# Please review and offer feedback regarding threading and tapping issue



## NT_2112 (Dec 9, 2019)

Hi all.  This is a great site for a newbie like me, a big thank you to all the members.

I'm running into an issue joining a kitless pen cap and a pen body.

I made my own mandrel, as shown below.  I plan to use it to hold the pen body and pen cap when I shape them on the lathe.




I used a M13x1 tap and die.  You can see the right hand side is threaded and the left hand side is drilled and tapped.   I was going to use my new M13x.8 tap/die but I didn't have a die holder that size.  I will try the M13x.8 one next time. 



As you can see, the pen cap and the pen body screws on very nicely with the new mandrel and feels very secure/tight.


At first the pen cap and body screws and unscrews well but after a few times on and off the connection fails and the cap will slide off the body with almost no force.

What is strange to me is that if I thread the pen cap and pen body back on the mandrel, they are still very snug and tight on the mandrel.  The same with the pen body, I can slide it on the mandrel and screw it onto the threads and it's on there tight.

I cutoff and resurfaced the body multiple times.  My first attempt I used the die at 12.9mm thickness, that eventually failed.  The 2nd attempt I started over and used the die at 13.1mm thickness and that failed in the same manner and the final attempt I cut it off/resurfaced and used the die at 14mm thickness and that failed as well.

Sorry, if I am missing something obvious.  I am not sure why the pen parts connect snugly with the aluminum mandrel but not with each other.



Any ideas/suggestions?


Thank you.

Regards,
Harry


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## ramaroodle (Dec 10, 2019)

Something about the words newbie and kitless pen with a machined mandrel don't go together.  

Are the threads deep enough? Are they wearing on each other but the mandrel is harder? Never tried a kitless, just looking at the pictures.


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## 1080Wayne (Dec 10, 2019)

What resin is the blank made from ?


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## More4dan (Dec 10, 2019)

If the tendon is too large, the die will shear off the threads. Try a different material with the correct dimensions. It’s likely the material at fault. What is the blank made from?

Danny


Sent from my iPhone using Penturners.org mobile app


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## MikeinSC (Dec 10, 2019)

It's not the fault of the material. The material appears to be acrylic acetate, a standard pen blank.

For 13mm, I would go with a 12.7mm tenon and your cap drilled at 31/64 for its threads. 
Make sure that the pitch in both tap and die are the same.

I make 100's of kitless fp's a year with those exact dimensions.


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## duncsuss (Dec 10, 2019)

This photo doesn't show clearly what the threads look like in profile, but from this angle it looks like they are rounded over rather than a crisp profile. If that's true, I suspect the threaded metal hole you made for it is contacting only by the tips of the threads, and the pen barrel you made also has rounded peaks so there's not enough overlap for a good connection.


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## Dalecamino (Dec 10, 2019)

I think you may have a couple of things going on here. Maybe drilling, and outside diameter of the tenon. Here is a printable chart for tap & clearance you might find helpful. Welcome to the dark side!


			https://littlemachineshop.com/images/gallery/PDF/TapDrillSizes.pdf
		


If you are using 13m x .8, subtract .8 from 13, = 12.2, look at the chart. That will show you what size drill you should use for a corresponding material. There is also an adjusting set screw on the die. If the threads are not cutting deep enough, you can turn the set screw to the left to tighten it. I've only had to do this one time, but it worked.


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## Paul in OKC (Dec 10, 2019)

I would think the hardest part of this is that taps and dies of the same size are generally made for nuts and bolts. That being said, a fine thread will be shallow, maybe too shallow to use as a fixture. Over sizing the tenon will result in torn thread tops most of the time. You might try undersizing the drilled hole by about .01 if you can. Hard to do with just drill sizes, but.........just some thoughts.


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## bmachin (Dec 10, 2019)

I think that you're going about this in the wrong way. Your cap mandrel is okay, but you should build your barrel mandrel similar to your cap mandrel with the thread the same as whatever you will be using for your section. This will give you a lot more freedom to adjust the threading on the barrel to fit.

Also, with the barrel mandrel that you have, you will have a barrel that is unsupported on the inside as you shape it--not the best of all possible worlds.

As usual, I strongly recommend this book:






						The Pen Turner's Bible: The Art of Creating Custom Pens: Kleinhenz, Richard: 9780941936613: Amazon.com: Books
					

The Pen Turner's Bible: The Art of Creating Custom Pens [Kleinhenz, Richard] on Amazon.com. *FREE* shipping on qualifying offers. The Pen Turner's Bible: The Art of Creating Custom Pens



					www.amazon.com
				




and this guy's videos (especially if you only have a wood lathe):









						Steve4948
					






					www.youtube.com
				




Hope this helps,

Bill


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## 1shootist (Dec 10, 2019)

bmachin said:


> As usual, I strongly recommend this book:
> 
> 
> 
> ...


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## bmachin (Dec 10, 2019)

Haven’t hears a negative response yet. Richard was a fantastic pen maker and artist. 

Steve’s Toastmaster videos are a hoot!

Bill


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