Resizing Die Opinions

[kvd]

Good discussion gentlemen. As the Irishman said as he passed by two men fighting "Is this a private fight, or can anyone join in"

In this day and age of very expensive brass I did not want to scrap any of it. So I measured each case as I zeroed in on the perfect die setting. I noticed the head to shoulder datum lengths varying about .002 depending on how much lube was used, how fast I sized and how much dwell was used at the top of the stroke.

I have observed the same thing. Measuring every case before and after sizing and then testing the fit in the rifle chamber with the bolt stripped, one can get a good feel for the relationship between the reading from the comparator and the feel of the bolt closure. A thousandth of an inch makes a hugh difference in whether the bolt will essentially just fall or if there will be just a slight amount of drag on closure - which to me is more desirable since the bolt will drop with no resistance if the case is sized excessively. Doing this, I've found some cases in a lot will not size on the setting the die is at so these are set aside and the process is repeated again with the die adjusted down ever so slightly - I'm talking barely turning it down. Check, recheck and test fit until it is right. I like to spray the cases with an isopropyl alcohol (99%)/lanolin mixture and let the alcohol flash off in order to obtain the thinness film of lubricant possible. Go slow, dwell a few seconds in the die after the press cams over, rotate the case and repeat. I should point out that not all reloads receive this royal treatment. Only short range BR stuff. It is good practice though to check a few cases every now and then during normal reloading to make sure things are still working as expected.

On an angled case or any other angled surface, a flat face mic can only measure off the high side and only then if you can manage to get the exact center inline with the center of the object you are measuring.

Have to agree here. Spent many years around precision machining (aircraft parts). For our purposes, the tip ends of decent calipers would produce an adequate measurement of the case body at different points along the length.

Ken

 

[ireload2]

Sorry to disappoint you but I learned to use precision measuring equipment in high school and worked my way through an engineering degree with them working as a machinist for 5 years full time and 2 years part time. Then I worked as a manufacturing engineer for 45 years. That is 50 years of precision machined parts and assemblies. That means that I started before you and I continued working in that field way after you. During that time I hired and set up 2 different calibration labs for my employers. These labs calibrated in house measuring equipment. In addition I provided to engineering support to many shops in the US, China, Singapore, UK and Germany. Basically I have seen how the best shops around the USA and the rest of the world machine and measure their work. I managed as many as 20 engineers, technicians, programmers and quality personnel.

Now if you knew anything about plane geometry you would know that you cannot get your spherical anvil and spherical spindle micrometer on the exact top of the poles of the contacts when you are measuring a non-parallel surface. You might go review ASME Y14.5M Geometric Dimensioning and Tolerancing. It is the US national standard and you do not seem to grasp ordinary plain geometry and how it affects your proposed measurement.
The poles are the only places that can provide an accurate measurement. With a non-parallel object you cannot get right on both poles at the same time. You can't do it no matter how loud you want to shout.
You say my way is not easy? Sure it is easy if you have a tiny bit of skill and patience. You might actually have to put out a little effort to learn how. It works for me and I have used the edge of an 0-1 mike face to do it for more than 40 years.
So you claim your measuring device has to be perpendicular but you cannot seem to grasp that your spherical mike cannot be perpendicular to two non parallel surfaces at the same time.
Your calipers are not repeatable to .0005. They are only guaranteed to be within .001. You should check out the reality of caliper accuracy in the specifications. You are simply deluding yourself because you want to use a process that you think is easy. Yes it is easy but it is not very accurate. You can get within plus or minus .0002 with a mike and you cannot touch that with a caliper.
Even with your calipers you are still using 2 parallel faces to measure on the surface of 2 NON parallel surfaces. You still have the same edge hunting issue and you are using an instrument that is about 1/10 as accurate.

