Application Information T-15 HSS spade blades are recommended: • For providing straighter and more consistent holes with superior surface finishes than can be produced using either HSS twist drills or carbide indexable drills. • When rigidity of the machine or the fixture requires a more forgiving, durable, and tougher tool; T-15 steel possesses a higher transverse rupture strength and is more impact-resistant than comparable carbide spade blades and/or carbide indexable drills. • In applications requiring hole depths up through 15x to 20x diameter; pecking may be required for depths above 7x diameter for some materials. • As a cost-effective alternative to carbide indexable drills since T-15 steel spade blades operate at comparable penetration rates to single-effective indexable drills in materials <35 Rc, and one spade blade holder accommodates multiple diameter blades. Spade Blade Holders Generally can accommodate a range of blade sizes up to 1.30–1.35 times the smallest blade size. It is therefore possible to cover the entire range of hole sizes with just a few spade drill holders. Contrast this with the inventories required for indexable drills and steel taper shank drills. widia.com U27