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Romanian '3' Front Trunion

4K views 22 replies 12 participants last post by  Tommo 
#1 ·
Have a Romanian front trunion that is stamped with a '3' on the top flat area where the rear sight base goes over it. It is easy to push a standard size Romanian barrel into it with light finger pressure. Are there any barrels available to fit this oversized trunion?

Thank you very much in advance for any information.
 
#4 ·
I had one like that, trun and bbl from diff rifles. What the boys said about stippling is what I did, I dont have a lathe to knurl. Just punch where the bbl and trun contact a coupla hundred times, the metal around the punch mark will raise and give you a good press fit.The pic shows really agressive stippling, u dont have to punch that close together, but the more the better.
 

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#5 ·
another trick is to use the aluminum tape applied by hvac contractors. .003" if I remember correctly. Just enough for a good interference fit.
 
#6 ·
The hand knurling tool does not require any other tools. For $39 plus ship it is a handy tool for any less than adequate interference fit.
So tape can be actually used in a press fit barrel? Seems like it woud simply push out of the journal or trunnion vs stand up the 1,000's of pounds of interference press? But if that works it is a good idea. Just never saw it used.
 
#7 ·
I learn something new everyday. I need to get a hand knurling tool. We would knurl on the lathe in high school shop. Good to know, wish I had known earlier, would have saved me much time and labor.Thanks again, blue.
 
#9 ·
I kinda a gree with blue how does the alum tape stay on once you start pressing the barrel into the trunnion, stippling with a hand tool is fairly easy, no need for expensive tools, the work MTDEW pictures we did that on the alum and steel sig p-228/9 pistol frames for better grip, when we did the big build program back 2004 era just a steel punch and hammer
smiths have been doing this for many moons for realign open break shotguns and lose sights
 
#10 ·
Inquiring minds want to know. I would like to see how you get alum tape to stay on something you are press fitting?
 
#11 ·
It is easy to push a standard size Romanian barrel into it with light finger pressure. .
It's barely an interference fit to begin with -- the chamber end has a taper so starting is not a problem. The tape can be coated with an anti seize. I've got an old thread here somewhere, I'll see if I can find it.

Edit -- couldn't find that one but did run across another way of handling the same problem.

http://www.gunco.net/forums/f163/epoxy-block-mounting-39748/

It's still working fine after all these years. It's the method used now to hold in barrel liners.
 
#13 ·
Could the tape melt or the bond of the epoxy break-down from the heat?
YES

IMO ITS BETTER TO HAVE STEEL TO STEEL CONTACT . THE BARREL HAS TO COOL THE BETTER THE FIT IS TO THE TRUNION THE MORE HEAT WILL TRANSFER TOT THE TRUNION KEPPING IT COOLER LONGER AN ALLOWING IT TO COOL FASTER .

ID THINK AN EPOXY WOULD WORK LIKE AN INSULATER .

THESE GUNS ARE NOW WORTH $500 - $1000+ WHEN BUILT RIGTH NOW IS NOT THE TIME TO DO A COBBLED BUILD.

THE FIRST HING YOU NEED TO DO IS FIGURE OUT HOW MUCH CLERANCE YOU HAVE . YOU NEED TO KNOW WHAT THE ID OF THE TRUNNION IS AN THE OD OF THE BARREL BEFORE YOU CAN MAKE ANY DECISION.. IF IT GOES TOGETHER BY HAND THATS PRETTY DAMN LOOSE . I KNUREL BARRELS WHEN THEY PRESS FIT TO LOOSE OR A MALLET CAN BE USED TO GET IT IN. YOU CANT MAKE ANY DECISION UNTIL YOU KNOW YOUR SPECS.

IF YOU KNURLYOU NEED TO USE A PATTERNTHAT IS GOING TO GIVE YOU AS MUCH CONTACT AS POSSABLE . A HEAVY LARGE PATTERN WILL GIVE MORE OD TOTHE PART BUT YOUR GOING TO LOOSE CONTACT . A SMALL PATTERN WILL GIVE LOTS OF CONTACT BUT YOUR PART STILL MIGT NOT BE TIGHT ENOUGH.

YOU CAN ALSO LIKELY TURN IT TO AROUND 19MM AN MAKE A SLEAVE THAT FITS CORRECTLY.

I DONT SEE HOW TAPE WILL GET IN THERE UNLESS ITS REALLY LOOSE AN IM NOT SURE HOW WELL ALUMINUM WILL HOLD UP ON VIBRATING BARREL THAT HEATS UP AN COOLS DOWN.

