Barrel breaking when installing mechanism

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les-smith

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I just turned a pen from a material I bought from Woodcraft called Polygem. It didn't feel like resin, it felt more like rock/stone. Anyways, I was turning a 7mm mini-european and as I was installing the twist mechanisim the material cracked slightly at the end I was installing the mechanisim in. It wasn't that bad, but it's noticable to me. I feel that I had everything lined up straight with the press when I was installing the twist machanism. What do I do to avoid this in the future? Why do you think it cracked?
 
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LanceD

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Did you make sure that you didn't leave any dried glue inside the tube ? That's another major cause of cracked blanks.
 

Dario

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What you mentioned + Lance's are the main things I can think of.

Here is another advantage of using poly (as far as I am concerned) vs. CA or epoxy. I believe poly provides little (very little but sometimes enough to make the difference) "cushion" unlike the harder glues.

This is my opinion only and can't be substantiated. [;)]
 

smoky10

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When you square the ends of a blank with the tube installed, you sometimes leave a burr inside the tube. Run a round file inside the tube to remove the burr or any dried glue that might be in it.
 

Dario

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Chuck,

I use Gorilla glue but the last I bought was the cheapest I can get from Walmart [:D]. It is Elmers and almost half priced, but haven't tried it yet so not sure how it will compare [:I].
 

les-smith

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I've never checked for a burr after squaring, so I'll start doing that. I've got some gorrilla glue, so I'll start using it with this material. Thanks for the input I know it will help.
 

airrat

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Les,
Along with all the ideas here is my procedure before putting pen parts into tubes. First, I take a counter sind and twist it with my hand on the end of the tube, then either take a round file or a piece of sand paper rolled and run it inside (cleans out any burs or glue).

On stuff prone to crack I seal the end of the blank with thin CA. Have to be careful doing this, if you get too much on it and it gets onto your finish you have to sand it down again and even start over. I don't know if this truly helps or just makes me feel better but I have only had one barrel crack lately and I believe that was due to a poor glue up with some corian. (I was in a hurry)

Some might say its a waste of time to do everything I do between the finish and installing the kit. But the way I look at it is after all the time I put into making the pen, I don't want to lose it the last 2 min. (Somewhat like watching the Cardinals playing, they can be winning till the 2 min warning and then lose by 21)
 

les-smith

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I agree with you Tom. It really hurts to put the time into a pen just to see it ruined. Anything I can do to keep that from happening is time well spent. Look at it as insurance. We all pay for insurance, we don't always need it, but when we do we're glad we had it. The way I see it ruining a nearly finished pen is money down the tubes and aren't all trying to maximize our dollars.
 

gerryr

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Two things and neither of these may apply. Frist, when I started making pens, I didn't have any instructions other than the little sheet I got when I purchased the kits at Woodcraft. That sheet did not say anything about the wood or resin or whatever needing to be milled right to the tube. First pen I made, I guess I was lucky, second pen not. The wood cracked right at the nib as I was pressing the transmission in, it was a slimline so basically the same things as a 7mm euro. So, make sure the material is milled right to the tube. The second possibility is the size drill bit you used. Lots of people use a 7mm bit for these, others use a "J" bit and I use an "I" bit. You can also use an "H". The point is that if whatever drill bit you use leaves minimal clearance for the tube and you use CA or epoxy to glue the tubes in, the tube doesn't really have anywhere to go when you press the parts in. If you have a pretty tight fit which is usually the case with the Cross transmission, the tube has to expand and if it is already basically in contact with the material, the material will try to expand. You can't do that with resin, or antler, or and even some wood.
 

bjackman

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Originally posted by Dario
<br />Chuck,

I use Gorilla glue but the last I bought was the cheapest I can get from Walmart [:D]. It is Elmers and almost half priced, but haven't tried it yet so not sure how it will compare [:I].

I've used Elmer's PU glue now for a few years. Works well. I've had no issues with it, but when my current supply runs out or more likely expires/thickens with age, I'll be trying Sumo glue. I can never resist the temptation to buy the bigger bottle for a buck or two more, getting twice as much, but end up throwing away whatever portion I don't use before it goes bad.
I probably haven't learned my lesson yet and will continue to buy the bigger bottle in the hopes that I really will do more turning/gluing, etc this year.
This reminds me of the definition of insanity: continuing with the same actions and expecting different results. [:I]
 
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