Mystery TM 504 screws.


Colin Herbert
 

Can anyone shed some light on this mystery? I was carrying out some repairs to my TM 504 mainframe, I noticed that there was a particular screw missing. I further noticed that an eBay seller (from who I had purchased before and was sure of their honesty) was selling these screws. On checking in my TM 504 Service Manual (ID# 070-1716-00) I ascertained that the description of the screws in the manual and on the seller's listing were substantially identical. The eBay listing was:

211-0040-00 TM 504 Plastic Screws 4-40 x .25"

The Manual has:

211-0040-00 SCREW, MACHINE: 4-40 x .25", BDCH PLSTC

The manual also shows in Fig. 2 Exploded that these screws are attaching a frame section and that nine are required.

This is where the mystery starts. The screws actually in place on my TM 504 are steel, countersunk head and of a much greater diameter than the plastic ones (which is what you might expect). Does anyone have any idea of what these plastic screws are for and how did such an anomaly happen in the TM 504 Service Manual?
TIA, Colin.

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