Fitting Rifle Bolts

[gc1054]

All,
Question wrt fitting rifle bolts (No1s in my case...but could be No4, 5...etc.):
When fitting a replacement bolt and checking for equal bearing of the bolt recoil lugs (using eng blue, etc) in the body and say the right side (long lug) is bearing evenly (exercise bolt...blue nicely & evenly removed from lug surface) but the left side lug shows no evidence of bearing (eng blue unmarked), how far can you stone/adjust the bearing lug until the other lug (in this case the left or body lug) starts to bear? Can you incrementally go through the fitting process (stone...blue...re-check) and stone one, two, or a few thou off the lug that is bearing? Key part of question.....is there a point in the process where you need to stop (say at three thou for example) and investigate for other problems?
Thanks!
GC
PS: I've read Peter L's Bolt Fitting articles many times and have successfully fitted a couple of bolts so far that didn't need much tweaking What I'm looking for is advice or info & some means (dim check, etc) of determining when to stop tweaking Also, I thought Bruce_in_Oz posted about bolt & body recoil lug absolute and relative dimensions and associated tolerances but for the life of me I cannot find it. Any helpin finding this info would be appreciated:}

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Bruce_in_Oz]

Here we go:

From: SMLE Specification 1938
SPECIFICATION NO. S.A./462 P
Approved 14. 12. 1938


15. Body
(a) Hardened, cleaned off, and adjusted. - The body will be gauged for size and figure, position of thread and resistance shoulders from barrel seating (a toleration of .004-inch will be allowed in the overall distance of the shoulders from the barrel seating, but the distance of the shoulders in any body must not differ from each other by more than .002-inch);

16, Bolt, breech. - Will be gauged for size and figure, and tested for straightness and concentricity of bore, also for position of lever with rib, position of cam, resisting shoulder and lug (a toleration of .004-inch will be allowed in the distance of the bearing surface of the resisting shoulders and Lug from the front end of the bolt, but the distance of the resisting surfaces of the resisting shoulder and lug in any bolt must not differ from each other by more than .001-inch)

[Maxwell Smart]

Not too many gnat's knackers in that tolerance!

[gc1054]

Here we go:

From: SMLE Specification 1938
SPECIFICATION NO. S.A./462 P
Approved 14. 12. 1938


15. Body
(a) Hardened, cleaned off, and adjusted. - The body will be gauged for size and figure, position of thread and resistance shoulders from barrel seating (a toleration of .004-inch will be allowed in the overall distance of the shoulders from the barrel seating, but the distance of the shoulders in any body must not differ from each other by more than .002-inch);

16, Bolt, breech. - Will be gauged for size and figure, and tested for straightness and concentricity of bore, also for position of lever with rib, position of cam, resisting shoulder and lug (a toleration of .004-inch will be allowed in the distance of the bearing surface of the resisting shoulders and Lug from the front end of the bolt, but the distance of the resisting surfaces of the resisting shoulder and lug in any bolt must not differ from each other by more than .001-inch)

Bruce_In_Oz,
That's the info I was looking for....many thanks!
It appears from this info that if the relative dims on the body shoulders are at max tolerance (left body shoulder .002 "long" rel. right body shoulder) and that the bolt lug relative dims are also a max tolerance but running the opposite way to the body shoulder (left bolt lug "short" rel right bolt lug) then the maximum adjustment range on the bolt lug (right lug in this example) to achieve proper bolt lug bearing is 3 thou (.003). Sound correct?
GC
PS: Of course the example applies to a body and bolt that are in spec.....not necessarily a 94 year old body and a mismatched 85 year old bolt

---------- Post added at 08:11 AM ---------- Previous post was at 08:06 AM ----------

Not too many gnat's knackers in that tolerance!

Maxwell Smart,
Too true.....Stretches my ability both to measure repeatably by hand (even using digital gear) and adjust things properly. On the plus side given the info provided by folks here I've managed to do it twice and am working on a third
GC

[Bruce_in_Oz]

And don't forget that the locking surfaces of bolt and body are cut to a 1: 0.10" helix; they are NOT straight or at 90 degrees, like most modern sporting rifles.

There were a couple of "shaving tools" used at point of manufacture / assembly to final-cut the "resisting shoulders" in the body. I have never seen a complete kit, but I suspect there would have to be a hardened "guide-helix", to keep things operating to spec. There would also have been a set of extremely expensive and precise gauges that went with these tools.

[gc1054]

And don't forget that the locking surfaces of bolt and body are cut to a 1: 0.10" helix; they are NOT straight or at 90 degrees, like most modern sporting rifles.

