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What is Kerfing?
“Kerf” by definition means “width of a saw cut”. “Kerfing” is a term that many woodworkers have adopted to define the process of making several cuts within a piece of wood to achieve the removal of material. Often this removal of material will allow one to then bend the wood sheet material thus making a nice professional and appealing curve that can be incorporated into a project.

Kerfing and Car Audio:
What can Kerfing do for you in your quest of car audio domination? It is important to note that in any ported 
subwoofer box hard edges and corners should be avoided. Hard edges do not allow efficient air flow, this can result in less output and more port noise. Kerfing your port will allow you to maximize efficiency and create the most non-turbulent flow for the air moving in and out of the enclosure. 

 

Kerfing can also be used to make an enclosure or other part of your build more appealing to the eye. You could use it for corners of an amp rack, or to make a custom arm rest  of a center console. Kerfing is a great process to learn to take your builds to the next level. 

What you need:
This is outlined in the video but you will need the following (* items are not required, but recommended):

  • Circular Saw (Or table saw but the process will differ from the video)

    • Note: My Saw blade is 1/8” wide. I recommend the same width!

  • T-Square (Or table saw fence)

  • MDF

  • Wood Glue

  • Safety Glasses

  • Tape Measure

  • Marker/Pencil

  • Clamps

  • Fiberglass Resin*

  • Fiberglass Chop Mat*

  • Body Filler*

  • Sand Paper*

The Math:

I go through the math in the video but in case you are having a hard time understanding this should help. Please note this is used for slot porting applications so when I reference “diameter” I am NOT talking about a circular port, I am referring to the curve of the kerf if you were to look at it along its cross section.

 

  1. Determine diameter of your curve.

  2. Find the circumference of a circle at that diameter. 

  3. Take the circumference and divide by 4 for a 90 degree turn or 2 for a 180 degree turn. This will be the length of the Kerf curve.

  4. Record your value for the length of the kerf. This is how much material along your mdf “linearly” must be used to make your curved kerfed section. This is the value you want to “mark off’ for your kerf on the mdf. (Note that this method can also be used to find the “length” of this part of your port so that you can build your port to the target tuning length. Instead of using the diameter of your kerf arc, use the diameter of the arc that is the centerline of the port)

  5. Now that you have marked off where your kerf will be on the mdf you are going to take your “length of kerf value” and divide it by 12. This will give you your distance between cuts.

In the video I show a trick for making the divisions from step 5 above the perfect distance. This trick makes using a value like .6384 easy to use so you do not have to guess on a tape measure. My method is also much faster as it doesn’t require the math from step 5. Once you have marked out all the cuts you can proceed with cutting and making your kerfs!

Other Notes:

  • Do not apply screws in the curved section of the Kerf. It will likely split. Instead use clamps and wood glue.

  • If your blade is not 1/8" thick you will need to do some math to determine how many cuts to make. I generally remove an inch and a half of material, so if your blade is smaller, you will need more cuts, if wider, you will need less cuts. Note that fewer cuts will lead to a "rougher" curve.

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Kerf bend wood for use in subwoofer box ports or other curved features of a build!

Kerfing 101