Interesting issue...

[Sooter76]

So I recently bought a 1903a4-gery built off a reclaimed drill receiver and found that the rear bolt tap wasn't done quite right. I took it to my gunsmith to have it redone proper and the receiver chipped away the tap. He'd had the tap for awhile and figured it was just at the end of it's life and ordered a new one. When he tried with the new tap the same thing happened. He now going take it to his machinist and see if he has any insight.

Has anyone ever run into this issue?

 

[kraigWY]

Sounds like a Smith Corona receiver. Even if Remington its a hard receiver. I've done a ton of drilling and tapping receivers. When I built my A4, I knew I would have problems. I cheated. I took it to Chad at Long Rifles, Inc. He used his fancy CNC Milling machine and milled the holes and then milled the treads. It came out perfect.

 

[buffalowinter]

You need this special single flute carbide drill for hardened receivers, available from Brownell's
[IMG2=JSON]{"data-align":"none","data-size":"full","src":"http:\/\/cdn-us-cf2.yottaa.net\/53ff2f503c881650e20004c9\/www.brownells.com\/v~13.76\/userdocs\/products\/p_080660056_1.jpg?yocs=p_&yoloc=us"}[/IMG2]For Hard Receivers


Specially ground, single-flute, solid carbide drills ideally suited for use by the professional gun trade on hard receivers (as the 03A3 and harder).
• Cuts a clean chip in hardest file steel, giving true hole.
• Does not "crumble out" the steel; thus, no chatter.
• 2" long to give quill clearance when using with Forster and other scope/sight mounting jigs.
• Kept properly cleaned, will not bind or break.
• Properly fed, won't work-harden hole surface like spade drill does; decreases tap breakage.
• Drills "all the way through" hardened steels. Note: Common sense must be used. No guarantee against breakage! Use only to crack the skin on Krags and the like. DO NOT USE IN SOFTER STEELS. Use only after other drills have failed or hardness of steel is preknown.

 

[sirhrmechanic]

^^^ This. Carbide tooling is great for specialty stuff. Of course it is delicate and brittle as all get up. But I use carbide drills and mills to remove broken taps and drills... and to cut the hardest parts and components.

Note that these drills, etc. are best used in a milling machine, not a drill press and certainly not a Black and Decker. That said, a talented and patient soul can make one work in a drill press. It takes skill, but does work. In a mill, it works great. Use either a ton of lubrication (fed coolant) or compressed air as a coolant/chip remover.

When I did my cutaway half-scale Colt SAA, I had to use compressed air as a coolant. The .020" carbide mill bits would not stand up to the slow movement of coolant. But 100 PSI compressed air blew chips out fast enough to clear the mill and cooled the cutter. 20K rpm, too...

Cheers,

Sirhr