Drilling, Or Milling Overlapping Holes

redgalvin

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I'm fitting Uberti '51 grips to my 1860 Pietta Colts. The screw holes, expectedly, are off a smidgeon. The counter bored portion of the hole is 5mm and I have a 5mm end mill, a drill press and a cross slide vice. I'll experiment on some scrap first. The backstrap is steel and the trigger guard is brass. Any insight appreciated. Red
 
If you are sure you can eliminate any sideways movement you could use the end mill and drill press.
Otherwise I would use a mill to tackle this job.
 
An end mill is the way to go. Rather than come in from the side, go down from the top. You need a rigid setup though if any of this is to work on your drill press. Come down from the top and let your cutter do the work slowly.
 
I agree with Xalky - but make sure you have a center cutting end mill! If you do decide to come at it from the side, from the existing hole, do it in small bites, stopping short of your desired end-of-slot. Then do a final cleanup pass to make sure the slot is uniform from top to bottom.

The Morse taper for drill press chucks isn't really intended for side forces - just vertical, downward pressure. If you push too hard, the chuck can rapidly and quite energetically come off the taper and cause all sorts of mischief.
 
Your doing it the hard way.
Fill the old holes with screws and solder them in place. Flush them with the surface of the frame and re drill the holes.
 
Your doing it the hard way.
Fill the old holes with screws and solder them in place. Flush them with the surface of the frame and re drill the holes.

I'm thinking that enlarging the holes in the trigger guard and backstrap a smidgeon would be less work than buying expensive screws, soldering them in the holes in the frame, grinding them flush with the frame, then drilling them, buying a tap, and a bottoming tap, and tapping the holes.
 
I got my first lathe, G4ooo Grizzly, and a milling attachment. Don't know when I'll get back to this project.
 
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