Caliper +/- question on tolerances

[ElKellym]

I know that the more precises is the better of course but the all mighty dollar comes in to play more times than not. I got a set of digital calipers that have a accuracy of +/- 0.008 is this enough or should I look for a set will less tolerance?



Thanks

 

[turbo54]

+/- .008" ??

Sure it's not +/- .0008" ??

Where is the accuracy of the instrument claimed?

If it is indeed .008", I'd look for a better set, because that is pathetic, and you legitimately need more accuracy. Most any set of calipers will provide ~ +/- .001", which will work fine.

 

[ElKellym]

Turbo

yeah its .008 I guess they are crap. I, going to swing by Harbor Freight and grab these with a +/- 0.001 in. (0.03 mm) for 20.00

 

[captcoop]

My calipers have a .0005 tolerance. Starrett, .008 is horrible !

 

[Fuzzball]

Harbor Freight often has their digital 6" calipers on "sale" for $10 and those I own or have used are easily inside a thou for accuracy which is quite sufficent for reloading needs. The calipers sold with various reloading company logos on them are made in the same Chinese shop, they just charge more much more.

 

[zuke]

A caliper is "pretty close".
A micrometer is accurate.

 

[Temp9]

"Pretty close" is good enough for reloading, though. .008" is not even "pretty close". The Harbor Freight ones are surprisingly accurate, at least the one's I've checked. I'd say they're accurate within their resolution limit.

 

[steveptr]

.008!! That's a mile those aren't for measuring they are garbage. At least .001+/- .01 is terrible.

 

[deadnbrkn84]

Mitutoyo. End of story

 

[steveptr]

Mitutoyo. End of story

Harbor fright for loading. Mits are nice but 100+ bucks the harbor fright clappers work just fine.

 

[zuke]

I have both Mitutoyo and chinese and their both about the same.
I made part's for jet engine's at one time in my life and wanted the best so I bought Mitutoyo. On a dare and a lunch room argument I went to Princess Auto and bought one of their chinese digital caliper's. I submitted it for calibration at the end of my shift.Next time I came in they weren't in my box so I went to the calibration room and asked about them.
They had passed with flying colour's, but no one believed they would so everyone double checked everyone else's work. It had been calibrated a total of 6-8 time's to make sure it was good enough put on the shop floor.
That caused a real uproar with the guy's. The "tool queen's" were all pissed off that their $300+ tool's were just as good as a chinese made $12 digital caliper.

 

[captcoop]

A micrometer is truthfully a more accurate way of measuring, but a pair of Starretts is the way to go for me. Dial caliper , not electronic. Or a verneer capiler.

 

[P7id10t]

Mitutoyo, Starrett, Futaba. I'm sure there are a few others, but anything with a tolerance > +/- 0.0005 is junk. 6" are all you should need.

 

[turbo54]

I have both Mitutoyo and chinese and their both about the same.
I made part's for jet engine's at one time in my life and wanted the best so I bought Mitutoyo. On a dare and a lunch room argument I went to Princess Auto and bought one of their chinese digital caliper's. I submitted it for calibration at the end of my shift.Next time I came in they weren't in my box so I went to the calibration room and asked about them.
They had passed with flying colour's, but no one believed they would so everyone double checked everyone else's work. It had been calibrated a total of 6-8 time's to make sure it was good enough put on the shop floor.
That caused a real uproar with the guy's. The "tool queen's" were all pissed off that their $300+ tool's were just as good as a chinese made $12 digital caliper.

My experience has been pretty similar to yours. I worked in quality at a previous employer and helped get the company up to ISO9000 certification. We had to calibrate and test every instrument in the shop for qualification. I checked many of the cheap chinese digital calipers against a set of grade 00 Mitutoyo gage blocks and never found a set that wasn't good to go.

Conversely, I did have to fail a Mitutoyo "Absolute" caliper because it was messed up in the mid-range. It would read a 1.0000" gageblock @ 1.0000", a 2" block @ 2.0010", a 3" block at 3.0015", a 4" block at 4.0020", a 5" block at 5.0010" and a 6" block at 6.0000". Not bashing Mitutoyo - they make fine tools. Perhaps that set had been dropped or something.

 

[P7id10t]

Not to hijack, but how many of you here remember how to or ever had to read vernier scale tools?

 

[seanh]

I be an old fart...I remember vernier scale calipers, used to have a couple sets (might still have one in an old tool box)

as has been stated, .008" is too far off for anything useful with reloading, gunsmithing etc. You can get .001 at the auto parts store for under 30 bucks.

 

[Fuzzball]

A general machinist rule of thumb is to only use calipers for accuracy to a thou and use a micrometer for better than a thou. Mics normally only have a one inch range so they're great for dieameters but virtually useless for gaging case length or seating depth. Regardless of ego feeding brands and prices, a common 6" steel caliper of any make is all a reloader has much use for.

My fifty year old Swiss made 6" vernier caliper, my Brown & Sharpe mic reading in tenths and several Jo Blocks say my five Harbor Freight calipers, digital and dial, 6" and 12", are easily within a thousanth across their useful range. I would never suggest any reloader spend the money for a profession machinist's measuring tool, what would be the point?

 

[turbo54]

A general machinist rule of thumb is to only use calipers for accuracy to a thou and use a micrometer for better than a thou. Mics normally only have a one inch range so they're great for dieameters but virtually useless for gaging case length or seating depth. Regardless of ego feeding brands and prices, a common 6" steel caliper of any make is all a reloader has much use for.

My fifty year old Swiss made 6" vernier caliper, my Brown & Sharpe mic reading in tenths and several Jo Blocks say my five Harbor Freight calipers, digital and dial, 6" and 12", are easily within a thousanth across their useful range. I would never suggest any reloader spend the money for a profession machinist's measuring tool, what would be the point?

Agreed.

Except that from an ISO9000 perspective, you can only trust an instrument to provide a measurement 10 times it's resolution... Which is to say a caliper is good to .005" or .010" because it reads ten times smaller (.0005 or .001"), and most mics for .001, because they resolve down to .0001".

In practice though, you're right. If I want to measure something and +/- .001" is satisfactory, I grab a caliper.

 

[captcoop]

I use a vernier everyday , it's a good way to go.

 

[Walt K]

I just purchased 3 Mitutoyo dial calipers. Had to send one back because it read .001 undersize at 2.000.
That was the standard caliper. Told them to keep it. The two others were the "extra smooth" models.
Really had nothing over my Harbor Freight models. It fact the HF units were smoother to operate.
Accuracy wise the HF were just as good.
My main reason for the "MIT" purchase was I wanted a non battery caliper(s).

 

[Fuzzball]

"Except that from an ISO9000 perspective, you can only trust an instrument to provide a measurement 10 times it's resolution... "

As soon as we start reloading to ISO9000 standards we will need to get concerned about that. But for now .... ??