I started removing/replacing pins in the Sig pistols using a cheap
Palmgren 1 ton arbor press which holds the special driver pins. It is so
effective and takes so much of the work out of it that I want my customers
to know about it.
Just about any 1 ton arbor press will do nicely, but especially if all
slop is removed from the ram. I simply took the front plate and fitted a
1/8" thick gib to fit the recess beneath it, the original as shipped
uses direct contact by the set screws to press against the ram. The gib
works much more smoothly. In the process I made another gib for the side
which has the adjustment screws, for the same reason. Also, since I had the
ram out anyway I grabbed it in the four jaw chuck and drilled and reamed a
1/2" hole about 1 1/2" deep as a soc for a socket to hold
the special drive pins. The shank of each pin has a turned down groove for
set screws to bear against and hold it in place. I also made a carrier to
hold the punches so they don't get lost.
The pin punches themselves are made of 1/2" diameter 4142
chromoly tool steel, turned down to .078" at the working end, one a
short length and the other long enough to push the pins all the way through.
The .078" pin ends have a small hemispherical concave end, a hollow end
that centers well on the pins for pressing, I use the short one for the
first movement and change to the long driver to push it out. These drive
punches are heat treated to about 45 Rc so they stand up to the forces. If
one tried to push the trigger pivot pin out with the long punch it wold
likely bend over under the strain.
The way the holes are made in the Sig P238 and P938 is that the holes
are drilled, then reamed all the way through with a slightly undersized
reamer, and then reamed just short 1/8" with a reamer a thousandth
So, the smaller end of the hole being on the right side, if you push
it out from the RH side to the left it will go hard for 1/8" or so and
then go easier. But if you try to push it out from the left side it will
push hard all the way through!
As seen in the photos I use a block of 1" thick aluminum with
blue masking tape to prevent aluminum from smearing onto the guns finish.
Whether using a press or a simple nail set these precautions are useful,
plus the addition of Kroil or some other really good penetrating oil. Make
sure your gun is laying on it's left side and the hardwood or aluminum block
has a hole for the pin to drive into. The block should be laying on
something substantial so the shock is transmitted to the end of the pin and
not wasted moving a light table around.
A nail set is good and rigid enough to get the pin moving and a longer
punch can drive it he rest of the way. Before I altered the Palmgren arbor
press I used Brownell's cup pointed pin punches.
Model 8 3mm (.118") diameter/short length $12.99
must be tapered down to .078" or so or it will damage the finish of the
hole. That's the first punch, the second doesn't need any improvement;
Model 3 .072" (1.8mm) diameter/long length $17.99
These aren't absolutely necessary but very helpful.