Importance of truing threads?

[butchlambert]

So, If I do not take the time to read and digest the above post, my jobs are junk? You guys fight the small stuff and I'll continue to make a part for an antique sparkplug tester.

 

[TRA]

Precisely the response I expected.

 

[butchlambert]

Precisely the response I expected.

You a comodian?

 

[TRA]

You a comodian?

haha, this all reminds me of an old saying here on the north coast...."You know the real reason lawyers use Latin?

 

[butchlambert]

haha, this all reminds me of an old saying here on the north coast...."You know the real reason lawyers use Latin?

North Coast? Didn't know that you lived in Northern Canada. I'll excuse you then. Too cold to shoot!

 

[Roeder]

So far as Stiller putting taper in the Viper, I have heard that too. I have heard it was only about .0003". Nothing I have seen would make me expect that tolerance to be held. And if it was that slight I doubt most gunsmiths would notice it let alone complain.

My explanation about the early Viper threads came (as best as I can remember) straight from Jerry Stiller. A shooting partner has one early and one late action. He started with the new action and acquired the older one later. He questioned why the barrels that were fitted to his new action would thread almost all the way on to the older action and then become too tight to safely go the last little bit. I don't know how much taper there actually was but it was closer to .003 than .0003. In practice he was able to interchange barrels that were fitted to the tapered thread action to the straight thread action with no loss of accuracy. I am in your camp about thread fit not being a critical factor in getting the most out of a barrel. I fit them loose enough to mitigate the risk of galling and I do take pains to get the best thread form possible simply because I consider it to be a point of pride.

 

[carlsbad]

So, If I do not take the time to read and digest the above post, my jobs are junk? You guys fight the small stuff and I'll continue to make a part for an antique sparkplug tester.

Butch,
Absolutely not. The post above has almost nothing to do with making a good quality joint. It confirms that the joint is designed correctly. But that wasn't actually necessary since we already know it works from Millions in service.

It was mostly an academic exercise to respond to a question. It does have one interesting fact in it--the tenon stretches .0002". This affects headspace--so I've confirmed that the stretch of the tenon has almost no effect on headspace, but not zero effect.

--Jerry

 

[carlsbad]

TRA,
Sorry I wasted my time on you. I won't do it again. Fortunately, this is engineering I've done so many times that I was able to do it without reference in 10 minutes before I had coffee at 530 in the morning. Glad I didn't do anything that required real work. --Jerry

 

[TRA]

TRA,
Sorry I wasted my time on you. I won't do it again. Fortunately, this is engineering I've done so many times that I was able to do it without reference in 10 minutes before I had coffee at 530 in the morning. Glad I didn't do anything that required real work. --Jerry

Just keep it in mind that behind every man made disaster are thousands of educated and over documented folk. It's unfortunate that in present day, that creative writing is an engineers most important trait. I asked you a simple question and 8 hours later you come up with .0002. That is not a reasonable explanation for your ~30% thread contact claim. Btw, what makes you so sure that the .0002 is from tension or compression, ie, the tenon or the action?

FWIW, there is no straight, concentric, or any other dead nuts when it comes to metal working. Everything has tolerance. There is no perfect. It's impossible. I'm surprised that actions are as precise as they are, especially those machined on various machines and transferred from fixture to fixture. In this industry claims of .002 would be more in line with reality. Trust me holding .0002 over say 250 pcs.....is a bitch. With those tolerances you better be using a grinder, a damned good grinder. All this accuracy expectation or claims would be better served with getting barrels with straight holes, BUT I'm sure there would be plenty who will claim, that straight don't matter either. Sooner or later we will be back throwing stones at targets.

 

[carlsbad]

TRA. the .0002" is real. It's called physics, simplified by mechanical engineering. I am muting you now. --Jerry

 

[TRA]

TRA. the .0002" is real. It's called physics, simplified by mechanical engineering. --Jerry

Yes, and your math clouded by alloys and heat treatments, surface treatments, surface finish, yada yada yada. It's been fun Jerry, you just need to learn to tolerate those of us less fortunate. Clips or mags?

 

[TRA]

Just some food for thought for those confused by all this edumacated verbiage....

Cambering reamers are ground on high precision grinders. Super accurate right? Note that on the prints for them, linear dimension tolerance is .005. Now ask yourself how my 60-70 year old hobby lathe pares up to that precision grinder.

 

[johnfred1965]

Clips or mags?

A clip is what holds my mag pouch on my belt.
When someone says: "Trust me", that is usually the last thing you want to do.
.0002 may very well be hard to hold over 250 pieces, but most of the men and women building rifles or actions on this forum are making them one at a time.

 

[johnfred1965]

I don't know how much taper there actually was but it was closer to .003 than .0003.

I"m no professor and I don't quote calculus off the top of my head, just a good ol' kentuc redneck; but I can read, and that .003 matches closely the .0025 taper suggested in Vaughn chapter 6 I had mentioned earlier. It's a 25 year old book, but I haven't heard of anyone else's research debunking him. I've also mentioned before, I'm not an engineer, machinist, or gunsmith, nor did I stay at a holiday inn express last night, but if the book has a lot of neat pictures, I can usually figure it out. If that action is tapered .003 and you cut a good straight tenon, it should shoot lights out.

 

[johnfred1965]

One more thing and I will stop ranting for a while. Dan posed the thread compression question several pages ago, Where has he been? Sitting back and watching the flames?

 

[mram10]

TRA and Jerry, though you are on slightly different sides, you guys have introduced numbers instead of opinions, thus helping a lot. So thanks guys.

 

[PWS]

It's too bad Vaughn isn't here to join in these discussions. IIRC, his main concern with the threaded joint (and subsequent suggestions for improvement) was that he found the joint would move each shot and allow the barrel to settle pointed in different directions.

There appears to have been very little success in following Vaughn corrective measures and most suggest "loose" threads that function primarily as a method of holding the barrel and receiver together. In that case, what serves to keep the barrel and receiver in the same orientation, shot after shot?

 

[Alex Wheeler]

If barrels are moving shot to shot you wouldnt know it by the aggs shot today. I love Vaughn's work and its a very interesting read, but I dont take it all as hard fact.

 

[Dusty Stevens]

If barrels are moving shot to shot you wouldnt know it by the aggs shot today. I love Vaughn's work and its a very interesting read, but I dont take it all as hard fact.

After all, he didnt have the internet to correct his findings, right?
It is a good book to get when you start building i think- then do your own testing after that.

 

[PWS]

While I'll give Vaughn the benefit of the doubt on what he found, he did state (IIRC again) that he just didn't have enough time to pursue this issue further. No question that the vast majority have not had the same movement problem as Vaughn, as you point out Alex, so I wonder if it was just a quirk of his particular test rifle/s. I do not recall that he did anything to his receivers even so rudimentary as measuring them, let alone truing them.

Perhaps the combination of "loose" threads, true receiver face, and true barrel shoulder is all it takes to keep the receiver/barrel joint from moving?