Calculation Help

[Brian Riley]

Good Afternoon......

Most lumber yards sell their 1/4" stock based on square footage as opposed to board feet. After doing some research online in regards to a standard calculation for converting from SF to BF I'm even more confused. I'm trying to see if it's worth even buying the the stock at 1/4" thickness.

For instance what would the calculation be to figure out the total BF for 20 SF of 1/4" thick stock.

Different methods have provided different results.


Thanks,
Brian

[Steve Jenkins]

A board foot is one square foot 1" thick. I guess you could say that 20 sq. ft 1/4" thick is the same as 5 board ft. 20/4. Except it really isn't when you are talking about price. If you want to resaw and get your 1/4" pieces you will get no more than 3 pieces out of a 1" thick board, or less depending on the length and straightness of your stock.What are you using it for and how big are the pieces you need?

[Ted Shrader]

Brian -

A board foot is 144 cu in of wood.

Consider a 1" thick piece of wood (called 4/4), one foot long and 12" wide. Only thing is, the wood in this case is rough cut. By the time it is dressed (S4S) it is about ¾" x 11.5" x 1'. So iin your particular case with 1/4" thick (finished) wood, the rough size would be say 3/8" thick to allow enough for dressing the wood.

Let's take a perfect 1" thick board that can be resawn into three (vice four) pieces which can be dressed to ¼" final thickness. I recommend we change Steve's analysi to 20/3 so it works out to 6.67 bd ft ¼" thick stock. (At the very least.) Pratically you would need to resaw to ½" then dress. So now we are up to 10 bd ft for 20 sq ft.

Lots of variables. Lots of machining done to the wood. Hence $$$$.

Regards,
Ted

[Brian Riley]

Thanks guys......

I'm familiar with the board foot measurements, S2S, S4S, etc. and based on what both of you have said it appears I was on the right track with my initial calculation method.

.25" x 12" x 12" = .25 BF

I then took that .25 x the number of square feet and came up with the same basic answer.

.25 x 20 = 5 BF

From a pricing standpoint I was quoted about $85 for 20 SF (5 BF) of S2S 1/4" stock as opposed to $118 for 20 BF S2S 4/4" stock.

1 BF of 1/4" = $17
1 BF of 4/4" = $5.90

Think I'll go with the 4/4" and resaw it myself.....

Thanks again,
Brian

[Michael Perata]

Think I'll go with the 4/4" and resaw it myself.....

...and that's why we all have really nice bandsaws!!

[Chris Padilla]

Think I'll go with the 4/4" and resaw it myself.....

...and that's why we all have really nice bandsaws!!

....yeah, and mine is bigger than yours!

[Michael Perata]

..oh, yeah?

...oops, I forgot, you got a 20"

but at least I can use mine, 'cuz my shop is finished.

[Chris Padilla]

Ooooo....that was below the belt...that REALLY hurt, Mike...really hurt....

[Charles McKinley]

I believe that was a:
Gotcha

Point Michael.

[Bob Hovde]

Thanks guys......
Think I'll go with the 4/4" and resaw it myself.....

As noted above, you can't get four 1/4 boards out of a 4/4 board. Besides the kerf width, you have to take into account the jointer/planer waste. According to my lumber guy, most dimensioned/finished boards are cut fairly loosely and then planed to size to avoid twisting/cupping/etc. You have to pay for the waste. Doing it yourself is probably cheaper, but not as much as you calculated.

Bob

[Brian Riley]

Thanks Bob....

Yes, I understand in regards to the kerf, jointing, facing, planing, etc. I was just trying to come up with a ballpark figure. I realize there is no way I'd get (4) 1/4" boards from a 4/4" stock especially not knowing the thickness once they do the S2S. The calculation I did was based on figuring out a rough difference between the two......not really trying to come up with an exact figure that I'd be paying for the usable stock once I run it through the process.

Thanks again,
Brian