complete kitless building - a few questions

[Mark Scrivener]

Hello,

Thought I'd try my had at pen making but I'm not interested in using kits or purchased components (other than an ink cartridge). I have a metal lathe and a CNC mill, so the plan is to make everything from stock materials. Most of the components are straight forward though a few have me thinking. Since I didn't find any posts on these I thought I'd ask:

1. Twist pen transmission. Anyone making their own? I can think of how one might do this with a simple cam, but I'd rather mimic a proven design than build 5 or 6 trying to get it right. Unfortuantely the only twist pens I own have press fit transmissions and I don't want to destroy them taking them apart.

2. "Snap" on cap. I've never made a "snap" type mechanism before, so a simple drawing with some guidelines would be great. I assume the "ring" that "snaps" over the nibb/front end is slit and designed for a slight interference fit. How much interference? recomended materials for the ring? etc.

3. Clips. It looks straightforward to cut a simple clip/ring and bend it to shape, and I assume some of the clips I see are cast. However, I haven't found any threads on this so I'm sure there are lots of ideas which haven't occurred to me. Any pointers on custom clip making would be great.

Thanks again and I'd like to say I've been impressed with the workmanship I've seen on this site. Looking forward to learning some new tricks!

Cheers,
Mark

 

[BRobbins629]

Check out this thread for one style of friction fit.
http://www.penturners.org/forum/showthread.php?t=55625

Custom clips can be machined, cast, bent, and made from sheet, wire, welding rod, or cast metal using lost wax method. Pick your poison. There are no rules.

If you have a 2 piece pen with a friction cap, you don't need a transmission. Use a roller ball refill or fountain pen nib. They stay put. If you go roller ball you will need a spring at the bottom.

If you hurry, enter the freestyle contest running this month. We could use some new blood.

 

[penmaker56]

I sell German Schmidt mechanisms on my website.

 

[workinforwood]

It wouldn't be too difficult to build a twist mechanism. You could use a screw with a large thread. Heck..if Steve see's this he'll probably have one made up with a tutorial by midnight tonight!:smile-big:
I suspect a twist mechanism is basically just a big piece of threading inside, the curve on it is long enough that a half turn equals about 1/8 or more of length. If the pen was a custom pen, it wouldn't be that big a deal if you had to turn the pen a full turn to achieve that length, but you wouldn't want to have to twist the pen too many times. The screw bottoms out in the bottom and the top. If you were to make your own screw and cross cut it with a right and a left hand thread at the same time, then that would be a double twist mechanism..or that's my theory anyhow. Now if it was just a single twist, although it would need to bottom out, it would not have to bottom up. This means that if you were to twist it too many times that it would actually completely unscrew. Now that I'm thinking about this..I can see an advantage to that as well. If you were to build a single barrel cigar style pen with a finial twist, the you would not need to have a nib that unscrews. unscrewing the inside of the home made twist mechanism would allow you to drop in a new refill. Damn...maybe I'm on to something here. I need to try this idea sometime soon! That would take the cost of a ballpoint twist pen down to just a refill and a spring.

 

[rsmith]

Hmmm, Jeff you may be on to something...tapped twist mechanism...now my head hurts from all the idea possibilities. BTW, if you just "happen" to "borrow" a counter pen from the bank or gas station or wherever, the cost for that spring and refill goes to zero

 

[Mark Scrivener]

The friction fit cap is a nice idea. Thanks!

For twist pens, if a 1/2 twist moves the tip 1/8" (approx), that is 4 threads per inch. Rather than a "thread" I think I'll try cutting a ramp....that way I can use a Delrin or HDPE follower so it feels smooth. Humm.....

 

[workinforwood]

Thanks for telling me that...4 threads per inch. So anything 3-8 threads per inch would work fine. Those are some big threads..but somehow do-able I'm sure. I would tap it in metal and use a threaded plastic or delrin rod and a touch of oil..should work great. Have to do something with this.

 

[btboone]

I've done my own retracting mechanism for a fountain pen. I made it from a brass piece that worked in a titanium housing. Some ball bearings acted as the rotation actuator. The trick is to not use too high a helix angle otherwise it will lock from friction.

 

[rherrell]

Here's some photos of my PMG submission pen. It's TOTALLY kitless, except for the refill. I even made the spring from one of my used guitar strings. The body is a homebrew PR, the black parts are Delrin and the rest is brass, with a stainless pin to lock in the clip.

You turn the finial to extend and retract the refill. It doesn't look so hot in the retracted position but hey, what do you want for a first try.:biggrin::wink:

 

[Paul in OKC]

Got to thinking about this. If you have room for a 3/8 diameter thread, you can get a 10 pitch thread tap and die through some cue making suppliers. One turn would be .100, so.....

 

[Mark Scrivener]

Rick,

That's pretty cool! I esp like the recycled guitar string for a spring....no shortage of guitar strings in my house. I like what you did with the clip too - very nice.

-Mark