Keeping mandrels cool

adamsgt

adamsgt

Jerry Adams
I've noticed in some discussions on turning necks a caution to keep the mandrel cool so it doesn't expand too much and change the resulting neck thickness. Mike Schmidt uses a mister on his lathe but that would be difficult to use on a K & M or similar hand turner. Was wondering if the canned air dusters would be effective in keeping the temp down? A blast of that air periodically might do the job. Anybody try this yet?
 
It doesn't have to be complicated. Just set the turner in some water after each case. Change the water when if it starts getting warmer.

JIm Carstensen
 
I'm with Jim,

And to further elaborate, the "blast of air periodically" is one of the things that kills it for me...... The name of the game is CONSISTENCY, absolute sameness case to case. If the mandrel gains heat and gets fatter-Fatter-FATTER- blast- thin- fatter- Fatter -see what I mean?

This is also why I think the "body die" concept for resizing is flawed. Why would a person fire a case 2-3-4 times and then "BUMP" it or resize it to start the cycle over again???

Keeping the cutter in a tub of water keeps it consistent AND allows you to swish a lot of the hangys and big gunk off each time.

al
 
adamsgt said:
Was wondering if the canned air dusters would be effective in keeping the temp down? A blast of that air periodically might do the job. Anybody try this yet?
Click to expand...

Frankly I doubt it. I think someone suggested cooling by dipping in a bucket of liquid that might well work . But blowing with air isn't going to do very much I don't think. Not near enough any how.
 
Keeping Mandrels Cool

Get a plastic bowl. Fill with crushed ice. Cover the top with saran wrap. Set neck turner on top of saran. No water to co-mingle with whatever lube you use. Ice is cheap. A junk rag and a hammer makes good crushed ice if your referigerator does not have an ice dispenser. ( Crush the ice in the shed or garage, not on the kitchen counter. Some of them don't have any sence of humor ( LOL )). Turner stays nice and cool. I'm a firm beliver in KISS. ( Keep it simple stupid ). Just my .02 cents worth. Ron :)
 
ronsroom1 said:
Get a plastic bowl. Fill with crushed ice. Cover the top with saran wrap. Set neck turner on top of saran. No water to co-mingle with whatever lube you use. Ice is cheap. A junk rag and a hammer makes good crushed ice if your referigerator does not have an ice dispenser. ( Crush the ice in the shed or garage, not on the kitchen counter. Some of them don't have any sence of humor ( LOL )). Turner stays nice and cool. I'm a firm beliver in KISS. ( Keep it simple stupid ). Just my .02 cents worth. Ron :)
Click to expand...


That is perty good thinkin' right thar!!

Thanks Ron

al
 
I doubt that frictional heating is much of an issue when turning necks on a lathe, since, with the usual setup, the case and the mandrel do not rotate relative to one another. (The case is shoved on the mandrel and they both turn together.) Other types of turning setups (that do have this relative motion) can generate excessive heat if the neck fits the mandrel too tightly, there is inadequate lubrication, the RPMs are too high, or the finish of the mandrel and/or the material it is made of are not suitable. While you can turn necks to an excellent tolerance with a wring on fit, it is not a necessary part of the process, and a lot of problems are alleviated without it. One of the most important parts of the process is an expander mandrel that is sized correctly relative to the turning mandrel.
This is complicated by the fact that different manufacturers' brass has different spring back when expanded. Expander dwell time in the neck, and time between expanding and turning also have an effect...unfortunately.
 
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Mandrel Lube

A 1/2 drop of Speedy Turn on the mandrel and you'll be twice as amazed. ...Dave
 
A James Mock tip that works....

I fill a plastic bowl with cheap-o denatured rubbing alcohol and drop the turner in that between cases. Keeps it cool and the alky is a decent solvent for brushing the chips off the turner with an old toothbrush.
 
A slush bag--

I once had an injury that required COLD treatment. The PT I had gave me the directions for making a slush bag. Two 1 Qt zip lock bags; the inside bag gets a 50-50 mix of water & rubbing alcohol, that bag goes inside the second bag for protection. Plop it in the freezer for a few hours. The water never freezes beyond a slush. This might work; haven't tried it, me.
 
Why not just measure the mandrel when warm, and see if you have something to be concerned about.
 
Body Die concept

alinwa said:
This is also why I think the "body die" concept for resizing is flawed. Why would a person fire a case 2-3-4 times and then "BUMP" it or resize it to start the cycle over again???

al
Click to expand...

Al,
Do you mean you are a proponent of sizing every time? I have been body sizing after three or four firings but minimally re-sizing makes sense in keeping everything consistent. Jim Carstensen has converted several of my body dies into accepting the neck sizing bushing and I have them set up so that they bump the shoulder back only .001. Should I be doing this after every firing and not wait until the bolt gets stiff?

