Tag: Greenlee Hand Knockout Punch Part Numbers

Dear Mr. Electrician:  What are the actual electrical conduit hole saw sizes for the various trade sizes of electrical conduit? Answer:  Electrical conduit hole saw sizes and knockout punch sizes for conduit are posted below.  NOTE: Some text links below go to applicable products on Amazon.  As an Amazon Associate, I earn from qualifying purchases. Electrical conduit hole saw sizes are not the same dimensions as the trade name size of the conduit. Table of Contents: Drilling With A Hole Saw Hole Saw Sizes and Knockout Punch Equivalent Hole Sizes for Tapping Conduit Threads Knockout Punch Operating Instructions Greenlee Knockout Punch Replacement Part Numbers DRILLING WITH A HOLE SAW When drilling with a hole saw it is important to use a slower-spinning drill with a lot of torque rather than a high-speed drill.  It is best to drill at 400 revolutions per minute (RPM) or slower when using a hole saw. 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. 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 RPMs are just right.  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 suggest wearing work gloves when using a right-angle drill.  Some angle drills have an accessory handle to gain extra leverage and control when drilling.  It is a good idea to use it. 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.  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.  As the hole saw heats up from drilling, the oil will trickle down onto the metal being drilled. Put something on the floor to protect it from oil leaks such as flattened boxes or an old piece of plywood.  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.  Amazon sells cutting oil which is used for these purposes. At the bottom of this post is a list of old Greenlee hand knockout punch replacement part numbers that I scanned.   CLICK HERE to see Electrician's Hole Saw Kits on Amazon Two types of hole saw arbors are depicted in the above photo and they are not interchangeable.  The three arbors on the top left can only be used with a hole saw that has a rectangular round shape.  The others screw into one of two standard-size threads on hole saws with threads. HOLE SAW SIZES AND KNOCKOUT PUNCH EQUIVALENT 1/2″ conduit, drill using a 7/8″ or 22mm hole saw.            1/2" conduit knockout punch is 0.885" or 22.5mm. 3/4″ conduit, drill using a...