# Metric threading



## ktmmudd (Sep 1, 2013)

New member here. I just picked up a Clausing 4901 lathe and was wondering if it was possible to do metric threading with this lathe. I'm still learning to operate this machine, so any beginner books or videos ( I'm checking out the tublican videos listed on this site ) would be appreciated. Thanks, Keith.


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## Tom Griffin (Sep 2, 2013)

I think you need a 127/100 gear cluster in the gear train driving the leadscrew. John "Doubleboost"  has a video on that subject on YouTube. He doesn't have a Clausing, but the principle is still the same.

Tom


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## DAN_IN_MN (Sep 2, 2013)

I think some guys have found imperial threads that are very close to metric in thread to thread dimensions and used them when cutting meteric threads on a lathe that isn't equipped with the correct gears.


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## ktmmudd (Sep 2, 2013)

Thanks for the replies, I guess I have some more research to do. If anyone can recommend some books on machining basics and or lathe operation that would be much appreciated. Keith.


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## Ray C (Sep 2, 2013)

I gather the quintessential source for how to use a lathe is a book called "How to run a lathe" by South Bend.  It's commonly available and I believe is available free from google books.


As for turning metric threads, I can't help you with setting-up the gears on your machine as, I'm not familiar with it but, I do metric threading on a US pitch machine all the time.  My machine has the 100 (US) and 127 (Metric) tooth gear set.  With metric threads, you never release the halfnut lever until you're done.  I always run the lathe in reverse and cut on the far side.  If the part is too long, I don't do it on the lathe but rather, use a die.  If I can't use a die, I don't do the job.

Anyhow, for a typical bolt, cut the customary recess of the proper depth at the starting point.  Set your lathe so the chuck is spinning in reverse and the carriage moves away (toward the tailstock).  I usually use a boring bar with an external LH insert.  Engage the halfnut lever in any position you want.  Jog the machine to the groove/recess then, dial in the depth to make the first cut and turn on the machine.  It will cut from left to right.  When it finishes the cut, do not disengage the halfnut lever,  shut the machine off and coast to a stop.  Dial outward to give clearance, jog the machine back to the starting position, dial in the next depth and repeat until the thread is cut.

The problem with this technique is that you cannot use a live/dead center to support the piece thus, I only do this on very short and larger diameter pieces of stock.  I make and rethread broken boat propeller shafts which are stainless steel and pretty beefy.  The description I gave does not discuss how I setup to do a re-thread.  -That's a topic for later.

You could cut from right to left in the traditional way but, it's very tricky as you must stop the thread in the right spot and hit the brake for a quick stop before crashing the cutter.  I've only done it this way twice and hated it so much, I devised the other method (one of those evolutionary moments in life LOL).

Of course, you need to setup the proper gears for the thread rate desired (usually 1, 1.25 or 1.5 mm/thread).  It's a pain and it needs to be done this way because our leadscrews are not metric pitch.


EDIT:  If you have a spin-on chuck, I do not recommend running the lathe in reverse.  -Don't do it.  It can unscrew.  At low speed, it will just drop off and bang the ways.  At high speed, it can get ugly.

Ray





ktmmudd said:


> Thanks for the replies, I guess I have some more research to do. If anyone can recommend some books on machining basics and or lathe operation that would be much appreciated. Keith.


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