Electrical Conduit Hole Saw Sizes

Electrical Conduit Hole Saw Sizes

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 exact dimensions as the trade name size of the conduit.

Table of Contents:

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 danger of 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 his hole saws whenever he drills into metal.  As the hole saw heats up from drilling, the oil will trickle down onto the drilled metal.

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

My two types of non-interchangeable electrical conduit hole saw arbors with standard pilot bits are used for different electrical conduit hole saw sizes
My two types of non-interchangeable electrical conduit hole saw arbors with standard pilot bits are used for different electrical conduit hole saw sizes

The above photo depicts two types of hole saw arbors that 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.

Top Of Page

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 1 1/8″ or 29mm hole saw.         3/4″ conduit knockout punch is 1.115″ or 28.3mm.

1″ conduit, drill using a 1 3/8″ or 35mm hole saw.            1″ conduit knockout punch is 1.362″ or 34.6mm.

1 1/4″ conduit, drill using a 1 3/4″ or 44mm hole saw.     1 1/4″ conduit knockout punch is 1.701″ or 43.2054mm.

1 1/2″ conduit, drill using a 2″ or 51mm hole saw.           1 1/2″ conduit knockout punch is 1.951″ or 49.6mm.

2″ conduit, drill using a 2 1/2″ or 64mm hole saw.           2″ conduit knockout punch is 2.416″ or 61.3664mm.

2 1/2″ conduit, drill using a 3″ or 76mm hole saw.           2 1/2″ conduit knockout punch is 2.914″ or 74mm.

3″ conduit, drill using a 3 5/8″ or 92mm hole saw.           3″ conduit knockout punch is 3.539″ or 89.9mm.

3 1/2″ conduit, drill using a 4 1/8″ or 104mm hole saw.   3 1/2″ conduit knockout punch is 4.044″ or 102.7mm.

4″ conduit, drill using a 4 1/2″ or 114mm hole saw.         4″ conduit knockout punch is 4.544″ or 115.4176mm.

5″ conduit, use a 5 1/2″ or 140mm hole saw.

6″ conduit, use a 6 5/8″ or 168mm hole saw.

Top Of Page

HOLE SIZES FOR TAPPING CONDUIT THREADS

Electrical Conduit Trade Size, Not the Actual DimensionsDrill Size For Conduit or FittingDrill Size For NPT Tapered Tap.
Taper is 3/4"per foot.
Threads Per Inch
1/8" Pipe or Fixture Nipple (NPS)13/32" Q (21/64" or 0.332"), (NPS 0.348" S)27 Threads Per inch
1/4" Pipe or Fixture Nipple (NPS)35/64"7/16" (NPS 29/64")18 Threads Per Inch
3/8" Pipe or Fixture Nipple (NPS)43/64"9/16" (NPS 19/32")18 Threads Per Inch
1/2" or 16mm Conduit (NPS)7/8" or 22mm45/64" (NPS 47/64")14 Threads Per Inch
3/4" or 21mm Conduit (NPS)1 1/8" or 28mm59/64" or 7/8" (NPS 15/16")14 Threads Per Inch
1" or 27mm Conduit (NPS)1 3/8" or 35mm1 5/32" (NPS 1-3/16")11.5 Threads Per Inch
1 1/4" or 35mm Conduit1 3/4"or 44mm1 1/2"11.5 Threads Per Inch
1 1/2" or 41mm Conduit2" or 51mm1 47/64"11.5 Threads Per Inch
2" or 53mm Conduit2 1/2" or 64mm2 7/32"11.5 Threads per Inch
2 1/2" or 63mm Conduit3" or 76mm2 5/8"8 Threads per Inch
3" or 78mm Conduit3 5/8" or 92mm3 1/4"8 Threads per Inch
3 1/2" or 91mm Conduit4 1/8" or 104mm3 3/4"8 Threads per Inch
4" or 103mm Conduit4 1/2" or 114mm4 1/4"8 Threads per Inch
5" or 129mm Conduit5 1/2" or 140mm5 9/32"8 Threads per Inch
6" or 155mm Conduit6 5/8" or 168mm6 11/32"8 Threads per Inch

CLICK HERE to See Pipe Taps on Amazon

 Top Of Page

As an alternative to hole saws, knockout punches can be used.  You would drill a pilot hole sized for the draw stud of the punch using a step drill or a small hole saw.  Then use a hand knockout punch or a hydraulic knockout punch to make the desired size hole.

KNOCKOUT PUNCH OPERATING INSTRUCTIONS

I found old knockout punch instructions with a parts list among my father’s tools.  I scanned it and broke it up into sections for easier viewing.  The paper is not in the best condition, as I surmise it is from the early 1960s.

Below are the operating instructions for Greenlee electrician’s hand knockout punches.

A section of an old operating manual for Greenlee hand knockout punches, instead of using electrical conduit hole saws
A section of an old operating manual for Greenlee hand knockout punches, instead of using electrical conduit hole saws

CLICK HERE to see Greenlee Knockout Punches on Amazon

 Top Of Page

GREENLEE HAND KNOCKOUT PUNCH REPLACEMENT PART NUMBERS

The following two images depict the replacement part numbers for Greenlee hand knockout punches.  I do not know how useful they will be today for obtaining replacement parts for Greenlee knockout punches.

In addition, the hole size of each knockout punch is provided.

A Piece of an old (Maybe 1960s) Greenlee Hand Knockout Punch operating instructions. Shown are the dimensions of the knockout punch parts and their Greenlee part numbers
A Piece of an old (Maybe 1960s) Greenlee Hand Knockout Punch operating instructions. The dimensions of the knockout punch parts and their Greenlee part numbers are shown.

Listed above are the dimensions of the knockout punch parts and their Greenlee part numbers.

Four Emergency Disconnect, Not Service Equipment Stickers on one sheet. CLICK ON THE IMAGE to see more Emergency Disconnect Stickers at my Redbubble Shop.
Four Emergency Disconnect, Not Service Equipment Stickers on one sheet. CLICK ON THE IMAGE to see more Emergency Disconnect Stickers at my Redbubble Shop.

 

A section of a very old (Maybe 1960s) Greenlee Hand Knockout Punch operating instructions. Depicted here are the dimensions of the knockout punch parts and their Greenlee part numbers.
A section of a very old (Maybe 1960s) Greenlee Hand Knockout Punch operating instructions. Depicted are the dimensions of the knockout punch parts and their Greenlee part numbers.

The dimensions of the knockout punch parts and their Greenlee part numbers are depicted above.

The front and rear pages of the Greenlee Knockout Punch Operating Instructions and Parts List are below.

Front and back page of old operating instructions and parts list for Greenlee knockout punches and cutter
Front and back page of old operating instructions and parts list for Greenlee knockout punches and cutter

Click for my blog post on descriptions of a variety of electrical conduits.

All of the categories of electrical topics discussed by Mr. Electrician can be seen by clicking here.

Click here to see Mr. Electrician’s merchandise for sale.

If you need to find an OEM replacement part for commercial or industrial equipment, you may find the IQS Directory of suppliers and manufacturers helpful.

LINKS TO CONDUIT MANUFACTURERS

Aluminum and Steel Conduit Products – https://www.westerntube.com/

Fiberglass Conduit Products – https://championfiberglass.com/

PVC Conduit products – https://www.cantexinc.com/

Steel Conduit Products – https://www.alliedeg.us/

Visit my Link Tree for links to my YouTube, social media, electrical supplies, merchandise, and more free electrical wiring information.

Top Of Page