Tuesday, January 19, 2016

Gun Build, Frame/Slide Fitment.

Now, out of the box the frame and slide didn't fit together.  You've filed on the slide, and they still don't fit together.  Now we are going to make it even harder to fit together.  We are going to hammer on the frame.  With a hammer.  A steel hammer.  Bang bang bang bang.  On the most expensive and hardest to replace part.  Joy!

There is a lot of this in 1911 gunsmithing.  "Careful on this part.  One misstep and you ruin it and might as well throw it away."  Phew.

You put your frame in a jig, you put that jig in a big vise.  Remember the measurements on the slide?  It was 0.1170.  You get a precision machined steel spacer that is 0.1170 into the side groove on the frame.  Then you carefully, yet pretty hard, bash on the top of the frame rails with a hammer until it hold onto the spacer.  Now the frame rail 'dado' is .1170 and the slide rail 'mortise' is .1170.  BAM.

When you fit the slide to the frame you have to know what parts of the frame are not fitting or coming in too close a contact.  For this you blacken the rails all over with a smoke lamp.  A flame that leaves carbon all over.  Where the black rubs away that part you file.  You also use these marks to determine what is happening.  They leave a distinct pattern when you are just flexing the slide outward, for example, when you are jamming the two together.

This is the 21st Century.  It is easier to use a black Sharpie marker instead of a smoky flame as your 'smoke lamp' medium.

See this green spot?  Inside it is a part of the marker that has been rubbed away while fitting, and it isn't inboard on the rail the rails are too tall.

You also see the stubby steel hammer for smashing the frame down.  The rawhide is for tapping the slide off of the frame.

After ever few fittings you clean off the marker with alcohol.  It actually adds thickness and gums up the works after a while.

Mark, fit, file, mark, fit, file, clean marker.  Always clean off filings.

When they mate together but still aren't smoothly working, we lap with 800 rip lapping compound and in an oil slurry.  Then a thinned down slurry.  Then just work it together with oil.

At the end they should fit together with a gentle tap and not rock side to side, up and down, or roll. 


B said...

So, essentially ZERO tolerance fitment, right?

At what temp? Room temp?

if zero(or nearly zero) at say, 70F then will it work at 20F or less?

Or am I missing something here?

New Jovian Thunderbolt said...

Not zero tolerance. Compared to a factory gun or a milsurp? There is no movement.

When done it will work on the first shot. It won't need a break in period to wear it loose enough to function.

Oil is important. See when Tam tested her one off custom gun over many rounds without cleaning or lubing. Three drops of oil got it running again after it got all cacked up with powder residue.

New Jovian Thunderbolt said...

Comparative zero tolerance.