This type of screw was first introduced by Vicmarc®. The thread type provides extra strength and is ideal for holding wood safely on the chuck. Pictured is the standard Chuck Wood Screw that comes with each Chuck.  We also make a Heavy Duty Chuck Wood Screw (HD) that is larger in diameter and can be used for for heavy duty holding of larger parts.
 
Chuck Wood Screw - Part No. V00991
Chuck Wood Screw HD - Part No. V00989