My first bespoke pen

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DutchPlatypus

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Aug 2, 2016
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I don’t have the right tap and die for the cap threads yet but overall I am very happy with the outcome of my first bespoke pen. I used a #6 Jowo nib and wanted to keep the overall diameter to a maximum of 14 mm since that appears to be a comfortable size for (my) daily use. Also included, an image of the mandrels I made to turn this pen.

Best Regards,
Edwin

IMG_4823.JPGIMG_4822.JPGIMG_4819.JPG


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magpens

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Congratulations on your first bespoke pen !!! . Very nicely done !!!

One of your mandrels seems to be marked "1/2 - 28".
Is that the thread size of the cap to body thread ?

BTW ... you could have entered this pen in the Kitless Contest that closed only about 15 hours ago !
 
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DutchPlatypus

Member
Joined
Aug 2, 2016
Messages
21
Location
Escondido, California
Congratulations on your first bespoke pen !!! . Very nicely done !!!

One of your mandrels seems to be marked "1/2 - 28".
Is that the thread size of the cap to body thread ?

BTW ... you could have entered this pen in the Kitless Contest that closed only about 15 hours ago !


I did use the 1/2-28 thread which was not the best choice in retrospect. 1/2-20 or even 1/2-13 would have taken less turns to remove the cap. I was concerned that M12x1.0 would be to small with M10x1.0 section threads. I’m trying to decide which size triple start tap and die I want to get. Until then, I’ll experiment with the other thread sizes first to get a feel for the impact the thread pitch has. I’m trying to find a good balance between all the different diameters of the pen parts, also for when I add a clip and some decorative rings. I still have lots of learning to do but that is the fun part.


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magpens

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I believe I am correct in saying that a 12 mm triple start will just do it, with a 10 mm section thread ... you could put out a question specifically on this point. . Or you could research some of the similar pen designs in the Show Off Your Pens Forum.

A 13 mm triple start cap to body thread will definitely do it.

For 12 mm, the pitch is usually 0.75 or 0.8 mm. Then the 10 mm section has 10 mm size as the o.d. of the thread (and this would not be t.s.).

A rough rule, for this 12 mm t.s. thread would be that the depth of the thread is very close to the pitch.

So ... 12 mm (o.d. of body thread) - 2 x 0.8 mm (once for each end of the diameter) = 10.4 mm

Subtracting from this the o.d. of the section thread: 10.4 mm - 10 mm = 0.4 mm

Then you have to divide this by 2 to get the "wall thickness" between the two sets of threads = 0.2 mm.

That is really awfully thin and I would be inclined to go for 13 mm t.s. as the cap to body thread.

I don't have as much experience as many others, but that calc. is only intended to give you the idea.

Of course, you have to also consider the overall diameter of the pen (14 mm) and the fact that you have to tap the cap also. . If you go for a 13 mm cap to body, you are going to have a very thin "wall thickness" under the 14 mm overall o.d. . (14 mm - 13 mm) divided by 2 = 0.5 mm and that is OK for the 13 mm choice. . If you do try for a 12 mm cap to body, then you get the same result if you go down to a 13 mm overall pen o.d.

I know that tap and die sets are expensive. . So it would be good if you could borrow a 12 mm tap/die set and give it a try. . It just might work out.

The fact that the 12 mm is triple start whereas the underlying 10 mm is not may work in your favor.

If the pitch is 0.75 mm instead of 0.8 mm that will also work in your favor.

It might be possible to go to a section thread of 9.5 mm instead of 10 mm and that would work.

If I have made any gross error, I hope an expert will correct me.
 
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DutchPlatypus

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Aug 2, 2016
Messages
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Location
Escondido, California
I set my mind on an M13x0.8 triple start tap/die set. I think it will give me the best balance between body diameter and having enough meat for internal and external threads. I may have to make the cap a tad bit bigger but with the decorative ideas I have in mind, that wouldn’t be a bad thing.


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