Major Thread Diameter

K

KenG

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Just looking for how you figure out your major thread diameter after single pointing the threads in your action. Is there a way to get an accurate measurment without the cutting until it fits snug method?
 
KenG said:
Just looking for how you figure out your major thread diameter after single pointing the threads in your action. Is there a way to get an accurate measurment without the cutting until it fits snug method?
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I use a shop-made plug gage, which I made to a major diameter of 1.075 nominal, minus an allowance to my liking. I used the 3-wire method to determine the pitch diameter of + .0125 over that of the standard 1.062-16 thread. Since I'll be fitting the barrel to the receiver myself, I don't see any reason to hit an exact size. JMHO, do not consider these comments to be instructional in any way.

You could also order a set of oversize Go/No-Go plug gages from a company like Greenfield, for example, but you'd better be sitting down and well braced when you ask for price and delivery time........you'll probably start to think of an alternative method before you even hang up the phone.

-Dave-:)
 
KenG said:
Just looking for how you figure out your major thread diameter after single pointing the threads in your action. Is there a way to get an accurate measurment without the cutting until it fits snug method?
Click to expand...
If you are talking about the threads on the barrel tenon? Assuming you have a known thread in the action like on a Stolle Panda or that is unaltered like the 1-1/16-16 on a Remington 700, measure the thread by using the 3-wire measurement. The Kelbly brochure gives dimensions for theirs. The Panda 1 1/16-18 thread measures 1.0715 +/- 0.002" over 0.032" diameter wires. In this case buy 3 1/32" drills and use the shanks.

http://www.threadcheck.com/html/catolog_page18.html

Measuring an action thread you just trued up do like Dave explained. Then use the method above to get the correct thread measurement for that action from the plug you just made.
 
Look Ahead

When I used to true Remington actions, I would always machine a short counterbore, just like in most custom actions, in the face. After the last pass, just use the treading tool, fed by hand, to do this.
That way, I new the maximum diameter of the ID thread root by just measuring the counterbore.........jackie
 
Yes, I was talking about the threads on the barrel tennon. Jackie that's a great idea thanks a bunch!
 
Guys, are we talking about the same thing here. The thread major diameter is one thing, based on thread form percentage, thread pitch diameter is where the thread fit is determined.
 
Jerry, I was talking about thread major diameter not pitch, thanks for your reply; sorry if my original post was not clear.

Ken
 
KenG said:
Jerry, I was talking about thread major diameter not pitch, thanks for your reply; sorry if my original post was not clear.

Ken
Click to expand...
Ken, the only way to accurately measure thread clearance without having the mating part or a gage is by measuring pitch diameter.

If you grind the internal threading tool to a sharp 60 degree point it will bore a larger hole than a 60 degree tool that has a slight flat on it even though the thread fit would be the same. In most cases sharp Vee threads are not used.
 
I don't think this is rocket science here, I normally take a light cut at the front end after threading, and to the same depth at the threads at the last cut, basically a sight counterbore that was mentioned earlier. Measure that with a dial caliper and subtract about .010" for the major diameter of the barrel tenon.
 
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