Came across these, mixed in with some bolts.
Maybe someone has to hand the excerpt from EMERs describing their correct usage?
https://www.milsurps.com/images/impo...96923247-1.jpg
https://www.milsurps.com/images/impo...96923246-1.jpg
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Came across these, mixed in with some bolts.
Maybe someone has to hand the excerpt from EMERs describing their correct usage?
https://www.milsurps.com/images/impo...96923247-1.jpg
https://www.milsurps.com/images/impo...96923246-1.jpg
Nice, for gauging the bolt runway in the body when new or worn I assume? Peter!!
Very nice find Thunderbox! I've never found one in all these years, although I do have the equivalent for the No4 rifle.
ATB
Very nice, and in good condition. Never seen one before.
I'll explain it tomorrow...............
GAUGE, inspectors, selected breech bolt......... Haven't seen one of these for a few years. Yes....! Only used by the most senior examiner, this bolt was a calibrated bolt made to the EXACT size. It was kept in an oily drawer along with the other gauges. It's main use was as the final arbiter as to whether a body was worn out. I seem to recall that the No1 gauges came with a matched bolt head which your are missing (oh no they're not, I've just looked properly......!) The locking shoulders were specially hardened so NEVER use one of these bolts as a true bolt and the distance between them and the face of the bolt was the datum. When it was impossible to get CHS, using the old bolt and boltheads then a new bolt, you'd use the gauge bolt do the final check. If this failed then the rifle was scrapped as this calibrated bolt had deemed that the body locking lugs were worn through.
The No4 bolt didn't come with a bolt head as a matched set BUT there was a special bolt head to be used with it that was a special measurement that I forget at the moment. This did the same thing.
This gauge bolt also dictated wear in the boltway. For example, the smaller left locking lug MUST clear the nose of the sear when loading and unloading. If it does foul, then the gauge bolt is used to verify that the body is worn and not the new bolt. This test should be carried out with the bolt lightly pressed down towards the sear nose to give an accurate assessment of the condition of the body. Obviously, it could also be used as a gauge to test other worn bolts too but in those cases, we had the 'inspection standards' specifications to refer to.
Alas, the same bolt was used to gauge L42 bodies too and these were all getting quite old and as such, some would fail the worn body test so you were allowed to put a line punch mark across the sear stop in the body to lower it very slightly........., JUST sufficient to allow it to clear the gauge bolt small/left side locking lug. But this line punch 'allowable bodge' could only be used once. After that, you were permitted to take a gnats knacker off the apex of the rounded surface of the rifle bolt................ But the days of the service No4's and L42's were numbered.
Off the subject slightly............. I'll continue on the next thread.........
The gauge bolt was also used as the condemnation level for other things, apart from being scrapped. DP for example! The gauge bolt will also tell the Armoutrers whether the body locking lugs are worn unevenly or whether one side of the rifle bolt has run through the hardened shoulder. The rifle will still function perfectly and is suitable for training but NOT for service use.
Anyway, there's a few examples of how the GAUGE, inspectors, breech bolts were used. Kept by the senior examiners, calibrated initially by the Chief Inspector of Small Arms at Woolwich (the CIA mark) and then annually or so at the calibration laboratory,
There, yet another few bits of useless Enfield information. Next question................
Why useless?. This is excellent stuff and surely exactly the sort of technical detail owners and dealers must think about and need to know so that they can ensure their rifles have not crept into the DP zone!.Quote:
Originally Posted by Peter Laidler
How are these things determined now in the absence of these and presumably other similar gauges?.
Quote:
Originally Posted by Peter Laidler
Peter, please don't think of any of that info as useless. I am quite thankful for everything that you and so many other knowledgeable people share with us. I enjoy reading all this info. I love knowing not just about the rifles I own but how they were cared for, inspected, and repaired when they were in service. For me it's all part of the rifle's history and I am quite happy that you are willing to fill in those bits for those of us that wouldn't know any different otherwise.
