There must be days when you just sit back and smile. Thanks for including us.

Looking forward to this build journey Bob!
Jeff P

I spend lots of time checking and double checking my numbers, and thinking through the steps to machine a frame like this.  So for now I am just opening up the frame to within around .015 per edge of the final size of all the openings.  When fully opened up it will then be similar to machining a casting set to get to the final finish to size. 

In these two pictures I am machine very deep into the steel blank in order to get below some of the features inside the final frame.  I first drilled 1/4 inch holes over 2 inches deep, staying inside my layout lines, this save some work with an end mill.  As can be seen in the first picture (larger hole at the front) I tried drilling the front area of the breech block, knowing the risk involved because of the barrel shank hole intersecting this area, it didn't go well, but no harm done.  I ended up just picked away at this area with the end mill, it needed to be below 1.310 inches from the top of the frame.

Once the holes were drilled I continued picked away at it with a 1/4 inch end mill, the largest I can use in this area.  I was milling over an 1 1/2 deep at some points which stretched the ability of the end mill I was using.  Since I was rough out the holes I wasn't overly concerned about side straightness, I have a slight taper on all side currently. If I was machining to my final sizing I would have taken the time to grind the shank of the end mill, in order to gain clearance, as I went deeper past the cutting flutes.  Being carbide end mills, grinding the shank isn't as easy as walking over to a grinder. It takes special grinding wheels, diamond in my case, that I only have on my tool grinder.

This first picture shows the roughing out after drilling.  You can still see where the drill went through in the side of the opening.

This second picture is what things looks like after machine to final rough opening size.  These two larger front tracks or openings are where the breech block moves. The rear, longer cut, is the hammer path.  These round corners will need to be removed later.  Once the frame is opened up and the profile is closer to final size there will be much less material and depth to work with and I will use a smaller diameter end mill in order to reduce the size of the corner radius so the final truing up is easier.  The final truing up will be done, as a few of us have shown here in the past, by using a scraper to square the corner and sides for the breech block.

Bob

It would drive me bonkers if I lost my DRO. A tip o’ the hat to you Bob.
Cheers Richard

Understand, my DRO just quit on me. Can't argue, 1977 model.
Helpless without it. In the process of replacing it.
Chuck

bobw wrote on Nov 22^nd, 2024 at 7:50pm:

Yes they are.
A short story if I may concerning the lines. When I was a toolmaker back 40 years ago or so, working in a mold shop we had a dedicated bridgeport with an Advance Rotary Table on it. If I may brag, there were and are few people in the world who are as good as I was on that table (we don't need no stinking CNC). And the bridgeport table dials were marked and the dial locks locked on zero, clockwise turning direction (so the backlash was taken up correctly) and X was on the left table dial, so you knew where the center of the Advance table was. It was a crime for anyone to adjust those zero's or table marks. Then we got a new hire and he, maybe not experienced, changed them. OMG the boss went off on him like no ones business. So those marks are most important, I know where you are coming from.  

I'm not a Hepburn expert, but am learning, and I understand the standard version has a rebounding hammer.  I did not check this action before it was disassembled but I am assuming it also has the rebounding hammer.  I say this because it has the same screw, all the other versions have, above the back trigger assembly screw, which on the surface looks to do absolutely nothing.  See the yellow arrow in the picture of the Walker.  I assume this screw has something to do with the rebounding of the main spring, maybe someone can verify this for me.  

Anyway, when I removed this screw it was bent, as seen in the second picture.  I installed this screw and the hammer and found the hammer has definitely hit the screw, the marks line up with the hammer as shown on the last picture.  But, the only way this can happen is with the breech block removed letting the hammer fall past the normal stopping point against the breech block.  This must have happened several time in order to bend this screw this much.
Bob