On 2013-12-27, Doug White wrote:
The collegiate pistol team I help coach has two Russian target air
pistols that have broken cocking linkages. I have replacement parts,
but I need to disassemble a linkage that has a swaged pin in it. The
ends of the pin are even with the sides of a piece I need to rescue
undamaged. I had originally planned on drilling/milling out the center
of the swaged part enough to press the pin out, but I discovered that
the pin is free to rotate. There's nothing exposed enough to hang onto
that I don't need to largely cut away.
I can probably grind out the swaged bit VERY carefully with a Dremel,
but it's going to be tedious & fussy.
I can see that.
The pins are about 5/16" in diameter,
Likely 8mm then. That is one of the ponts where metric and inch
measurements come close. (5/32", 5/16", 5/8").
and each end has a shallow drilled
out section.
How shallow? I can't tell from the photo.
It looks like they pressed ball bearings into the ends to
spread them. The linkage the pin goes through is countersunk on both
sides, so the swaged bits hold everything together.
There a picture he
http://www.pyramydair.com/blog/image...inkage-web.jpg
The only way I can think of to physically hang onto the pin is to make
an expanding collet that goes into the drilled out pocket on the far end
of the pin. That is going to be tenuous at best, and it's a lot of work
to fabricate for a high likelihood of failure.
My thought is to get a 5/16" diameter multi-flute countersink
bit (used to be Severance, now some other company, IIRC), and mount it
vertically so it sticks out just enough to allow the force to be applied
to the cutting edges. Use it as an anvil to support one end of the pin,
and use a smaller drill bit (perhaps 5/32" or so) to drill most of the
way through. (You use the smaller drill bit so the torque from its
cutting edges is likely less than the torque needed to start the
countersink cutting.)
When you get say 3/4 of the way through (set up the quill stop on
the drill press to prevent the tip of the drill bit touching the tip of
the countersink), flip it over and drill from the other side.
Then increase the size of the bit to do something like the same
hole area increase (5/32" would be about 0.245 square inches, so
increase by the same for 0.395" diameter -- too big, looks like you can
target the final diameter of 0.315" (8mm) on the second step. (Or,
maybe you'll find that you need to start smaller, and increase by the
area of the first bit which works. Maybe start with a 0.125" bit, then
the next would be 0.176", and then the 0.216", and finally 0.315".
Or -- maybe skip the final 0.315", and put it over a bench block
and drive it out with a pin punch, as the walls will be thin enough
to give way by this time.
One other option would be to crazy glue everything together, mill out
the swaged bit, and then soak it in acetone until the pieces free up.
That assumes the crazy glue can handle the machining forces.
I strongly doubt that the crazy glue will be strong enough, even
if you could get it into the holes between the pin and the walls.
Before I drag out the Dremel, does anyone have any better sugestions?
You have what I would try, at least.
It looks like you can remove that linkage assembly from the
action by removing C-clips, so you won't be juggling as heavy a bunch of
metal, and controlling it will be easier.
Good Luck,
DoN.
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