Cutting Threads

[watch_art]

If I wanted to cut threads in acrylic, would I need to do that on a lathe or could I use traditional tap and die type tools to do it with? If I had a section and drilled the hole out, then used a tap to add threads to the back end, would I be able to find any taps that would match any nib units put out by Bock? Or are they all special order and unique threads?

 

thanks!

[Chthulhu]

Does anyone know what those threads might be? My notes say that Bock "Quad System" sections are 8.5 x 1 mm to the barrel, but I have no idea where that came from, and no way of confirming it. You'd want the Triple System units from your description, though:

 

http://www.peter-boc.../index_eng.html

 

There's a contact link; it won't hurt to ask about technical specifications and drawings for the ones you're interested in.

Edited August 4, 2011 by Chthulhu

[Left FPN]

I understood that cap threads are multi start, to make removal quicker. As such they can only be machine cut. Section to barrel threading is single start where taps and dies can be used. Threads on or into acrylic are not easy while trying to produce a nice aesthetic finish.

Edited August 4, 2011 by Force

[Rich L]

I'm looking at a 250 triple system and the eyeball says M8 x .60 metric thread and that would be an oddball size. If you could find a tap you can easily tap acrylic as long as your tap is sharp and preferably of the "taper" variety. Or make a tap yourself - it's not too hard to do.

 

 

 

 

Rich

[watch_art]

I can live with single start cap threads if it means I'm making it myself. I'd just really like to find out the specs on that threaded bit of the bock units. Could I just measure the OD of the threads with my calipers and then the height of all the threads divided by the number of threads in that area to get some meaningful information?

[Rich L]

Talking about the nib unit and not the cap - You can use calipers on the OD but you'll need to add a bit since threads are rarely cut without a flat crest. It's going to be metric. Count the threads in a centimeter (or the biggest fraction you can manage) and do the math to get the metric pitch in millimeters per thread (not threads per millimeter). You don't want to mess with trying to measure thread height on tiny threads. (Or maybe I misunderstand what you mean by thread height). Have fun!

 

Cheers,

Rich

[Left FPN]

I can live with single start cap threads if it means I'm making it myself. I'd just really like to find out the specs on that threaded bit of the bock units. Could I just measure the OD of the threads with my calipers and then the height of all the threads divided by the number of threads in that area to get some meaningful information?

 

The pitch dictates the depth irrespective of the OD. Once you know the pitch, Google 'screw threads or screw thread data' and from various sites you will get depth data. Or come back here and we will provide it.

Edited August 4, 2011 by Force

[fountainbel]

I can live with single start cap threads if it means I'm making it myself. I'd just really like to find out the specs on that threaded bit of the bock units. Could I just measure the OD of the threads with my calipers and then the height of all the threads divided by the number of threads in that area to get some meaningful information?

 

The pitch dictates the depth irrespective of the OD. Once you know the pitch, Google 'screw threads or screw thread data' and from various sites you will get depth data. Or come back here and we will provide it.

 

Hi Shawn and all,

Bock uses non standardised threads for there larger nib units, being M7.9x 0.6mm, pre-drill 7.4mm.

I've odered these special fabricated taps at E-taps

Pelikan uses respectively :

The M150 to M 600 uses 9/32" -36 pitch, pre-drill 6.3mm

The M800 uses 11/32"- 36 pitch, pre-drill 8.1mm

The M1000 uses 3/8"-36 pitch, pre-drill 9.3mm

Neither these taps are standard

As for the cap barrel threads, depending of the brand mostly 9 or 12 TPI ,3 or 4 leads are used.

This results in a thread profile of 36TPI ( 9x4 leads or 12x 3 leads = 36TPI thread profile.)

Aiming for a "stronger", hence deeper thread prolile I use 8TPI- 3leads on my pens, resulting in a thread profile of 24TPI

Hope this helps.

regards, Francis

[watch_art]

This is all very interesting.

I also got an email from Mr. Gray, and about the nib unit threads he says:

The specs on my internal section threads are .5mm pitch, with .285" major diameter.

You can't buy this stock, it would be a custom tap. But don't take .285" and order a custom tap. I would recommend sending the housing itself to whoever is going to make one for you, just to make sure of it's accuracy.

 

But then I say:

Thanks very much for the help.

I think a custom tap is out of my budget.

What if I cleared the threads from the housing and rethreaded it a bit farther up so it's a common metric instead?

Is that plastic strong enough to take something like that or am I totally crazy?

 

And he says:

The housings are pretty soft when it comes to machining qualities.

If you are really going to "jury rig" this, then why not do this?

Bore the section so that the housing is a slip fit - no threads will engage at all. Then glue the housing into place. Keep glue away from the nipple.

This is not the best solution. I hate gluing any part on a pen, as it's irreversible.

But if you are just doing this for fun, this is what I would do, rather than trying to thread.

 

:eureka: :eureka: :eureka: :eureka:

 

BRILLIANT!!!

 

I love it!!

 

This is what I'm going to do since the nib and feed on these units pull out relatively easily.

YAAAAAAY!!!

[fountainbel]

Hisi Shawn

Using a slip-fit as Brian suggested surely is the proven "classic" alternative, if you don't need the easy removal advantages of the complete nib unit assembly.

Note the slip-fit bore tolerances are however very tight.

Given the feed and nib you want to use one initially determines the exact bore diameter by gradually enlarging the bore in steps of maximum 0.1mm till the disered pretension is obtained.

Wishing you succes !

Francis

[watch_art]

Check out this link I was given by a custom turner...

http://silverpenpart...p_dfdf98a0.html

 

$33!!!

Edited August 4, 2011 by watch_art

[dfurlano]

Instead of glue you can also try the Shellac that they use for sacs. That way you can get it apart if needed with hot water or air.

Edited August 5, 2011 by dfurlano