Threading Casein

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Stevej72

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I have been wanting to try a kitless pen using Casein. Since the blank I had was rather expensive I have been putting it off. I didn't have enough to make the cap so I started on the body and section. The section treaded fine and so did the inside of the body. My problem was the outside of the body with the triple start threads. I could hear the Casein cracking just as I started cutting the threads and a chunk broke out.

Any ideas on how to avoid this? Not sure what to do next. I don't want to throw out the pen, but there is nothing left to thread. I wonder if I could make a snap on cap?

Sorry for the bad pictures but my white balance is not working for some reason. Also didn't spend a lot of time polishing it up.

Any suggestions would be appreciated.

Thanks in advance!
 

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Too deep a cut? Too thin a wall? What are those dimensions? Can you try thread milling? How about threading before boring? Does your threading tool have the appropriate relief for the high helix angle? Anything to reduce stress on a fragile material.

I love that material, by the way.

Just dunk it in water and glue it back on! :) :)

Cheers,
Rich
 
Thanks guys! I think the material was too thin and the diameter of the tenon could have been a little too much as well. I should have cut the outside threads first and then done the inside, maybe. The tenon diameter was about .462.

I didn't have any white material left but I did epoxy a piece of scrap inside. Since my section is a little long I think I can cut off the damaged end and put my threads on.

Won't get much time the next three days as I will be working.
 
Steve; There was another thread that discussed putting the tap inside the tube while threading the outside to strengthen the threads and prevent a collapse while threading. You may want to make a small piece of plug to put into the threads while you are threading the outside.
 
Thanks Randy, That does sound like the way to do it. I just glued a piece inside and did the outer threads again. They turned out nicely. But when I did the inside threads I had the same cracking problem.

It will be awhile before I get a chance to try again as these blanks are rather expensive. At lease I have a usable section out of this blank.
 
Stevej72 said:
Thanks Randy, That does sound like the way to do it. I just glued a piece inside and did the outer threads again. They turned out nicely. But when I did the inside threads I had the same cracking problem.

It will be awhile before I get a chance to try again as these blanks are rather expensive. At lease I have a usable section out of this blank.
Click to expand...

Try making something like a nut to go on the outside to support it, and when threading the inside, turn only a little bit 1/16th or there abouts and back it out. Take your time on this, and make sure you use plenty of lubricant I think its PAM that a lot use over there.
Kryn
 
Oops! My silly suggestions were based on turning threads, not tapping. How about tapping before you turn? Or, can you single point the threads? Casein has obviously crappy tensile strength. Your multi-lead tap will put greater expansion forces on your workpiece (greater DOC) than an ordinary tap with the same taper.

Cheers,
Rich
 
Rich, I do have a metal lathe but haven't learned to do threading with it yet. I could try a single point die though and see how that works. Of course you can't buy a fine enough thread locally.
 
I make up a threaded collar from scrap material and screw this on the outside thread of the barrel when I tap the inside thread. This supports the material while tapping the inside thread.

IMG_4194.jpg


Like a fool I forgot to do this a couple of days ago and this was the result.

IMG_4272.jpg
 
I know that feeling, too, Fred. Chuck had made the suggestion in a PM like your treaded collar. When I made the second attempt I had planned on putting that collar on after turning the outside threads and in the excitement to finish I did the same thing in your picture above. I need to slow down and pay attention to what I'm doing. Thanks for the suggestion!
 
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