Shotgun Bead Tap and Bit Size Question

Travis Bickle

Travis Bickle

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Upper Lower Middle Alberta
Looking to put a front bead on my old Model 12

Picked up a 1/8" Brass bead with a 6-48 thread pitch.
Obviously tap is going to be a 6-48

But what drill bit size should be used? I would assume 1/8" (0.125) would likely be too big an initial hole.
I'm assuming a #31 at 0.120 would be the correct bit for the initial hole and then thread with 6-48 tap.
Any guidance on this from actual smiths?
 
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DILLIGAF is always here to help when hes not to busy trolling... lol...

If you cant find a #31 drill bit let me know ill hook you up.
 
DILLIGAF said:
DILLIGAF is always here to help when hes not to busy trolling... lol...

If you cant find a #31 drill bit let me know ill hook you up.
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I just checked. I still got my old carbide set with a #31 in it.
Just need to find a 6-48 bottom tap now without paying mountains in shipping costs.
That's an odd pitch tap. Basically a gun smith specialist thread for sure. Noone around here carries it. Ebay has them but shipping is fackin' brutal. $8 Tap and a $20 shipping fee :(
 
DILLIGAF said:
Ill see what I can find at work tommorow I know we got them somewhere.
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I would greatly appreciate it.
I'm just over the mountains in Cold Lake watching the snow pile up lol
I can't see myself ever needing it again. All these years shooting and tinkering with guns and this is the only time it's ever come up.
Cheapest I can find it for taxes and shipped to the door is about $35 and that's in about 1 month delivery...
 
I found this in my parts bin, lol but its not a bottom tap unfortunately.But usually shotguns go right thru. If that works for you PM your address and ill throw it into en envelope.

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6-48 is just about the standard for sight and scope mounting in the firearms industry. #31 is the standard drill. Sometimes smaller threads are used for bead mounting, 6-48 is about as big as is used for this purpose.
Bottoming tap? You're going to try for a blind hole in a shotgun muzzle?
This a new hole, or are you opening out an existing one? If it is new, be really carefully when locating and drilling. Get the bead slightly off-centre, and you'll see it every time you shoulder the gun.
 
tiriaq said:
6-48 is just about the standard for sight and scope mounting in the firearms industry. #31 is the standard drill. Sometimes smaller threads are used for bead mounting, 6-48 is about as big as is used for this purpose.
Bottoming tap? You're going to try for a blind hole in a shotgun muzzle?
This a new hole, or are you opening out an existing one? If it is new, be really carefully when locating and drilling. Get the bead slightly off-centre, and you'll see it every time you shoulder the gun.
Click to expand...

It's a new bead. Aye I believe I've seen 3-56 as well.
Picked up a beat to hell 100 year old Winchester. Externally beat anyhow. Barrel tip was damaged and I had to cut it back 2 inches. Turned out very good but now she needs a new bead.
And tracking on the off center, I have a small press for the initial 31 drill bit and will be doing a lot of measure 6 times cut once ;)

I guess there is no point trying to bottom tap it. Now that I look at it the metal isn't thick enough. I know the original went right through and just filed flush.
Diligaf, PM inbound, that will do very nice Sir thank you very much.
 
Mc Dugall Machining supplies in Calgary carry those "specialty" taps...they wont be cheap anywhere you buy them, I think the last one I bought (picked at the store, no shipping) was over $ 24 a few yrs ago.

A bit of advise if you ever have to do this again...mark the new sight location before you cut the old one off. I use a piece of ordinary sewing thread...fold the tread around the old sight ( or pin in the hole if bead is gone) and pull both ends of thread tight back to the center of the receiver sight plane then simply center-punch between the two thread strings at new sight location ...perfect centering every time.
 
fingers284 said:
Mc Dugall Machining supplies in Calgary carry those "specialty" taps...they wont be cheap anywhere you buy them, I think the last one I bought (picked at the store, no shipping) was over $ 24 a few yrs ago.

A bit of advise if you ever have to do this again...mark the new sight location before you cut the old one off. I use a piece of ordinary sewing thread...fold the tread around the old sight ( or pin in the hole if bead is gone) and pull both ends of thread tight back to the center of the receiver sight plane then simply center-punch between the two thread strings at new sight location ...perfect centering every time.
Click to expand...

Ha! S**t....Good point.
I'll figure it out. It wouldn't have mattered I had to bead blast the whole surface due to the vanished bluing and in some spots medium to heavy rust.
She is now refinished, I had to trim the damaged barrel tip off before the refinish process.
Any tips on how to get a perfect center line on a barrel with the old bead tap hole already gone?
 
Travis Bickle said:
Ha! S**t....Good point.
I'll figure it out. It wouldn't have mattered I had to bead blast the whole surface due to the vanished bluing and in some spots medium to heavy rust.
She is now refinished, I had to trim the damaged barrel tip off before the refinish process.
Any tips on how to get a perfect center line on a barrel with the old bead tap hole already gone?
Click to expand...

Put a straight edge or small ruler between the drill and the barrel. Move the barrel until the ruler is level, remove and drill.
 
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