Cox .020 PeeWee/TeeDee prop-screw

It's a size 3-48 UNC machine-screw. Now for my story; Up until this past week, I'd never owned a model engine smaller than .049 cu.in. I'd never even "held one" in my hand.. then I got a letter from my brother from another mother.. "Eric" (@getback) telling me that something was coming in the mail... but he didn't let-on as to what it was..



A PeeWee!!!!



There's something about a handwritten letter...    So it just needed a prop-screw.

I have a stock of 3-48 X 1" length cap-screws (black oxide coated) so I cut a few to the required length. This engine's crankshaft bore had a depth of close-to 3/8" (10mm).. but I found that the 3-48 threads weren't tapped nearly that deep. Just-over 1/4" or maybe 7mm.



My screw kept running-out of threads before the propeller would tighten up..  

89

I didn't have any flat-washers the correct size (which naturally bothered me..    ) so I came up with an unlikely adaptation. I have a stock of 3-48 lock-nuts.. so I decided to drill-out the threaded (steel) section to receive the body of my 3-48 cap-screws (.098") and then drilled-out the plastic (lock) part of the nut to receive the screw-head.. (.159") which provided a consistent bearing-surface on the prop-hub.. when snugged-up.





That's gonna' work just fine.. and I like the look..