Math and Edge to End Grain Conversion? - missing an inch.

[Patrick Irish]

I used this cutting board template site http://ofb.net/~uranium/cbdjs/cb.html and it initially had my board at 19" but then I put in I guess more accurate dimensions and my final board was to be 17 7/8 with 1/8" of left over.

Well.... my board is 16 5/8 long and I have an 11/16" piece of left over. Not sure what happened. It's not a huge deal as it was random board I made and I can add strips to make it long BUT I'd sure like to know where I went wrong.

Edge Grain board started out as 17 13/16 and was 1 5/8 thick. When going edge to end grain, the thickness of the edge grain board becomes width of the strips for the End Grain, right? Height of the END GRAIN board is determined by the THICKNESS the strips of edge grain board is cut. I chose 1.5"

Used a full kerf blade.

According to the site, I should be 17 7/8. But I'm 16 5/8. Can anyone explain that too me? I'm sure my math is off somehow.

Link to the cutting board layout site with my numbers. Only the length and thickness I entered.

http://ofb.net/~uranium/cbdjs/cb.html

[John K Jordan]

I don't see the numbers you indicate on the link, but I'm a bit confused - can't you just use calipers and measure the 12 pieces of the actual finished end grain board and see why they add up to a little less? Seems like the edge grain board might have been finished planed to a little less than than planned.

JKJ

[Andrew Pitonyak]

First, I considered ONLY the walnut. The bottom most table tells me that I have two 1" wide strips and three 1/4" strips. To get these, I will make 5 rip cuts. This means that I will lose 0.625" to rip cuts so my board will now be 3.375" narrower than when I started. At least, that is what the math suggests to me. These values agree with what I see on the page.

It looks like you need 12 rectangles from each of the two patterns. If you make 12 of these cross cuts, you lose 1.5" based on the saw kerf. If I understand correctly, each cross grain cut produces a piece that is 1.5" long. If there are 6 in each row, that produces 9" for each row. Oh, wait, this assumes that you do not have end grain facing up.... If end grain is facing up, does that mean that the total length is the original board thickness (1.2" was it) times 6?

Clearly I have no idea what you are doing here.... :mad:

Sorry....

[Patrick Irish]

Well I think I figured it out. For starters, I think that website is wrong. I don't think it calculates the total kerf of wood lost correctly.

My #1 board (edge grain) was 17 5/8 x 1 5/8 thick. The width of the board is irrelevant for this discussion. If I want board #2 (end grain) to be 1 1/2" thick then I divide 17 5/8" by 1 1/2" and get = 11 3/4" which is tecninically saying I can cut 11 strips at 1.5" thick BUT BUT not so fast. Dont forget the kerf.

That's 11 cuts x 1/8" (kerf) = 1 3/8"

That 1 3/8" needs to be subtracted FIRST then divide the 1.5" into it.

So now board #1 (edge grain) 17 5/8 - 1 3/8" = 16.25" total length of useable wood. 16.25 / 1.5" = 10.833 number of 1.5" strips I can cut. Well only 10 are usable so the .8333 left over is total loss.

I now have 10 strips of 1.5" x 1.625".

10 x 1.625 = (1.625 is now my width in order for the end grain to point upwards) and that equals 16.25" which is where I'm at.

I thought for a second I lost a strip I just cut but nope, it's all there.