mini mauser bbl threads

M

mike in co

Guest
i have a mini mauser bbl...the threads appear to be 21.5-1.5(metric).

first anyone seen this thread before...i have looked in my engineering book and find nothing in 21.5......20,22,24....no 21.5...is this just a special for the action ?

what is the recv min bore ? anyone worked on mini mausers ??

this is the bbl i plan on bushing up to a larger recvr.

thanks
mike in co
 
Hi Mike;
I do not know what the thread is on a Mini-Mauser action but it is pretty east to figure out. Since you have the action in hand you , in effect, have a custom thread gage. Take a .100 scale and lay it in the action threads. Using a magnifies or an Opti-visor measure the distance between thread points.If the pitch is 1.5 it will measure about .060". If you kave a Machinery's Handbook look up the double-depth of a 11.5 pitch thread. Measure the inside diameter of the threaded bore in the action and add the double depth to this. What you now have is a very close approximation of what the actual thread is. If you like, chuck up a piece of machine steel(1018-1020) and turn a dummy barrel stub. If you get the action to fit it well then take your thread wires and measure the thread and record the number. Nothing high tech here. I would take a threading insert and see how it looks in the thread in the ACTION. This action may require a 55 degree insert.

Good luck;

Mike Swartz
 
If you don't have a Metric pitch gage you will have to use an optical comparator or maybe be able to match another 1.5 pitch thread to the barrel threads. It should be just a little courser than a 16 tpi. I think that the standard M10 thead is 1.5 pitch.
I'd try to determine the thread angle using a "fishtail" gage. Then, I use a three wire system to determine the pitch diameter and go from there.
Just some thoughts.....
 
thanks guys, yes i have a metric thread gage and it is 1.5.

while i own a mini mauser in 223, this bbl is going on a non-mini,mauser action.
right now trying to decide if i should change gears to cut metric, or just have a local shop cut them for me( he said what!). this will be the bushing i was discussing. i'll still cut the new od threads for fitting to the reciever.


machinery lists 20,22 and 24 threads...no 21.5....try 3/4 of the diff between 20 and 22 ?

mike in co
 
guys,
i have the gear set to convert to the 1.5 thread i need,BUT a while back i read that when cutting metric threads the thread dial on the lathe is not used, and one must reverse the drive to back out the cutter.

if this is true, i'm screwed.....the previous owner has an idiot replace the control box and was not able to get REVERSE to work....i aint got no reverse!

is this ture ??? if so i guess i have to farm this out.

thanks
mike
 
Mike;
Just stop the lathe and run it back by hand but if you disengage the half-nut you will have to pick the thread up again... and still have to back it up by hand.

Mike Swartz
 
Maybe this is a good time to think about moving the control box to a better place and correct the wiring so that reverse works as it should.
If it has a screw-on chuck/spindle it might be better to NOT be able to reverse the spindle.
 
Mike

Have you considered rethreading to bbl to an inch size thread or is the tennon not large enough to turn off and thread?


Sam
 
mike...,
thanks..that may be doable...no brake, but only about 1 inch total thread....i like challenges...this rifle will just be a fire form tool when done.

jay,
i wish....i know a little about electics, and i have the schematic for the control both original and the current......but it is on the back side of the lathe which means moving and then releveling......i'd like to pay someone to do it...but it aint in the budget. its a "d" style three pin spindle.

sam and all,
this is a lite wt factory bbl in 7.62x39...will eventually be a 30 beggs fire form chamber. for this reason i resisting cutting anything back till i can dial it in and see how much i HAVE to cut off to do the smaller chamber.
the tennon is only .7 and the straight section before the taper is 1.55, another 1.5 to a .8 dia, final dia at muzzle is .55.( 20 inch bbl)
i do not know how much material i can take off and still be safe with ppc type loads( remember fire form only)

again thanks to all

mike in co
 
metric threads

Cutting metric threads is not witchcraft depending on your lathe.You may have to switch out a gear .Once you start cutting you never disengage the half nut,just come out and reverse your machine and make another pass until you get to depth.

Chris
 
You must log in or register to reply here.
Back
Top