The Whiteside HMA1/4A Screw Type Helix Mortise Cutter Arbor is for use with Whiteside's Helix Mortise Cutters (sold separately). Can be used in either hand held or machine routers. Arbor has a 1/4-24 end thread size. Whiteside Machine Company - Claremont, North Carolina.
SH = Shank size TH = End Thread size. OAL = Overall Length.
1/4 SH X 5/16-24 TH x 1-3/4" OAL