At the moment i use a fairly ordinary stainless steel dial caliber and was cosidering upgrading to a digital for the ease of conversion between meteric and imperial and the ease of reading it ect.

After looking around the web, I find the prices vary from around $25 for a cheap made in China instrument, to around $100 for a certified, calibrated top class tool ) For reloading purposes (as opposed to working in an Engineering Shop) is there any point in spending $$$ for the top class tool? Or more to the point, will any extra accuracy or repeatablity be an appreciable benifit to a reloader?

I was also thinking of getting a digital micrometer as well as I found a couple of deals on sets of both instruments. At the moment I dont take any case head measurements ect, but would like to at least familiarise myself with that area of reloading. I was give an ordinary micrometer 0-1" (with no instructions!) and even reading the scale has left me some what puzzled..a digital looks like it would be far easier to use!

Also, with regards both instruments, is there any way for the home reloader to calibrate them from time to time? Test blocks or something? I have never seen calibration mentioned here on these boards but when dealing with micrometers and measuring case head expansion, surely it must be an issue once you've owned the instrument a few years?

Regards,

Pete

Any industrial supply place should be able to sell you some gage blocks to check calibration from time to time. They are not horribly expensive. They are probably the simplest way to periodically check your equipment.

For reloading purposes, I don't see any need for anything more expensive than the $20 digital jobs sold at Harbor Freight. If you're working in a machine shop, then you probably want something better.

For years, I used dial calipers, and was happy. Today, I use digital, because they are about the same price, and I think they may be more rugged, besides making it easier to convert from mm to archaic units.

Yeah, the vernier type micrometers take just a little more time. But there are probably better ways to spend your reloading money than upgrading your mike.

Pete: I bought a Midway dial caliper about 12 years ago. I also took machining courses in technical college where we used Starretts, so I took the $25 Midway's and checked them on a 1" precision gauge block and the measurement was 1.000", just like the Starrett. There are 25.4 millimeters in an inch and the conversion is good to 3 decimal places. Good enough for most machining operations.

quote:

Originally posted by Pete E:
At the moment i use a fairly ordinary stainless steel dial caliber and was cosidering upgrading to a digital for the ease of conversion between meteric and imperial and the ease of reading it ect.

After looking around the web, I find the prices vary from around $25 for a cheap made in China instrument, to around $100 for a certified, calibrated top class tool ) For reloading purposes (as opposed to working in an Engineering Shop) is there any point in spending $$$ for the top class tool? Or more to the point, will any extra accuracy or repeatablity be an appreciable benifit to a reloader?

Hey Pete, There are two types of Digital Calipers and Micrometers:

1. Mechanical - has a read out similar to an Odometer on your truck.
2. Electronic - has an LED read out.

The difference in cost between the two is significant. Using one of the Electronic types is real nice once you get used to it. But, they tend to "shift" between dimensions by going back and forth between 2-3 tenthousandths if your anvil tension(hand pressure) on the object being measured is not steady. You can master it over a short time, but if you only use them once every couple of weeks, the "shifting" between dimensions can drive you crazy. You begin to wonder what the correct dimension really is and don't trust the results.

quote:

I was also thinking of getting a digital micrometer as well as I found a couple of deals on sets of both instruments. At the moment I dont take any case head measurements ect, but would like to at least familiarise myself with that area of reloading.

Since PRE and CHE are the very best Pressure Detection Methods of ALL TIME, that does sound like a good idea.

quote:

I was give an ordinary micrometer 0-1" (with no instructions!) and even reading the scale has left me some what puzzled..a digital looks like it would be far easier to use!

One thing you need to check on it is if the Micrometer is 0.0001" capable. If it is not, then you might as well be using a 0.001" capable Caliper.

You must have 0.0001" capable Micrometers to measure both CHE and PRE, because 0.001" just isn't accurate enough.

