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One of Us |
I don't want to rob the match grade thread but I want to know what air gageing is? I have been a Moldmaker/Machinist for 22 years and nobody I know has a clue what this REALY is. Does anyone have facts on this meathod of measurment? ________________________________________________ Maker of The Frankenstud Sling Keeper Proudly made in the USA Acepting all forms of payment | ||
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It is my understanding that it is a gauge with air flowing through it and as the push it down a barrel it use air to measures the differants in the inside barrel. the closer the measurements the better the barrel. | |||
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I stole this from the handloading forum. """"A air gauge is a accuratly sized cylinder with air ports out the side, when you put a calibrated amount of air pressure into the center, you get a flow rate that varies with the gap between the gauge and the bore. The lower the flow rate the closer the fit. You can measure the variances in the bore diameter as the gauge is passed from one end to the other from the change in flow rate. Does air gauging make the barrel better? No. It only tells the manufacture what the variance is. Their tolerance level is what determines the quality (the guy that accepts .005 variance is using it (the phrase) as a sales tool, the guy that scraps anything with more than .0001 variance is using it as a quality control device) looking at those 2 examples of it's usage and tolerances levels, guess which catigory a $75 contured, threaded and shortchambered barrel is in compaired to a $200 blank from a top name barrel maker"""" As usual just my $.02 Paul K | |||
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so from my point of view "air gauge" and "match grade" are just catchy words to make the consumer think WOW I'm buying quality!!!!  ________________________________________________ Maker of The Frankenstud Sling Keeper Proudly made in the USA Acepting all forms of payment | |||
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Air gaging is a common practice in the aircraft industry. Extreme Custom Gunsmithing LLC, ecg@wheatstate.com | |||
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To me "match grade" is a catch phrase. As to "air gauge" it depends on what they do with the info. Just running it means nothing unless they use the info to scrap poor quality barrel. Then it would depend at what quality level they scrap. In a hunting rifle barrel from a "name" supplier I won't pay extra to have it air gauged. As usual just my $.02 Paul K | |||
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Ramrod I was going to post a answer to this question, and than I saw that I already had.  Glad you liked it, and thanks for digging it out of the archives. | |||
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 I thought it was the perfect answer. I think I referenced the wrong forum. I think it was actually on Gunbroker forums that I first saw it. I had read it a while back when my son in law asked this question and I thought you answered it perfectly. So when this question came up I went back to pull it. Thanks for adding your name for some some reason it didn't click for me to tie your handles together.As usual just my $.02 Paul K | |||
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If you can get a barrel maker to sit down and have a beer with you, out of earshot of his customers, (I have done it), most will tell you that gauging means little when it comes to that instant when the bullet meets the paper or meat. They do everything they can to get good quality steel, drill and ream a straight hole, rifle that hole and lap it to perfection - but in the end it may not shoot any better than Remchester's worst. It probably will but they sure won't guarantee it. JMHO Ray Arizona Mountains | |||
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Military has long used Air Gauging as a means of measuring barrel erosion . Old DCM selling surplus referred to it on weapons grading condition . It's simply another tool in which to measure accurately through the entire length of a Bore . Shoot Straight Know Your Target . ...  | |||
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I understand how Air Gauges work in a Bore(or any tube) prior to Rifling. But I am at a loss about how it could possibly work in a Barrel that has rifling in it. Anybody care to explain how that would work? | |||
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I'm not sure as to the operation it's self as I wasn't in Armory myself . I had heard this was a measure in which throat erosion could be better determined ?. Or did I some how mix up the DCM's throat gauging or barrel erosion measuring method ?. Unissued Rack grade Service grade Etc. has to do with condition of wear and appearance ?. Barrel manufactures use Air gauging prior to rifling being cut , I do know that according to Lilja . I'm not an expert in this field by any stretch !. Shoot Straight Know Your target . ... | |||
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I actually used and set to masters a lot of air gauges in the hydraulics business in the '60 this fits well!!
