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Single point threading accuracy

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Twinsquirrel:
Hi all,

I have an old imperial cross slide of unknown origin which I want to use as the basis for a vertical slide for my mini-lathe, of course it would be nice to convert it to metric while I am at it.

Do you think the mini lathe is accurate enough to cut a thread for the x-slide screw, how accurate does the thread need to be and how do I measure it?


Thanks in advance  :coffee:

David

Darren:
I did a post on this here http://madmodder.net/index.php?topic=460.0

I think a rolled thread would be better than a cut one as it will be a lot smoother to operate. Therefore give you a better finish on your work.

BTW, the mini is fine for cutting threads, plenty of peeps make some really accurate threads for scope lenses and such.
I've only tried a couple of times myself and it seems ok to me.

NickG:
The only limiting factors will really be the pitch error of the lathe and your ability to machine the thread! If it's not accurate over the full length of thread, your handwheel graduations won't give you the right distance! The easiest way would be to leave it and find a digital scale? Not sure how good these are? They seem OK for vernier calipers. I am planning to put these onto my vertical milling machine as although it's supposed to be imperial, it's not very user friendly graduations! I know it's a cheap and cheerful DRO and the glass scales must be far superior but they are far more expensive too!

Nick

Twinsquirrel:
Aaah Thanks Darren, It seems there is nothing new under the sun!!

Nick, I'm liking the idea of scales very much, I think I will do that first as in my mind I had this as a scrap box project and do the screw replacement at a later date.

Cheers both

David

bogstandard:
David,

Digital calipers costing less than a tenner can easily be modified to fit for uses such as yours, my old mill used to have the digital type scales on all three axis and they worked just fine, as long as you can keep swarf and moisture out of them.
A quick strip down, clean and dry out got them up and running again. Oh, and a dozen batteries in stock, once they get wet, the scales tend to eat them like they are going out of fashion.
I still use one on my new mill, for the quill feed, and it works perfectly. But I have fitted a remote readout, and a mains transformer kindly supplied by another member on here. Only because of me, making life easier for myself.
They are usually accurate to 0.0005" (0.001mm)



I have gone over the top with my machines, but you would find, even cheapo scales can allow more accurate and easier use of your machinery, and can transform difficult jobs using handwheels, into run of the mill machining exercises.

John

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