2 1/2″ conduit knockout punch is 2.914″ or 74mm.ģ″ conduit, drill using a 3 5/8″ or 92mm hole saw. 2″ conduit knockout punch is 2.416″ or 61.3664mm.Ģ 1/2″ conduit, drill using a 3″ or 76mm hole saw. 1 1/2″ conduit knockout punch is 1.951″ or 49.6mm.Ģ″ conduit, drill using a 2 1/2″ or 64mm hole saw. 1 1/4″ conduit knockout punch is 1.701″ or 43.2054mm.ġ 1/2″ conduit, drill using a 2″ or 51mm hole saw. 1″ conduit knockout punch is 1.362″ or 34.6mm.ġ 1/4″ conduit, drill using a 1 3/4″ or 44mm hole saw. 3/4″ conduit knockout punch is 1.115″ or 28.3mm.ġ″ conduit, drill using a 1 3/8″ or 35mm hole saw. 1/2″ conduit knockout punch is 0.885″ or 22.5mm.ģ/4″ conduit, drill using a 1 1/8″ or 29mm hole saw. HOLE SAW SIZES AND KNOCKOUT PUNCH EQUIVALENTġ/2″ conduit, drill using a 7/8″ or 22mm hole saw. The others screw in to one of two standard size threads on hole saws with threads. The three arbors on the top left can only be used with a hole saw that has the rectangular round shape. Two types of hole saw arbors are depicted in the above photo and they are not interchangeable. Amazon sells cutting oil which is used for these purposes.Īt the bottom of this post is a list of old Greenlee hand knockout punch replacement part numbers that I scanned.ĬLICK HERE to see Electrician’s Hole Saw Kits on Amazon My two types of non-interchangeable electrical conduit hole saw arbors with standard pilot bits are used for different electrical conduit hole saw sizes

Although you can probably use most general purpose oil or motor oils for lubricating when drilling, there are oils made especially for drilling, tapping, and threading. Put something on the floor to protect it from oil leaks such as flattened boxes or an old piece of plywood. As the hole saw heats up from drilling, the oil will trickle down onto the metal being drilled. I read in a trade magazine of one electrician who puts an oil soaked cut-to-size piece of Felt inside of his hole saws whenever he drills into metal. When drilling into metal, it is a good idea to oil the hole saw a few times during the drilling process to prevent premature wearing of the hole saw teeth.

Some angle drills have an accessory handle to gain extra leverage and control when drilling. I suggest wearing work gloves when using a right angle drill. The extra length of the right angle drill makes it easier to maintain control of the drill if the hole saw does get jammed. I usually use my 1/2″ Milwaukee Electric Right Angle Drill when using a larger hole saw as the torque is very good and the RPM’s are just right. Drilling at a slower speed will help the hole saw last longer, and there is less of a danger of the hole saw getting jammed and causing damage or injury.

Hole saw