Help with my kerf cuts please.

[Jessica]

So, i want to just cut this wall from one solid piece, it will be 12.5 X whatever. Not sure on that.

What i want to know is, where the first and last cut should be on each kerf using the dimensions in the pic below.

edit: the actual box is 34w X 22D

I think there is enough info to figure it out, but i don't know. If you guys have a easier method that i could use just tell me.

I just would like to be able to reproduce whatever you recommend into sketchup so i can check the volume when i am done.

[sprkn_ranger]

Take the circumference of the 6" diameter circle and divide that by 4 (because the 90 degree bend is 1/4th of a full circle) and then that will give you the distance between the first and last cuts.

Edit- I just saw that the inside of the kerf'ed bend is a tad under 2", and that is the dimension you want to find the circumference for. And I would just round it up to 2" to make it easy on you.

[ear2ear]

The o.s. radius of the kerf is 3".

The circumference of a 6" diameter circle is 18.849"

Your 90 degree bend is 1/4 of a full circle

18.849 / 4 = 4.71"

So your total piece is:

19" + 4.71" + 28" + 4.71" + 19" = 75.42"

[sprkn_ranger]

The o.s. radius of the kerf is 3".

The circumference of a 6" diameter circle is 18.849"

Your 90 degree bend is 1/4 of a full circle

18.849 / 4 = 4.71"

So your total piece is:

19" + 4.71" + 28" + 4.71" + 19" = 75.42"

Well you want to get the circumference of the side you are going to be cutting the kerfs into, not the outside...I almost missed that as well

[Jessica]

So 19+3+28+3+19?

I just have to get it pretty close, I mean, i've kerfed before so i know i can tweak it a bit to make it work.

[n8ball2013]

the easiest way to pull that off is to also not try to work with the precise lenght you want. Get your kerf right and match up your radius then put your back baffle on and flush trim it with a router. That way you wont have to worry so much about being off on your calculations. AS long as you can get the radius you are after right. Takes out one more factor

[ear2ear]

The o.s. radius of the kerf is 3".

The circumference of a 6" diameter circle is 18.849"

Your 90 degree bend is 1/4 of a full circle

18.849 / 4 = 4.71"

So your total piece is:

19" + 4.71" + 28" + 4.71" + 19" = 75.42"

Well you want to get the circumference of the side you are going to be cutting the kerfs into, not the outside...I almost missed that as well

Sorry buddy, that's wrong.

Think about how a kerf works. The outside stays smooth and untouched. You remove material from the inside surface so that it can collapse on itself.

By what you're saying you cut the material for length of the inside radius and have to STRETCH the outside radius.

That is not the case.

Use the outside radius for the calculation.

[Jessica]

I guess once i get the first cut done, the second one should explain itself once i lay the board down on the bottom sheet. I could cut the board longer than i need and trim off excess.

Then like nate said, get it glued together and router the top and bottom baffles with a flush trim bit to make them match.

[ear2ear]

Exactly. I would cut the board @ 78".

The most important part becomes centering the 28" portion and then cutting kerfs 4.71" either direction.

Trim to length later.

[Jessica]

ok, i think i can figure that out that way. I planned on cutting the full 8ft at 12.5 anyway. Thanks for the help everyone.