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.
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. 080-620-301WB
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;
3 .072" (1.8mm) diameter/long length $17.99 These aren't absolutely
necessary but very helpful.