Neck "Turning"- the inside, not outside?

[BoydAllen]

FWIW as a reloader who's never turned necks but always wanted to I'm inclined to agree with this. Concentricity ultimately comes from uniform neck wall thickness so it seems to me it would easier to just turn the outside and then fire-form. Where I get lost is having to use an "expander" die to get new brass snugly onto a pilot.

Why is that a problem? It is simple to do. Neck turner manufacturers make expander dies and mandrels suitable for use with their tuners. Lube the inside of your necks, and the mandrel for the first one, and get busy. Sometimes we can read so much detail about a process that in our minds it becomes a bigger deal than it actually is. Sure, there will be a learning curve. So what? You will learn from your mistakes and get better as you go along.

 

[ireload2]

Single point inside neck machining is called boring. Yes you can do it but I don't know of any ready made tooling other than the old Lee Zero Error Target model loaders of the late 1960s and early 1970s.
Such tooling is NOT adjustable in the sense of a neck turning tool with a movable tool bit.
You could make it some what adjustable with a selection of reamers.
This entire process would be much better to execute on an engine lathe with small boring bars. But it would require specialized case holders to keep the case body exactly on axis while you bore the neck. All of it is sort of do able for the guy who has the patience of Job but why bother when it is much easier to turn the neck with a piloted tool.

 

[mikecr]

Like Boyd said, standard neck turning is pretty easy. On the first case or two you might mung it up. But a few more and you're producing good results. With a little trial & error and careful measure you dial right into desired thickness.
Thickness is all this is about.

Turning is not boring.
Straight boring requires concentric centerline feed, while turning does not(remember this). So in order for boring to cut the target thickness of a tube, that tube would have to be very concentric to begin. Any banana to it, and forget notions of boring for desired thickness. You're just wallowing a hole..
Now, if that tube was pressed into a chucked concentric sleeve, you could then run the reamer into a true center of it, removing thickness variance and establishing desired thickness.
This could be done, but isn't for cartridge cases, because there is no advantage in it over turning. At best, the results are just the same.

Again, what you need to know about turning is that it's about thickness. It has nothing to do directly with eccentricity, or runout. You'll normally get your best results turning new cases, which are in every way crooked. This, not because they're crooked of course, but because it doesn't hurt anything, and it's easier to push thickness variance outside before it was all driven inside with fire forming. There is donut mitigation in this as well.

Runout, and eccentricity (they're different), are handled with culling of cases (with high thickness variance), fire forming, and minimal sizing.
It doesn't matter here if you've turned necks or not. The entire case length contributes.
Anyone who reloads cartridges with turned necks, and any body sizing, sees runout just the same, and it grows a little or a lot with each sizing cycle. So you're not solving any of this with neck turning.

Then you might wonder what are the true advantages to neck turning. Different thread.

 

[ireload2]

mikecr,
You need to pull out ASME Y14.5M Geometric Dimensioning and Tolerancing and review it a while. This is the national standard that is used to interpret drawings in the US. The M means is also covers drawing interpretation of metric drawings. You will find that some of the things you say are not in agreement with the national standard. Some of what you said is nothing more than circular logic to make a bad pun.
Runout is a combination of concentricity and circularity.
So if you turn something perfectly round but it is off axis run out and eccentricity (or the lack of concentricity) are the exact same thing.
I guarantee you I can bore a straight hole if there is enough material to clean up.
You should drop the concentric centerline feed BS because it is the same process whether you turn the part of you turn the tool. All good machinists know that you turn with the tool on center just like you bore with the tool on center.

I guarantee you that I have bored many out of round and deformed forgings until they cleaned up and had a straight round bores. All that is required is enough material planned in the beginning so that the work piece cleans up. It matters little to the boring bar.
As far as wallowing a hole goes you don't know what you are talking about. I doubt that you have ever bored anything based on that little bit of miscellany.
Thickness does you no good at all unless the thickness is uniform such that you turn or bore the part and the results leave the ID and the OD concentric with each other. Remember it really is all about run out and concentricity so don't be spreading-mis information.
>>>The entire case length contributes.<<< This is totally false when it comes to neck turning using a piloted tool. The pilot aligns on the neck and nothing else.

