Step 69: Bristol 4-Spline Drive
Bristol Spline Drive suggested applications include set screws and smaller cap screws requiring severe tightening, and for screws with shallow sockets. For frequent removal and resetting of screws and plugs, such as for tool inserts, purge screws, drain/filler plugs, template retainers, and replacement of worn parts. In applications requiring softer screws such as stainless steel or non-ferrous materials.
Decades ago, Bristol engineers invented the Bristol Spline Drive System for use in electromechanical instruments. They required screws and wrenches that could stand up to industrial environments, vibrations, and frequent removal and resetting. Bristol wrenches have been in continuous production in the United States since their original introduction. Usual number of flutes is 6, but some diameters come with 4 flutes. Sized in inches:
0.048, 0.060, 0.069 (4 flute), 0.072, 0.076 (4 flute), 0.096, 0.111, 0.145, 0.183.[[br]]