View Full Version : frame-to-slide tightening

January 5, 2002, 02:41 PM
before we get off topic and tell me how only 5% of an auto's accuracy is frame-to-slide fit, let me say that i'm using frame mounted optical sights on the gun, and IT DOES AFFECT ACCURACY, much more so than using slide mounted sights.

now to the question......

i have a 10mm full size witness in wonder finish, and i'd like to tighten the slide up a bit. it's not sloppy, but not as tight as i need. the question is how the wonder finish affects and is affected when using the normal techniques for slide tightening.

i know of three basic ways to tighten a slide on an auto.......

1-peen the slots where the rails slide, to reduce the dimension, giving a tighter fit.
2-squeeze the slide or frame(depending on whether the gun has internal or external rails) to reduce the dimension, giving a better fit.
3-welding some metal into the rails so it will build up the rail, so some material can be removed, giving a better fit.

the wonder finish apparently makes the steel VERY hard, and i think that the metal would crack before bending or peening, so 1 & 2 are out(that's a question)???

welding is welding and that would work, but the finish may be damaged.........or changed so it's not as strong.

does any body have any experience or ideas on how to tighten up the slide & frame fit in general and/or specifically on the wonder finish?????


Eric Larsen
January 5, 2002, 10:53 PM
I will start by saying "I am not a smith". So take it for what its worth.

The wunder finish can't make steel harder, it is not a case hardening process. The coating itself may be longer wearing than a blue gun. But that hardness is only as thick or thin as the coating.

Leave the welding part up to a GoOd smith. If done incorrectly it can alter the "designed temper or strength" of the frame and
may cause work hardening. Could make it brittle or too soft....
Therefore the smith...just thought I would jump in.

Shoot well

Art Eatman
January 6, 2002, 09:00 AM
For me, peening is more controllable--to avoid the old "Oops! Too much!" problem.

Because of the springiness of the frame or slide, method #2 needs more experience in knowing how many thousandths deflection gives how many thousandths permanent set.

Either way, getting the system a smidgen too tight can be solved with "Clover" valve-grinding compound (the "fine" side of the little can) and elbow grease--which gives a near-perfect fit.


Joe Portale
January 6, 2002, 12:19 PM
Let say right off, that I am not a professional gunsmith, just a hobbist. Yet, I have done slide to frame tightening a bunch of times and done some extensive research on the subject.
Art is dead right. The asiest and most controllable method is to swag down the frame rails. Use a 4 ounce ball peen hammer. Be sure to take the time to true up and polish the hammer face before tapping the rails. A series of light taps is much better than just wacking the tar out of the rails. My technique is to tap along the rails, check the fit, repeat as necessary. There is great truth in the old saying "Haste makes waste". I also follow the recommendations of Kuhnhausen in his 45 Colt automatic books. Swag the rails to within 0.04 (this will be .02 on each side)free play vertically and laterally and then lap with grit. You can check this measurement with a slightly modified feeler guage.

The idea of welding the rails gives me the willies. FWIW, I am a certified welder. There is more to adding material than just running a bead. Gas or stick put too much heat into the surrounding areas and will definitly mess up the hardening. Also, to properly do this type of welding on the rails, you should anneal the area first to avoid later stress cracking. You can then re-heat treat the piece, but that opens another can of worms. I also doubt that most people could lay a small enough bead that will not call for considerable milling to get the rails into spec's. MIG would be the way to go, but then you may have an alloy mismatch. Blueing and other finishes do not respond well to alloy mismatches in terms of color. This wouldn't matter with complete coatings like Guncoat, Robar or Toughcoat. Wonder Coat or any coating can not make the steel harder. It is merely a coating, like paint.

Your mileage may vary.