Sorry to obviously disappoint you but I wasn't born yesterday, or even the day before and I have worked with measuring equipment in several jobs over the course of my working career back to the early '70's. Machinist, inspection, engine builder, and several others. I think I know how to read a mic by now. On an angled case or any other angled surface, a flat face mic can only measure off the high side and only then if you can manage to get the exact center inline with the center of the object you are measuring. Not saying it can't be done but it's not easy, at least for me. Any measuring device also needs to be perpendicular to the centerline of the object or there will be an error in your reading. A ball head is much easier and probably more likely to be accurate given the possibilities of not getting the flat surfaces aligned properly.
View attachment 1017989
And with calipers. I would use the sharp edge, not the flat wider surface for a measurement like this. And from my experience, most decent quality calipers are repeatable to 1/2 thousandth. I'm not saying you'll the the correct measurement as compared to a micrometer. Most all calipers are rated to +/- .001". The purpose of this post wasn't to show the exact measurement, just the variance after resizing.

Good luck to you in measuring any way you choose. I'll use a method that works!

 

[Hal]

You guys done measuring your equipment yet ?

 

[ireload2]

You guys done measuring your equipment yet ?

 

[T-shooter]

Sorry to disappoint you but I learned to use precision measuring equipment in high school and worked my way through an engineering degree with them working as a machinist for 5 years full time and 2 years part time. Then I worked as a manufacturing engineer for 45 years. That is 50 years of precision machined parts and assemblies. That means that I started before you and I continued working in that field way after you. During that time I hired and set up 2 different calibration labs for my employers. These labs calibrated in house measuring equipment. In addition I provided to engineering support to many shops in the US, China, Singapore, UK and Germany. Basically I have seen how the best shops around the USA and the rest of the world machine and measure their work. I managed as many as 20 engineers, technicians, programmers and quality personnel.

Now if you knew anything about plane geometry you would know that you cannot get your spherical anvil and spherical spindle micrometer on the exact top of the poles of the contacts when you are measuring a non-parallel surface. You might go review ASME Y14.5M Geometric Dimensioning and Tolerancing. It is the US national standard and you do not seem to grasp ordinary plain geometry and how it affects your proposed measurement.
The poles are the only places that can provide an accurate measurement. With a non-parallel object you cannot get right on both poles at the same time. You can't do it no matter how loud you want to shout.
You say my way is not easy? Sure it is easy if you have a tiny bit of skill and patience. You might actually have to put out a little effort to learn how. It works for me and I have used the edge of an 0-1 mike face to do it for more than 40 years.
So you claim your measuring device has to be perpendicular but you cannot seem to grasp that your spherical mike cannot be perpendicular to two non parallel surfaces at the same time.
Your calipers are not repeatable to .0005. They are only guaranteed to be within .001. You should check out the reality of caliper accuracy in the specifications. You are simply deluding yourself because you want to use a process that you think is easy. Yes it is easy but it is not very accurate. You can get within plus or minus .0002 with a mike and you cannot touch that with a caliper.
Even with your calipers you are still using 2 parallel faces to measure on the surface of 2 NON parallel surfaces. You still have the same edge hunting issue and you are using an instrument that is about 1/10 as accurate.

That's an impressive background. And you are absolutely right about the geometry involved. But is it relevant to measuring brass cases? This is the SAAMI spec. for a .308.



Given the dimensions above, you can calculate the angle/taper of the side of the case body. .015" over 1.250" gives an included angle of .6875°. The difference in the contact point as measured by the micrometer (if it had a true hemispherical head the same diameter as the shaft, which on mine is .250") is approximately .00000225" rounded off. Measuring the case diameter at 2 points would show about .00000450" smaller than the actual size. (the drawing is just for demonstration) I have yet to see any hand held measuring device that can measure to 6+ decimal places. Even if it were possible, it wouldn't in any way apply to reloading.



The whole purpose of the post was to determine if the difference between a fired and F/L resized case is reasonable. 1/2 thousandth should be close enough for that purpose. This has been entertaining!