This post is on making cross-dovetail front sights if the need arises. Lets say you are doing a Novak front sight and mistakenly use a Bomar 60 degree x .360 cutter instead of the proper 65 x .330. Well you can weld the slot but I don’t like welding on guns unless absolutely necessary. Easiest thing to do is fabricate a new sight. Best to make your customer an extra because it’s a bastard size sight.
If you must weld the front of the slide make sure you use a copper mandrel in the bore. Make the copper mandrel .695 diameter and pre-heat it to about 800 degrees, you don’t want the cold copper sucking the heat out of the weld quenching it and making it to hard to cut, warm-up the weld area with a propane torch to about 400 degrees, if the steel starts to turn brown stop, it’s hot enough. The copper will act as a heat-sink and keep the weld from cooling rapidly hardening the weld area. You can use standard 60 or 70S rod; this lower carbon rod will dilute the higher carbon in the tool steel and make it easier to cut. 4130 rod is ok too and matches well, the 30 is the carbon content in the 4130, most slides being 4140 the lower carbon content in the 4130 rod makes it a little more weld able.
I make the blanks .450 wide because that’s the width of Gold Cup solid ribs.
We’ll make a sight .450 wide, .125 blade x .250 high, .360 x 60 degree, .075 thick.
½” x ½” standard 1018 cold roll is good enough for the job. Cut the bar-stock about an inch longer than your vise jaws so you have a ½ inch hanging out the end of the vise.
Machine the piece of bar-stock .450 wide x .500 high.
First make-up a dovetail gauge, use a piece of the ½ x ½ bar-stock about 3 inches long, cut a dovetail lengthwise .070 deep and about 1 inch long, open the mouth of the dovetail cut +.002, -.002 for about a ¼ inch and +.004, -.004. for another ¼ inch.
Step 1: Put the .450 wide side in the vise on a parallel leaving plus .250 above the top of the vise jaw. Get the center of the .450 and zero mill; now mill your .125 blade on center the full length of the bar.
Step 2: Flip the bar in the vise and clamp the .125 blade lightly in the jaws, place a piece of shim stock or paper about .010 thick in between the top of the solid vise jaw and the bar-stock. Tap the bar down tight to the vise top, if the bar warped when the blade was machined you want to snug-up the vise and make sure it taps down level with the top of the solid vise jaw, do not put the shim on the moveable clamping jaw. The sight blank is now upside down in the vise with the dovetail blank sticking out the top.
Step 3: Next face the excess metal off the top of the dovetail blank with a ½” end mill, you will cut .175 off leaving you with a .075 thick blank.
Step 4: Move your ½” end mill to the end of the sight blank and raise the table .075, touch-off the end of the sight blade and walk the mill in .100.
Now you want to cutout your .360 blank and then locate the center of the .360 and zero the mill.
Step 5: Next coat the blank with marking ink and put your .360 x 60 degree dovetail cutter in and touch-off the top, zero and raise the table .078, (the extra .003 should be enough to remove the thin burr left on the bottom of the sight blade) cut the dovetail into the side of blank till the top almost comes to a knife edge, leave about a .010 ledge on the side and record the measurement from the center of the .360 blank, lets say your + .300 off zero, now move to the opposite side and cut it -.300 ( this measurement will depend on the diameter of the cutter and depth of dovetail).
Now de-burr and take your dovetail gauge and try the fit, if the dovetail is to large re-cut +-.299, +- .298 and so on till you get the nice snug fit you like. Separate the blanks with a fine hacksaw blade.
Hope this enlightens some on the subject, MetalSmith
