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Old May 3, 2011, 01:15 AM   #1
deepcore
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Caliper technique

Curious how you prefer for measuring case length (from the mouth to the base) when trimming do you use:

1. The very tips of your caliper? With the jaws just touching one side of the case mouth.
2. A little further in but still on the thin blades with the thin blades touching both sides of the case mouth?
3. Further in at the thickest portion in the middle to inside third of the jaws?
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Old May 3, 2011, 02:03 AM   #2
Marco Califo
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You should develop your specific technique.
Then, practice it for absolute consistency.
I use the thick part, making sure the head is centered, and the neck is also centered, and the both are flat against the caliper arms.
You want to get the same result every time.
I like to turn the dial, or screen, away from me until I am satisfied with the positioning. Then, turn it and see what it says.
Pick-out a single case and mark it. Then measure it once an hour and write down the measurement. If they are not the same you need more practice.
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Old May 3, 2011, 07:16 AM   #3
Shootest
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The thin portion of the jaws are only for measuring anything that the thicker part can not. Such as case wall thickness. Whenever the thicker area can be used it should be used, it will also aid in keeping the case square inside the jaws. Calipers are always more accurate deepest it the jaws (less play).
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Old May 3, 2011, 12:37 PM   #4
Jim243
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Quote:
Calipers are always more accurate deepest it the jaws (less play

Not on mine, tip to tip is how you are suppost to measure. Don't take my word for it, get a ruler and see for yourself.


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Old May 3, 2011, 12:40 PM   #5
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The thick part is on the same plane as the tips, as long as they're not stressed it should read the same.
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Old May 3, 2011, 12:42 PM   #6
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They are not, get a ruler and see for yourself.
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Old May 3, 2011, 01:19 PM   #7
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"They are not, get a ruler and see for yourself."

IF they are not the same across the full width of the jaws something is wrong. It is normal for calipers to have two tiny adjustment screws in the sliding portion that ride gibs along the fixed base. Those screws are used to correct any jaw misalignment.
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Old May 3, 2011, 01:23 PM   #8
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Fair enough Jim, I just checked with a ruler since I didn't before. I think your calipers may be sprung. I could not back up your statement with a ruler. The tips are on the same plane as the thick part and the measurement is the same at the tip, or anywhere on the thicker part.
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Old May 3, 2011, 01:29 PM   #9
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Notice my name...

If the calipers measure differently at the tip of the jaws then they need an adustment. The jaws should be parallel their full length.

I've inspected thousands of aircraft parts with the tips and that's completely acceptable and is the way I use them most of the time.
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Old May 3, 2011, 01:45 PM   #10
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How could you possibly use a ruler to check the accuracy and/or precision of calipers? Seems like going to sea in a dinghy to check if it's safe to go in a yacht.
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Old May 3, 2011, 03:27 PM   #11
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If anyone is checking aircraft parts with the tips of calipers, I don’t want to be on that plane. Real precision requires the use of micrometers, indicators or electronic measuring equipment. The calipers typically used for reloading are cheaply made, wear easily and are temperature sensitive. I work for an unnamed firearms company/ military contractor, and calipers are not allowed in the building, let alone a scale. A ruler is a piece of wood used by elementary school, students in arts and crafts class. What I believe you mean is a scale, and there is a difference. Using a scale to check calipers would be like using a cars odometer to check the hem line on your pants.

Try this test.
Clean the jaws and close your calipers.
Hold them up to a bright light.
If you can see any light between the jaws, usually happens at the tips.
Then calipers are not accurate and need adjustment or replacement.
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Last edited by Shootest; May 3, 2011 at 03:39 PM.
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Old May 3, 2011, 03:33 PM   #12
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Quote:
If anyone is checking aircraft parts with the tips of calipers, I don’t want to be on that plane. Real precision requires the use of micrometers, indicators or electronic measuring equipment. The calipers typically used for reloading are cheaply made, wear easily and are temperature sensitive. I work for an unnamed firearms company/ military contractor, and calipers are not allowed in the building, let alone a scale. A ruler is a piece of wood used by elementary school, students in arts and crafts class. What I believe you mean is a scale, and there is a difference. Using a scale to check calipers would be like using a cars odometer to check the hem line on your pants.
What is your point?
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Old May 3, 2011, 04:59 PM   #13
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"If anyone is checking aircraft parts with the tips of calipers, I don’t want to be on that plane."

The required accuracy of any measurement largely determines the needed measurement tool. Calipers are generally considered +/- 1 thou tools and that's often plenty, including for virtually all reloading tasks. The shape of the item usually determines which part of a caliper's jaws will be used; both the thick and thin parts of the jaws will be equal unless they have been damaged by rough handling.

Micrometers are tops for absolute accuracy but it can be quite difficult to measure largish things with a micrometer. I have a 12" caliper but I don't have 12" mic! And even larger/longer calipers are available.
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Old May 3, 2011, 05:08 PM   #14
Brian Pfleuger
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I use the thick part of the blade because the case head sits flat and reasonably securely in that area. However, I have checked many times all along the blade length and they are consistent.
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Old May 3, 2011, 05:49 PM   #15
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Thick part of the blade. I normally don't measure case mouth to base, just ut the cases with a lee cutter and be done with it. Only lengths I'm concerned with is measured from the datum line on the shoulders, or off the ogive on the seated bullet.

