Looking for screw thread info?

[gcollins]

I know that gun screw's are of there own breead, I am in hope maybe someone would happen to know what the stanard threade size for the screws that come with the weaver scope mounts? I know that I can thread the holes anything I want, but I want to stay close!
Thanks for reading.
Greg

[elk hunter]

Weaver bases come with either 6-48 or 8-40 screws, the 6-48 is the common size for all most all US made firearms the 8-40's are generally used for side mounts and I use them on regular bases for hard kickers for extra strength. Either tap and the proper drill bits can be ordered from Brownells.

[KCSO]

Weaver base Screws 6-48x180 to 245 Weaver clamp screws 6-40x 313 Weaver ring screws 6-40x250 Import Weaver copies Ring screws 6x32 by who knows.

[W.R.Buchanan]

It is a good idea to assemble a bunch of different size screws in a kit to use as test screws to figure out what thread pitch you actually need for any given application.

Virtually all American Sight fixture screws, be they scope mounts or iron sight mountings have been 6-48 since the last century. However more and more oddball sizes are creeping in.

8-40's came along for heavy duty mountings, and lately 6-32's ,which is the standard #6 course thread size, have been appearing more and more. Mostly from Chinese Krap because they don't know any better.

The 6-48 thread is a NEF thread. National Extra Fine, and is a standard thread.

A copy of the Machinery's Handbook has every thread known to man explained in detail. My College Machine Shop teacher Al Christensen actually compiled the tables for the Handbook. Great man, and a great Mentor,,,sad to say he's gone now, but he had a very productive life and was still teaching at 75 years old when I met him in 1983.

As stated above Brownells is a source for these taps, however McMaster-Carr, and MSC have much better prices. Also you need to buy "Spiral Point High Speed Steel Machine Taps" for your use. if you need to tap a blind hole then you grind the tip off the SP tap. I use reground broken taps for this, as there is nosense in modifyiong a new tap if you have others.

UNdserstand this: The #6 size tap is the weakest tap size in existance due to the relationship between the web thickness and the flutes. Buying the best quality taps you can get will save you many heart attacks from tap breakage. No chinese stuff here if you want success.

Also any kind of mechanical assistance in the form of a tap guide or doing the proceedure in a mill or other fixture where you can control the tap perfectly will greatly reduce the number of FU's. Some kind of magic spuge on the tap helps as this is a case where you need every advantage possible to insure success. Most taps are broken simply by the act of not having them enter the hole strait. When they enter the hole crooked one side of the tap is loaded heavier than the other side and thus the tap breaks. Avoid this by using the same setup you drilled the holes with or using a fixture or tap guide whihc insures that the tap is perpendicular to the work on both planes.

I am very good at this. I own a machine shop and have all the tools. When tapping the holes in my Springfield receiver for the Lyman 48 sight It took me 2 full hours of sweating blood and breaking the end off the tap 4 separate times to get 2 usable holes in the receiver. Springfield receivers are case hardened and are very hard for about .015 into the surface as are many guns and especially Military guns so inferior tools are not going to give you anything but grief!

I was using an OSG brand tap which is one of the best brands made and doing the operation in my mill and really taking my time.

Lesser quality taps would have not worked in this case.

My dad always said "Buy the best, only cry once!" This certainly applys to taps used on guns!

Luck was also a very big factor, and I maintain that lots of times it is better to be lucky than good.

Randy