It's simply an extremely accurate method of determining the actual measurements compared to a class XX (+/- .000005) master! Measurements to .0001 are magnified to 1/2" if desired. /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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Only guessing, but maybe the airflow would increase where the grooves are deeper and decrease where they are shallower? Making a gauge to accurately measure the difference would be the trick. | |||
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Hey Craigster, I agree that is the problem I see. I can't see how the very sensitive Air Gauges measuring the Pressure Variations would be able to compensate for the "Grooves". It would be my "guess" that anyone using an Air Gauge on a barrel is doing it prior to 'Cut Rifling". It seems like it would be a total waste of time to do it on a tube that is to have the rifling Hammer Forged or Drawn with a mandrel. As Vapo posted, it works because of a very snug fit in the tube which allows the very sensitive air gauges to detect minute diameter variances due to the air flow(Pressure) changing. So, I just don't believe it is possible to use it in a tube that is already rifled. Good Hunting and clean 1-shot Kills. | |||
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i can mean a more consistent barrel, if the tolerences are set... it will let the maker know if there are any tight tight spots or loose loose spots... ALL AB barrels are air gauges, according to midway jeffe opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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Like Vapo said an air gauge measures differential pressure as compared to a master ring. To check a rifle barrel the gauge plug would have to be star shaped...hint hint...with the same number of points on the star as grooves. Many of you might have trouble checking an ID to the nearest .001 with normal shop tooling. An air gauge such as those manufactured by Federal can resolve ±.0000050 easily. That is plus or minus a half ten-thousandth or 50 millionths. As I remember a 4" dia. dial would have a range of ±.003. That is a 12" sweep to show a total of .006. | |||
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Both Green Mountain barrels and Douglas barrels advertise that they air gauge their barrels. I am getting good groups from both brands, so air gaging doesn't seem to hurt. http://www.gmriflebarrel.com/AboutUs/riflebarrelqa http://www.benchrest.com/douglas/our_barrels.html | |||
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Hey ireload2, Does that Air Gauge "rotate" to follow the Grooves as it is being moved through the barrel? | |||
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HC, You are correct the air plug has to be the same shape as the feature you are gauging, it is just undersized, creating a gap between the air plug and the feature. For a rifled bore the air plug has to have lands and grooves slightly smaller than the bore to be measured.. It also has to have the same twist rate. The principle of the measurement is the pressure drop across an orifice is proportional to the exit area, which in this case is the difference between the air plug and bore. The pressure difference can be very precisely measured and amplified for the output. All air gages have masters that allow the gage to be set and zeroed prior to use. In this case the master will also mirror the lands and grooves. I hope this brief description helps, Pat  | |||
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OK, now that we know about air guaging, what I want to know is, do all barrel makers air guage their barrels? Are air gauged barrels also air gauged after rifling? It would seem that in order for a barrel to be "match grade", (whatever that means) groove depth would have to be consistant from the throat to the crown, and that depth measued after the rifling operation. Or, are the tubes just air gauged and rifled without regard to groove depth and become "match grade" because the maker says they are. Just how important is groove depth? | |||
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Would it not be possible now with computers to pass a laser-fitted device down a bbl and get a more precise picture? Or is that in the "possible theoretically" but not cost effective category? | |||
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Thanks Pat. I've only seen the kind that works in a non-rifled tube. Your post cleared it up and that style could be used just as Dr. K mentioned. | |||
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Lasers don't have nearly the accuracy level of an air gage. They are generally in the .0001 resolution quality as opposed to millionths. | |||
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Don't fool yourself into thinking Lasers aren't more accurate than an air gauge !. Lasers are FAR MORE ACCURATE than one could ever imagine !. I KNOW this for a FACT . How ever it would be impractical to use one down a bore for measuring dia. . I've not only seen but Personally Ran a YAG Laser that cut .000042 from a pattern for HP . That " LASER " also cost more than our combined salaries !. Unless one of you is Bill Gates in disguise ?. Besides how do you think Buckey balls or Nano carbons as well as several other extremely small objects which are invisible to the naked eye are measured ?. Put it this way the visible and invisible light spectrum can easily be measured , how ever it's not done with an Air Gauge or Micrometers !. This is the smallest units of measurement I Know of . The smallest measurement would probably be the extrapolation of the unification scale to the Planck scale. Planck distance or (1.6)X10*/36 meters !. At this point I do not have any hints from experiments that what we regard as point particles, i.e. photons, electrons, gravitons etc. will show any structure above this scale. And at this scale everything will show the same structure. This is more of an educated guess, of course. But it is backed up by all relevant measurements from particle physics. And for all I know people have tried very hard to find a scale in-between. But so far those attempts have failed. The Good Doctor Rest . Shoot Straight Know Your Target . ... | |||
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This is not a laser you will find in a normal Machine shop. In a normal manufacturing environment an air gage is the most accurate and practical measurement device commonly available. If a barrel had a thin layer of oil from broaching would the laser clean the surface while it was measuring? An air gage does blow the contaminates off the surface while measuring, this is very helpful at the manufacturing level. Also the laser you ran cut off .000042 how was the measurement verified? An air gage doesn't cut material it measures finished size and the resolution of air gages used in an everyday aerospace machine shop environment is .00001. I am not debating that lasers are accurate I am simply stating that a normal laser used for measurement in a machine shop doesn't have nearly the resolution of a normal air gage used in a machine shop. | |||
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