Metric Thread On LM8x14

[pzzamakr1980]

So I've been trying to figure out how to make metric threads on my LM. Is there no other way besides reversing the motor and running it back to the start position in that manner? Someone on the yahoo forum said you just have to start at the same place on the indicator dial but that doesn't seem to work. Any suggestions and thank you.

[nbritton]

Why do you need metric? "At least 85% of the world's fasteners are dimensioned to Unified thread dimensions, and the biggest selection of fastener sizes and materials are found supplied in this standard." --

http://en.wikipedia.org/wiki/Screw#U...hread_Standard

It would be nice to have an all metric world, but it ain't going to happen.

[pzzamakr1980]

Really, its funny that you say that, because of the two motorcycles, three cars, 6 bicycles, and a myriad of assorted machine tools including the lathemaster and my x3 and my x2 and my new emco are all metric. So if I take all the stuff that has screws, nearly 100% of them use metric. So that is why I want metric.

[cam1]

A workaround I heard of suggested to engage the half nut (motor off,carrige backed away from the face of the part), and then clamp a piece of square stock onto the ways at the backside of the carriage, so that it's contacting the carriage on a good reference surface. Now, when you have completed a cut, disengage the half nut, and return the carriage until it contacts the stop block. The half nut should (don't flame me if I'm wrong) only engage at one position of the screw with this setup, which is what you require. My source for this information is from a fellow named Guy Lautard who published 3 books titled " The machinist beadside reader v1,v2,v3", full of sage advise and tested techniques.
Great reading, and some fantastic machining information in an easy to read format.

hope this helps

regards

[cam1]

PS, Metric will happen, it's just a matter of time. This will not be our Century.......

regards

[Kiwi]

A workaround I heard of suggested to engage the half nut (motor off,carrige backed away from the face of the part), and then clamp a piece of square stock onto the ways at the backside of the carriage, so that it's contacting the carriage on a good reference surface. Now, when you have completed a cut, disengage the half nut, and return the carriage until it contacts the stop block.

I'm having trouble accepting this method. I believe this will only work if the stop is put at the correct position relative to the pitch being turned.

The new position needs to be in multiples equivalent to 127 turns of the pitch being turned.
eg: 127 X 1.5 / 25.4 = 7.5 inches.

With a 8 TPI leadscrew and Dial gear of 24 then the dial will need to be rotated 2.5 times from point of disengagement. (8 / 24 X 7.5)

This is my understanding but open to corrections.
Check before cutting.

[cam1]

Kiwi: I'll verify my reference and get back to you.

regards