# Help with Thread cutting



## tangoman (Jan 5, 2015)

G'Day Folks and Happy New Year to you all !

I need some help with cutting the external threads on pen bodies where the cap screws onto.

I got a lovely Christmas present from SWMBO of a 13mm triple start tap and die. I've successfully cut threads on harder type plastics i.e the cheaper swirl types - in fact no problems at all cutting this material !

But I really want to use some beautiful blanks that I have that seem to be made from a very different material.  I cant say for sure exactly what type of material it is.  This just cracks and splinters into pieces when I try and cut the thread ( tapping the internal hole is a lot easier with only very little cracking).

I turn the tenon to just below 13mm (approx12.9mm), lubricate it with either WD40 or engine oil and it just splinters or cracks off pieces when I try and turn the die. I tried using a die holder as well as handheld die wrench but the same result each time. 

What do I need to do ? What am I doing wrong ? 

HELP !!!! 

Regards,
Cam


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## jj9ball (Jan 5, 2015)

Triples are always tricky. You are cutting 3 threads at a time instead of one.  My first suggestion is that if the material is tricky you might want to try single start threads first.  They take much less torque to make.  I know that if the material you are using gets cold it may be more brittle.  I would turn the tenon to the 12.8mm range and try again making sure that your blank is room temperature or above.  Also, make sure that the die is located correctly.  I once ruined 3 pens in a row because the die was in the holder backwards... yeah, I'm THAT smart.  I always use Pam cooking spray as lubricant and have had good luck, but your threads shouldn't split just because of a different lubricant... you're still using a lubricant.  If the material you are using is Polyester resin or some version of that then I would say you might want to practice more on some regular old acrylic PR is REALLY brittle and can be fussy to work with.  I prefer acrylic or alumilite.   Try and get some alumilite material. Its not as generic and "boring" as swirly acrylic but its also not as fussy and brittle to work as PR is.  I hope this helps.  Good luck.


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## soligen (Jan 11, 2015)

For tougher blanks I have used a hair dryer to warm the blank - seems to help, but is not a fix all.  I turn the lathe on slow and prop the hair dryer pointing at the blank then go do something else for several minutes.  Sometimes I try to get the die in the warm air stream too.

Note: a heat gun will probably be way too much heat - I don't have one so never tried it, but seems a reasonable conclusion.


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## mredburn (Jan 11, 2015)

If your trying to thead acrylic you are not going to get good results, and that is what is sounds like your matereial is.   I would suggest  a brass or aluminium threaded sleeve that is glued onto a tenon cut on the pen body.


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## bosipipes (Jan 13, 2015)

I just picked up this. Wow it works great


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## dwilson (Jan 13, 2015)

The above is for sale on ebay. To bad i spent my Christmass money all ready on blanks. 
Lathe Tailstock TAP DIE Holder South Bend Atlas | eBay


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