# Threading PR in the cold



## PTownSubbie (Dec 14, 2011)

I have had some success with threading PR (maybe it was beginners luck) but lately have had some trouble. I have changed nothing but last night I cracked 2 blanks while trying to thread them. The only thing that has changed is the temperature in my shop.

Is there a possibility that he colder temps makes the PR more brittle and prone to cracking?

Could possibly heating the PR give me more chances of success? I am going to try this but just wondering if anyone has had the same experiences.....


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## Timebandit (Dec 14, 2011)

PTownSubbie said:


> I have had some success with threading PR (maybe it was beginners luck) but lately have had some trouble. I have changed nothing but last night I cracked 2 blanks while trying to thread them. The only thing that has changed is the temperature in my shop.
> 
> Is there a possibility that he colder temps makes the PR more brittle and prone to cracking?
> 
> Could possibly heating the PR give me more chances of success? I am going to try this but just wondering if anyone has had the same experiences.....



Heating it will definately help with the threading. PR is brittle as is, then you throw in the cold, im sure they are like glass then. I would heat it in some warm water.


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## seamus7227 (Dec 14, 2011)

hey Fred, I cant really help you on the threading part, but i would say that Yes, the PR is more brittle when colder than when warmer. The reason I say this is because when my blanks have sat in the garage over night(they are like a rock) and I throw them in the toaster oven, they soften up in a way. So if you can find that sweet spot, so to speak, with the temperature, then I would say you could "temp" your blanks to that temperature and thread when ready. Not sure if that helps ya


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## PTownSubbie (Dec 14, 2011)

Toaster oven may be too high in heat but the Ultrasonic cleaner I have will keep them right at the right temp! I am going to have to give this a shot!

Thanks for the recommendations!


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## Dalecamino (Dec 14, 2011)

Fred, it will help if you clear the shavings out completely while cutting. FWIW


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## soligen (Dec 14, 2011)

I have has success using a hair dryer to wam the blank, but then sometimes the part warps a little and doesn't spin true anymore. I wont thread PR any more - it isnt worth the toubles it casues.


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## avbill (Dec 24, 2011)

Dennis,  if you don't thread PR  what do you use?


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## soligen (Dec 24, 2011)

avbill said:


> Dennis, if you don't thread PR what do you use?


 
Polyurethane Resin (like Alumilite) or PMMA (Polymethyl methacrylate). PMMA is the generic term. Brand names are Perspex, Lucite, Plexiglas. These materials don't need tubes either, which simplifies things greatly. I would not trust PR to survive a drop test without being tubed.

I think most of the woodcraft acrylic planks that are not specifically labeled PR are also PMMA. (Whatever they are, they worked well for me, except the Invisaview blanks)

Even with the friendlier materials, some colors (more opaque ones maybe) it sometimes helps warming with the hair dryer right before threading. I think more pigment affects the blank and can cause pitting in the threads, which warming helps. I just prop up my shop hair dryer and turn the lathe on low and let it run for 3 - 5 minutes while I do something else.


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## EBorraga (Dec 24, 2011)

I'll agree with Dennis. I've been really experimenting with threading PR. My shop is cold, about 45f. I've mounted a hair-dryer behind the lathe. Let it run for about 5 minutes, with the lathe on slow. No problemo threading then.


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## drgoretex (Dec 26, 2011)

Not sure this will add much, but my Canadian experience has most definitely been that I am much more likely to get blanks shattering in the cold while threading.  I do find PR more prone to this than acrylic, but when the shop is at -10, even the acrylic can have trouble.  I have used a space heater (small portable one) to heat up the blank before threading, with some success.  Also, lots and lots of WD40.

Ken


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