Home Forums Hunting & Shooting Gunsmithing 1917 Enfield barrel tenon dimensions

I understand this is for an Enfield, but the Springfield was mentioned in a post.

41+49=90. On some lathes, the compound zero is marked right in front of your belly button as you stand at the machine. On others that is 90*. So, as you swivel your compound "X" degrees, on one lathe it will move to "Y" and on another it will move to "90-Y". Basically some lathes are marked in degrees to the axis and some to the end of the work piece.

One thing we know is that everything is manufactured to a tolerance. So, your thread width is going to be 50 thou +/- that tolerance or more likely 50 thou -. The only way to sneak up on that is to use a bit smaller than .050. The only really critical measurement when fitting a square thread tennon is the major diameter, as this is what centers the chamber to the axis of the action bore. A couple thou smaller on your thread width is not going to make any difference.

The easiest way to find the actual cone angle of a barrel is to set it up in a lathe and zero a DTI as it is run across the cone. In practice, we know that the cone is also cut to a tolerance and a degree or two off of the call out will be okay. I have run a DTI across a small number of Springfield barrels, and they all came very close to 41* on my lathe. Since the call out for the Enfield is 45*, it will not matter how how your lathe is marked.

I bought the bit from Brownells. Pretty thing. I guess I could grind something that would work if I had to, but this one is nice. It's .050 wide. I understand the thread width must be smaller than the width of the groove it runs in. They both can't be .050. As I cut the groove wider I'm also making the thread narrower, so it won't take much to make it work. Actually, as I understand it, thread width isn't critical in the least, but major diameter is the only thing that will center the barrel in the receiver. So, we're going to match the outside diameter of the barrel shank, to the diameter at the bottom of the thread grooves in the receiver. Since everything is going to center on the bottom of those threads cut some 90 years ago, I wonder how they were cut. Single point on a lathe, big tap, big tap with a pilot? Wonder what the tolerance was for major and minor thread diameters in 1917. I never thought about the centering aspect of barrel threads before. Very interesting. I don't have the old barrel. I do have a P14 barrel. Hence the questions about the cone angle. Thanks again for the help.