IM SURE THERE ARE GUYS HERE WHO CAN KNURL IT FOR YOU FOR VERY LITTEL . ITS A EASY JOB AT ANY MACHINE SHOP SHOULD TAKE ABOUT 15 MINUTES .
 
#14 ·
I think big gun is right the solder would tend to lossen over time with trunnion and barrel, steel to steel is best

barrel liners do hold and are a great solution when relining the whole barrel and distubting the heat and i could even see using this method for the front site or gas block as winnR stated

tape i don't know, if it were way out then maybe a collar around the barrel end but the tolernances are to tight here
 
#15 · (Edited)
Anybody have any figures for the maximum discrepancy that has been successfully overcome with knurling? My #3 trunnion's journal measures in at .910"-.913", and my M70 barrel (#3) is between .906"-.907".

After reading all of AKBlue's advise both here and on the Files, I just ordered the Enco hand tool. We'll see what happens.

I played around with a center punch, and after about a minute or two of stippling, I increased the tension enough that the trunnion will now stay on by itself if I hold it upside down. Haha, that's good right?
 
#16 · (Edited)
I do not know the nominal diameter increase you can achineve with the knurling tool. It is substantial. As you rotate the tool 360 degrees a couple of revolutions you tighten the knurling wheel and then turn again in the same spot. This raises the knurled area diameter more each time. Far more coverage and uniformity than hand knurling., particularly when the diameter gain required us large.
 
#17 ·
Anybody have any figures for the maximum discrepancy that has been successfully overcome with knurling? My #3 trunnion's journal measures in at .910"-.913", and my M70 barrel (#3) is between .906"-.907".

After reading all of AKBlue's advise both here and on the Files, I just ordered the Enco hand tool. We'll see what happens.

I played around with a center punch, and after about a minute or two of stippling, I increased the tension enough that the trunnion will now stay on by itself if I hold it upside down. Haha, that's good right?
hMMMMM you need a better tool to meaure with if you cant tell with ina .003" range what you have.

you will want a about .0015 interference with a knurled set up . if tis not knurled a little less will work I like .001 for a barrel im making my self.

The part needs to press on fairly tight if it dosent it will wear an get looser.
 
#19 ·
Most or some Romanian barrels should have 4 numbers on the top of the barrel, toward the back.
Why? Smart thrifty people over there.. In America, if a building tool requiring very tight tolerances wears, we heave it..
To save money during the cold war years, nothing was heaved..
Not a machinist so bare with me here.. As the tool wore, tolerances changed ever so slightly.. Holes became smaller with wear..
Frist number should represent front sight.
Second. Gas port fixture.
Third. Rear sight.
Fourth. Trunion..
As a part was needed to complete the weapon, workers would go to say, barrel 4 for the correct trunion..
If they drank to much vodka the night before, they did not give a damn..
That is why de-milling some Romanians, you need a bulldozer to get the barrel out.. Lite sanding and lube to get it back in.. Or vise versa, loose fit..
Look at your Romanian barrel, you should see the 4 numbers..

The BIG Guide To Romanian AK Variants And Accessories! - Weapons Cache Forums
Go too "Other Markings" about a third of the way down the page..
 
#20 ·
Most or some Romanian barrels should have 4 numbers on the top of the barrel, toward the back.
Why? Smart thrifty people over there.. In America, if a building tool requiring very tight tolerances wears, we heave it..
To save money during the cold war years, nothing was heaved..
Not a machinist so bare with me here.. As the tool wore, tolerances changed ever so slightly.. Holes became smaller with wear..
Frist number should represent front sight.
Second. Gas port fixture.
Third. Rear sight.
Fourth. Trunion..
As a part was needed to complete the weapon, workers would go to say, barrel 4 for the correct trunion..
If they drank to much vodka the night before, they did not give a damn..
That is why de-milling some Romanians, you need a bulldozer to get the barrel out.. Lite sanding and lube to get it back in.. Or vise versa, loose fit..
Look at your Romanian barrel, you should see the 4 numbers..

The BIG Guide To Romanian AK Variants And Accessories! - Weapons Cache Forums
Go too "Other Markings" about a third of the way down the page..

that is the way it was-- if you ran too much scrap you ended with a real job on a work farm on some gulag--

if you made 500 working ak a day you got a bowl of turnip soup!

socialism --you got to love it!:salute:
 
#21 ·
Less than half of the surface area of the barrel journal may be in contact with the trunnion ID, not a 100% interference fit.
Well said

that is why I suggest a tighter interference fit for a knurled part. those bumps you make are going to compress a lot easier than a solid uninterrupted area an will also weae a lot faster if there is any movement , flex etc in the joint.
 
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