This Classic Chrome Twist Pen Kit is easy to make, economical and will make a popular gift.
I measure the diameter of the threaded coupler for the twist mechanism ..... measures as 6.8 mm
The thread pitch seems to be 0.5 mm ...... bear in mind my aged eyes trying to use a thread gauge !!!!!
So I would say THIS thread is .... M7 x 0.5 .................. but YOURS may be different ........... I don't have your exact kit to measure from.
I have found Berea to be very helpful in the past. . So if you were to send an email asking who to contact about the threads on YOUR kit you just might get a referral to a person who would know the info you need. . I have forgotten the name of the person I spoke to ... I think first name was Jim
I have done a lot of work with this particular pen kit. . But for some reason I had a mental lapse until a few minutes ago.
It has similar architecture to yours ..... twist mech screws on in a similar way.
Only problem is that this kit has bigger thread OD ..... measures at 7.3 mm, so I suspect the spec is actually M7.5 x 0.5 mm
Twist mech has female threads; coupler piece has the male threads (which I think is the same as yours).
So, while not fully compatible with yours it may be an example to keep in the back of your mind.
Many companies sell this style of pen kit (some "better" than others) and you should be able to find in the UK if you should ever want to.
I really like the general features of this pen kit styling. . The Berea model which I have referenced is probably the best available for smooth operation and reliable plating options.
I hope that some of the info I have provided in the above 3 posts will be interesting and/or useful to you.
Please keep in touch and let me know what you come up with for your project .... also feel free to send along any questions you may have.
Thank you very much for taking the time to reply. I am trying to modify a transmission to create a bullet pen using original casings problem is the cases are short so I need to make the transmission longer. Finding the right tap size has proved very difficult. I think you might be right about the M7.5 x 0.5. I have ordered some taps in M7 X 0.5 and M7.5 x 0.5 I will let you know how I get on when they arrive. Thanks.
I feel that M7 x 0.5 is more likely the correct thread, but I could be wrong because I have not had the pen parts in my hands.
From country to country (vendor to vendor) there can be differences in kits, even those marketed with the same names.
There is one other thought I have had, assuming that what you want to do is basically to extend the twist mechanism a bit .....
..... if you have an alternative method for refill replacement that does not involve unscrewing the twist transmission.
You could make up a short tube of the appropriate length/diameter and glue it to the existing parts with 2-part epoxy.
To do this, I would recommend doing any parts modification/fabrication with a metal lathe, but a wood lathe might be "up to the job" using suitable cutting tools and taking suitable care.
Looking forward to hearing about your success !! . . Good luck !!
I am lucky in so far as I have a small workshop with a metal lathe a wood lathe and a milling machine. I am more at home with a metal lathe I do most of my pen turning on a metal lathe. The taps should arrive sometime next week. I will keep you posted. I need something to cheer me up I spent today in my shop I had two expensive blanks blow up on me. Another pen I had to fight with all the way to the finish only to find the bushings were undersized so hangover at both ends of the pen. One step forward and three steps back. Why do we do it.
Just an up date.
The thread is M7.5 x 0.5.
At first I thought It wasn't I tapped a 8mm tube but it was a loose fit on the male part it screwed onto but what had happened because 8mm pen tube walls are so thin the tap bulged the tube slightly resulting in a sloppy fit.
I asked a machinist friend to measure the thread and he came back with M7.3 X 0.5.
So I started again I cut some 8mm brass rod into 4 inch lengths and put a piece in a four jaw chuck on the metal lathe. I drilled a pilot hole then worked my way up in drill sizes until the internal diameter was 6.5mm I then switched to reamers starting with a 6.6mm and worked up in increments to 6.79mm. I then ran a M7.5 x 0.5 tap into the tube. I cleaned it up and screwed it onto the fitting on the pen kit and it fits perfectly. So Cigar pen and bullet twist pens kits threaded bit the transmission attaches to is M7.5 x 0.5. I can now crack on and make my custom pen I have had on hold whilst working this problem out. Thanks for every ones input.