CNC Lathe Threading

[lathe guy]

How do I remove the first and last partial threads with the same threading tool I just threaded with? Is there a name for this operation?

[dertsap]

i thought your solution was to pass the part off to me to deal with

[eject_21]

we mill them off in a seperate op. Time the part so the beginning of the first full thread is at the x+ y- pisition. its called op 40 lol.

[Geof]

Do a search using "higbee" it has been discussed before.

[SteelCutter]

I've heard of passing the buck, but passing the "thread burrs" is new to me

(( get a pair of tweezers, and peel them off, one by one til done ))

[DonutSlayer]

Originally Posted by lathe guy How do I remove the first and last partial threads with the same threading tool I just threaded with? Is there a name for this operation?

I don't think it's possible with the same tool, I've used .125 wide grooving tools to do it, you have to get the leading edge of the grooving tool lined up with the tip of the thread tool, then use it to "thread" the end of the part usually about 1 pitch of the thread deep, you have to play with the depth and start point some to get it lined up right, now doing the rear of the thread is a complete nightmare that I've only tried once, had to use a left handed grooving tool and spin the chuck backwards and lots of trial and error but I got it to work great. But the best and easy way is to pass it off to the mill guys

[Larry83301]

Just cut a chamfer at the lead in and out that matches the angle of your thread. This will take care of most of the burr problem that you are having. Cut it about .005" below the root of the thread.

[Geof]

I searched my own computer and found I had saved this from somewhere. I don't remember where but thank you whoever it was.

I will try my best to explain how it is cut.
First what you want to acheive is to remove the part of the thread which is usually a small fin on the turned 45 degree angle portion of the part blank up to where it is a full profile 60 degree thread form.
To do this you use a grooving tool after you are done with the threading cycle. First off you must calibrate your threading and grooving tools to the face of the part (or zero.This is where an important trick lies hidden. The center or tip of the threading tip has to be calibrated so it is equal to the leading edge of the groove tool and the groove insert must be as wide or wider than the base of the thread form (an 1/8" wide insert will work up to 8 pitch. etc) Lets say you are doing 10 pitch threads 1" thread length. Now with your regular threading cycle when you program your length you will get 1 full inch of thread and your first full thread length will be z-.100" (a starting length to be deburred) Now program your grooving tool(also in the same threading cycle as used to thread with) to a depth of z-.100" and you are starting to get a deburred thread. You will only need a couple of deburring passes to remove the burr (so play with the starting x value). But there is more to explain !! Spindle rpm and the machines rapid traverse rate will determine the amount of angle of ramp on the deburred thread. The machines rapid rate will stay constant so for a squarer ramp run slower rpms and a tapered ramp more rpms. Only one more tip if after calibrating the tools you have to adjust the z length of cut you must offset the z length equally on both tools.

Possibly use G32

[eject_21]

60* or acme? You can do it with the same tool if they are acme threads, not if they are 60* threads.

[Hursty]

The attached pdf file gives instruction on how to do the thread relief. This is a page from my book 'The Journeyman's Guide to CNC Machines'