My Sporterized #4 Mk1

 

They should look good when done.

 

I will post some pics of the process tomorrow.

 

Randy

 

The biggest problem in this project was Divining the position of the two holes in relation to each other and from a common origin.  I was able to find the location of the Ejector which was .850 from the top of the receiver.  I also knew that the pivot hole was .187 from the top of the ear and front of ear.  I then drew a radius using that measurement which intersected the vertical line thru the ejector hole and had the computer tell me where the X axis location was for the ejector hole in relation to the pivot hole.  There is no way to get these dimensions without a computer other than trial and error or possibly the original drawings,,, where ever they may be?

 

I now have a real drawing of the part that I can make in the shop. This took 4 hours to figure out!

 

This however is not the biggest problem...

 

I have to make a longer Ejector for the gun.  The thread is an 8-36 NF!  This is one of the most bastard threads ever concocted and is considered to be obsolete, like in 1950! Find a screw to start out with is a big problem.  Most outfits like McMaster CARR which has nearly everything known to man don't have any 8-36 screws of any type at all!!!!

 

I have one local hardware store I will try tomorrow that may have something otherwise I will have to make it from scratch.  I would rather not have to do this as it will be time consuming, and I would prefer starting with a screw that is already Grade 9.  With the screw counterbored into the adapter plate below it's surface the new Screw will have to be @ .062 longer than the original.

 

Making good head way on this part of the project.

 

Randy

 

 

 

Shamu: Thanks for loading that chart, I will include it in my Shop Data.

 

 

Standard Govt callout for 8-36 would be .161-36 or like .250-28 for 1/4-28 NF. With the diameter of the thread called out in thousandths.

 

I had my wife search the internet for 8-36 screws and surprisingly Brownells has them. So I'll get some there. I was unsuccessful at finding them locally.

 

The whole kicker here is that this screw on this gun is not that unusual.  But this thread size has effectively been obsolete since about 1940.

 

However this screw thread on a newly designed part, like the ones I just made for Raytheon a few months ago, shows a complete lack of understanding of current machine shop practices.  The idiot "engineer" (and I use that term very loosely) who designed this part wanted to use fine threads on everything on the parts he was designing.  But when it got down to the small stuff where the common thread pitches make the transition from fine to coarse, and this screw holds a lanyard to the side of a large and very expensive to make Stainless Steel block, he simply kept going with the fine threads because he didn't know any better.  It was pointless to use this thread size on this application.

 

 

 

The reason why 8-36's are bastard is because there is almost no difference between that thread pitch and 8-32's.  If you look at the progression of UNF threads in the book between NC and NF thread pitches, you will see that it is 4-40/4-48,,, 6-32/6-40,,, 8-32/8-36,,, 10-24/10-32 and so on.  Note how close the #8 thread pitches are to each other.  Usually there is at least 8 threads difference.

 

There is virtually no advantage to having both as there is not enough difference to make a difference.

 

If you look at the next finest thread pitches available you will see 6-48 NEF for guns and 8-40 NEF for guns.  They are National Extra Fine threads and they are used to increase thread contact area for situations which experience High G loads or get banged around a lot. Like Scope mounts. 

 

Notice they didn't use 8-36 threads for this purpose.

 

Anyway, life goes on.

 

Randy

http://www.ba-bolts.co.uk/socketcaps.html

 

On another note::  Front Sight Adjustment Tools are done and will be ready to ship tomorrow. $35.  Anyone interested can PM me.  These include the Tool Block itself and a pair of both Hex Head and Allen Head bolts so that you can decide how you want to drive the bolts.  7/16" Wrench or 3/16 Allen Key.  Also includes instructions which I still have to write.

 

These are designed for #4 rifles and I don't know if they will work on #1's or not since I don't have a #1 to test it on.

 

Here's Pics of the finished tool.

 

They came out nice!

 

Randy

 

Randy