Like Boyd said, standard neck turning is pretty easy. On the first case or two you might mung it up. But a few more and you're producing good results. With a little trial & error and careful measure you dial right into desired thickness.
Thickness is all this is about.

Turning is not boring.
Straight boring requires concentric centerline feed, while turning does not(remember this). So in order for boring to cut the target thickness of a tube, that tube would have to be very concentric to begin. Any banana to it, and forget notions of boring for desired thickness. You're just wallowing a hole..
Now, if that tube was pressed into a chucked concentric sleeve, you could then run the reamer into a true center of it, removing thickness variance and establishing desired thickness.
This could be done, but isn't for cartridge cases, because there is no advantage in it over turning. At best, the results are just the same.


Again, what you need to know about turning is that it's about thickness. It has nothing to do directly with eccentricity, or runout. You'll normally get your best results turning new cases, which are in every way crooked. This, not because they're crooked of course, but because it doesn't hurt anything, and it's easier to push thickness variance outside before it was all driven inside with fire forming. There is donut mitigation in this as well.

Runout, and eccentricity (they're different), are handled with culling of cases (with high thickness variance), fire forming, and minimal sizing.
It doesn't matter here if you've turned necks or not. The entire case length contributes.
Anyone who reloads cartridges with turned necks, and any body sizing, sees runout just the same, and it grows a little or a lot with each sizing cycle. So you're not solving any of this with neck turning.

Then you might wonder what are the true advantages to neck turning. Different thread.

 

[Harvey McCraw]

K&M makes inside neck reamers. I only use them to take out pesky doughnuts though.

Dan

I have one of those from K&M and they are terrific

 

[dkhunt14]

mikecr,
You need to pull out ASME Y14.5M Geometric Dimensioning and Tolerancing and review it a while. This is the national standard that is used to interpret drawings in the US. The M means is also covers drawing interpretation of metric drawings. You will find that some of the things you say are not in agreement with the national standard. Some of what you said is nothing more than circular logic to make a bad pun.
Runout is a combination of concentricity and circularity.
So if you turn something perfectly round but it is off axis run out and eccentricity (or the lack of concentricity) are the exact same thing.
I guarantee you I can bore a straight hole if there is enough material to clean up.
You should drop the concentric centerline feed BS because it is the same process whether you turn the part of you turn the tool. All good machinists know that you turn with the tool on center just like you bore with the tool on center.

I guarantee you that I have bored many out of round and deformed forgings until they cleaned up and had a straight round bores. All that is required is enough material planned in the beginning so that the work piece cleans up. It matters little to the boring bar.
As far as wallowing a hole goes you don't know what you are talking about. I doubt that you have ever bored anything based on that little bit of miscellany.
Thickness does you no good at all unless the thickness is uniform such that you turn or bore the part and the results leave the ID and the OD concentric with each other. Remember it really is all about run out and concentricity so don't be spreading-mis information.
>>>The entire case length contributes.<<< This is totally false when it comes to neck turning using a piloted tool. The pilot aligns on the neck and nothing else.

It's not all about run out. It is also about bullet grip and more consistent tensions.

Reaming brass that is only .012 to .015 thick is not an easy thing to do. The Reamer wants to push the brass away unless it is held by a die. It also didn't give a great finish on brass. Turning is way better and more accurate with a better finish. Matt

 

[mikecr]

Ireload2
I realize the term runout is often considered w/resp to a part centerline. To describe variance from a centerline.
But with cartridge cases, runout is any departure from straight, end to end, and any side. The product of all representing TIR.
Establishing uniform thickness alone, which is what neck turning does(for only necks), does not establish concentric cases, nor straight cases.

No matter how proud you are of machining potentials, you will not bore cartridge cases worth a damn.

 

[.22gongzilla]

Lube the inside of your necks, and the mandrel for the first one, and get busy...

I feel confident enough to tackle neck turning at this point but I really don't need to with my present rig because premium brass is available. The only time I would consider turning necks for my present rifle would be if I needed to use different brass for some reason, like experimenting with FMJ's or, more likely, converting to .222 rem mag.