Barrel thread for a Sako L461 action

S

spmorgan

Guest
Hi, can any one tell me what the barrel thread is for a L461 Sako action thanks. Shane
 
Thread spec for a L461 SAKO

The thread spec for a SAKO L461 action is 22mm x 16TPI.

To thread a barrel tenon to fit a L461 action, machine the tenon 21.8mm diameter for a length of 19.4mm and thread at 16TPI x 60° until the action will screw on by hand.

The tenon length of 19.4mm is close for most of the later actions but you should measure your own action from the receiver face to front leading edge of the extractor with a depth micrometer to get an accurate measure.

Tony
 
Dennis, we'll never know

What a half a grunt or a full grunt means, but it's a great site. Thanks for posting it.

Shoot better
Peter
 
Thankyou for the info Tony, why would they have a metric diameter in tpi rather than metric pitch as well, strange hey? thanks again anyway. Shane
 
Off another forum...

According to Stewart Otteson's book, "The Bolt Action Rifle" the barrel thread is .864 X 16.

I usually used .860"... but it has always been 16 tpi.
 
I think I have pointed out before that these actions are not really 16TPI. They are actually a 1.60mm pitch. This is so close to 16TPI that they have always been described as such in North America. It really doesn't matter and I'm certainly not trying to be argumentative but this is why you see a metric diameter and a TPI thread. I wish they would have stayed with this pitch on their later rifles so I didn't have to change gears every time I re-barrel one. I guess they didn't care about my problems! Regards, Bill.
 
Made in Europe, expect Metric

I don't know what's your machinery like. I've herd about it, but personally I've never seen a lathe where I would have to do anything, but to move two levers to cut any thread at any pitch. I always thought, that we were always behind, however it doesn't look like it. I'm talking about from late 60s. where everything old was scraped and replaced with new user friendly stuff.
Maybe we were lucky afterall.

Shoot better
Peter
 
PPP MMM said:
I don't know what's your machinery like. I've herd about it, but personally I've never seen a lathe where I would have to do anything, but to move two levers to cut any thread at any pitch. I always thought, that we were always behind, however it doesn't look like it. I'm talking about from late 60s. where everything old was scraped and replaced with new user friendly stuff.
Maybe we were lucky afterall.

Shoot better
Peter
Click to expand...

If I want to cut metric threads I need to change some gears and refer to a chart... I have never bought the gears as it is really rare I need to thread metric on my lathe. On a few hunting rifles, when I do require metric I simply have another shop thread what I prepare... then I finish it off...

My quick change gear box threads from 4 tpi to 227 tpi... (Rockwell lathe)

1.6mm is .0630" tip of thread to tip of thread...
16 t.p.i. is .0625" tip of thread to tip of thread...

That is pretty close to being the same!:D
 
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Dennis,

Doesn't that half a thou per thread add up over the whole tenon length ?

If you had say 3/4 inch threaded length you'd have 12 threads and the last thread would be 6 thou out of place when cutting 16TPI versus cutting 1.6mm pitch.

I know 6 thou isn't a lot but it's still enough that it isn't quite right, the last few threads must be in a bit of a bind ???

Or am I missing something ??

Bryce
 
Rear Entry wrench for L461 Sako

spmorgan:

A few years ago I had a customer bring in about a half dozen L-46 and L461 Sako actions for rebarreling. He borrowed a rear entry wrench from Butch Lambert. The customer said he would pay me to make him a rear entry wrench for these actions. I made 3 copies of that wrench. The customer never offered to pay for the wrench so it and two others are still hanging in my shop. The first time you remove a barrel from one of these actions I recommend using a true external action wrench. IMHO when you rebarrel one of these actions the barrel should be well lubricated and put on only so tight that a rear entry wrench can break the barrel action loose.
Rustystud
 
BJS6 said:
Dennis,

Doesn't that half a thou per thread add up over the whole tenon length ?

If you had say 3/4 inch threaded length you'd have 12 threads and the last thread would be 6 thou out of place when cutting 16TPI versus cutting 1.6mm pitch.

I know 6 thou isn't a lot but it's still enough that it isn't quite right, the last few threads must be in a bit of a bind ???

Or am I missing something ??

Bryce
Click to expand...
No you are not missing anything...

I always have tried the action onto the barrel while threading and make the fit so it can be done by hand up to the shoulder... I would think, when torqued tight, the 6 thou difference would not affect anything, the threads may even permanently distort to fit correctly ... there must be many thousands of incorrect non metric barrels threaded into L461's out there...
 
I thankyou all for your advice. I threaded the barrel today using the 1.6mm pitch which suited me as my lathe is metric anyway, but because of the pitch I had to change both small drive gears which I hate doing at anytime but the thread came out Ok and its finished, thanks again for your advice all. Shane
 
I must confess that I, just like most North American 'smiths, also thread Sako rifles at 16 TPI.
Dennis,
The correct answer when someone asks about the variance in pitch is that the slight mismatch adds stability to the threaded connection and improves accuracy. I think we can sell this! Regards, Bill
 
Dennis Sorensen said:
1.6mm is .0630" tip of thread to tip of thread...
16 t.p.i. is .0625" tip of thread to tip of thread...

That is pretty close to being the same!:D
Click to expand...
Dennis the actual calculation is 0.0625 vs 0.06299 or a difference of 0.00049" error per thread. For a 1" long tenon that would be a 0.008" total error.
 
JerrySharrett said:
Dennis the actual calculation is 0.0625 vs 0.06299 or a difference of 0.00049" error per thread. For a 1" long tenon that would be a 0.008" total error.
Click to expand...

No that is not total "error" ... it is .008" accuracy interference fit... designed to add stability and positive vibrations.... :D
 
Same pitch everytime

Dennis Sorensen said:
No that is not total "error" ... it is .008" accuracy interference fit... designed to add stability and positive vibrations.... :D
Click to expand...
,,,,,,,,,,,,,,,,,,,,,,,,

I'm with Jerry on this one.

The seamingly minute (0.0049") difference in pitch per one thread adds up to a total difference (0.008"). As the total difference is always governed by the total number of threads means, The longer the tennon, the bigger the error.

The longer the tennon is, the looser the fit must be to compensate for the total combine difference. In other words, as one end is getting tighter, the other end is getting looser.

The tighter the fit per one thread, the shorter the tennon can be. I can't be bothered to get my calculator, but any difference in pitch can run only X number of threads before it runs out of the pitch itself. One can run the same pitch threads to infinity, but one can't do the same with different pitch threads.

The distorted threads or a looser fit needed, is giving the false impression of tightness, is actually masking the overall poor fit between the two parts. In this case, just because one can get away with it, it doesn't mean that's not a poor practice.

Shoot better
Peter
 
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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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