Came across an American GunSmith article in which the authors described how to fit the slide stop pin to the barrel feet (instead of fitting the barrel feet to the pin), as hown below:
PICTURE 404
They cut the feet with the usual hand-cranked rotary cutter, but then instead of finishing off by dressing the feet they used a home-made jig to dress down two places on the cross pin to do the final fitting. The center portion of the pin for the link was not altered.
They claim this method will last longer than the conventional method as it provides more surface contact area. And, if the fit loosens it can be tightened just by fitting a new slide stop - no barrel work needed.
Sounds like a good idea to me, but it's probably got drawbacks I can't see.
Anybody know what these drawbacks might be?
I've seen a few pins fitted like that in guns that were smithed years ago. It'll work well, done correctly, and does allow a retightening for the cost of a new slidestop. The drawback is that if the flat is cut just a few degrees of rotation too far rearward on the pin, the lower lug hits it pretty hard on the return to battery. In other words... not a job for a kitchen-table smith with a mill file and little patience. A good jig would be the way to go for this one.
Thanks 1911Tuner: The article was in the September 1996 issue. Your comment about getting the angle just right and the lack of commercially available jigs probably explain why this method didn't catch on. Doubt if the jig described in the article could be made without a mill. Cheers
This is what we refer to as the "Marine Corps Cut" and it does work. I have 2 jigs that I use rarely but neither of them allows for the center part to remain untouched. For that reason I always work the lugs down to within a couple of thou and then finish by using the jig with the pin. And I never make this cut except at a customer's request.
Thanks robot1911: Had heard or seen "Marine Corps Cut" somewhere long ago, but never knew (or remembered) what it was.
Quote:
This is what we refer to as the "Marine Corps Cut"
Yup... but I don't think they've used it in a long time. The last pistol that I saw with the pin flat was... in or around 1980 I think... and the job was probably 12-15 years old at the time.
Seems like it was an Ithaca...
It is still very much alive among military armorers in both the AMU / Corp. and I use the method exclusively. I make the cut on the surface grinder in a rotary index, (gives a perfect radius) and find that including the link area, prevents link contact while in battery, however slight, on closely fit links. The top portion of the link/pin relationship, during function, is negligible anyway. How about a fixture that cuts the lower lugs on the mill... while locked in the frame and slide...? There are some very innovative techniques out there, especially among the military armorers. What better proving ground...
Interesting... Thanks Jerry. I haven't seen it done in a long time. Necessarily a precise cut/fitting arrangement... otherwise the lugs would wind up standin' on a point instead of a flat. Do you cut the bottom of the lug parallel to the bore axis... or adjust the flat on the pin to agree with the lug?
Yes, I cut the lugs to the bore line. I've experimented with different angles. One school is 1 degree 18 minutes, but very rarely are two barrels sitting at the exact same angle. For bullseye guns I tend to use a much smaller angle, and because we are seating the lugs on a radius, the angle merely moves the location of the resting point. I want a delay in barrel drop, so I prefer a very small angle, which moves the resting point forward. I don't like flats. Every barrel sits at its own angle, and flats make full contact difficult to achieve.
I stick with the traditional radius.
Whew! I've always said that you Bullseye wrenches are a different breed of animal.
I hope niemi's wrong and this is not the way you've been doing it... 'cause if it is, I've been doing it all wrong since the stone age!
neimi:
Pulled the drawing up at the shop last night.
Yes, that's a pretty good view of it. As you suggest, the depth is exaggerated, as the depth of the cut would only be approx. .005 / .008 in most cases. A 5mm end mill ground to produce a .094 /.095 radius works about right to give full contact on a .200 slide stop pin reduced to give solid lock up. These figures may not work on older out of dimension frames/slides.
Bob;
It's all the same, I just use more machinery than most. I am also a believer
that fixtures are a necessity for repetitive operations. I never could
file/stone in a straight line...
Thanks Jerry. Just wanted to make sure my mental picture of your version of the Marine Corps Cut was correct.
Now that I think about it, the flat version would probably end up getting rounded off a bit after getting hit by the feet for a while - unless the corners in the feet were modified to clear the aft edge of the pin's flat.