# Add-on threads



## skiprat (Apr 4, 2010)

I wanted to try something different with cap threads and here is what I've come up with so far today. If I don't wreck it, then I'll finish it tomorrow

Pic 1 shows two pieces of PR. The hole and the outside diameter are a nice slip fit.
Pic 2 shows the first of dozens of cuts done with the lathe gears set to do a 3.5mm pitch. These were done with the lathe off and by cranking the leadscrew. Because of the high gearing, it may be easier to turn the chuck, but be warned, never alternate or you will discover all about backlash.:redface: DAMHIKT
Pic 3 is the finished male threads. I did the same with the female threads for the cap. Took over two hours to thread both!!
Pic 4 is of a transfer punch which is slightly smaller than the pen body. I wrapped a 1.5mm stainless welding rod around the punch and kept it tight and even with a pair of pliers. These are cheap pliers that I filed the grip off of the jaws.
Pic 5 is spreading the coils to suit.
Pic 6 is a trial fit.
Pic 7 is the thread fitted and a brass tube installed. The brass will be threaded to take a nib.
Pic 8 is the body screwed into the cap.

I'll turn it down and add trim rings etc once I figure out how to make it look decent......unless I break it first:biggrin:
The coil threads will also act as a 'grip' for the pen.


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## barkisini (Apr 4, 2010)

Very cool!  How is the thread coil secured to the body?


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## BRobbins629 (Apr 4, 2010)

You've gone thread whacky with this one Skip, but I think I like it.


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## desertrat (Apr 4, 2010)

Wouldn't a Helicoil work?

John H


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## skiprat (Apr 4, 2010)

barkisini said:


> Very cool! How is the thread coil secured to the body?


 
At the moment, the spring tension holds it in place. The coil diameter is a bit smaller than the groove it fits in, so it's pretty tight. The trim rings will make sure it can't move. ( I hope:biggrin: )



desertrat said:


> Wouldn't a Helicoil work?
> 
> John H


 
Sure, I guess, but I don't have any that size and those that I do have are a bit sharp ( 60deg) and not stainless. I particularly wanted the rounded edge as it is more comfortable to hold. I also wanted the gaps between the threads and my insert tool can only fit internal Helicoils. :wink:


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## RAdams (Apr 4, 2010)

wow. That is amazing.


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## cnirenberg (Apr 5, 2010)

Talk about thinking out of the box.  That is an awesome idea, and pretty darn cool execution of it.


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## mbroberg (Apr 5, 2010)

cnirenberg said:


> Talk about thinking out of the box.



I don't think Skip has ever seen a box.

That's pretty cool Stephen!!  Brings up some interesting possibilities!  Looking forward to seeing the completed pen :biggrin:.


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## skiprat (Apr 6, 2010)

Well it's almost done, but the cap is HUGE !!! :redface: As I was using round wire for the thread, I really should have rounded the tip of the internal cutter. This meant that my threads inside the cap were a lot deeper than they needed to be. But re-grinding the cutter is a pain to do and I was lazy. I cut the wire threads shorter and thickened the body in an attempt to make the difference a bit less.:frown:
I'll post the finished pen in SOYP soon.
Here are the pics of the trim rings for the cap and the mod to the body.
Oh well... at least I don't have to re-gring the cutter:biggrin:


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## workinforwood (Apr 6, 2010)

Wow...that cap is HUGE!   Crazy Brit.  Oh wait...that's a cricket pen bat right? :tongue:   How about putting another spring over the body of the pen to offset the large cap?  Then your pen could be the shock absorber pen. :rotfl:


On a more serious note though...it's very cool.  That is some radical thinking Steve..I like it!  I just can't help but have some fun with you sometimes.:biggrin:


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## skiprat (Apr 6, 2010)

LOL, maybe it's supposed to be one of those old German hand grenades

Hey, did anyone notice the problem with pic 5???? I actually made three different sizes before I realised the problem:biggrin:


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## jthompson1995 (Apr 6, 2010)

skiprat said:


> LOL, maybe it's supposed to be one of those old German hand grenades
> 
> Hey, did anyone notice the problem with pic 5???? I actually made three different sizes before I realised the problem:biggrin:



You twisted the wire the wrong way.


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## ldb2000 (Apr 6, 2010)

I wanna see a triple start version :tongue::biggrin:
Great job Steven , very inovative idea .


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## skiprat (Apr 6, 2010)

jthompson1995 said:


> You twisted the wire the wrong way.


 
Yep:redface: Well spotted. When I was a squeeky clean newbie here I showed a little core cutter that I made. I was really proud of it, but a female member ( can't remember her name though )pointed out that I ground the teeth the wrong way.  Luckily I had a reverse on my machine:biggrin:



ldb2000 said:


> I wanna see a triple start version :tongue::biggrin:
> Great job Steven , very inovative idea .


 
Gee Butch....triple start with gaps to see the material  That would have to be something like 2TPI. Where is Randy when you need him? He'd work that out in two ticks. Where is he anyway???

But Butch, now that you mentioned it, I might try 2 start ( no gaps ) but with one thread stainless and the other gold ( brass)...mmm watch this space:wink:


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