6-Lobe Drive Flat Heads (Floorboard)
T B F  
Nominal Size or Basic Screw Head Dimensions Recess Dimensions  
Diameter           Drive Size
    Max Sharp Abs. Min Ref Ref Gauge Penetration Min  
1/4-20 0.2500 0.520 0.452 0.160 0.221 0.060 T30
5/16-18 0.3125 0.648 0.568 0.199 0.266 0.090 T40

Description A countersunk, 6-lobe drive thread cutting screw with machine screw thread pitch, blunt point, tapered entering threads, and multiple cutting edges.
Applications/ Advantages Floorboard screws are specifically designed for installing wood floors into truck trailers or wood to the interior of containers.
Material AISI 1016 - 1024 or equivalent steel
Heat Treatment Screws shall be quenched in liquid and then tempered by reheating to 650 degrees Fahrenheit minimum.
Surface Hardness Rockwell C45 minimum
Case Depth .005 - .011
Core Hardness (after tempering) Rockwell C28 - 38
Thread Dimensions Same as those for Type-F thread cutting screws.
Plating Black-Phosphate