What size screw and thread count

[jacketch]

I am wanting to mount a Weaver scope mount base to the top of a rifle that does not have the threaded holes for the screws. Drilling for the holes should not be a problem on my drill press once I know what size tap and drill I need. The base is made for a Camp-9 carbine (and a lot of Mossburg, Marlin and Glenfields also) and I think the screws are a standard size. I don't have a thread gauge small enough to check but as a last resort I could use a dial caliper and a fine machinists rule. Anyone know what the size is or where I could find out?

 

[Mal H]

In general, most scope screws are either 6-48 or 8-40. The 6 and 8 are easy to determine, so you can take it from there.

[an added afterthought]
If they are 6-48's, be sure to have a broken die extractor (or two) on hand.

 

[jacketch]

I miked them and they match the dimensions for the 8-40. Numrich has the taps and the #28 drill bits.

Thanks.

 

[P95Carry]

Doncha just hate tappin those 6-48's ... yeek .... not my fave job!!

I would suggest, tho expensive .. to consider getting a box of Brownell's assorted gun screws .. many are of these threadforms and can get you out of a scrape now and again.

 

[Art Eatman]

Hey, P95Carry, some 50 years back I stood in awe of my uncle, who made 6x48s on his lathe! Even scarier was the fact that he had 20/200 vision; the lenses on his glasses looked like milk-bottle-bottoms!

, Art

 

[P95Carry]

I too Art would stand in awe with 6-48's on the lathe .. I have cut many a screw thread on the lathe but I think 8's were smallest ever I went. Much prefer the ''big stuff''!

Mind you ------ a jeweller's type lathe would make that more feasable I guess.

And I don't have milk-bottle lenes either!! He was good .. little doubt on that!