Threads for Jowo and Bock Nibs

[keithy]

I am working on my designs for a series of kitless pens. The body and cap are working well but the sections are driving me crazy.

For both Jowo and Bock nibs the threads on the nib fit the threads cut by the taps when I drill and tap holes in scrap material but the same size holes in the section will not grip the nib at all.

I'm working in ebonite and M3 and don't want to waste too much material.

I even set everything up in my metal lathe with collet holders for the section and used end mills to size the tapping holes but no improvement.

Do I need to use reamers to get the size right or will I have to make test sections in decreasing drill sizes to find the working drill

Any advise appreciated

Keith

 

[Aces-High]

I would:
-Re-run the taps a few times.
-Re-run the taps with the body connected

Some materials I will actually use a slightly wider bit. Also, if the material get a bit hot during drilling, it will shrink by the time you tap it and make the fit too tight.

Not sure if any of this helps, but its my 2cents

 

[d_bondi]

... the same size holes in the section will not grip the nib at all.

So, are you saying that the nib housing goes all the way into the section and just spins?

If so, this would suggest that either you are drilling to large a hole resulting in shallow threads or that the threads are stripped. What size drill bit are you using before you tap the threads?

 

[keithy]

So, are you saying that the nib housing goes all the way into the section and just spins?

If so, this would suggest that either you are drilling to large a hole resulting in shallow threads or that the threads are stripped. What size drill bit are you using before you tap the threads?

I am drilling 6.9mm for the 7.4mm x 0.5 jowo tap. what puzzles me is that this size drilled in a flat off cut is a perfect fit

 

[d_bondi]

I am drilling 6.9mm for the 7.4mm x 0.5 jowo tap. what puzzles me is that this size drilled in a flat off cut is a perfect fit

Sorry, still need clarification, when you say "...will not grip the nib at all" are you saying it is too loose and spins or it is too tight and won't start into the threads you tapped?

 

[keithy]

Sorry, still need clarification, when you say "...will not grip the nib at all" are you saying it is too loose and spins or it is too tight and won't start into the threads you tapped?

too loose and it spins

 

[duncsuss]

When you get a perfect fit in scrap - are you drilling on the lathe or some other way (such as using a drill press)?

If it's a perfect fit using a drill press but too loose when you drill on the lathe - I'd say your problem is the drill bit is not perfectly aligned on axis.

That could be because the drill bit isn't properly centered in the Jacobs chuck, or the Jacobs chuck is not properly centered in the Morse Taper, or the tailstock is out of alignment. All of these things could result in a drilled hole that is larger than the drill bit.

 

[keithy]

When you get a perfect fit in scrap - are you drilling on the lathe or some other way (such as using a drill press)?

If it's a perfect fit using a drill press but too loose when you drill on the lathe - I'd say your problem is the drill bit is not perfectly aligned on axis.

That could be because the drill bit isn't properly centered in the Jacobs chuck, or the Jacobs chuck is not properly centered in the Morse Taper, or the tailstock is out of alignment. All of these things could result in a drilled hole that is larger than the drill bit.

This is possible. I drill the scrap on my mill and the section on the metal lathe with the Jacobs chuck in the tailstock. I'll test with the drill in a collet rather than in the chuck and check the runout

 

[Dannv]

Are you using me 7.5 or m7.4 for the Jowo #6? DId you check the center alignment of your lathe? If it's off, the hole will be too big and the threads won't fit.

 

[darrin1200]

@keithy it could also be compression. I have found that if I really tighten my collet chuck, on softer materials, it will compress the material. When I drill the hole out, especially if the drill I'd run multiple times, the hole is the right size until I release the chuck and the material expands back to normal. This, in conjunction with other tolerances, can easily leave you with a to large hole. Remember, you are talking about a thread that is only .25mm deep.

 

[RLR350]

I am working on my designs for a series of kitless pens. The body and cap are working well but the sections are driving me crazy.

For both Jowo and Bock nibs the threads on the nib fit the threads cut by the taps when I drill and tap holes in scrap material but the same size holes in the section will not grip the nib at all.

I'm working in ebonite and M3 and don't want to waste too much material.

I even set everything up in my metal lathe with collet holders for the section and used end mills to size the tapping holes but no improvement.

Do I need to use reamers to get the size right or will I have to make test sections in decreasing drill sizes to find the working drill

Any advise appreciated

Keith