cutting 20tpi on clarke cl430

as anyone cut above thread?

listing in manual starts at 22 tpi up to 40.

thanks

don't worry had another look and it's numpty operating lathe that read it wrong.

In general when you have this sort of thing look for a thread you do have the settings for that is a simple multiple like 2:1 or 3:2 as you can probably modify part of the gear train to provide the ratio.

Set it up per manual and comes out really coarse thread.

Going to have another look tomorrow as might end up using hammer on it.

t

Try looking in the second column of the changewheel / tpi chart, bottom row, with the speed selector lever set to position 2 ie handle to north east.

I did.

Even stripped them all of to double check I had put right gears in.

Got it running on its slowest speed as well.

The chart in the manual is looking a" bit crap".

It gives, for 20 tpi 50/36 56/27 that speeds up the leadscrew so cuts a coarser thread than the leadscrew.

What is the leadscrew pitch?

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Bazyle,

Did you spot Fig.21 on the next page of the manual ?

It shows a reduction before gear 'A' ... so that's not the full train.

MichaelG.

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Edit: I just found the Parts List ... which may be useful

Edited By Michael Gilligan on 03/09/2015 00:01:02

AH, well spotted but it is the pair behind A in permanent position that are the extras, and look to be 2:1. It must have a metric leadscrew as the metric .table aligns quite well, but not accurately to a 3mm pitch.

You struck unlucky with choosing 20tpi. The relative ratios of all other threads, metric or imperial are correct one to another, except for the 20 tpi setting. It is over 30% off. Not sure if the starting position is quite right still as I think that fixed pair I mentioned above need to be 16/35 (or 32/70 ) with a 1.5mm leadscrew, ie not quite 2:1.

cheers for replies.

be glad when i get full set of gears for southbend.

Exploded View in the parts list appears to show both a double gear and a triple ... this could get complicated.

Probably worth turning the headstock spindle by hand, and counting turns of gear 'A' to establish a baseline.

MichaelG.

right just been out to reset it for normal turning.

had a look at chart on inside of cover and it gave a totally different set of gears.

gave it a go and worked great.

gears it listed were

a=50

b=36

c=56

d=42

Excellent Result !!

sent clarke e-mail explaining.

they say they will look into it and if required update manual to match.