If the Micrometer is 0.0001" capable, then it will work great for PRE on all cases and can measure CHE on Belted cases and cases with Rebated Rims. Standard style cases like a 223Rem, 308Win, 30-06, etc. really need Thin Blade((Anvil) Micrometers to make sure they are not being interfered with by the Rim. Or you can "file" the Rim down in two spots directly across from each other to allow some clearance. I've done this and it is a pain. I found my 0.0001" capable Thin Blade Micrometers in a Pawn Shop and got a heck of a deal on them.

By the way, I'd just recommend you just stick with the Dial Calipers you already have if they are 0.001" capable and repeatable, unless you just want to spend the money for an upgrade.

quote:

Also, with regards both instruments, is there any way for the home reloader to calibrate them from time to time? Test blocks or something? I have never seen calibration mentioned here on these boards but when dealing with micrometers and measuring case head expansion, surely it must be an issue once you've owned the instrument a few years?...

Sure, Calibration is absolutely necessary on ANY type of measuring equipment.

First off, the Calipers and Micrometers need to be "Zeroed" by cleaning the anvils with the end of your T-shirt and cranking them in until the Anvils touch. Don't force them and it is obvious how to change the Dial to acomplish the Zeroing if needed.

The Electronic ones have a feature similar to "Tare" and you do need to check them from time to time, because some of them will drift a bit.

As for wider dimensions, I have some Mitutoyo Cera Blocks that are Grade FS which are relatively inexpensive. But, you really don't need them. Just take a couple of bullets of different diameters and scratch a Witness Mark across the Base of each one. Measure them "after Zeroing" the Caliper and Micrometer and record that information on a sheet of paper when they are new. Then when you want to see if they are still retaining their accuracy, just re-measure those exact same bullets (after Zeroing) and see if you get the same diameter.

Calipers and Micrometers are fairly rugged as long as you don't drop them on concrete.

Hotcore makes a very good point. You definitely want your Mic to read .0001" or "tenths". Especially for measuring bullets for match grade potential and casehead expansion measurements. non-digital (or vernier) Mics are not that difficult to read and the instructions should be able to get you started with confidence.

I've been a machinist for 30 years. Save your money dude. We have 5 pair of digital calipers, and two digital micrometers at my shop and they sit in a cabinet until it is time for me to calibrate them every three months.

If you need to measure that close, in tenths, which is the vernacular for a ten-thousanth of an inch, there are easier ways to do it.

If you can read a vernier scale, then you can read a micrometer, and if you have one that will read in tenths, it should suffice. Just takes a little practice.

I bought one of the El Cheapo electronic calipers at Harbor Freight and Tool a few months ago ($16.95 on sale), and I'll have to admit that I got much more than I bargained for. It seems to be accurate, repeatable, and SUPER fast. And I think it cost $10 less than the twenty-five year-old vernier I had been struggling with (them things ain't easy on 50-year-old eyes!).

My experience with the Chinese tools is that you get something usable about half the time, so be sure to only pay half what it should be worth and you'll come out okay.

Thanks for the advice folks...

I had a play about with the micromete last night and realised it measures to 0.001" rather than 0.0001"

I also measured across a case head with both my calibre and the micrometer and got a 0.005" difference in readings

Both look correctly zeroed when the "jaws" are shut and neither seems to be dirty, pitted or damaged..So which one is wrong I wonder???

As quick and dirty check, friend suggested measuring the shanks of a variety of drill bits and I will do that when I get a chance..

I did look for some gage blocks on the Net, but its seems most places in the UK sell them in large sets costing a few hundred dollars a go, depending on the grade..If one of the instruments I have was new, I would be happy to use a bullet head or something similar (RCBS calibration weight was what I thought) but at this stage of the game its not going to tell me much..

Regards,

Pete

Pete: Try a visit to a local machine shop, they will have precision gauge blocks, or should.

quote:

Originally posted by Pete E:
...As quick and dirty check, friend suggested measuring the shanks of a variety of drill bits and I will do that when I get a chance...

