While looking through a machinist supply catalog I came across an interesting discovery for me. Good measuring device cost money but it seems so does accuracy. I knew intuitively that inexpensive electronic calipers were less accurate but it is the degree of inaccuracy that was a revelation to me.
The more expensive electronic calipers have resolution to +/- 0.0005 inches but the accuracy is less at about +/- 0.001 inches. Resolution is not accuracy. Resolution is how fine the reading are where as accuracy is how close to reality the measuring tool measurement really is.
The inexpensive electronic calipers have the same +/- 0.0005 inch resolution but the accuracy can vary from +/- 0.005 to 0.008 inches. Now, that is crude for anything I do.
The break point for the better calipers is in excess of $100 but it may vary. To be sure the calipers you select are accurate enough, read the specifications. They probably should be in the +/- 0.001 inch class for reloading. An accuracy error or +/-0.005 inches or more is not conducive to making accurate ammo.
As for a source of good calipers, machinist supply houses are a better choice than reloading tool manufacturers or Harbor Freight. I have used MSC before. The have a catalog that is as thick as an unabridged dictionary and an online version just as informative.
I bought some standards to ensure my calipers are ok. I then bought 3 sets of Harbor Freight calipers and picked the best one that compared to the standards (ignoring that I have no idea what that last digital place I can't see actually is at and it not being able to get past it's digital limitations). I also bought a set of Hornady dial calipers and that is more/less in the same boat with parallax, how well I actually have the zero set, etc). But it gets me close enough for what I do and my present knowledge base. Besides, I shoot a Mosin and my equipment won't put that .000x to use.
You guys must be shopping real bad calipers. I havn't bought a calipe rin the last 5 years that wasn't .001 accuracy. A couple sets i have are fine, expensive machinists calipers to go with the mic set i use for working on engines. the others varry all the way down to 13$ HF calipers up to to the 50$ level japanese brands.
( even the HF caliper i have in my hand claims .001 accuracy? is anyone seeing other than this? ) Mind you i havn't bought a set this year.. have they changed and put out lesser models now?
I don't mess with digital. I see no need for half-a-thousand's resolution, when all measurements given are in thousands.
I have both expensive Mitotoyu and cheap Frankford Armory dial calipers. I also have a set of Jo blocks, and calibrate them. They are all (I think I have five sets) right on the money.
But if you REALLY want to be precise, get a set of verniers. You have to learn how to read them, but they are, in my experience, both more accurate and more reliable.
I don't mess with digital. I see no need for half-a-thousand's resolution, when all measurements given are in thousands.
I have both expensive Mitotoyu and cheap Frankford Armory dial calipers. I also have a set of Jo blocks, and calibrate them. They are all (I think I have five sets) right on the money.
But if you REALLY want to be precise, get a set of verniers. You have to learn how to read them, but they are, in my experience, both more accurate and more reliable.
I bought the Harbor Freight calipers to get to my seating numbers easer than having to read the ruler on my dial calipers. Once I have the setting, I go to my dial calipers because it is faster and easier to read cause I no longer have to rely on the ruler aspect. They both read the same value, but I really like the dial. It is also a quick redundancy verification on the initial startup setting to ensure I didn't let Murphy dyslexia myself.
My point was the specification is what counts. If the manufacture says they are only good to 0.005 to 0.008 inches believe them. I quote these from the machinist supply catalog (MSC). Go there yourself if you don't believe me. Vernier calipers may or many not be more accurate (??). They sell them too. Checkout the specs if you care. I also wanted to point out that the resolution shown on the readout is not the accuracy that you can measure to.
I have two good digital electronic calipers. My son and I both have an additional calipers from Harbor Freight. Both eat batteries whereas both my good ones do not.
If your cheap ones are accurate for the whole of its range then you won. But don't tell the manufacture as he will down grade the quality because they are better than their specs say they should be. Quality cost money for him.
I worked for Boeing and if you want some accuracy, they work hard for it. A .001 over on titanium in an aircraft translates to some serious dollars. When an engineer wants a certain size, it has to be that size or the parts may not go together. Quality matters and is impressive that it can be achieved with confidence.
