Description:  Doughnut shaped flat hub for audio tape reel.

Operation: Disc cut on lathe for accurate center hole size, then outside
           of disc cut for high concentricity (+/- 1mil if possible).  
           Marks made on lathe to indicate hole and notch positions with
           respect to center hole.  Disc cut for proper thickness.

           On vertical mill with rotary table, three holes made 0.4" from
           center hole on line drawn previously, every 120 degrees with #7 bit. 

           Mounting notches milled into edge of center hole with 0.2" end
           mill, 60 degrees from holes.

           Holes countersunk as indicated.

           Notch cut 1/2" deep into outer rim (width noncritical).

Material:  2011 aluminum recommended, but other materials can be substituted
           including high density styrene or 1100 aluminum at the discretion
           of the machinist.

Observation: Part is effectively identical to plastic sample except for outer
           diameter and notch.  Large holes and honeycombing in plastic sample
           are due to plastic fabrication demands and do not need to be 
           replicated.

           

           S. Dorsey, 2/2018.