SMLE bolthead manufacturing process

[spentprimer]

At the end of the tour, when asked for some thoughts, the GM engineer said something like: "You guys don't make guns, you make swarf; guns are your by-product!"

Bruce, that is a little bit like a hairy cut ... the important part is what is left when done removing the swarf!

[jmoore]

Just a thought regarding the bolt head threading operation: If the step was prone to rejects, one would think that it would be incorporated as early as possible during mfg. From the photo, quite the opposite seems to be the case. Threading the shank is one of the last operations.

[Bruce_in_Oz]

If you are making one sample, you would probably do the thread first.

If you are doing 5,000 a week. doing the front bit first makes more sense.

Clamp it in a special jig, line up the appropriate datum surfaces and check the tool setting.

The trick MAY have been, especially with the "fully-treaded" SMLE types, to invert the thread cutter and run the lathe IN REVERSE. That way you are cutting AWAY from the critical bearing face on the rear of the body. Some folks also set up a tool post at the BACK of the saddle/cross-slide and run the tool the "right way' up but the gearbox in reverse, still cutting AWAY from the shoulder. Diff'rent strokes, etc.

[jmoore]

The trick MAY have been, especially with the "fully-treaded" SMLE types, to invert the thread cutter and run the lathe IN REVERSE

I would not be surprised that they were cut with the head fixed in place. Moving threading tool with spring retracting jaws/forming cutters that do the operation in one fell swoop. I think there's one in storage somewhere, but haven't seen it in years.

[Son]

Is the thread cut and not rolled?
I have cut a few threads up to shoulders with a reversed lathe and the tool in the post upside down. I haven't had any time on modern lathes, so make do with what I have available and a few Jedi mind tricks when it comes to "creative" processes.

[Surpmil]

Bruce, I must confess, that little slot has had me perplexed as to how it was done. My first thought was perhaps a double broaching operation? I would have loved to see the entire step by step machining of these rifles. If made in the same way, I wonder what one would cost to build in today's monetary values?

As I have stated earlier, I am quite new to Enfield Rifles, but, the more I look at them and try to guess what the manufacturing process might have been, the more I marvel at them. There was a lot of work put into each one. I would think that very few, if any, were actually assembled and not fitted.

And with all that, Lithgow managed to make the SMLE in about half the man hours if I remember correctly(?) Didn't the chaps from Pratt & Whitney make some suggestions as well?

After Canada adopted the Ross, HMG suddenly became much more cooperative with dominions wanting to set up arms factories...