Quote:
Micrometers are tops for absolute accuracy but it can be quite difficult to measure largish things with a micrometer. I have a 12" caliper but I don't have 12" mic! And even larger/longer calipers are available.
You can put a dial indicator on an adjustable stand and you measure that against a standard. I have an old mitutoyo set up, but rarely use it. Its almost too sensitve for reloading purposes, unless you are checking something like bullet runout.
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Old May 3, 2011, 06:03 PM   #16
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[QUOTEHow could you possibly use a ruler to check the accuracy and/or precision of calipers? Seems like going to sea in a dinghy to check if it's safe to go in a yacht.][/QUOTE]

Very astute observation Watson, but hand-loading is not Rocket Science so calipers work well enough for us to pretend we are doing things scientifically even though we are not. So a Ruler is an acceptable device for confirming calibration and adjustment of the jaws. Heck Bubba, Calipers were an upgrade for me, I used to set oal by if it would fit in the Mag, er Clip...
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Old May 3, 2011, 06:19 PM   #17
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Very astute observation Watson, but hand-loading is not Rocket Science so calipers work well enough for us to pretend we are doing things scientifically even though we are not. So a Ruler is an acceptable device for confirming calibration and adjustment of the jaws. Heck Bubba, Calipers were an upgrade for me, I used to set oal by if it would fit in the Mag, er Clip..
Oooh that is scientific to use a ruler to check a set of calipers. I just close the calipers and zero the dial, if it needs it. If I'm really curious, I check it aganst the diameter of a SMK, in fact I use a SMK to check my powder scale as well.
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Old May 3, 2011, 06:22 PM   #18
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Sadly my eyes can't resolve a ruler's 1/1000th's of an inch marks (if such a nutty thing existed). I use a micrometer. I have two of them. One measures to a maximum of 1", and the other can measure between 1" and 2".
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Old May 3, 2011, 06:27 PM   #19
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Very astute observation Watson, but hand-loading is not Rocket Science so calipers work well enough for us to pretend we are doing things scientifically even though we are not. So a Ruler is an acceptable device for confirming calibration and adjustment of the jaws.
No, only for [maybe] confirming that the caliper is working well enough for reloading, and only if you don't care a lot about the quality of your reloads, or your health. And if that's the case, why bother with calipers in the first place?
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Old May 3, 2011, 06:41 PM   #20
Greg Mercurio
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I have to say that sometimes the comedy routines on these forums are enough to go National with. A ruler to check calipers? Sure.

Case length measurement is just dandy at dial or digital caliper resolution. In fact if you push on the thumb roll hard enough they will read whatever you need them to. Repeatability will be incredible and you can brag to your buds that you trimmed all your cases to EXACTLY x.xxxx

And then you can use the caliper for an emergency pipe wrench. Everyone needs one of those.

For the rest of you:

http://www.machinist-guide.com/machinist-calipers.html
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Old May 3, 2011, 08:02 PM   #21
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Tough crowd tonight I see..

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No, only for [maybe] confirming that the caliper is working well enough for reloading, and only if you don't care a lot about the quality of your reloads, or your health. And if that's the case, why bother with calipers in the first place?
Nah, I laid the ruler flat and set the dial to 1". Then I was able to eyeball the tips and the 1" lines, and then the thicker flats and the 1" lines and got the same measurement. I did not use Greg's technique of stressing the thumb wheel.

If I can see a .001 difference in case lengths with my eye then that's close enough for me to be able to use a ruler and have confidence in what I see, (benefits of a Mechanical background?). I've trimmed thousands of 223 cases and checked them all, I got to where I could quote the length before measurement. I was able to spot false readings when the calipers slipped zero. I digress, you asked why bother with Calipers? Because it instills good reloading practices. I am all for good reloading practices, but it is good to know that I can load ammo without calipers, and only the gun. I wholeheartedly recommend calipers for the reloading novice.

That you would state that I do not care about the quality of my ammo or my health from such an uninformed position as you did, reveals your own lack of experience and sense of humor...
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Old May 3, 2011, 08:24 PM   #22
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Measure with a micrometer, mark it with a crayon, cut it with an axe....

All measurements and tools are relative to the task at hand. Use some common sense, guys!
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Old May 3, 2011, 09:19 PM   #23
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"You can put a dial indicator on an adjustable stand and you measure that against a standard. I have an old mitutoyo set up, but rarely use it. Its almost too sensitve for reloading purposes, unless you are checking something like bullet runout."

Yeah, and I use an indicator on a base for some machining work. But, it's meaningless to reloading, for measuring ammo stuff a caliper is plenty good enough.

My eyes are going now so I rarely use my original 6" caliper anymore. It's a Swiss made vernier type and it DOES require the user be able to match two marks within a thou of resolution! That's not as hard as it sounds and it's dead-on accurate across the full scale if used carefully. Dial indicator calipers killed that type off tho.
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Old May 3, 2011, 10:01 PM   #24
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Quote:
Micrometers are tops for absolute accuracy but it can be quite difficult to measure largish things with a micrometer. I have a 12" caliper but I don't have 12" mic! And even larger/longer calipers are available

Wncchester, now what rifle case is 12 inches long? (LOL) I knew you were loading some strange stuff, but 30mm rounds?(LOL) (just joking)

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Old May 4, 2011, 01:26 AM   #25
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You can measure with any part of the calipers you want.

Case length measurement does not require that much accuracy compared to the variation over the length of the caliper jaws.

To get good with calipers, practice in completion against guys with micrometers.
Measure gauge blocks and pin gauges.
Play for money.

Using calipers is like playing guitar, you can get better at it.

But using calipers like El Kabong played a guitar, is good enough for case length.
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