Electronic caliper accuracy

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Georgezilla
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Electronic caliper accuracy

Post by Georgezilla » Thu May 28, 2009 4:05 am

I've been measuring .45acp cases to within .002" of each other with a General UltraTech caliper. I've noticed that the measurements are very inconsistent. Measurements are varying up to .004" on the same case -- I should point out that when I get a variation of that degree, it's usually when I have rotated the case a bit to measure at a different angle, but even just resetting the caliper in the same place it isn't always consistent.

In recent weeks I've been reading a lot about accurizing 1911s. Most of the stuff I have read warns to stay away from using electronic calipers to do your measurements -- even if it's a high end caliper.

In your opinion/experience do you find dial calipers to be superior in terms of accuracy? If so I'd appreciate it if you could recommend me a decent dial-caliper in the $50ish range.

Thanks.

lucam
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Post by lucam » Thu May 28, 2009 9:13 am

If you want better accuracy, a micrometer might the way to go. However, I have found most electronic calipers very accurate. I trust Mitutoyo the most. Experience: 4 years in small part manufacturing QC.

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bearandoldman
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Post by bearandoldman » Thu May 28, 2009 10:32 am

LCM wrote:If you want better accuracy, a micrometer might the way to go. However, I have found most electronic calipers very accurate. I trust Mitutoyo the most. Experience: 4 years in small part manufacturing QC.
I use both and see no real variations in accuracy. Many years as an engineer, machinist and service tech have made me familiar with measuring object. You rnatural feel has a lot to do with it also especially with a mike, for the inexperienced an electronic caliper is probably better. Mitutoyo does make very good tools and their entrance into the precision tool sales in the US, put the company I used to work for out of the precision tool business and then they moved out of state and I had no job, that was 45+ years ago. I still use most of my precision measuring tolls that they bruit and they still work very well, the company was the Lufkin Rule Company
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Measuring cases

Post by stork » Thu May 28, 2009 11:54 am

George,
I've gone the route of measuring and trimming 45ACP cases and doing a lot of Ransom testing. To sum it up, don't waste the time. I've never seen any difference in group size between carefully matched cases and just grabbing them out of the bin and loading in any of my match 45's.

Just watch the bases and the diameter of the bullets for your 50 yard loads. If the bases are'nt perfect, regulate them to the practice pile. diameter should be .0005-.001 OVER groove diameter. Bullet weight can vary up to 3 grains and the bullets will still group within 2" or less at 50 yards, if the gun is capable of it. But if the base isn't perfect, you have a 4-6" gun.

When I first started, I even went as far as weighing every bullet down to the tenth of a grain. After about 6 months of that a High Master told me to just watch the bases and any obvious defects in the casting of the bullet.

FWIW
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Post by Georgezilla » Fri May 29, 2009 3:30 pm

I did some more testing and have determined that it is the brass (I am using untrimmed range brass) that actually has different OAL on different portions of the case. I measured some 1911 pins and they always came up the same.

Stork, the reason I am doing this is because the rounds I've been making chrono'd very inconsistent. You are probably right that it has to do more with the bullet than anything, and using range brass doesn't help. I am going to order some Zero lead SWC, hopefully they will fair better.

45dave
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have to learn to feel

Post by 45dave » Sun May 31, 2009 11:06 am

Dial or electronic calibers will do ok, if you read the manuals most state that they are rated to plus or minus .001 of an inch but I have used many that are far more accurate depending on the operator. Part of the deal with calibers is you can manipulate the reading by how hard you squeeze them, basically springing the back. What I teach apprentices is to get some known block such as a gauge block or gauge pin, then practice reading it until you develop a "feel" on how much force you apply and what the reading is. You can affect your reading by cocking your calibers or if you are not careful where you measure such as on the broad edge of the blade or on the narrow area near the tip.
One of my most accurate pair of dials were an offbrand I picked up for 30 bucks, it was fantastic until it was dropped by an apprentice (ouch, he was a good apprentice, just clumsy like me)
As for mics, give me a Starret, Brown and Sharpe, or Etalon give me best results.
Bear...one of my prize possession is a Luftin depth gauge, one of my favorites and weren't they made in Saginaw for quite a while, I think I go by the old factory when I visit family in that town.

Oh..my background using measuring stuff, Tool & Die maker for over 30 years, progressive dies, jigs, fixtures, tooling, prototype, one off dies, spank dies, carbide dies and now in Body dies.

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bearandoldman
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Post by bearandoldman » Sun May 31, 2009 11:24 am

Far more accurate depending on the operator, how true, how true. Like you say you have to have the feel for them and be consistent with that feel.
Yes the factory was in Saginaw on Hess. They terminated my engineering position about 1967 and went out of the precision tool business and moved the tape and rule division to Apex NC about 1970. Do not know if thee make anything other than tape measure any more. I still have some mikes and steel scales and machinist squares yet.
The factory is no longer there it was abandoned and vandalized and most of the plant was early 1900's, there was a big fire and all of those oil soaked old wood floors burned very well. Some of the upper floors in the older buildings were 12 inch or better 2 inch wide stock on edge, built back in the old lumbering days. There was a new building put up that is now used by a pickle packing plant.
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