There were a couple of "shaving tools" used at point of manufacture / assembly to final-cut the "resisting shoulders" in the body. I have never seen a complete kit, but I suspect there would have to be a hardened "guide-helix", to keep things operating to spec. There would also have been a set of extremely expensive and precise gauges that went with these tools.

Bruce_in_Oz,
Thanks. The helix "angle" on the bolt lugs is pretty subtle and doesn't seem easy to measure and check using calipers, mics, etc. During the bolt lug fitting & stoning process I've simply been working toward achieving the largest bearing area on the lug face that mates to the body shoulder. So when the lug is blued & the bolt exercised most of the blue is equally removed across the shoulder to lug contact area. The assumption is that this indicates that the bolt lug matches or follows the body shoulder contour. Given the tools I have available I can't think of another way to address the body shoulder helix shape and maintain it on the bolt lug. Do you know of a different way to address this when fitting a bolt?
Thanks!
GC

[Peter Laidler]

Just a minute..... You shouldn't be adjusting the body when you fit a bolt. You fit the BOLT to the body. Or am I mis reading something.

Just as a little aside, the body helix is there and is all part of the complicated geometry but the reason for it is to give a degree of a) bolt locking leverage and more importantly, b), a primary extraction leverage that you cannot override. Remember BOLT to body

[Alan de Enfield]

Just a minute..... You shouldn't be adjusting the body when you fit a bolt. You fit the BOLT to the body. Or am I mis reading something.

Tues 4 Dec 2007 12:07 pm some bloke wrote this :

.....................BUT, that's not quite the end of the story because you won't have this 'Gauge, Inspectors, bolt' but it's only right that I tell you. Now for a little secret. If you have ever bought a rifle that has a sploge of red paint on the left side, adjacent to the internal left side locking lug, then you now know that the rifle was condemned for 'worn locking lugs'.

If you are going to fit a second hand or new bolt, then do the same thing. If the dye pattern is one sided, then stone the high surface of the bolt until BOTH locking lugs bear evenly against the locking surfaces of the corresponding surfaces in the body. BUT DO NOT ATTEMPT to stone the rifle to get a bolt to fit (you can only get to the right hand surface in any case ....). The rifle body is induction hardened at these points to a depth of .004 - .006" but we have found it deeper

[gc1054]

Just a minute..... You shouldn't be adjusting the body when you fit a bolt. You fit the BOLT to the body. Or am I mis reading something.

Just as a little aside, the body helix is there and is all part of the complicated geometry but the reason for it is to give a degree of a) bolt locking leverage and more importantly, b), a primary extraction leverage that you cannot override. Remember BOLT to body

Peter,
Understood......I'm only adjusting & stoning the bolt lugs....not the body shoulders. As you stated....fit the bolt to the body
One question: When you were fitting the bolts did you measure any bolt lug dimensions (say from the bolt face ( where the bolt head fits) to the lug face) so that you had some idea as to how much you may need to tweak a lug to get initial bearing? Or was it more an initial check with the blue and go from there? Understanding that in a workshop that there were many weapons needing service but if there was time how would you tackle the job?
Thanks,
GC

---------- Post added at 12:19 PM ---------- Previous post was at 12:10 PM ----------

Tues 4 Dec 2007 12:07 pm some bloke wrote this :

.....................BUT, that's not quite the end of the story because you won't have this 'Gauge, Inspectors, bolt' but it's only right that I tell you. Now for a little secret. If you have ever bought a rifle that has a sploge of red paint on the left side, adjacent to the internal left side locking lug, then you now know that the rifle was condemned for 'worn locking lugs'.

If you are going to fit a second hand or new bolt, then do the same thing. If the dye pattern is one sided, then stone the high surface of the bolt until BOTH locking lugs bear evenly against the locking surfaces of the corresponding surfaces in the body. BUT DO NOT ATTEMPT to stone the rifle to get a bolt to fit (you can only get to the right hand surface in any case ....). The rifle body is induction hardened at these points to a depth of .004 - .006" but we have found it deeper

Alan,
Thanks. Peters papers on bolt fitting are a great reference
GC

[Surpmil]

Was abrasive lapping of the lugs and shoulders against each other part of the final fitting process? It would I suppose cause some wear to the hardened surfaces of the shoulders, but surely the unhardened lugs of the bolt would wear in much more quickly?

Hand stoning by eye does not seem a very efficient method even with the use of engineer's blue.

"figure", as in "...gauged for ... figure" refers to what; eyeballed for overall fitness and appearance or actually gauged for some specific dimension?