Mk-III - Chassis

The black chassis is now fabricated; punched, drilled and riveted:

Mk-III "Black" Chassis

The component spacing follows closely, but not exactly of the known Mk-III transmitters.  The original plan wa in an earlier post.  <<HERE >> As you can see not much changed since the original plan:

The spacing for the coil plugs are not  0.75" like the crystal sockets but is closer to 1.0" based on B&W coil stocks.  It is also painted black to match my 1935 National HRO radio's chassis.

Close up of the Oscillator Tube's Socket Area

Wires that pass through the chassis will either pass through rubber grommets or brass eyelets.  One of these is in the incorrect hole!  If you look to the right of the octal socket the brass eyelet looks a bit off? 

That is because it is in the wrong hole, which is intended for a #6 screw to pass through, which is slightly larger than needed for the eyelet holes.  It should be in the hole just above it.  This eyelet passes the plate choke lead, and the second hole is actually intended for a ceramic standoff.  In this hole, the stand off would interfere with the output coil, so it will be drilled out and a new eyelet rivet set in the correct hole.  

The front panel mounts to the chassis so corresponding openings are also on the chassis.

The slight haze around some of the holes is from the glue that attached the drilling plan to the chassis for a drilling guide. 

Mk- III Chassis is Ready for Parts

The chassis itself is made from 20 AWG steel.  I was a little worried that the metal would be too thin to countersink the flat head screws properly, but they sit nice and flush to the surface.  The holes were punched, drilled and countersunk on the chassis box.