Barrel thread for a Sako L461 action

Everybody has a choice of pitch to follow

BJS6 said:
Peter,

If you had a thread of 7.8 inches you'd have run out of room for the extra thread when comparing 16TPI to 1.6mm pitch.

Obviously you will never have a barrel tenon that long but like you said eventually the "error" would become very obvious. Logically even at around 2 inches in thread length it would fail to fit unless cut very loose.

Bryce
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Bryce

I still didn't get my calculator out, but the line of your thinking is correct. The only reason why this can be done and get away with it is, that the barrel material is soft (26-30HRC) and quiet possibly it can be distorted on tightening.

If the barrel thread is cut in such a way, that it can be screwed by hand all the way to the shoulder and overcompensate for some 0.006" in the pitch accumulated difference it tells me nothing, but a very loose fit indeed. One can do much closer fit with the same and correct pitch on the both parts bearing all the way through and with the same load on every thread and without the need of "excessive" and uneven material distortion adding extra stress.

If a tap was used to tap a hole in a block of a tool steel and then the block was hardenned to (64-66HRC) a fraction harder than the tap itself one could use the same tap and run it into the tapped hole again with the closest fit possible virtually into the infinity.

One can only wonder, just how deep a same size diameter tap with everything being equal, but a 0.0005" different pitch would go without breaking up somewhere?

I don't think, that it would be very deep.

Shoot better
Peter
 
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Follow-on question

Can anyone verify that the L46 and L461 actions used the same barrel thread? Also, how close are the stock inlets? i.e. will an L46 action/barrel fit in a slightly modified L461 stock? Thanks. Great forum, BTW.
 
You would have to more than............

"slightly" modify the L46 stock to accomodate the L461, the magazine is much wider(proportionately speaking), plus the 46 stock with that divot in the wood.... It may be possible to do, but it would probably have a look that only a "Mother"(the guy that did it)could love. But, if you have one of your own you want to do, I'm sure there are many on this board who'd LOVE to LOOK!!! :eek::D ;) As for going the other way, (46 in a 461 stock), you'd have a LOT of wood gone, for a single-stack magazine!! :eek:;)
 
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Ahh, I see. I have an L46 action, so you're saying that the magazine well for the 461 is wider? That's no good. Thanks for the reply.

Anybody on the barrel thread? Anybody know difinitively if the thread and thread length are the same?
 
Ski, The difference on the two....................

is, the L46 has a single-stack detachable magazine and basically a miniaturized Model 70
trigger. The L461 has a mauser-type magazine(staggered) and a modular trigger, (which the careful, utilizing either model could goof-up :D been there) The L469, however, was between the two, and had the magazine and trigger of the former. Clear as mud, right?? :D:D:rolleyes: I hope it makes sense
 
Does anyone know of an external action wrench to fit a Sako L461? If not, the only option I see - in order to avoid distorting the integral dovetail scope bases - would be to buy a blank block from Brownells (or just get a chunk of square stock of the correct size) and machine my own.
 
To add to the pot.............lol..........

According to my Sako Finland info/schematics, The L461 and A1 use: W22x1/16", (guessing W22 is meant to be M22 but if it is I wonder why they have "W" referenced at two different locations....) Pitch 1"/16, Pitch Dia. 20.946 +0.10, Thread angle 55 degrees (not 60 degree). S491, M591 and L691 are identified in schematic as: 1"-16UN Form Special B; noting the words "Form Special B (also applied to the Sako L61R, AIII , AIV, and AV)" .

The metric designation1.6 pitch is not mentioned. Of course 16tpi is really 1.5875..............
 
This all brings up the larger question of thread dimensions and forms. I for one would love to have a set of drawings and specs for the various Sako threads, the real dimensions and forms of the various Mausers, and the CZ550 (as in just what the h*** does the "sp3" mean in "M26x2sp3").

Most of the "information" from over the years (as in Frank DeHaas who is about no help at all) has led to using "almost" thread forms (60 degree threads turned against 55 degree threads, English "sort of" equivalents, and so forth) and has more or less "worked". But we are increasingly working to more exact standards.... and we do need to be... By now we've stopped working on modern automobile engines with huge hammers and blacksmith technology, and we need to stop putting rifles together the same way.

Soooo.... does anybody have some or all of this information already compiled? Or can they compile it in a format that we poor benighted gun tinkerers can actually understand and use? The drawings and specs must exist somewhere. Anybody??
 
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Yeah, Joe, I tend to agree with you. But it's one thing to be an old- timey hammer mechanic back in the 1950's trying to fit a barrel to a surplus Mauser and maybe getting it "sort of" right. It's quite another in the 2010's to have all this technology around us, to be able to dial in a chamber job to less then .0002", and still be pretty much guessing at barrel threads. And the other thing that really p****s me off is all these folks like Sako (who sold bare actions for years and still do afaik) and CZ who also sell bare actions today, and don't include a basic set of thread schematics so they can be safely and correctly assembled into a rifle. Then you have Brownell's who sell CZ actions and publish the wonderfully cryptic "M28x2sp3" thread specs for everybody to wonder about, and they probably walk away dusting off their hands and feeling pretty wonderful, thinking they've done their job, when all they've done is confuse the issue.... and yes, I DO know what M28x2 means, or should mean... ISO metric (60 degree) thread form, 28mm major diameter, pitch 2mm. But the sp3 part remains a mystery. Maybe Brownell's or CZ would like to chime in here. It might be important and it might not. And we might need to know.

I do know that if somebody were to fit a barrel that had out of spec threads and a lawsuit occurred, it would sure pay to sue the manufacturer / importer / distributor for failing to provide the proper information on how to use the product. So maybe CZ, Brownell's, Sako, and a couple of others ought to rethink this whole issue and start providing some good information. Are you reading this??!! When I buy, for example, a Stiller action, there'sa nice drawing right in the box. That's how it should be done. Anything less just ain't enough.
 
Oh, and Joe. My "guess" from your previous message about the 55 degree Sako threads is that the "W" in the thread spec means "Whitworth" form which would be 55 degrees. Yup, I get to guess too.. :)
 
I know this is an old thread but for the benefit of those like myself that arrive here through a search. A link to a Web site giving an " to mm conversion and vice versa was posted above.
We do not always have a computer handy when working at the Lathe. If you do have a calculator handy then to find the conversion simply, for example .500" multiplied by 25.4 =12.7mm. 22mm divided by 25.4 = 0.866". So multiply your " and divide your mm by 25.4 and you have a quick and easy calculation that can be done at the machine with a calculator, without having to go use the computer with oily hands.

Big thanks to all on the Forum for sharing their knowledge freely. I for one tip my cap in appreciation. I am learning a lot from you guys.
 
hi all
here is a little xmas tip try divide the top number in drill with the bottom number eg 3/4 3-:-4=.750 try 1/4 1-:-4=.250 neat

merry xmas all
tasy_ted
 
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