Building The Steven's Favorite

[TomG]

A couple more parts for the sight, the center section that holds the peep sight and slides up and down in the frame. The two parts were just simple rectangular blocks with a couple of slots and a pocket in one. The only thing difficult about making them was the small size as shown in the pic.



Cutting the 1/32" radii with a form tool in a fly cutter.




The frame to hold these first parts is well underway and will be posted tomorrow. It's a bit more complex and will include some rotary table work, so I'll include more pics of the build.

Tom

[DaveH]

Tom,
Clever use of a fly cutter as a form tool

DaveH

[TomG]

Thanks Dave.

My corner rounding end mills only got to 1/16", so I had to improvise. Brian does a similar thing when cutting gears for his clocks.

Tom

[EdK]

Interesting setup for rounding the edges of those small parts.

Ed

[TomG]

The frame for the sight turned out to be fairly involved so I took a few more pics of the process:



It's in there.




Squared up and sized for width, with extra stock on the ends and the thickness for the rotary table work.




The 1" radius belt sanded on one end.




Roughing out the blade thickness.




Blade finished to size.




the 1/8" pivot hole reamed to size and ready to be set up on the rotary table.




This is the method I use to center the rotary table on the spindle. I made a snug fitting plug for the center of the table with a snug fitting hole in the center for a 3/8" dowel. With the dowel chucked in a collet, it is inserted in the plug to center the table, the DRO is zeroed out and the table bolted down.




The same process is used to center the part. With the rotary table centered on the spindle, a 1/8" pin is held in a collet and the part placed on it, then the angle plate is clamped to the part and then bolted to the table. The part is then indicated parallel to the X axis and the rotary table zeroed out.




The part was then counterbored with the end mill and the profile milled. Then the part was flipped and the other side was counterbored.




The holes for the detents, a spring and two balls, being drilled.




Assembled and partially polished.




All that is left is the thumb nut for setting the windage, the #1-72 threaded rod that it rides on and the base.

[Mayhem]

Nice looking work, as usual Tom. I may have to visit MI again to take a closer look!

[TomG]

I finished machining the base tonight. There is a fair amount of shape to it, such as radiused corners and surfaces typical to firearms, and that will be done by hand, but all the machining is complete.



This is the radius on the underside of the base that matches the radius on the tang of the receiver (tang sight, get it?). It was accomplished by mounting a fly cutter in the boring head to achieve the 1.500" radius.




Here the basic shape is roughed out and the mounting holes added. The top surface will ultimately have a convex curve to it that will be machined with a 3/4" ball end mill on the rotary table.




Here, the base is mounted to a fixture on the rotary table to generate the convex top surface using the 3/4" ball end mill. The fixture is just a piece of 3 1/4" aluminum round with a slot the width of the base and a couple of tapped holes. I figured the slot was good insurance to take some of the load off the 4-40 mounting screws since some of the head on them would be milled off.




The base was then mounted to an angle plate on the rotary table to machine the .200" radius on the center section. Both the table and the part were located using gauge pins in the spindle just as with the frame.




Here it is as machined. To finish it up, all surfaces will be polished and many of the corners rounded. Since everything is O1, it should polish up nicely. Unfortunately, on a part like this, that will all need to be done by hand. It's the extra work that goes into shaping parts like this that gives a firearm it's character.




Almost done. I still need to make the windage thumbnut and assemble the detent mechanism. I see the parts showed up today, some 3/32" compression springs and balls, and the 1-72 threaded rod for the windage adjustment. That will be tomorrow evenings project.

[Highpower]

Tom, outstanding work as always.

I do have a question. I'm not seeing any graduations on the ladder. Are you planning on making some type of sight micrometer for it as well, à la PJ OHare?

[EdK]

Beautifully made part Tom.

Ed

[TomG]

Thanks Willie.

Yes, I am planning on engraving graduations for both windage and elevation. Not sure if I want to try calculating the spacing or just wait until the project is finished and derive them empirically. The windage would be easy, but the spacing on the elevation graduations would vary significantly over distance. I'm sure there's a chart somewhere for the .22 rimfire that would cover it.

Oh, and thanks Ed. It seems that you posted while I was typing.

Tom