threads on the lathe?

basic q i know but not sure.

will be on a clarke cl 430 when i get it up and running.
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7 February 2017 at 07:47 #15910
mick70
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@mick70
7 February 2017 at 08:15 #282818
Neil Wyatt
Moderator
@neilwyatt
Most lathes have a tumbler reverse that lets you reverse the direction of the leadscrew (the spindle rotates in the usual direction), or you can add in an extra idler gear to get the same result.

All in all it's easier as the cutter moves away from the headstock making things less stressful!

Neil
7 February 2017 at 09:32 #282832
Circlip
Participant
@circlip
Yes, but it's difficult threading to a shoulder without a run "In" groove.

Regards Ian.
7 February 2017 at 10:38 #282843
Martin Connelly
Participant
@martinconnelly55370
You can turn the tool upside down, run the lathe spindle in reverse and use the tumbler gears to run the tool towards the head and up to a shoulder. The usual warning regarding screw on chucks applies with the lathe running in reverse.

Martin
7 February 2017 at 14:10 #282876
richardandtracy
Participant
@richardandtracy
I have a CL430 and a Warco WMT300, so can compare these 'identical' machines.

On neither of them is there a tumbler to reverse the chuck relative to the power feed. On neither of them is there a screw on chuck. So one helpful thing and one worry disposed of from people who know lathes, but unfortunately not these specific ones.

In the belt box, where you put the gears – see fig 14 in the Clarke Manual on page 15, where it says 'gear train', you will find on the Clarke a slotted piece of metal with a straight slot and the curved slot visible in fig 14. The straight slot is where a single shaft for two reduction spur gears can be attached. This is, unfortunately a problem, as you need to put an idler gear between the first or last gear and the reduction pair, which needs a second slot perpendicular to the main straight one. Sorry, not describing it well. The Warco I have has the facility to put in an idler. If you want me to, I can get a photo of each to show the shape difference so you could make a plate that enables an idler to be used.

If I didn't make it clear, at the moment the Clarke cannot cut LH threads. But it can be made to.

Regards,

Richard

Edited By richardandtracy on 07/02/2017 14:17:12

Edited By richardandtracy on 07/02/2017 14:24:03
7 February 2017 at 19:26 #282942
mick70
Participant
@mick70
pics would be great thanks.
7 February 2017 at 21:47 #282974
richardandtracy
Participant
@richardandtracy
I'll add 2 bad ones tomorrow morning. To get better photos, I'll have to take the drive gears off to see the plates, and given there's no power to the shed where the Clarke is at the moment, and I can only get there after dark.. I will try to get it sorted tomorrow evening, but it's not going to be perfect!

Regards

Richard.
8 February 2017 at 08:34 #283018
richardandtracy
Participant
@richardandtracy
The photos are in my album. The yellow box gear train is the Clarke 430, the one with a green box is the Warco. To clarify things a little, I have outlined the gear spider (where hidden by the gears) in white. I hope this shows what you need to be able to cut LH threads.

I was wrong in my first post that the second slot is perpendicular to the first, it isn't, instead it's at about 45 degrees. It is a right old fiddle to get all the gears to mesh with a LH drive idler in there, you need about 6 hands, and there's barely room for 2.

Regards,

Richard.
8 February 2017 at 08:37 #283019
mick70
Participant
@mick70
great cheers will have to work something out.
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