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Old 11-18-2014, 06:04 PM   #1 (permalink)
 
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Exclamation Expanding Brass Tubes

Hello all,

I recently glued up about a dozen pen blanks with 7mm brass tube in my garage which was about 40 degrees Fahrenheit and left them there to cure overnight. The next day I turned two blanks on my lathe and pressed the parts together to make a pen with no problems.
I brought the rest of the glued blanks in my house for the night. The next day I turned another two blanks on my lathe but this time when I tried to press the parts together the brass tubes had expanded very slightly to the point where the inner parts of the pen did not fit and the parts were too loose to finish the pen.
My question is did the brass tubes expand overnight by bringing them inside where it was much warmer? If so, how can I get them to shrink back down to useable size?

Thanks in advance!
-Travis
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Old 11-18-2014, 06:20 PM   #2 (permalink)
 
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I'm not saying that wasn't your problem, I've just never had this problem from temp. I have stretched a few tubes in the trimming process and scraping glue out of them, resulting in loose fittings. My solution was a little epoxy in the tube to fill the gap in the very loose ones and some red Loctite on the lesser ones. Just give it time to set up and don't assemble the transmission until they are dry so it doesn't lock up the action. Good luck!
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Old 11-18-2014, 07:03 PM   #3 (permalink)
 
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I thought it may have been the trimming process that stretched them at first but because I was able to turn one pen flawlessly before I brought them inside I figured it may have been the temp issue. Your probably right though I can't imagine the temperature could have changed the barrels that much.
Thanks for the advice on using a little epoxy or loctite I will have to try it!
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Old 11-18-2014, 11:39 PM   #4 (permalink)
 
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Update: It was definitely the trimming process that stretched the brass tubes. My drill press is an older model that doesn't grasp drill bits perfectly square without extreme attention.
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Old 11-19-2014, 02:22 AM   #5 (permalink)
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I handle loose fits similar to the way John suggested, but I use CA rather than epoxy. I put a drop or two of medium CA in the tube and let it dry before pressing the parts in. By letting the glue dry first, you can still disassemble the pen if needed.
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Old 11-19-2014, 04:02 AM   #6 (permalink)
 
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With 7mm brasses I made a holder from brass to hold them as I rough them up it serves as a go no go guage some brasses are found out that are too small needing expansion so far I just belt them in the bin. I always keep a hundred spares anyway so I can glue up in batches without opening kits.Slack fit is so seldom I would glue up.

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