I was looking for an "easy" way to machine the bronze hanger castings but I
could not figure out how to get
16 identical parts from the rough castings. I had thought of a hardened
steel master and use a Dremel tool
with carbide burr to do the outside profile and spot the holes. I sought
the wisdom of the Live Steamers List
and Harry Wade basically said that the easy way is usually to just grind it
out and do it. I ended up doing a
CAD drawing of the part and printing it out 16 times. I then cut them out
carefully with a X-Acto knife and
rubber cemented them on the parts trying to get them centered as best I
could on the castings. The critical
features are the pivot radius and the four holes for the spacer screws and
spring mounts. I had the centers
for these holes on the CAD drawing and drilled the one in the center of the
pivot 1/16" dia. This was 0,0
for the part.

The plate on the bottom of the fixture is similar to a tooling plate I saw
at a machinery show. It has a
1/4-20 tapped hole and .250" reamed hole alternating on 1/2" centers. Mine
is Jig Plate Aluminum
and the commercial one is steel. The idea is that you can make all sorts of
modular fixturing pieces
for it to minimize special tooling costs. I made a 1/4" steel pin with a
1/16" dia. section to fit the 0,0 hole
in the hanger and a scrap piece of AL plate. I then indicated this to equal
the center of the rotary table
underneath and clamped the tooling plate firmly to the RT (which was
already zeroed to the spindle of the
Bridgeport) and clamped the scrap plate to the tool plate. Now you can dial
off the X-Y coord's for the
spring hanger holes at the ends of the legs. Using the cross hairs on the
CAD drawing for reference and
a pointer in the drill chuck, I drilled 1/16" dia. holes in both legs and
the scrap AL. plate, inserted a 1/16" pin
to locate them and used some aluminum strap clamps found in the scrap box
to hold it all down. Spot the holes
for the spacers in the middle of the legs.

Now you can mill the radius and the adjacent flat areas on each part, then
the top flats. I used a 1/4" 4-flute
carbide cutter. Swing the RT to the appropriate angle, offset the table as
needed and mill the legs. Then I placed
the radiused ends on the center pin and milled the radii there. Then back
to setup one and used a 3/4" cutter to
do the inside radii. The external rdius was done with a belt sander.

Now I opened up the holes at the ends of the legs for a 10-32 tap or .250
ream for the spring ends and drilled the
spacer holes either 5-40 tap or 1/8" clear as per print.

Now I can take any part from the pile and it fits either chassis anyplace I
want. No match marks. Just what I wanted.

Like Harry said, "The easy way".