Hey Pete, That sounds like a fine idea and should tell you if the "Caliper" is accurate. I believe I'd loose the 0.001" Micrometer.

That suggestion by Stonecreek sounds pretty good if you can find a similar deal over in the UK. Just save the receipt.

Hotcore, Stonecreek

I have such a deal book marked on another PC..They are "no brand" digital calibres reduced from around $55 (about the usual prices for these) to about $30..I just need to check there are no hidden extras as some places quote prices without tax..I also want to make sure they are stainless steel and not plastic too as the site does not specify..

With regards the micrometer, ditching it is my thoughts as well especially as I don't know its history..Still, I will do some tests first and then go from there.

Off hunting for the weekend in an hour or so, so all this theoretical stuff will have to wait a while!

thanks again,

Pete

Pete
The most common reason for such differences is, "operator error". The touch is somthing you need to learn/experance. You want a light but firm contact, if you have a set of ignition feeler gauges they make a good training aid. As bullets are normaly within 1/2 a thousanth (+/- .0005) of nominal they also make a decent referance.
Drill bit shanks normaly run undersize (the actual diameter is smaller to compinsate for the runout removal of extra material, same thing is true of reamer flutes, there spec'ed for finished hole size not tool size).

A few general statements:

1. If your work requires measurements accurate only to one "thousandth" of an inch, good calipers will do. If you want consistently accurate measurements finer than that (one ten-thousandth of an inch, for example), only a "mic" will do. The two work on different principles.

2. It does not matter what the dial on the tool supposedly reads in...what is important is the accuracy guarantee in the "specs" (the fine print). You'll find almost all of the cheaper ones are only guaranteed to .001" accuracy, even if the dial supposedly tells you measurements to .0001".

3. Just because they repeat the same reading does not mean they are accurate. They may be repeating the same error.

4. If you really want to compare dimensions of similar items in the .0001" range. make sure both items are at the same temperature when you measure them.

5. Calibration IS important if you are working to specific set dimensions finer than .001"...that's why machine shops have their measuring tools certified regularly.

There is nothing theoretical about using a precision gauge block. In fact, it's about the surest solution you'll find to determine which instrument is in error. Vernier or digital they have to be checked for accuracy in thousandths or ten thousandths and drill bits are nowhere near precise enough for absolute accuracy. In this case I think I would be listening to the Guy with 30 years of machining experience. I believe he knows what he's talking about without regard to post count.

Theoretically, a dial caliper is accurate to .0005" or 5 tenths because you can read between .001" increments.

quote:

Originally posted by Pete E:
Thanks for the advice folks...

I had a play about with the micromete last night and realised it measures to 0.001" rather than 0.0001"

Regards,

Pete

Are you sure about that? I've only seen Mic's that measure to .0001. (you mentioned you were a bit confused with the measurements, join the club). The ones I have seen, you have to go to another completely seperate scale to get a vernier reading for the 10 thou. (usually just above the zero base line.
JL.

quote:

Originally posted by KLN357:
There is nothing theoretical about using a precision gauge block. In fact, it's about the surest solution you'll find to determine which instrument is in error. Vernier or digital they have to be checked for accuracy in thousandths or ten thousandths and drill bits are nowhere near precise enough for absolute accuracy. In this case I think I would be listening to the Guy with 30 years of machining experience. I believe he knows what he's talking about without regard to post count.

Theoretically, a dial caliper is accurate to .0005" or 5 tenths because you can read between .001" increments.

--------------------------

You may be able to read between the increments on the dial, but you sure can't call it accurate. If the tool itself is only accurate to within .001" as its inherent capability, then when it reads say .387", all you know is that the measured dimension is either .386", or .387", or .388", or somewhere in between. All three are within .001" of the reading on the face of the tool. So, you can't realistically expect to accurately read halfway between that supposed .387" and some other figure when you can't even for sure know what the .387" really is.

