Drill bit and tap size?

[gpracer]

Mounting a weaver base on a rifle, the rifle is already drilled and tapped for a different style of bases, but one of the holes does not line up. I need to drill and tap, but what is the standard size?

 

[vondnik]

http://w w w.engineersedge.com/tap_drill_chart.htm

just have to figure out witch size you have on your rifle

 

[gpracer]

pretty sure its a standard size, I have three different rifles, all factory tapped, 2 different types of bases, and all have the same screws, so it's definately a standard size.

 

[gunasauras]

sounds like you need a #31 drill and a 6-48 tap....

 

[ringo]

The usual size for scope mounting is 6-48. A #6 screw has a diameter of 0.138". The second number denotes threads per inch (tpi), so a 6-48 screw is a #6 with 48 tpi. Industry standards for #6 screws are coarse (32 tpi), fine (40 tpi), and special (36 tpi). The 6-48 size is an oddball.

With heavier recoilling rifles some gunsmiths use a 8-40.

 

[gpracer]

Ok, thanks. The screws I have are 0.136, close enough. Don't have a thread pitch gauge handy, have to check when I get to work in the AM.

One rifle is a Tikka T3 Light, brand new, the other is a 12 year old Rem 700 Classic, both are drilled and tapped with the same size.

 

[gunasauras]

They'll be 6-48...

 

[Beater]

6- 48 is pritty standard for scope bases in the industry

 

[ben hunchak]

Theyre either 6-48 or 8-40 both std gunsmith threads.

 

[Papaneil]

Mounting a weaver base on a rifle, the rifle is already drilled and tapped for a different style of bases, but one of the holes does not line up. I need to drill and tap, but what is the standard size?

I am wondering why the holes don't line up. You probably have wrong base for that rifle. Check the chart.

 

[gpracer]

I am wondering why the holes don't line up. You probably have wrong base for that rifle. Check the chart.

This is probably correct, I'm just trying to use a set of weaver bases that I have on hand, I only need to drill one hole and the extra will be hidden under the base out of sight anyways...

 

[gunasauras]

This is probably correct, I'm just trying to use a set of weaver bases that I have on hand, I only need to drill one hole and the extra will be hidden under the base out of sight anyways...

Many pers on here would call you bubba! Weaver bases are cheap. Swiss cheesing a receiver to save $10.00 or less is foolhardy....just my opinion though...

 

[gpracer]

Bubba!,, Ha! you shoud see my Enfield Moose gun!

 

[mouse]

major diameter of the thread minus the pitch for tap drill size.

 

[trevj]

Drill and counterbore a new hole in the scope base.

Gold rule of thumb. Modify the cheap part to fit the gun, don't modify the gun to fit the cheap part!

Cheers
Trev

 

[gunrunner100]

Does the profile of the base correspond to the receiver you want to mount it on? What action is this for?

 

[gpracer]

Drill and counterbore a new hole in the scope base.

Gold rule of thumb. Modify the cheap part to fit the gun, don't modify the gun to fit the cheap part!

Cheers
Trev

I Was actually thinking of this!, I have the tools on hand for this, The 6-48 tap and # 31 drill I had to order today from my local Mac Tools distributor.

 

[gpracer]

Does the profile of the base correspond to the receiver you want to mount it on? What action is this for?

Good call, one of my bases did not correspond, quick trip to my friendly neighborhood gunsmith, matched up proper bases, and problem solved.

At least I have some new tools on the way that I can definately use for other projects!