Could a New(ish) No4 bolt be used on No4's as a substitute to some degree?. i.e. would they be manufactured to the same tolerances.
As I understand it, the Gauge bolt was ground and then calibrated to the EXACT spec. No plus or minus.., it was exact. The hardening was also extremely hard too so DON'T use one in your rifle. If I remember correctly, the channel down the top locking cam groove was hollow, right through on the No4 gauge bolt so that the standard and the gauge could never be mistaken. Can you confirm this DRP?
We also had similar breech blocks for the BESA, Bren and Vickers plus the Vickers lock parts
Thankyou Thunderbox and Peter!
Would it be possible to combine the two posts into an MKL entry on the topic? It would be very handy to be able to reference it to help persuade potential reactivators of DP rifles that there is more to headspace than the length of the bolt head,
From Peter Laidler's post: "As I understand it, the Gauge bolt was ground and then calibrated to the EXACT spec. No plus or minus.., it was exact."
One would expect that there were at least three gaging bolts- One of maximum allowable size, one of minimum size to check NEW manfactured action bodies for proper clearance, and one that was used at the shop/overhaul level to check for maximum allowable wear- "field gage". (Probably at least one more for the FTR program, which Captain Laidler notes was held to 80% of "new" remaining service life.)
Gaging bolts themselves WOULD have allowable tolenaces, but held to a maximum of 1/10 of the production tolerance- probably closer. (I.e., if the mfg. tolerance of a certain datum was 0.002", then the worst a gage tolerance could be is 0.0002". And the tooling to check the gage ought to be held to 0.00002"!!! At some point, this requirement can no longer be met, but today it's at the atomic level...)
Got that and the reasons JM but in service we only had one bolt. Kept by the examiner in an oily tray with its certificate of calibration after being calibrated annually. It doesn't look like the long locking shoulder was hollowed right through either. Ours were all silver too, just like the SMLE bolt shown by thonderbox.
The trouble with this now is that every would be expert will want an inspectors gauge bolt!
Nah, bugger them , just me!Quote:
Originally Posted by Peter Laidler
It would be safe to assume that such an animal only existed in small numbers- possibly two only per unit which had cause to draw the gauge. Would I be right in saying the only unit(S) with such an entitlement would be highest repair before factory, and the factory themselves? Here in Aus that would probably mean (on today's system) there would be four in the country, maybe five. Perhaps there were more in Great Britain.... They would be very expensive to manufacture/ replace, and requiring annual calibration makes them NOT a desirable item to have if you don't need one.
End result, Thunderbox, I'd think you can safely file yours behind the budgies teeth with regards to rarity.
"inspectors gauge bolt"- you're right! there would only likely be one of those available (outside the OEMs or FTR facilities). And probably only one available per shop unless it was big.
So, likely VERY few survive.
Hmmm....Maybe a rental service, like the chamber reamer rental guys? But a HUGE deposit required- refundable upon return and inspection.
These gages photo-ed above would be JUST for checking the condition of the locking surfaces, yes? It's not a multi-function gage, or, if it IS, what other features does it check, exactly?
ETA: Oops! Shoulda re-read Post #6 first:
Originally posted by Peter Laidler:
"This gauge bolt also dictated wear in the boltway. For example, the smaller left locking lug MUST clear the nose of the sear when loading and unloading. If it does foul, then the gauge bolt is used to verify that the body is worn and not the new bolt. This test should be carried out with the bolt lightly pressed down towards the sear nose to give an accurate assessment of the condition of the body. Obviously, it could also be used as a gauge to test other worn bolts too but in those cases, we had the 'inspection standards' specifications to refer to."
ETA2:
Back to my original thought:
Thinking about another similar thread where the radial play of the bolt seems excessive (i.e. "sloppy"). Would not a gage pin of the appropriate diameter be suitable for checking the "slop"? Pretty cheap to check in this case, as most tooling supply houses will sell gage pins individually- just need the maximum allowable diameter and possibly the allowable distance the pin can slide into the body as it seems most wear would be at the rear of the bolt raceway.