The
360Q plate is drilled from the factory to mount both the G-9.5 and the P-28s lamp
socket for use on both fixtures.
I recommend making or having made for you out of 14ga steel a replacement plate. Less chance it will
bend and break the lamp
socket during focus.
Use your old triangle
base plate as a
template to
mark your holes and the outline shape. Draw straight
line o.c.
thru the center of the marked holes for your lamp
socket mounting holes across the plate. Place your replacement lamp
socket on this
line to verify that either your lamp
socket mounting holes are in the same place, or with the newer and often wider o.d. the mounting holes might have changed. Align and
mark the new holes on that
line. Also
trace the o.d. of the replacement lamp
socket - especially where it has recesses.
In one of those recesses you will have enough un-obstructed area on your triangle to drill and tap for a
ground.
Drill and tap the plate = 8-32 tap for the
bench focus screws, 1/8" dia for if the
base mounting screws are 4-40 size. 10-32 for the
ground tap. Ream or file flush the holes so there is no burrs.
Install the plate into a bench vise with the outer
edge of the triangle aligned flush with the top of the jaws (plate area inside the vise.) Hack saw or
Sawzall your cuts with the saw blade riding on the top
edge of the bench vise jaws. 18tpi blade for hack saw, 14tpi blade for the
sawzall and use a little
bit of cutting oil on the blade.
Alternate method would be to clamp the plate of 14
gauge steel to a work table with your cut
edge hanging off the
edge. A
jig saw with metal cutting blade of 14tpi to 18tpi and a
bit of cutting oil should get it done. Final cut will be tricky given the
base of the tool. Use cutting oil also.
Note on marking for what to cut... if using a
power tool and cutting oil, Sharpee or pencil might
wash away, try a extra fine tip paint marker,
grease pencil or high temperature spray paint instead to
mark the outer edges of the triangle.
To make the rounded or squared off edges of the triangle, cut or grind or belt sand to match.
File,
wire wheel and or sand and file
etc. all exposed edges. All outer edges must be rounded over so they don't cut conductors. Clean the
base plate with oil/grease remover or at least soap to remove any cutting oil residue. Paint the
base plate with high temperature
flat black so it doesn't rust.
Make sure to use the
insulator which comes with the replacement lamp
socket - you do not want to short to the
base plate - fabricated or bought. Also on other lamp sockets not replaced, you still have to use an
insulator pad.
More details if wanted about
shock mounting the lamp
socket, how I do grounds or
wire the
socket etc. Lots of details learned over the years of literally hundreds of 360 type fixtures serviced. You get the
bench focus dialed in right... it's a very useful
fixture still. One of these days I'll get to inventing the P-28s lamp
socket extender which will allow such fixtures to use a BTH lamp. Got everything I need to do it ready to go.... too busy on work projects. Been at least a year since I restored my last antique even, and I have some really ancient ones in
line for me to work on.