Drilling and tapping M1917 receiver

[Inblighty]

Hi,

Can i please beg some advice from those wiser than me?

Drilling and tapping a Winchester M1917 for a picatinny one piece bridge, how would you best position the holes in the front receiver ring?

My jig is for a barrelled action, so would you just use one hole where its safe to drill through? am i right to worry about putting a hole into the lug lock up region? or should the hole closest to the mouth of the barrel be blind, and if so how deep would you go?

And it was already converted to a target rifle before i got it so i'm not going to hell for ruining a classic..

Thanks and best regards

Information

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[Salt Flat]

Inblighty, I would go with a blind hole. . The usual thread engagement rule of thumb is depth should equal the screw diameter. Salt Flat

[Chuckindenver]

i drill all the way through the locking lug weighs, drill all the way through,, why? ever break off a tap in a blind hole?

[usabaker]

it was already converted to a target rifle before i got it so i'm not going to hell for ruining a classic..

LOL!

[browningautorifle]

ever break off a tap in a blind hole?

Why yes, yes I have...

[Bruce_in_Oz]

i drill all the way through the locking lug weighs, drill all the way through,, why? ever break off a tap in a blind hole?

YES!

Use LOTSA GOOD lube, small "bites" and frequent "backing-out" and swarf removal, and one other hint:

Use best-quality SHARP, CARBON steel taps, not the new-fangled alloy-steel ones.

Why?

Even if you snap off a carbon steel one, and the broken off tip is fully in the blind hole, you can either try the appropriate tiny tap removers, or gently bash it with a small hard punch and it should shatter and be removable in pieces. (Caveat: Murphy was an optimist!)

Alloy steel ones are a lot less brittle, (but they still break) and if you start pounding on them, will distort and embed themselves deeper into the cut thread. Once that happens you only have a few choices.

1. Find your local EDM operator and have it "eaten out"; probably not a cheap exercise, but causes minimal damage.

2. Find someone who has Stellite, or better, diamond tipped tooling and try drilling it out.

Good Luck!

[rcathey]

1. Find your local EDM operator and have it "eaten out"; probably not a cheap exercise, but causes minimal damage.

Good tip to keep in your back pocket! I work with specialty tooling that costs many times more than the average sporterized 1917. Broke a tap off in a $1,500 one once. It’s good to know a good EDM guy