Thread Milling

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GlennW
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Thread Milling

Post by GlennW » Sat Aug 04, 2018 2:55 pm

I always wanted to give it a try.

I had a job that needed external 1/8" NTP threads on stainless.

I have a really nice taper attachment for my lathe that I have never installed, so I tried cutting the pipe threads using a Geometric Die Head and it worked, but the results were not as nice as I had hoped.

Soon after, I bought a thread milling cutter for 27 tpi pipe threads and never got around to tinkering with that either...

Today I figured I would give it a try, and after figuring out all of the specs that I needed using an Optical Comparator since I had no info on the cutter, and trying to remember how to run my CNC mill, the first attempt was actually successful. :shock:
DSC01189.JPG
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The L1 gauge actually likes it!
DSC01190.jpg
This was on aluminum bar, but it's a pretty good start, so next I'll try the stainless and see how it works out.

I may shorten it up one thread and reduce the diameter accordingly, but for now, it's not a problem.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

Harold_V
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Re: Thread Milling

Post by Harold_V » Sat Aug 04, 2018 3:51 pm

Nice, Glenn!
I've always been curious about thread milling, but have not had a reason to pursue the process.
The thread mill looks a lot like a tap. Do you see any significant differences between the two?

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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GlennW
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Re: Thread Milling

Post by GlennW » Sat Aug 04, 2018 4:03 pm

For one, there is no helix to it, as I ran it at 3700 rpm and 20 ipm feed and it just ran a spiral pattern down the stock equal to the thread pitch per helical orbit as if it was a single V cutter.

It's also Carbide.

I programmed 11 orbits since I plan on using it for stainless. If I was only cutting aluminum I would drop it down to two threads from full depth and only make two orbits using the length of the cutter to cut all of the threads.

Not sure any of that makes sense, but I understood it!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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Bill Shields
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Re: Thread Milling

Post by Bill Shields » Sat Aug 04, 2018 5:25 pm

thread mills are not like taps...and cannot be used as such.

for small IDs they are quite the way to go..or in as in this case one mill can make any OD you want as long as the pitch is correct (assuming it is a multi-tooth mill).

Single tooth mills can make literally any pitch thread - as long as there is enough back clearance to handle the helix.

You should see one of these things making 2 mm ID threads in titanium...

Harold_V
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Re: Thread Milling

Post by Harold_V » Sun Aug 05, 2018 3:56 am

Thanks, guys. I'm woefully lacking in CNC operations, but eager to learn.

H
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Bill Shields
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Re: Thread Milling

Post by Bill Shields » Sun Aug 05, 2018 7:43 pm

getting the thread mill in / out is a challenge, especially with an ID thread.

If using a single point tool, typically you helical mill down to depth, the make at least one full 360 degree arc move, then move radially until the tool is clear and pull it out of the hole.

The same can be applied to an OD thread if the design allows.

if using a multi tip tool (as shown here), you have to always move helically while cutting stock...then move away from the part

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