TIMCO Wing-Tip S/D Screws Countersunk PH Zinc 5.5 x 45 PK 200
Specifically designed to attach wood to heavy section steel (Max. 12mm). Metric thread with wings designed to ream out the timber, so the screw can achieve Max. R.P.M. without burning out. When the wings hit the metal they will break off to permit the thread to self-tap into the metal. NOTE: Partially threaded.