I agree. For engine work, there ar eplenty of places that a caliper. even one good to .001 simply ain't good enough.
measuring bearing journals and whatnot. I have a mic set ( multiple mic's ) that measure 1", 2" and 4" throats. you can lay a caliper on a journal and completely flub the measurement vs a micrometer.
The HF calipers are much more than 2 years old. I have zero trust in them and only use them for layouts of crude projects. They can be dropped and destroyed without breaking the bank. I am much more careful with the other two I have.
For more than 10 years I had all kinds of machining projects for our vintage motorcycle racing escapades and collected a combo lathe/mill and all kinds of precision measuring instruments. I have Mic's from 0 to 6 inches, a mechanical digital depth gauge, dial depth gauge, a engine bore measuring tool and all kinds of precision accessories. I am not a machinist and stubble along to do these projects but I had fun. I do understand precision. But calipers turned out to be the most useful, if they were good ones.
I thought I would pass along the lack of accuracy of some of the cheaper calipers. You can buy and use whatever turns you on but I for one am glad mine have a specified accuracy of +/- 0.001 inches over the entire range of the calipers. I trust them for anything (well almost).
if the calipers from HF are that old, i reccomend dropping another 13$ for a new set.
As with all things. you can get as much or as little quality out of china as you wish. From ultra high tech tablet computers, to cheap cast zinc tools that break before you use them. All depends on what QC standards the importer imposes and what he will pay.
Craftsman and sears tools now use chinese factories... if you didn't see the heche en el chine you might not know as the tools ar ethe same high quality they used to be.
Power full and high tech tablets like the ipads, etc are also made there.
Another issue is technology upgrade. It is said that every 18 months computer capacity/speed/technology nearly doubles. that holds true with other technology that is also based on computers. A set of calipers made 10ys ago in china are probably a FAR CRY from a set you could source today. While i wouldn't trade any of my japanese, swiss or german tools away.. using a HF tool, once checked for calibration doesn't bother me much.
And the key is calibration.. no tool should be relied upon unless periodicaly checked fro calibration.
The sensitive sound level meters I rely upon daily even require periodic check for calibration.. as do other devices, like speed radar guns.. etc.
For those complaining about battery life, make sure you use a Silver-Oxide battery, not a cheaper alternative. Makes a huge difference in a branded or cheap knockoff caliper.
fwiw, the reviews I read about calipers mainly conclude the difference is in the energy usage, not accuracy or resolution. The cheap ones drain the battery even when it is "off", the more expensive ones really turn off. For the cheap ones, disconnect the battery when not in use for longer periods.
other options for longer term storage batteries. like the spare that you might have setting ont he shelf are zinc-air batteries.. many hearing aid batteries are that type.
I have a set of Starrett dial caliper that I've had for close to 40 years. I got them when I was working as a machinist. They were kind of pricey back then, but are still accurate to .0005" or less. This a prime example of the old adage, buy the best you can afford and don't look back.
Here are the specs on the $19.99 ones at Harbor Freight that you can often find on sale for $9.99. that appears to be a far cry from the .005-.008 accuracy the OP states for the cheap ones. Ssssshhhh, don;t tell Harbor Freight, they may raise the price to the price of a Starrett. For reloading I could not even imagine needing better accuracy than +/-.001 inches or to spend more.
I have 2 of these and both have been calibrated each year at work with absolutley no problems after 7 years.
Name6 in. Digital Caliper
SKU47257
BrandPittsburgh
Accuracy+/- 0.001 in. or 0.03mm
Well, in my opinion, calipers, digital or dial, are not the most accurate way to measure OD. The design of the tool lends itself to "springing" and the method of closing the jaws, either pushing the jaws closed or using the "wheel" needs a lot more experience than a plain old micrometer. I've seen calipers that will give a different measurement at the tips of the jaws vs. next to the frame, once to .001". Without a good "feel" it's easy to be off by .001"-.002" with a caliper.
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