Smithing on a vintage Armi Galesi pistol.

S

Spokerider

New member
Gents,
I am in the process of working on an Armi Galesi Brescia, in model 512.
I am replacing the barrel, and will need to turn the barrel blank to size, form chamber with finishing reamer, "drill" a barrel-pin hole, cut the extractor slot in the barrel, instal into frame and ensure head-space is within spec.

I am contemplating the order of machining operations, the processes and techniques of drilling the barrel-pin hole, and machining the extractor slot, and trying to determine what / which tools will be needed to do this.

About drilling / machining the barrel pin hole..... well, actually, it is only one half of a hole, more like a round groove cut into the barrel, for the pin to reside in...... What is the preferred smithing-method for making this barrel pin groove? I have one chance to get it right.

The pin is small, only .118" in diameter.
Does one cut the groove in the barrel with round needle file, and "hope" the alignment is within a few thousandths with the frame hole? Ditto for using a ball end mill, to machine rather than hand-file this groove?

Or, should the groove be drilled, once the barrel is in place within the frame "hoop", or frame trunnion, remembering that this is a fixed barrel, interference fit?
If drilling said groove with barrel installed in the frame, the hole in the frame would be used as a pilot hole, helping to get the groove in exactly the correct place. However, this means that the barrel groove will be started on the slope of the barrel.....a recipe for a drill-wandering oblong hole.....

How to mitigate this wandering drill effect, cutting on the slope of the barrel?
Begin cutting the hole to the point of depth to where the cutting surface is no longer on said slope, with a diamond burr tool? Or, a centre cutting end mill to mill past the slope, and then switching to a cobalt drill, followed by use of a reamer?

No, I have not done this before, but maybe you have?

Thanks for helping me plan for success, with the first attempt.
 
Centerline of bore determines where everything else goes.

I'd mill the barrel pin hole first. Touch off w/edge finder and then set your mill up for precise milling. Bet the factory used a jig.

Then I'd turn the barrel down.

Then I'd needle file the extractor cut. That is much faster than trying to set up the mill.
 
Thank you Gary for your thoughts on the order of machining operations, and for your insight on how you would tackle this.

About the barrel pin hole.....
With the barrel pin mic'ed at .118", or 2.99mm, would you use a 3mm ball end mill for machining the pin groove, or perhaps a smaller diameter ball end mill, like 2.5mm? And then to follow up with a .115" reamer, aiming for an interference fit?

Thanks.
 
Hello Gary,

Here is a pic of a Galesi barrel, if you are not already familiar with the retaining pin groove.

Seeing that the groove is approximately 180 degrees of a hole.....do you still suggest milling it before inserting the barrel into the frame, vs "drilling" the groove after the barrel is fixed to the frame?

IMG_1427.jpeg
 
My suggestion about milling was to mill the unturned barrel first but if it's already turned like the barrel in the picture, I'd mill it once it's in the frame. Mill, not drill and with a mill bit, not a drill bit. You don't want it to wander and ruin the frame. For a straight hole, the frame must be perfectly horizontal in the mill and in the mill vise. I'd also tram the mill first too. If it's a bit off, so will the workpiece.

Heck, for something that small and it's down down already, I'd even start it with a needle file and if it goes well, use just a file. It all depends on your hand skills. Some people file unevenly. We had to file a round stock perfectly flat in anticipation of making a polishing stick. Instructor took a machinist square to it and held it against a light background to detect any defect.
 
Thank you Gary, for your insight.

I am leaning towards fitting the barrel into the frame, and then milling the pin slot, not drilling with a drill bit, as you have pointed out.

Since the end mill will be making initial contact of the barrel on an acute angle, what design of end mill might you suggest?
Four flute? Two flute? Centre cutting?

I was also thinking of using a diamond burr, to begin the cut on the acute angle to form a "flat", then switching to an end mill to complete the pin hole.

I am apprehensive to cut the groove with the barrel out of the frame. Setting the correct head space hinges upon the barrel end positioned flush with the frame trunnion. Filing or milling that pin groove that exactly aligns with the frame hole, AND setting the end of the barrel within the trunnion for correct head space may not go so well for me.
 
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