Sunday, December 9, 2012

Daisy 790 Sight Rail Part 1

With the Daisy 790's loading trough repaired, only the broken rear sight boss was keeping it out of action.   Considered milling out a pocket and making an insert with a new boss for the original sight. Except my other variant--the S&W 78G version--is still sporting iron sights and I wanted some variety.   Decided to add a full length sight rail to this one.

The Daisy 790 top half with the damaged casting.

With the piece on parallels to get it above the top of the vise jaws, I started by milling off the front sight.  It would be a straightforward project to make a new--better--front sight for this pistol, as the original cast sight with the rounded edges left a lot to be desired.

Going, going, gone.  Starting to extend the flat down the top.

The only difficulty is the rear sight pocket on the top of the casting.  It's not exactly the same height as the front half.  Milled away the boss for the sight.

Changed to a smaller endmill.

Slowly bringing the entire cutout to the same depth.

Done.  Now, I need to make an insert to fill in the gap then cut everything to the same height so a sight rail can be mounted flush.

Now that insert.  Found a strip of aluminum in the scrap box.

Did some math/layout to make it fit into the pocket and set it up against a work stop.  Also set the table stop so the notch would terminate at the same point on each side of the cut.

Made this workstop a few weeks ago.  The work butts against the brass rod.  Lets you remove the work, reinstall it into the vise and go back to the original location with good accuracy.

Notched.  Flipped over, (and butted against the work stop) and notched the opposite side.  (hint:  Don't move the z-axis.)  This creates an equal depth of cut.


Cut it to final length and angled the cuts to blend into the gun.

Found the sight mounting hole.


Spotted and through drilled.

Countersunk for a mounting screw.

Screwed the filler plate to the "slide".  Well, it looks like a slide...

The entire top was then milled down to the same height.

After milling.  There's not much left of my wafer spacer.

Good view of the space that needed filling.

Like a glove.  Later, I'll radius/blend the sides and add a finish.

In a few days, I'll have the rail fit and finished.  Thanks for reading.  Please check back soon.