Coin style head guage |
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Honkytonk
Senior Member Joined: December 30 2017 Location: Brandon Mb Status: Offline Points: 4770 |
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Posted: January 09 2020 at 9:05am |
My old friend the machinist (at work before I retired) called me for the specs of a coin style head guage. I had wanted him to make me a Foerster type, but he forgot about that (a little scatter-brained, but a great guy) and not wanting to look a gift horse in the mouth... By my measurements, the cartridge rim is .54" dia, (bolt face .57"). So I told him .54" dia x .074" thickness. He's going to take a .20" bite out of the .54" dia to clear the ejector. Sound about right?
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Honkytonk
Senior Member Joined: December 30 2017 Location: Brandon Mb Status: Offline Points: 4770 |
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Oh ya. He's making it out of Peek material. It's a super tough "teflonish" stock used for bushings on rotating shafts.
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Canuck
Special Member Donating Member Joined: January 17 2012 Location: Agassiz BC Status: Offline Points: 3535 |
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Sounds good to me. I would order a couple sets to have in my tool box. The fellow who used to make the older coin style gauges passed away I think a couple years ago. I managed to buy a set from him for the 303 and 7.62 x 54R.
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Castles made of sand slip into the sea.....eventually
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Shamu
Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 17603 |
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The guy who ran "Okie" is gone, but there is still one source: Valmont firearms (UK) Hi they are :
•GO –0,064inch•NO GO –0,068inch• FIELD –0,074inch yeah we can post you a set be about £15 shipping £60 for the set Lord Daniel Shallcross Valmont Owner
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Honkytonk
Senior Member Joined: December 30 2017 Location: Brandon Mb Status: Offline Points: 4770 |
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This may be my inner "Bubba" coming out, but "Answer me this, Riddler!" I take a .303 British brass, full length size it, adhere the Peek (superteflon) disc I'm getting made as mentioned above, knowing that the adhesive (thinnest of epoxy, JB weld?) will add the tiniest amount of thickness to the now easier to install head space gauge? Thoughts?
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englishman_ca
Senior Member Joined: September 08 2009 Location: Almaguin Status: Offline Points: 1089 |
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It would work but how solid would things be?
The resistance to the closing bolt handle comes from the bolt trying to crush the gauge. Usually hardened steel is used, mainly for wear and for the repeatability of the gauging. Use it a thousand times and it does not crush or change dimensions. I am not familier with the material of which you speak of by that name. Bushings and bearings are generally made from a material softer than the shaft they support. I can envisage some problems. But only one way to find out?....it's called prototyping! Other methods? Measure a case rim and fit a feeler gauge in the gap at the rib and resistance shoulder on the bolt closed and pushed forward. Do some arithmetic to get head space. The head space clearance would be the thickness of feeler gauge.. I've seen one made from a hard washer done on a surface grinder. Almost the same as a coin gauge but no slot. And I once did see a regular hardware washer filed to size by hand. Well made and it measured up with calipers on .074 within +/- 1 thou. There are tricks using feeler gauges cut up and stacked, glued, taped. Not a big fan. But nothing is as reliable as a hard steel top hat type. No d**king around. Just pop it in like a cartridge, gently try to close the bolt. If it dont close, all good! Flip the rifle upside down, open the bolt, gauge falls into my hand. Mine is made from hardened tool steel. It is harder than the extractor, so the extractor doesn't even leave a mark. I learnt the feel with the extractor pushing back. Finger tips on the knob, delicate touch required. If you crank hard enough, just about any bolt will close on a field gauge. Worth spending the money to get a good field gauge. Cry only once when you buy, it'll last you a life time.
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Honkytonk
Senior Member Joined: December 30 2017 Location: Brandon Mb Status: Offline Points: 4770 |
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Good points. Peek material is very tough. It takes a lot of hours (up to a year or three) to start it's wearing. On a properly aligned rotating shaft? I've seen bushings made of this stuff last 10 years. As mentioned, it's an experiment, and as far as I know, will be used on two rifles. JB Weld, in my experience, is not real forgiving, nor removable! I'll afix the Peek disc to a full length sized case, clamp, and then when adhered, buff the edges of the rim/coin. That brings me to another question. If a traditional Forster gauge doesn't have a slot cut out for the ejector, why would a coin style need it? Thanks all! I'll keep you posted!
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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I had this message sitting on my screen for a few hours, and before Englishman sent his reply. Seems we are thinking the same thing. Not sure I follow the idea of bonding the disk to the case head?
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Honkytonk
Senior Member Joined: December 30 2017 Location: Brandon Mb Status: Offline Points: 4770 |
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I hear your concern on the material. My thought process to bond the coin to the cartridge was for ease of checking head space. Fiddling with s .070" coin trying to get it to stay in place on the bottom of a cartridge seems finicky. Hence, make it one piece.
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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HT, unless I'm missing something, you would have to cut/grind the full thickness of the rim off of a case if you wanted to add a .074 thick "washer" to make up a gage. Or, do you mean measure the case rim thickness, then determine the thickness of PEEK "shim" to add up to the total 0.074 thickness of gage you want? The epoxy will have some thickness, at least a few thousands.
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Zed
Special Member Donating Member Joined: May 01 2012 Location: France Status: Offline Points: 5585 |
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The Okie gauges are slightly magnetic; so stay on the bolt face. Very easy to use.
before I bought a set; I had rigged a temporary, single use head space gauge to check my rifles. Basically some industrial aluminium tape stuck onto the rear of an empty case. The tape can compress slightly when contact is made with the bolt head. Then measure the rim and tape thickness. It's a single use method. I found that my rifle was close to the field limit, so invested in the Okie gauges. There is no real alternative to the proper tools. While my bodge head space gauge gave me a figure that was close; using the real gauges proved that it was not spot on! it was difficult to accurately measure the rim and tape accurately. |
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Shamu
Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 17603 |
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The trick with coin gauges is to remove the magazine, place the rifle muzzle UP & insert the gauge from the bottom. After testing remove the same way.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Honkytonk
Senior Member Joined: December 30 2017 Location: Brandon Mb Status: Offline Points: 4770 |
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Shamu. How does the cartridge stay in the chamber? I would have thought barrel down.
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Honkytonk
Senior Member Joined: December 30 2017 Location: Brandon Mb Status: Offline Points: 4770 |
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Wow. I plead total ignorance! I've useda full size Forster Gage before but... I just viewed a YouTube video on Okie gages on a Lee Enfield. It is just the coin, no cartridge. Man, do I feel stupid! The Okies must be the thickness of a rim plus .074" for the Field Gage. Is that correct?
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Goosic
Senior Member Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 8792 |
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HT. The Okey field coin gauge, like this one,is just .074" thickness, nothing else.
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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HT, the part you are missing is that headspace is defined as the distance between the bolt face (when locked and locking lugs of the bolt in contact with the receiver) and rear of the chamber for a rimmed cartridge. For the LE, that maximum (field) is 0.074 inches. The cartridge case rim takes up most of that space as it is intended to. The minimum headspace must allow for the maximum rim thickness of a cartridge. The maximum headspace relates to how much case web unsupported by the chamber is safe to fire.
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