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Neck Turning and the Heat

Grimstod

Machinist, Designer, and Shooter.
I am neck turning some brass. Necks are starting at 0.0125 and finishing at 0.0108in with a neck that is 0.365 long. Going in slow and turning out fast.
Now here is my problem. My neck turning tool is getting HOT. Like burn my hands hot. Only did 10 pieces this morning too. Should I dunk it in water to cool it? I am using a lot of lub.
 
I your tool offers a large aluminum handle as an option I suggest buying one as it serves as an excellent heat sink to draw heat from the mandrel and tool frame. I keep 'canned air' with me at my turning station to blow chips off the cutter between cases (as needed) and also invert it and spray the tool for a few seconds to cool down the heat sink. I use lanolin 'butter' dissolved in mineral spirits as a lube. My cutter gets warm to the touch at most...just a little warmer than body temperature and far from being uncomfortable.
 
Use carbide mandrels - they help a lot. As rardoin said, a big block of aluminum like the Sinclair 4000 is a great heat sink (and very comfortable to hold). Also play around with the speed at which you cut the necks. There is an optimum that gets you a good finish while minimizing heat build up. Think about both rpm and the "feed" rate. You should be able to get through quite a few cases without building up much heat. Mine never gets hot enough to even come close to burning anything, but I do take a quick break every 50 or so cases and let it cool back down for a few minutes. A blast of compressed air would do it pretty quickly if you're so inclined. In my experience, it takes quite a bit of temperature to produce a measurable variance in neck thickness.
 
Oh...yes....speed...I turn my 6.5/6mm necks at 160 RPM... Not fast by any means compared to most cordless/corded drills but I get a great finish and generate no more heat than necessary. Remember, heat is generated by the cutter tool shearing the metal away and the friction of the inside of the neck rubbing the mandrel. I dip my necks in my lube to help with both as the inside of the necks has a lubricant to 'ride' on and the evaporation of the solvent helps draw out heat from the cutter tool.
 
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I read about neck turning rigs generating heat all the time, occasionally LOTS of heat. Sorry, but I don't get it.

The only neck turning gear I've ever used is my 21st Century lathe and cutter head with the "normal" expanding mandrel and turning mandrel. I shoot three calibers and all three p;produce the same good results.

I use a little lube from time to time during the process, usually whatever is within arm's reach; Marvel Mystery Oil, Knockers Off, some kind of sizing lube, or what-have-you. I don't lube every case and usually apply lube right after I use a tooth brush to clear away shavings.

I use a cheap cordless drill as a power source and run it at about half throttle, which is pretty fast but the RPM is a mystery to me. I feed in and out at about the same rate and the cutting process is less than 10 seconds per neck; I'd guess about 8 seconds on average. I turn the next piece of brass as quickly as I can unload and reload the case holder. I'll do this over and over again until my brain gets foggy and/or my butt wears out and I have to stand up and take a short break.

If I touch the case and/or mandrel and pay close attention I can barely detect that the temperature of the components is slightly above ambient. Never does anything get what anyone would call hot. Calling it barely warm might be considered an exaggeration.

Everything seems to be working perfectly. Am I doing something wrong? ;)
 
I am neck turning some brass. Necks are starting at 0.0125 and finishing at 0.0108in with a neck that is 0.365 long. Going in slow and turning out fast.
Now here is my problem. My neck turning tool is getting HOT. Like burn my hands hot. Only did 10 pieces this morning too. Should I dunk it in water to cool it? I am using a lot of lub.

Is the heat coming from taking almost .002 off at one time or friction from the case on a snug fitting mandrill?

Is there lube on the outside of the neck and the mandrill?

Did you try taking less off at a time and reducing the amount of friction and heat?
 
I am neck turning some brass. Necks are starting at 0.0125 and finishing at 0.0108in with a neck that is 0.365 long. Going in slow and turning out fast.
Now here is my problem. My neck turning tool is getting HOT. Like burn my hands hot. Only did 10 pieces this morning too. Should I dunk it in water to cool it? I am using a lot of lub.

I had the same problem until last week when I discovered that using a drill (generating a shed-load of heat) causes inconsistency in the neck wall thickness.

I now lube the inside of the case with a graphite grease mixed with STP fuel additive and hand lathe the cases. I now get a VERY consistent .0135 neck wall thickness.
 
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Is the heat coming from taking almost .002 off at one time or friction from the case on a snug fitting mandrill?

Is there lube on the outside of the neck and the mandrill?

Did you try taking less off at a time and reducing the amount of friction and heat?

Are you expanding the necks to the proper size for your mandrel before you turn them?
 
I was having the same problem. Matter of fact, I would keep a bowl of crushed ice to soak the turner and my fingers. Then I went with PMA turner, expander mandrel and my problems vanished! I use an adjustable speed Hitachi drill that I bench mounted. I set the speed wheel and fire it up with a foot operated switch. Works slicker than frog's hair!
 
Update. I am using lub on both the mandrel and the outside of the neck.
I did switch to an expander that is 0.0003 larger and it did solve a lot of the heat issues.
 
Speed and friction produce heat. Use lubricant in the necks and on the mandrel. Also run your drill or whatever you use at a slower speed. I've turned at least 100 .308's at a time and the hand held K&M cutter I use had never got even slightly uncomfortable and I'm more heat sensitive than most.
 
What you use for lube is a factor, as is, how much lube you're applying. If lube is too thick in viscosity and/or to heavily applied, it might actually be counterproductive...
 
I wondered the same thing about heat causing my necks to be thicker or thinner than the others, actually lost sleep thinking of ways to avoid it. Then one day I just stopped neck turning all together and my scores went up? easy fix.
 
There are three things that can cause heat, and a fourth that helps. Lubrication, fit and how fast the case is turning. The fourth is mandrel material. I much prefer carbide. As far as not holding the tool is concerned, I disagree completely. I have been turning cases to very close tolerances for over 20 years. Here is a tip that I would like some feedback on. Measure a case's length just before you turn it and after you finish, allowing it to cool to the same temperature as the first measurement. If your case is growing a lot, your cutter is dull.
 
image.jpg I have a homemade version of the “pumpkin “ which is a big heat sink in itself. I expand cases to be about .001 bigger than the mandrel and turn from .0136 to .010 in one pass (No heat issues) then I use a PMA turner to finish at .0083 for a .262 chamber. The PMA mandrel is fitted to the expander thus better finish. I do lube the PMA before ever case , last time I used “unique case lube “ and worked out great.
Sounds to me the case is too tight on the mandrel or turning to fast. Any metallic colors on the mandrel?
I am using a dewalt 20v on #1 speed , seems slow but #2 speed is too fast and results in overheating.
 

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