Further, a caliper's accuracy depends in part on what portion of its range you are taking the reading in. Many calipers are dead on in some parts of their range and as much as .003" off in other parts of their range.

I, for instance, have a recently acquired caliper which measures off an average of .003" for every inch of its travel, cumulatively. It is an inexpensive caliper which I bought just as a check on how good or bad that particular brand is. Now that I know it is off .012" when it travels 4", I use it only for such simple things as identifying whether a bullet loose on my bench top is a .30 or a 7m/m. I still use Starret, or B&S, or various Swiss calipers and mics for finer work...have some really good ones which measure down to .00005" (50 millionths of an inch) under controlled conditions in a "clean room".

Incidentally both my dad and I worked in the aircraft industry as machinists...my dad most of his life, me just for a couple of years before I went in the service when I was young.

Anyone who really wants an education on measuring tools should join one of the many machinists' forums on the "net" and ask about the accuracy limitations of both calipers and micrometers.

Top measuring tools are just like the best custom guns...most of the time what you get has a direct relatioonship to what you pay.

Then you probably already know that precision gauge blocks come in a number of sizes other than 1" and you could acomplish what you need to know by checking precision gauge blocks from 1" to 6" to establish accuracy over the full instrument range, rather than things like measuring drill bits.

If your caliper is accurate and tested as such at each 1" increments, then over that range the hashes between the digits indicate .001" accuracy. If your eyes are sharp enough to see that the indicator is directly between the hashes the tolerance error is not in thousandths at that point. The error tolerance would be in tenths. True, you should be using a Mic at this point if you need .0001" accuracy.

Maybe I need to be educated by internet experts. Tell you what I'll do while I'm there. I'll check to see if any of them clepped metrology in college as I did when I was taking machining technology courses after I had been engaged as a professional designer for a number of years. If I hadn't been primarily interested in machining as it relates to gunsmithing when I was doing that, I might have accepted the offers for employment as a tool designer.

I think Roy Richardson already gave a fairly experienced, by 30 years, of which he speaks, logical reasoning for saving your money if you want precision instrumentation. This is a case of accuracy vs. convenience. Just as with balance beam and digital scales.

Thanx for the vote of support KLN357. I don't say that the digital calipers don't have their uses, but they don't get much use at my shop. And yes, there are micrometers that will only measure down to .001 of an inch, we have a couple of them.

In all of my reloading efforts I can't remember when, or if I have needed to measure .0001. I use calipers mostly to measure case length for trimming and after trimming and bullet seating depth (Cartridge Overall Length)).

And I don't remember which one of you guys said it, but it is very very true about operator error. The more practice you have, the better you will get at your measuring and reading of measurements.

I don't use a lot of sophisticated measuring devices when I reload. It makes me think of it like I am at work, and this is for fun. I know some of the bench rest shooters are absolutely anal about that kind of stuff, but I am reloading to shoot prairie dogs, so if I can get ammo that I can cover 10 shots with a quarter, thats ten dead prairie dogs to me.

And if you have a tool in question, take it to a machine shop. Most of the guys will be more than happy to help you check its accuracy

Roy: I've seen a good number of digital Calipers that constantly had to be re calibrated so I knew exactly where you were coming from. To me, a dial caliper was a convenience item because I had been using a vernier a dozen years before I splurged!

Glad you're here!

Pete,
I have spare digital verniers "mitutoyo"
I will speak to you later, got to dash

regards

griff

Thanks again for all the advice...

After doing some checking, it looks like its my calipers that are out although I can't see how that happened.

I found a deal on some Made in China "Mitutoyo" which are produced to the same spec and conform to the same DIN standard as the British made "Mitutoyo" but at about half the price..apparently the only difference is that they have not be submitted for official certification to the British National Standard unlike the British made ones...

Regards,

Pete