Magnetic Graduate blow out

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Bope

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Oct 24, 2018
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Location
Western NY
I was making my first roller ball and started pressing in the parts. When I press in the magnetic coupler the blank cracked. I was using an acrylic blank. I knew something was wrong when I tried to start the coupler and it was tight. My plan is to turn off the cracked area and add a band. What can I do to prevent it from cracking again?

Also I need to remove the clip. There is a screw and spring on the underside of the clip to allow the clip to flex. Am I going to run into any problems if I remove the screw and spring so I can remove the cap from the blank?
 
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Pressing the pen kit nib and finial hardware pieces into the nicely finished blank/barrel is a stressful event, both for you/me and for the blank.

Whenever I am assembling a pen, I have considerable fear that the blank will crack. . After all, you are expanding the whole brass tube PLUS blank from the inside. . In other words, you are putting the brass tube PLUS blank in tension (as materials scientists would say). . Most materials like plastic blanks do not (usually) like being put in tension and they can easily crack when that is done to them. . Even a wood blank can crack.

There may be several ways to avoid the possible cracking but each method will require some additional steps. . The way I do it is to ream a small amount of metal off the inside surface of the brass tube. . You can buy adjustable reamers for this purpose. . Harbor Freight or Grizzly may have such reamers. . I buy mine in Canada from .... www.BusyBeeTools.com ....

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The idea is to remove a very small amount of metal from the inside of the tube .... remove about 0.002" off the inside diameter. . And then use a bit of glue (I use epoxy) to make sure that the pen barrel is held securely to the pen nib and finial pieces of the kit hardware.

Doing this reaming is never a precise operation and there's a risk of removing too much metal. . You actually never know for sure if you've done that. . So the glue is actually necessary.

I have not tried to figure out an alternative method to avoid buying the reamers (which are not cheap). . Let me know if you develop an alternative method.

Some sandpaper on a small dowel might do the job but would require more work and would take longer.
 
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You could overdrill and stretch the tubes slightly before inserting in the blank but this would also risk a loose fit. I wonder if overdrilling and using a more pliable glue would help. Like gorilla glue.
 
Stretching the brass tubes slightly before gluing them into the blanks is a good suggestion.
Since you don't need to stretch by more than about 0.002" on the diameter, I would not think that overdrilling the hole in the blank is necessary (the recommended drill sizes are already oversized by more than the required stretching).

But my question would then be ... how do you stretch in a fairly controlled way (reproducible) so that you can get it "right" every time.
 
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I use a tapered reamer to remove burrs, bevel the tube for easier alignment of the pressed part, and most importantly removing everything from inside the tube (typically glue). I've been fortunate that I've not cracked a blank. They are about the best $3 you can spend at HF. I did make some passes with a diamond card on the edges, it improved it considerably.

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Small round rat tail file is the handiest thing in the pen assembly arsenal. That and a small reamer to clean any lip on the end of the tube.

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Thanks for the suggestions. I was able to tun off the cracked area and made a contrasting band to replace the area. I used a dowel with some 400 grit sandpaper to make sure nothing was in there. When I disassembles the magnetic coupler there were some scratches on it like there was something in the barrel when pressed in. This time I could get the coupler to start by hand. Last time it didn't feel like it was going in when I tried to start it. I knew I should have stopped and looked. All fixed and my daughter is happy.
 
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