### Author Topic: How generic are glass-scale linear encoders?  (Read 6248 times)

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##### Re: How generic are glass-scale linear encoders?
« Reply #25 on: October 29, 2023, 08:23:10 pm »
Note that even if you don't plan to cut on reverse you need to swith your lathe forward-and-reverse constantly if you ever need to make metric threads on a imperial machine or vice versa.

I have never done metric threads with a thread counter.  I thought one would just mark the number used and always go forward at that exact spot before engaging the half-nuts.

IIRC the problem was that if you thread metric threads on imperial machine the correct engagement points can be VERY far apart as the inch-millimeter ratios hardly match anywhere.

Today you might be able to use microcontroller to do the math and let the spindle turn to correct index before engaging the half-nuts.
Too much headache at the moment to think this trough but for 1 mm pitch the correct engagement points occur every 127 spindle rotations with imperial lead screw? and for M6 fine with 0,75mm pitch the correct engagement points are every 9525 spindle revolutions.
Or every 7143.75mm on carriage movement so you need LONG lathe to find the next correct engagagement point!

here's a trick, https://youtu.be/HXt4TWa382Q?si=lEPwSvisvSh1sO1P

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##### Re: How generic are glass-scale linear encoders?
« Reply #26 on: October 29, 2023, 08:27:24 pm »

The main purpose for the single Z-axis is for threading, particularly RH internal threads.  On another lathe I used a digital dial indicator with output* to indicate "zero" and stop the lathe (it didn't have half-nuts).  On the present lathe, I plan either to stop the lathe or electromechanically open the half-nut.

so a carriage stop with a microswitch would do the job simply and reliably

#### jpanhalt

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##### Re: How generic are glass-scale linear encoders?
« Reply #27 on: October 29, 2023, 10:45:24 pm »
Re: Microswitch

Yes, that accomplishes the same thing.  But using a dial indicator/linear sensor will give positive feedback in half-thousandths.  It's also fun.  During my long Winter days, I write code just for fun -- sometimes for no real purpose other than to see whether I can do it.  Nothing else to do.

I have a contribution on PICKList* that is the product of that and for which no other immediate purpose.

John

Unfortunately, PICList was taken down and everything is now on mirror sites.  It was probably a bad idea to post my email here.  Just look for base conversions and 17-bit binary to BCD.
« Last Edit: October 29, 2023, 10:48:00 pm by jpanhalt »

Smf