Early Delta Unisaws may be equipped with either a 3-3/32” or 2-11/16” Arbor pulley and either a 5.5" or 3.25" motor pulley. To confirm what size belt to acquire when replacing the belts, measure the diameter of the Arbor Pulley and the Motor Pulley. And reference the list below.
1725rpm motors (1939-1950):
5.5” Motor Pulley with 3-3/32” Arbor Pulley : 29” x 1/2” cross section - Trade size A27
5.5” Motor Pulley with 2-11/16” Arbor Pulley : 28” x 1/2” cross section - Trade Size A26
3450rpm motors (1951-????):
3.25" Motor Pulley with 3-3/32" Arbor Pulley : 25.5" x 1/2" cross section