Kitless Threads

[soligen]

I got a tap & die set, and started playing so I can give kitless a try. I'm basically following the process from this thread.

http://www.penturners.org/forum/showthread.php?t=51646

I'm using PR and trying to thread the inside of body with M10x1 to accept an el grande style front section, and put cap tghreads on the outside.

I thread the outside first, and put on a little "shop aid" like George suggested to help hold things together, then drill and tap the inner threads. I am having a problem in that the PR is cracking while taping the inner threads. I know, I could go slower, but teh PR still seems kinda thin.

My question is, how think does the PR need to be to have enough strength? I chose M10x1 inside threads becasue el grande front sections are readily available. For the outside (cap) threads I tried a 1/2 x 20 tpi, simply becasue it is the largest, finest tap/die in my set.

I know at some point I will want something different for the cap threads - just trying to get the first kitless without any more capitol outlay (may not be practical).

I dont think I can get smaller than M10 or 3/8 on the front section threads without running into problems there, so how big does the outher threads need to be so structural integrity is not compromized?

 

[mredburn]

What sized drill bit are you using to drill the pilot hole for the tap?

 

[soligen]

What sized drill bit are you using to drill the pilot hole for the tap?

The charts called for a 9mm bit, and I used 23/64, which is about .005 larger than 9mm.

 

[rstought]

I use an 11/32" bit and that seems to work well...

 

[cnirenberg]

Dennis,
I believe I have used a letter Q or R to drill for the M10x1. I have it written down at home. I can either repost and confirm or will PM you this weekend. I have used the 1/2x20 for the shoulder threads and a M10x1 nib thread with no problem. It helps to thread the shoulder first for the cap, then drill for the M10x1 threads. I believe George has a pic with a "cap collar" on the shoulder to help it not crack. Use plenty of lube-PAM when you tap.
I hope that this helps some.

 

[soligen]

Cris,

That pretty much sums up what I did. Maybe I just need to take it slower, or possibly my homebrew blanks are just a bit too brittle.

 

[cnirenberg]

Dennis,
That could be it also. Some of the resins do not thread like others. Possibly due to the additives. Who Knows? I have had the best luck with Alumilite and a material called Crushed Velvet. They thread beautifully and very clean. Do yourself a favor and go thru the Advanced Forum, the older posts do not appear unless you check off on the boxes on the left. Look for tap and die, kitless etc. those will set you in the right direction. I will PM you something this weekend of steps that I do.

 

[BRobbins629]

Some materials just take threads better than others. The most forgiving materials for me are Delrin, ebonite, and cellulose although I have cracked each of these. Pr can go either way. Finding the right diameters to drill to for the taps and to turn to for the dies can be a big help in success percentages. For pens, you really don't need too deep a thread to get sufficient holding force and the less deep the threads, the easier they are to turn. Experiment and take good notes.

 

[skiprat]

What style tap are you using? Taper, plug or bottom? You really want the longest taper one you can get.

PR likes to crack, therefore sand smooth any sharp corners ( beginning of hole ) before tapping.

Once you have drilled your hole and cleaned the edges, leave the blank in a cup of hot water while yoiu get the tapping stuff ready. It will be less likely to crack if it's warm.


Having said all that, unsupported or un-reinforced threads in PR have never lasted for me unless the pen was ungainly fat.

I'll try and find a pic or link to one where the threads are seriously big but I supported them with an external trim ring.......
Back soon:wink:

Ok, Dennis please have a look at these two post. ( You'll have to ignore the insults from my so-called friends - LOL )
The threads in the PR are rediculously big, but show the point. On the cap there is an external support trim ring.

http://www.penturners.org/forum/showthread.php?t=60423&highlight=wire+threads

http://www.penturners.org/forum/showthread.php?t=60499&highlight=wire+threads

But keep at it, you will get there. Just don't use all your favourite PR

 

[soligen]

My taps look like Plug to me.

I'll try the hot water thing, but based on these comments, I think a design or material change is in order. I'm chewing on some ideas.....

I know you weren't happy with the cap size, but the spring threads definately get a cool factor kudo.