Threading With Pictures

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donnyfl

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To start off, I have a G0752 lathe but changing gears on that thing is a pain in the butt! So recently went out and purchased a HF 7x10 dedicated just for threading 1/2 x 20 adapters.

I followed Frank Hoose's instructions but I can't seem to get the 1/2 x 20 nut to screw on an aluminum test tube. I can do it on delrin but I am guessing because delrin is more forgiving. Looking to see if you guys can spot what I am doing wrong.

1. Set compound to 29 degrees

C555B8C6-50B8-4A2D-96FA-3226D295C7BA.jpg

2. Use gauge to align 60 degree threading tool
693BC49D-2C6C-4D5A-AE7A-8B0A177CA8FD.jpg

3. I am using the "leave half nut engaged method". In this case I aligned it with #3. According to the thread chart on the machine, I could use either 1,3,5 or 7

5F826940-7914-493F-B996-17C8FE4F6910.jpg

4. I made a first cut and zeroed the cross slide and compound.

5. Cut .005, 004, .003, .002 and then the rest either half of .001 or full .001 until thread pitch matches the thread pitch tool

7E583BB0-B858-42C0-8534-86DB3AE7F11C.jpg

6. I made sure the diameter of the test tube is not too large for 1/2 x 20
87C664E6-255F-4AA5-A73D-0C85EF6ED0DB.jpg

As mentioned above, delrin works fine.
66CC5A52-B5E3-4D3B-A813-E78347ABDDA7.jpg

Does anything stand out to you guys?
 
Did you do a couple spring cuts after the thread was done. Spring cut is not adjusting anything, no feeding in just go back and cut again. All machines have some "Spring" to them, flex in the setup and the final spring cuts can take off a little more material and get it to the right shape.
 
The thread pitch gage is meant to measure the number of threads/inch, not necessarily the thread profile. Measuring the o.d. of the thread doesn't tell you anything. You need to measure the pitch diameter in order to determine the fit. In your fifth picture, it looks as you have an excessive flat on the crest of your thread. Barring measurement with a mike and thread wires a nut is probably the easiest way to determine fit. Most off the shelf nuts are rather loose so if your test nut goes on OK but your final fit is tight, you can adjust the fit to be looser with the test nut.

You are doing it right, you just have to cut your thread slightly deeper.
 
BTW, nice pictures. It really helps to diagnose the problem from afar when it is well documented.
 
Learned something new today :) Thanks Caddie, I'll try a few spring cuts and report back!


Cadillac STS said:
Did you do a couple spring cuts after the thread was done. Spring cut is not adjusting anything, no feeding in just go back and cut again. All machines have some "Spring" to them, flex in the setup and the final spring cuts can take off a little more material and get it to the right shape.
Click to expand...
 
donnyfl said:
Does anything stand out to you guys?
Click to expand...

You mean other than the flip-flops in the machine shop? :laughing:

Sorry...I just couldn't resist.......

But seriously, since (at least in the photos above) you are working in the chuck without a tailstock centre, you could try the nut on the work before disturbing anything by removing it from the lathe. That way if you need to take another thou. you still can.

...and yes, great clear pictures!

-brino
 
I am not the best photographer by far and I don't take 1000 selfies in order to post one on fB but I felt like a selfie whore taking a bunch of pictures just to get the lighting right and making sure you can see the work. You guys are all correct, I didn't cut deep enough and there were some play so it wasn't cut cleanly. I had moved the cross slide after posting earlier so I had to go back in slowly until it started cutting again. But after every two cuts, I did a spring cut and it did take some material off.

At the end, it was a success! And by the way, this is not the first time someone called me out on here for working in flip flops :)
7906A49F-ABFE-4399-AF48-A8FE3BE1A5C3.jpg
 
Yeah, if I have the nut, I usually get close, try the nut, keep cutting until the nut fits. Then stop.
 
Measure the PD over wires, a thread wire set will be the cheapest tool that you will EVER BUY. The book that has all of the thread dimensions will cost way more.
The Pitch Diameter is the most important dimension, measure it.
 
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