Thank you in advance.
Chino69
 
ronsroom1 said:
Get a plastic bowl. Fill with crushed ice. Cover the top with saran wrap. Set neck turner on top of saran. No water to co-mingle with whatever lube you use. Ice is cheap. A junk rag and a hammer makes good crushed ice if your referigerator does not have an ice dispenser. ( Crush the ice in the shed or garage, not on the kitchen counter. Some of them don't have any sence of humor ( LOL )). Turner stays nice and cool. I'm a firm beliver in KISS. ( Keep it simple stupid ). Just my .02 cents worth. Ron :)
Click to expand...

I've gotten some things pretty cold with that canned air(inadvertently) but I see that the consensus is against using it. Thought that would be quick and easy but quick and easy doesn't always lead to good. Another thought, my daughter bought me some fake ice cubes, a gel in small plastic packets. That might work in place of actual ice. How about some of those freeze packs? Just lay the turner on that in between cases. Somehow the thought of picking up a turner out of a bowl of some liquid dripping all over the place sounds rather messy.

Has anybody done an experiment to see what the actual expansion on a mandrel might be during the turning process? Maybe turn a dozen or so without cooling and measuring the mandrel after each one. See if it stabalizes at some point. If it does, then maybe the idea would be to pre-heat the mandrel before starting. Could be something to do on New Years day when there's nothing but football on TV. :p
 
My method is to turn 5 cases, take a 10 minute " worry break", and turn 5 cases. This tends to level out the mandrel tempature.
 
B.Johnson,

It's perty hard to measure.

GAUGE, yes---MEASURE, iffy at best. But the mandrel tension and cutter clearance offer a very consistent gauging capacity. In a perfect world my cutter cuts very smooth on the IN stroke, then I HOLD for a second or so while my cutter feathers into the shoulder forming a long and wide radius at the n/s junction. (I grind my cutters to stop on the shoulder, to quit cutting when they've run a certain distance up the shoulder. In other words, the shoulder IS the stop.) Then I get just the slightest cleanup cut on the way back out....BECAUSE the mandrel has gained a little heat and swolled up some.

Now, if I set everything aside, drop the turner back into the water bath and wait about as long as it takes to turn a case...... I take the SAME case and reinsert it onto the mandrel and 2 things are apparent. #1, it's a looser fit on the mandrel and #2 the cutter bit does not touch at all.

I call this gauging the fittage.



Chino69,

Absolutimally YES!!! That's a resounding YES to resizing every time. My bolt drops EXACTLY the same every shot. My system is preloaded EXACTLY the same every shot. And I try to set the shoulder back LESS than a thou. To me the idea of every 3-4 rounds going from tight to loose is just abhorrent. IMO NONE of the shots are truly consistent. loose-slightly tight-tighter-TIGHT! ("ooops, better bump")-LOOSE!-loose-etc





I had a lesson in this recently. I was shooting my 6X47. Now back when I set it up, I took several hours setting up and dialing in the combinations .......I changed out the die-shim stacks several times, wrote it all down and for several mo I've just been USING it. I have taken the die in and out several times. The other day was cold in the shooting room, I didn't have the heat on, I was worried that something had shrunk or change because the bolt handle was just falling closed. AND, this "jumping bullets" thing has me disconcerted, I'm used to feeling SOME tension on the bolt handle. On this rifle the bolt handle just drops.......clik.

So I dropped a thread from a cleaning patch into the chamber....LOCK!!

I went back in and added ONE THOU to my shim stack and continued loading and shooting. TWO FIRINGS and the bolt was hanging up.

I took my thou back out.......and all is right with the world. :):)

Some of these 6X47 cases now have 20 firings on them and you can't measure a difference from one with 3 firings. SIZED EVERY TIME :)

al
 
Yet another thought - - -

I was giving a friend a bit of history on some BR chamberings this morning and my toughts went to N0-Turn necks. With a credible source reporting no accuracy difference between turned and no-turn necks, why are we concerned about a few tenths difference in turned necks?
 
Pete Wass said:
I was giving a friend a bit of history on some BR chamberings this morning and my toughts went to N0-Turn necks. With a credible source reporting no accuracy difference between turned and no-turn necks, why are we concerned about a few tenths difference in turned necks?
Click to expand...

I do both.

IMO neckturning is not important for 100-200 yd bullets but it's critical for long range shooting.

al
 
Am I missing something?

Perhaps one of you much more experienced in metallurgy than I can expound on this.

When I run the numbers based on the coefficient of expansion for steel/stainless steel, I just don't get any really big upsizing (i.e., diameter) of mandrel sizes for temperatures I'd expect to see (below 200, or so, deg. F).

From what I calculate, one would have to get that mandrel REALLY hot to make a whole lot of difference.

What am I missing?

Thanks,

Glen
 
GlenO said:
Perhaps one of you much more experienced in metallurgy than I can expound on this.

When I run the numbers based on the coefficient of expansion for steel/stainless steel, I just don't get any really big upsizing (i.e., diameter) of mandrel sizes for temperatures I'd expect to see (below 200, or so, deg. F).

From what I calculate, one would have to get that mandrel REALLY hot to make a whole lot of difference.

What am I missing?

Thanks,

Glen
Click to expand...

Extra heat being transferred to the case neck?

al
 
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