Changing leadscrew pitch
#1
I'm looking at replacing the leadscrew on my lathe (Takisawa TSL1000D) as its very worn, but its a 30x4mm pitch and I'm having trouble sourcing that particular size.
30x6mm is quite common.

The manual for the lathe states that it can come with one of 3 leadscrew options - 6TPI, 4mm, or 6mm.

Without thinking about it too hard, if I changed from 4mm to 6mm pitch would it be a simple case of gearing the input down using different change gears to achieve the same threading pitches?
I know gearing it down would mess with the feed rates too, but I'm less concerned about that.

Steve
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#2
Make one.
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#3
(11-21-2017, 11:31 PM)Mayhem Wrote: Make one.

I'll happily have a crack at the one for the crossslide, but making a replacement for the main one that is longer than the lathe can take in one cut and using a existing badly worn (in a localised section) leadscrew to do it seemed a bit flawed to me.
Maybe there's a good way of tackling it that I haven't thought of....

Steve
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#4
There is Steve - find someone with a bigger lathe that you Big Grin

One other thought - can you reverse the leadscrew? The one on my lathe can be "unpinned" and reversed.
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#5
Yeah - thought of reversing it.
Would likely give me a better thrust face when threading towards the chuck (since that probably has little wear currently), but then I'm back in the same boat if I want to cut a long LH thread eg for a cross slide.

I'm still chasing around for a 30x4mm screw, but no luck so far. Got onto a supplier in QLD today that stocks a lot of standard stuff but brings it all in from overseas so can get other sizes. Hopefully they can come up with something - at a reasonable price.

If changing to a standard size was going to be an easy/cheap way out I'd probably just do that.

If all else fails I've got the option to reverse the leadscrew, make some steadies, remove the tailstock and progressively feed stock through the headstock and thread it in sections.
Really hoping to just buy some though :)

Steve
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#6
Doing it in sections would most likely end in tears, considering it is something that will affect every thread you cut thereafter. How long is the leadscrew? I'd offer to make it or let you come and use my machine but I don't (yet) have the capability to cut metric threads.
I looked into purchasing a length of 1"x 5tpi acme for my cross-slide screw and the prices were horrifying.
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#7
Thanks Pete.
Its possible that I might be able to do it in just a couple of sections, and I reckon with a fair bit of time/care I could probably get it pretty good. Off the top of my head the approach would be cut the first section to final size, then rough out the second section and sneak up on the final size by chasing through a bit of the first section. Just hoping I don't have to...
I haven't measured exactly, but length will be around 1400mm. My lathe can supposedly take 1000mm.

Did you end up making the cross slide screw yourself, or just living with it? I'm guessing its LH ?

I was hoping someone might be able to confirm my thinking on changing to the 6mm pitch, but looks like I'll just have pull together a few brain cells and work it out myself :)

Steve
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#8
I hope you're using a 4 jaw chuck. A 3 jaw won't grip it the same way each time and you'll have some out of roundness.
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#9
(11-22-2017, 10:20 PM)Vinny Wrote: I hope you're using a 4 jaw chuck.  A 3 jaw won't grip it the same way each time and you'll have some out of roundness.

Hadn't thought that far into it Vinny as was hoping not to have to cut one myself.
Good point though.

I finally found someone who can supply the leadscrew I need. Unfortunately they won't be as they failed to meet my "affordable" criteria.
Its custom made offshore, and over AUD$500/metre. Just low carbon steel - nothing special.
Around the same price again if I wanted a bronze nut to suit.

Hmmmm...

Steve
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#10
Steve,

Check out Nook Industries.  http://www.nookindustries.com/Product/Pr...w-Products  I plan to use a rolled acme screw when I convert my planner to a planner mill and I know its not going to be cheap given it will need to be at least 9 1/2 feet long.  However you're should be much shorter.

Stan
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