P.I.T. Four Spiral Flute Step Drill Bit Set 1/8"-7/8"(34 Size), Hss Industrial Four Spiral Flute: Our step drill bits are equipped with four spiral flutes,The fluted spiral drill-bit design automatically deburrs and expands holes for a cleaner drilling process every time without heating up, just like a hot knife cutting butter. Extreme Durability: Our step drill bit is made of 4241 high speed steel and is heat treated to have a hardness of up to HRC60-62; With a 1/4-inch quick-change hex shank, this step drill bit fits securely in most pistol drills or drill presses. Use this cone-shaped, versatile, and small drill bit for metal projects at work or home. [34 Step Size] : The size of the drill bit ranges from 1/8"to 7/8". including 34 sizes:1/4 ''-3/4 ''(1/4", 5/16",3/8",7/16",1/2",9/16",5/8",11/16",3/4");1/8 ''-1/2 ''(1/8",5/32",3/16",7/32", 1/4", 9/32", 5/16", 11/32" ,3/8", 13/32", 7/16",15/32",1/2");3/16 ''-7/8 ''(3/16",1/4",5/16",3/8",7/16",1/2",9/16",5/8",11/16",3/4",13/16",7/8"),1/4" Hex Shank Drill, quick release slot to eliminate slipping. ? HEAVY-DUTY DRILL BITS: With the HSS and four spiral flute designs, our drill bit can be suitable for multiple scenarios, and is able to drill holes of a variety of diameters quickly and smoothly, which on materials such as Thin Metal,copper, Carbon Steel,aluminum, wood, plastic board, and other metal sheets. Attention: Please wear a mask and goggles when using drill bits to avoid accidents. Using the corresponding drill bit in different scenarios can increase the lifespan of the drill bit. Please choose the drill bit that is suitable for your own work.