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[hounddawg]

@ CW page 212. Gages have tolerances also

https://saami.org/wp-content/uploads...sting-Copy.pdf

[cw308]

dawg
Thank you , never thought tolerances would be acceptable on a gage that is marked with a measurement of 1.630 not + or - Great download dawg , thank you again . Learn new things even at my age , I feel most times in reloading I'm doing better the in measuring then the ones designing the tools plus or minus , I'd like exact . I'll work with what I have ( precision mic & go gauge ) now that I know . What happens to people in the reloading sport that takes the measurement at face value . I just double-checked with the go gauge and found the difference , both tools could be off for that matter. Untill the next time . Be Well.

Chris

[Bart B.]

In some tool and die circles, the last decimal place indicates the tolerance spread. 3rd place shows spread in thousandths. .001" for a 1.234" gauge. 4th place in ten-thousandths.

[cw308]

Bart B
I didn't know that , thank you . Looking at it that way my go gauge should be exact or I'm missing something . The gage I'm using is for my 308 , go gauge is marked 1.630 . I didn't think most measuring instruments were + & - if it was marked 1.630 I took it as face value . Kind of disappointing knowing that . Nothing is exact , come to think of it we are talking thousands , maybe I'm just nit picking .

Chris

[Reloadron]

Hounddawg brings up a good point, everything has a tolerance or simply put allowable limits of error. During my early years what Bart B. mentions was pretty Greek to me in that when I became involved with machinist and they used terms like plus or minus 5 tenths I was like what the hell is a tenth and thinking for example tenths of an inch? Tenths refers to, as Bart mentions, ten-thousandths or a tenth of a thousandth. My world had me interfacing with the mechanical guys on a regular basis and fortunately they had a good tolerance of me. I was also fortunate in that I interfaced with some of what I felt were the very best mechanical engineers and machinist in the business.

Using the SAAMI data which Hounddawg was kind enough to provide and looking at for example a 308 Winchester headspace gauge a gauge labeled 1.630 Go Gauge has an allowable tolerance or limits of error of 0.000200 inch or 200 millionths. So a 1.630 headspace gauge may be anywhere between 1.6298" to 1.6302". That assumes the gauge manufacturer conforms to the SAAMI specification.

The entire thinking behind the allowable limits of error or uncertainty is that a gauge which conforms to prescribed limits of error will never have the error come in light of the gauge's intended use. That's really what it is all about in any measurement plane. So if my trusty 308 Winchester 1.630 is within tolerance any error in the gauge won't matter for the gauge's intended use.

Back to the RCBS gauge for a moment. Here is the RCBS claim:

A few twists of the Precision Mic and you'll know your chamber headspace and bullet seating depth to 0.001 of an inch. The Precision Mic measures from the datum point on the case shoulder to the base, giving you spot-on SAAMI tolerance readings. An indispensable tool for safe, accurate loads that extend the life of your rifle brass.

Now I am not sure what they are getting at with the 0.001" thing here. The gauge is graduated in 0.001 inch increments. I see that as the resolution of the gauge and resolution with something like this is what I see as the ability to read an instrument or of the instrument to be read.

This concludes my long winded thinking on the subject. Thank you and have a nice day.

Ron

[hounddawg]

and you will also have a tolerance on the comparator insert. Any differences on the comparators bore diameter will throw off the reading

[cw308]

Ron
Thank you , to be honest if the differences were 1.6298 to 1.6302 I probably won't even know it , I eyeball my measurements to the line or in-between . I was surprised when the Precision Mic's zero line with the Go Gauge of 1.630 thinking it should be in line with the zero on the mic . Even though I worked around it , it would of been nice if it was nuts on . Thanks again .

Chris

[Reloadron]

cw308, this is why I suggested a call or email to RCBS. I agree with you and I have never seen one with that much error and I also assume your actual headspace gauge is much, much closer to nominal that the error you are seeing. Nothing to lose in calling or contacting RCBS and question the gauge.

Ron

[F. Guffey]

I use my micrometers and gages, I verify, I adjust my gages to agree. And then there are transfers and standards. I have no ideal how you guys can get anything done because 'it can not be done' because of pluses and minuses.

I have dial indicators that are hand size (large), I can read .0001" to .0009", the gage is stamped .0001". If a reloaders understood ZERO they would have never had difficulty in understanding the Hornady/Sinclair tool was a comparator.

That would be the same for the Wilson case gage. reloaders continue to call the Wilson case gage a drop in gage and they get all giggly about Digital head space gage. The digital head space gage is a dial indicator stand; at best it is another comparator.

I have a Pratt & Whitney gage that did measure .00005", for me that was useless because of the limited travel and the cost of standards. I changed the gage to read in .0001" or .001". It is one smooth running dial indicator stand.

I can measure the length of the case from the datum to the case head with speed and efficiency, I can also measure the length of the case from the datum to the case head with speed and efficiency with tools that weight 35 pounds less.

