Keeping mandrels cool

Al

I thought about that and almost put in a reference to annealing in my post.

However, the thread seemed to be concentrating on the expansion of the mandrel that would/could lead to a neck thickness that would be less than desired.

From what I calculate the neck thickness would only be decreased by a very small amount, even if there was a significant increase in the temperature of the mandrel.

However, I don't really know what effect the increased temperature would have on the metallurgy of the brass in contact with the higher temp.

Glen
 
alinwa said:
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.
Click to expand...
Kaching! The penny dropped!

Thanks, al, for explaining why I've experienced that outcome.

John
 
GlenO said:
I thought about that and almost put in a reference to annealing in my post.

However, the thread seemed to be concentrating on the expansion of the mandrel that would/could lead to a neck thickness that would be less than desired.

From what I calculate the neck thickness would only be decreased by a very small amount, even if there was a significant increase in the temperature of the mandrel.

However, I don't really know what effect the increased temperature would have on the metallurgy of the brass in contact with the higher temp.

Glen
Click to expand...


What do you consider really big upsizing??

Hovis
 
Hovis

The numbers I have looked up for steel has the coefficient of thermal expansion as 0.00000645. It'll likely be slightly different for any given mandrel; but, I suspect, not significantly.

Applying that expansion coefficient to a 0.243" diameter mandrel and assuming a temperature increase of 100 deg. F, I calculate that the mandrell's diamter will increase by 0.000157 inches.

I would think a 100 deg temp increase might be somewhat on the high side.

I don't think 1.5 ten-thousandths decrease in neck thickness would be all that significant. Maybe, I'm wrong in that conclusion.

Thoughts?

Glen
 
Fix this "problem" all you want

Your scores won't improve as a result. It's likely the "precision" line of thinking is causing the heat in the first place. You know, the tighter the fit the closer the cut kind of deal. Loosen up the mandrel/neck fit a bit and just cut the cases. Measure the first and last one to make sure the loaded round has some neck clearance and you're good to go.
 
Wilbur said:
Your scores won't improve as a result. It's likely the "precision" line of thinking is causing the heat in the first place. You know, the tighter the fit the closer the cut kind of deal. Loosen up the mandrel/neck fit a bit and just cut the cases. Measure the first and last one to make sure the loaded round has some neck clearance and you're good to go.
Click to expand...

What was that old saying? Measure it with a micrometer, mark it with a grease pencil, then cut it with an axe. :eek:
 
Was thinking if ya turn your brass slowly by hand then the brass and mandrel might not heat up much at all.
 
Martin,

You're right :)

But ........ your necks will look a liddle scabby and your liddle hand will get SO SORE!




Here's a picture of my neckturning setup. The yellow thing with something in it is a small MTM cartridge box full of water in which resides a Time Precision Neck Turner.

The big silver pan is the reason I've posted the pic. A poster mentioned the mess and this is my solution. Believe me, the dripping water is small potatoes compared to the acres of brass shavings that you'll track all over God's Creation if you don't somehow contain them.

YES I did go down to the local restaurant supply house and bought my own huge stainless pans. They're donut display pans and I bought two. The other one has a clear plastic cover with a handle and it houses my Denver Instruments electronic scale AND a Juenke, all under the handy-dandy cover.

Actually, I did steal some cookie sheets and pans from my Totally Significant Other but ONLY after tempting Her Beautifullness with an offer for some brand new pans since "we'd had those old things since we were married"......... (this is SOOOO a Win/Win for me!! :D:D:D:D:D )

LOL


al
 

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GlenO said:
The numbers I have looked up for steel has the coefficient of thermal expansion as 0.00000645. It'll likely be slightly different for any given mandrel; but, I suspect, not significantly.

Applying that expansion coefficient to a 0.243" diameter mandrel and assuming a temperature increase of 100 deg. F, I calculate that the mandrell's diamter will increase by 0.000157 inches.

I would think a 100 deg temp increase might be somewhat on the high side.

I don't think 1.5 ten-thousandths decrease in neck thickness would be all that significant. Maybe, I'm wrong in that conclusion.

Thoughts?

Glen
Click to expand...

Glen,

A tenth and a half is peanuts and essentially meaningless for point blank BR but it's very meaningful for longrange shooting.

In 100-200 BR the match of components allows you to throw charges with alacrity, neckturn or NOT, neck tension or NOT, shoot loads which vary in velocity and generally concentrate on learning to drive. At 100yds a good BR gun will put three different bullet wts and 3 different powders through the same hole just dropping the bullet in on the charge.


But for long range BR with it's heavy bullets, larger cases, slower powders and YET a driving need to keep ES into single digits it's a whole nother ballgame.

The ES that even the winningest 6PPC typically exhibits would keep you also running forever at 1K as the typical PPC runs 45fps ES which is more built in dispersion than the winning groups by twice't.

Many folks feel that 1.5 tenths will significantly increase ES. It will certainly significantly change seating pressure and consequently "bullet pull."

al
 
I think the easy way to take care of the heat problem is to use a large heat sink. I noticed when I got out of the use of the K&N and went to Don the pumpkin's neck turner the hot neck turner/ mandrel problems disappeared.
 
Glen,
Thanks for the answer. I don't know about how much variance makes a difference but I pay attention to two things.

One, to have enough clearance I can use any of my current bullets. I do think a ppc shoots best at around .0007 to .001 clearance but it's more of a feeling than anything else. I like fresh brass so sometimes I vary some and have found if I get .0015 or more, there's a drop in accuracy.

Two, I size the necks enough during sizing that I past the point of diminishing grip on the bullet...thus making slight variations in neck thickness a null point as it pertains to the bullets consistant release pressure.

Or these could be just my own thoughts to make myself feel better...either way, it works for me.

By the way...good answer Wilbur.

Hovis
 
Big Al said:
I think the easy way to take care of the heat problem is to use a large heat sink. I noticed when I got out of the use of the K&N and went to Don the pumpkin's neck turner the hot neck turner/ mandrel problems disappeared.
Click to expand...

Or you can use one of the holder's for the K&N and it acts as a heat sink. Heat is the by product of friction. Wilbur is correct, don't have too tight of fit on the mandrel, use a carbide mandrel, use a good lube and turning necks is a piece of cake. See picture for tool holder.
 

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Tool Holder

If you will notice the Genuine Cherry tool holder in the photo. Very comfortable... and it was free. Cool mandrel provided by product in bottle.
...Dave
 

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???????

Ben Johnson asked, Why not just measure the mandrel when warm, and see if you have something to be concerned about.

Because once this was done then you would have some NUMBERS - most posters on this forum don't like numbers!
 
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