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Using a Nibbler to Cut Cage Walls for portal installation

Document Type: Information Sheet
Topics: Shelter Design and Housing
Species: Feline

Using a plasma saw can make portal hole cutting quick, but it has its drawbacks. Fortunately there is a cost-effective alternative that is safer, and will get the job done: a nibbler.

Great news for those who want to install portals but have built-in cages!  Portalizing can be done with a nibbler and some metal tapping tools. Read on to learn how…

Watch the video on using a nibbler:

Supplies Needed:

  • Hearing protection
  • Eye protection
  • Step bit – big one - Makita is a good option
  • Spray oil for cutting metal - Magic tap or similar product
  • Nibbler – Makita battery operated nibbler 18v works very well. Corded ones will work too, but the cord can get in the way a little  
  • Template - to mark portal cut-out area.  This can be ordered through Shor-Line.  This is also where the manufactured portals can be ordered.  Their phone number is (800) 444-1579.  Alternatively, templates can also be made locally near you.   
  • Electric drill – to run the step bit
  • Paper towel
  • Rubbing alcohol  
  • Vacuum/broom to clean up metal shards

1. Use a template (ordering info above) to mark the location on the cage wall where the portal will be installed

I. Measuring in 14” from the cage front and marking the cage floor will place the installed portal at 15” into the cage.  This is a good location for a cage that is ~28” deep.

II. The templates were designed for use with a plasma saw with an allowance for the width of the cutting tip.  

a. To make a proper size hole (not too big) place a felt tip marker inside a 1” length of ½” PVC pipe that just allows the tip of the marker to show

b. Tape the PVC pipe to the marker so the tip remains in the center of the pipe:

c. Use this to trace the template circle:   

  **This should give you about an 8 ¼” diameter circle.

2.  Spray some oil on the location where you will drill a small starter hole - about ½” just inside the marked area for portal cut out.  This starter hole will be the location where you will next use the step bit to cut a large enough hole in the cage wall to accept the nibbler head.

3.  Get the electric drill and put the step bit in.  Make sure your drill and step bit are sized for each other.  Some of the shafts on the step bits are ½” or 3/8”.  A 3/8” drill will not accept a ½” shaft.  Check the drill size before purchasing your step drill.

4. Use lubricating oil during the hole drilling process with the step drill.  We found it best to team up and have one person spray lubricant for the duration of hole drilling while the other person drills the hole to the depth needed. 

  • Check the drilled hole size with the nibbler head to see if it will fit in.  
  • Stainless steel is hard- if you don’t use lubricating oil you will dull your step drill in a matter of a few holes – this is a huge bummer as they are expensive.  
  • With proper lubricant you should be able to get 50 or more holes drilled per step drill.  
  • Now you are ready for the nibbler   
  • Practice with the nibbler before cutting the first cage.   The nibbler likes to run a bit and without some direction it can kind of get away from a person – give it a little direction and it is pretty easy to cut with.   
  • Spray the circular mark you made for cutting with lubricating oil – this is very important!   
  • The orientation on the cutting head of the nibbler will be important to allow it to cut the circle without the tail end of the nibbler getting in the way.  Set up the nibbler such that the cutting head is straight upwards (perpendicular to the horizontalness of the nibbler when holding the head of the nibbler in your left hand and the tail in your right). 
  • If you are cutting the hole on the wall of the left of the cage - when holding the nibbler parallel to floor (tail in) the cutting portion will be face up and you will begin cutting upwards on the circular pattern.
  • If you are cutting on the right side of the cage wall the nibbler tail will be in but the cutting side will be face down and you will begin your cut in the downward direction on the circular pattern   
  • With proper lubrication our nibbler has cut over 50 cage walls (enough for 25 portals) without having to change the cutting punch

For additional information, watch the clip below:

5.  The circular cut does not have to be perfect - it can be a little bigger or a little smaller than the marked circle.  However it cannot be a lot bigger or a lot smaller - though a lot smaller will be much easier to fix; just recut to the size it is marked at.

6. Remove all the loose metal shards from the cage floor and wipe up any oil that is on the floor and wall

7. Clean the wall with alcohol and a paper towel.  Make sure there is no oil remaining on the wall.

8. Install the portal--follow the plasma saw directions.

Questions: email Dr. Denae Wager at