F. Guffey

[Bart B.]

Originally Posted by hounddawg

and you will also have a tolerance on the comparator insert. Any differences on the comparators bore diameter will throw off the reading

Especially if the gauging diameter is .001" or more below the flat on the insert.

The gauge is designed to compare case headspace dimensions after firing to after sizing, not measure them. I wouldn't care if it was one fourth inch off exact.

[cw308]

F.G
I'm not into measurement so precise as you or have the equipment , education and experience . I thought tools such as a go gauge were exact , if it was listed 1.630 it was exact , as some posted of tolerances between 1.6298 and 1.6302 I guess it's what I consider exact . That's coming from a guy that eyeballs things . Far from talking exact , I know better now . As I posted before , I give it my best shot but I can't swim with the pros.
Thanks again.

Chris

[cw308]

Ron
I called Sinclair's tech support , the said you have to allow for some wiggle room . I got a better understanding on measurements from you guys , thanks to all for your time and patience .

Chris

[Reloadron]

cw308, well Chris as long as you can make your own good hand loads anything else is gravy. Everything has an allowable tolerance because nothing is perfect. As long as any error does not come in light of a gauges intended use life is good.

I am surprised at where you mention:

I called Sinclair's tech support , the said you have to allow for some wiggle room .

I guess we could say "wiggle room" but in your case it seems to be quite a bit of wiggle room.

Glad you came away with something.

Ron

[F. Guffey]

F.G
I'm not into measurement so precise as you or have the equipment , education and experience . I thought tools such as a go gauge were exact , if it was listed 1.630 it was exact ,

I believe we have too many members that believe verifying is a joke. If they can not make the measurements, they can not make the measurements.

I am the fan of transfers, a big pile of tools is not necessary, a good understanding of 'ZERO' is. I have tools that were designed to transfer measurements, most of them dated back 120 years, I do not have a complete set but of a few from a set.

F. Guffey

[F. Guffey]

Originally Posted by hounddawg View Post
and you will also have a tolerance on the comparator insert. Any differences on the comparators bore diameter will throw off the reading

Not if the tool is a comparator but reloaders should know before they get this far into a thread the datum is a .375" diameter hole for the family of 30/06 cases, .400" for the 308W and .410 for the magnum family of cases.

And again and again and again there is the case friendly radius datum. The Wilson case gage has a datum because it is a datum based tool; difference, Wilson knows how to zero a gage with a datum that has a radius.

F. Guffey

[Bart B.]

.410 for the magnum family of cases?

The mallet just smacked the gong on that old TV show.

[hounddawg]

Like Reloadron stated as long as it works everything is fine. Just for grins I measured by Forster GO gage with my Hornady .375 comparator. Gage is marked 1.630, using a Starrett caliper and the Hornady comparator I measured 1.657, the NOGO is marked 1.634 and measures 1.631. My bet is the Hornady comparator is off slightly. I use the gage as a standard and installed 5 barrels with it and also to set my bump on my sizing dies. Consistency is the key to precision reloading, when you find what works just keep repeating it

[F. Guffey]

My bet is the Hornady comparator is off slightly.

That is the reason it is called a comparator, measure before and again after. There was a time when there was a big rush to name all tools head space gage. The Wilson case gage had a name, it was called a case gage from the late 1930s to the beginning of the Internet. At the beginning of the Internet reloaders did not know the cam over press bumped twice and they got all giggly when the digital head space gage was introduced. It was cheaper to purchase as a dial indicator stand and the dial indicator was stronger.

F. Guffey

[Reloadron]

Bart:

.410 for the magnum family of cases?

The mallet just smacked the gong on that old TV show.

It's a new family? Mine are typically 0.420" but I see no reason why someone could not have the new reduced size.

Ron

[F. Guffey]

It's a new family? Mine are typically 0.420" but I see no reason why someone could not have the new reduced size.

Reloaders are not much on verifying, so who measures? Someone said the diameter of the hole matters; again the diameter of the hole determines if it is a comparator that requires measuring before and again after. And for years reloaders have referred to the Hornady gage as a head space gage, during all of that time I have said the Hornady/Sinclair tool is a comparator.

I have suggested reloaders verify the accuracy, that would include the radius at the top and diameter of the hole. And then there is the making of a datum.

I make datums, I have even purchased datums and I have verified datums.

F. Guffey

[Reloadron]

In Geometric Dimensioning & Tolerancing I believe a Datum is a theoretical reference. In the case of a cartridge case it's a feature which needs controlled. I think it is nice that you make theoretical things.

Not if the tool is a comparator but reloaders should know before they get this far into a thread the datum is a .375" diameter hole for the family of 30/06 cases, .400" for the 308W and .410 for the magnum family of cases.

Now please tell us a cartridge which has a .410 inch feature in a drawing, a SAAMI drawing. I can't find one. You are not the only person in this forum familiar with geometric tolerancing & dimensioning. Other than on a drawing there is no making a datum.

Ron