enclosure building- kerf math?

[jlund10]

I've watched a couple videos and tried out 90 degree kerf bending, the actual cutting technique makes perfect sense to me.
I also understand that in order to get a 3 inch radius, I need 9 inches of total kerf length

what I don't get is how to factor the kerf bend into the length of material I need to cut.
If I were building a normal slot port enclosure, I would have my baffle length of 25.75" and my first port wall length of 9.5 inches.

Now if i want to make a kerf port to this same size does that mean I would simply add the length of 25.75+9.5" and kerf a 35.25" long piece?
Secondly where do i begin the kerf? would it be right where the baffle would normally end or before it.


Thanks for the help. there are a lot of youtube vids explaining how to cut a kerf( the easy part) but it seems no one wants to share the secret to the planning behind it.

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[Popwarhomie 5,000+ posts]

Kerfing 101 - How to Kerf MDF for curved port applications!

Kerfing 101- UNDER CONSTRUCTION What is Kerfing? “Kerf” by definition means “width of a saw cut”. This is the width of the actual saw tooth itself as opposed to the width of the blade as a saw tooth flares out and away from a blade. “Kerfing” is a term that many woodworkers have adopted to...

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[SlugButter]

I do mine the wrong way. I start the first part of assembly with the kerfed piece. I cut the piece longer than I need, glue it and screw it, then i table saw it off, or use my router. I never did figure out exact math on how to have it land exactly where I want.

 

[jlund10]

I do mine the wrong way. I start the first part of assembly with the kerfed piece. I cut the piece longer than I need, glue it and screw it, then i table saw it off, or use my router. I never did figure out exact math on how to have it land exactly where I want.

so you’re saying you cut out the bottom piece and mount the kerf part to it first?

Tablesaws must make life so much easier

 

[SlugButter]

so you’re saying you cut out the bottom piece and mount the kerf part to it first?

Tablesaws must make life so much easier

Yep. I’ve tried to do accurate measurements, but it changes depending on how much you round over the kerf corner. I can get it close enough that I can adjust the curve and make it fit, but it’s just easier to do the curve how I want and just cut it off.

 

[SlugButter]

And you need to start your kerf cuts before where you would normally end your baffle. You have to curve it into where your baffle would normally end at the port piece. It kinda depends on how sharp of a curve you want. You have to cut closer together to get a sharper curve. Ive done a few kerfs, but I’m no expert at it. The inside of my kerfs usually end up with some fiberglass fill, since I find it easier to take out more than I actually need, curve it how I want, and fill it with glass. It may be the amateur method, but it works.

 

[GTSQ]

You figure the circumference of your radius then divide by 4 for 90 degrees 8 for 45 degrees. That will give you the length of the kerf. Example: 2 inch radius is a 4 inch dia. circle. The circumference of a 4” circle is 12 9/16. Divided by 4 (90deg) is 3 1/8”.
Or you could just use the kerf calculator on the Ultimate Car Audio App.

 

[jlund10]

You figure the circumference of your radius then divide by 4 for 90 degrees 8 for 45 degrees. That will give you the length of the kerf. Example: 2 inch radius is a 4 inch dia. circle. The circumference of a 4” circle is 12 9/16. Divided by 4 (90deg) is 3 1/8”.
Or you could just use the kerf calculator on the Ultimate Car Audio App.

Thanks. does this mean in order to cut my baffle and port to line up perfectly, I just need to use this equation and add it to the total length?

 

[GTSQ]

Thanks. does this mean in order to cut my baffle and port to line up perfectly, I just need to use this equation and add it to the total length?

it should if you are 90 deg. I would do a mock up out of cardboard or something first.