# Shiny PR Threads - How U Do DAT?



## LL Woodworks (Jun 10, 2012)

Good morning Pen Makers - I have two questions this morning.
 1) I've noticed the finish on external threads is very good from pic displayed on this forum. I'm having extreme difficulty getting threads to look "finished". They are dull and even white in some cases. What is a good method of buffing / polishing threads - M12 x 0.75 or 1/2-20?

2)  What is the  best diameter to make 1/2-20 external threads.  My research produced .450  (.5-.05) but this seams a bit small and the threads aren't tight.

Once again thanks for all the help.


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## cwolfs69 (Jun 10, 2012)

LL Woodworks said:


> Good morning Pen Makers - I have two questions this morning.
> 1) I've noticed the finish on external threads is very good from pic displayed on this forum. I'm having extreme difficulty getting threads to look "finished". They are dull and even white in some cases. What is a good method of buffing / polishing threads - M12 x 0.75 or 1/2-20?
> 
> 2)  What is the  best diameter to make 1/2-20 external threads.  My research produced .450  (.5-.05) but this seams a bit small and the threads aren't tight.
> ...


external threads are the thread size; 1/2, .500; 3/8, .375; etc. 
your class of fit is determined by the depth of thread you cut.


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## Brooks803 (Jun 10, 2012)

The way to get your threads shiny is to fullly polish your tenon before you cut the threads. I also cut that relief at the base of the threads at this time. Polish that too. The best way I've found to get any dust/debris from the inside of the threads is to put it in a ultrasonic cleaner.


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## LL Woodworks (Jun 10, 2012)

Just to clarrify - My questions above were concerning external threads on PR.


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## Brooks803 (Jun 10, 2012)

Doesn't change what I had to say


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## bluwolf (Jun 10, 2012)

I've used an old toothbrush with plastic polish on it, while it's spinning. Works well for me.

Mike


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## Texatdurango (Jun 10, 2012)

After polishing the tenon, I dab of canola oil on the tenon while cutting the threads gives you some nice smooth threads rather than the white crumbly looking threads you get if you don't use any lubricant while threading.  Then as Mike above, I hit the threads with a toothbrush and some Novus polish after threading.


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## Robert111 (Jun 10, 2012)

LL Woodworks said:


> Good morning Pen Makers - I have two questions this morning.
> 1) I've noticed the finish on external threads is very good from pic displayed on this forum. I'm having extreme difficulty getting threads to look "finished". They are dull and even white in some cases. What is a good method of buffing / polishing threads - M12 x 0.75 or 1/2-20?
> 
> *2)  What is the  best diameter to make 1/2-20 external threads.  My research produced .450  (.5-.05) but this seams a bit small and the threads aren't tight.*
> ...



I read a post once by Ken Cavers (DrGoretex) who said he subtracted .2 mm from the nominal thread size for the male threads on a tenon. So the tenon for M12 threads would be about 11.8 mm. Seems to work for me.


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## Curly (Jun 10, 2012)

LL Woodworks said:


> 2)  What is the  best diameter to make 1/2-20 external threads.  My research produced .450  (.5-.05) but this seams a bit small and the threads aren't tight.



I think you missed a decimal point in your formula. .5-.005 would be better. Probably should be closer to .490 to .495 for the tenon. You will need to experiment a little to get something that works for you.

The .2mm mentioned above is just under .008" so that would be a .492 tenon.


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## watch_art (Jun 10, 2012)

I usually make my tenon a touch smaller than it needs to be too.  Creates semi-flat threads rather than pointy sharp threads which can be rough on your fingers, depending on where you grip.

Like Brooks I polish my tenon before I thread.  Threading is last last last.
Like Robert, I use cooking oil on my tenon when I cut the threads.

But I think your die is too coarse.  I'd never use 20tpi for anything.  My 1/2 inch pens have 28tpi, and pretty soon I'll be switching over to M13x.75.  Nice fine threads.  They don't bother the fingers too much and they look real clean.  Plus it's super easy to thread PR with such fine threads.  Just be sure you don't get your tenon too small or you won't have ANY threads.


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## LL Woodworks (Jun 10, 2012)

Thanks for all the help - Polishing B4 threading, tooth brush etc. I'm sure all will help me.  The .490 sounds better - I did have a decimal place off  - and I mis-spoke on the 1/2-20; I do have 1/2-28.

Thanks again to everyone.


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## glycerine (Jun 10, 2012)

If there is also a set of internal threads that will connect to those external threads... What I have done is put a little plastic polish on the threads and then screw the parts together, then unscrew and repeat a few times, I'll also get a rag or paper towel and "buff" them a bit as well...


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## InvisibleMan (Jun 10, 2012)

A couple have already mentioned lubricating with cooking oil (I use pam spray), and I think that's as important as pre-polishing.  The couple times I've polished, but forgotten to spray with Pam, the threads have looked white and yucky.  I've not had luck with the toothbrush after forgetting the oil either.


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## glycerine (Jun 10, 2012)

Oh, if you're talking about while cutting them, I use 3 in 1 oil on mine...


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