[OP]
Contributor
I've been wood working for years now and still, figuring out how much of what lumber I need to buy is a big ?. Is there a simple way for one to figure this out?
Here's a real-world example...I'm making a set of cabinet doors. They will be 2" wide rails and stiles, with 1/4" panels. I have 2 cases, each having openings of 25" x 31" and will take 2 doors for each case, with a total of 4 doors for the 2 cases. If I buy 1x rough lumber, how much will I need? Wow, just like my old math classes.
This will vary with your approach to making parts but, I read 10 to 15% spoil figures a lot. My "spoil" rate is higher as I select the figure I am after in the part and make the blank out of that. This is often not right along the edge and the next place in line.
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I have no issue with this as I probably consume the majority of my spoil in other projects.
Scrap Trivet (11).jpg
We have all seen commercial cabinets that are made with whatever the next piece on the stack happened to yield; straight grain on one stile and cathedrals on the opposite stile, panel glue-ups of mismatched boards and that sort of thing. there is less spoil using that method but, the piece suffers aesthetically.
"A hen is only an egg's way of making another egg".
– Samuel Butler
Member
Figure out the board foot calculation of your project parts and that should give you the amount you need and then add a % of spoil like Glen mentions. That percentage may be less if your using FAS graded material. It also doesn't hurt to have enough to make an extra component in case a mistake happens.
[OP]
Contributor
How do I figure out the board foot calculation? Ya...lazy to ask, but I"m here, so...Originally Posted by Bryan Lisowski
Moderator
1 board foot = 144 cubic inches. That's 12"x12"x1" for 4/4 material...adjust for different thicknesses and then divide by 144 to get the number of board feet after you do rough sizes for your required components. So a table top, for example, that's made of 8/4 material, is 5' long and 2.5' wide would be: 60x30x2=3600/144= 25 board feet of 8/4 material. I always buy a lot more than I need, even above a typical 25%. The nature of the species makes a difference, too. Really clear and clean material has better yield than material that has more defects you need or want to keep out of the project.
--
The most expensive tool is the one you buy "cheaply" and often...
Contributor
I think the amount of waste will depend on how the lengths you buy compare to the lengths you need so buying based on board feet may not work. For example if you need 25" lengths and you buy 8' (96") lengths you will only get 3 pieces per board (3 x 25=75) and 21" offcuts. I think you need to look at each board and estimate how many pieces you can get from it and then add one or two extra boards to allow for miscuts, defects and grain matching. With your case of a total of 4 doors, that should not be too difficult.
Note the required width can affect waste also. If you buy 6" wide boards and you need 4" wide your waste just based on ripping to width is 33%.
Last edited by Doug Garson; 06-30-2018 at 12:22 PM.
Contributor
For the example you cited, with allowance for waste, you would need about 10 lineal feet for the stiles and about 5 lineal feet for the rails. If you are getting 1x6 stock, that would be about 7.5 board feet. Round up to 8 board feet to be on the safe side, allowing for end checking, figure matching, etc.
-- Jim
Use the right tool for the job.
There is no hard and fast rule for this. As others have mentioned it depends on your amount of waste and other factors such as your desire to grain and/or color match as perfectly as possible. If you are working around knots or defects in the wood then you will need more. I use an optimizer program that I can enter the sizes of the pieces needed and the size of stock and it will optimize the cuts so that waste is minimized. I can also enter phony amounts of materials and it will then show me how much to buy. I can use it to cut smaller pieces out of wider boards. I generally buy 5-10% more than I need as mistakes happen and it gives me flexibility to grain and color match.
Lee Schierer
USNA '71
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If calculating the # of board ft in a board, I find it easier sometimes to measure the length in ft and the width in inches. In this case,
bdft = length (ft) times width (inches) times thickness (inches) divided by 12.
But to me figuring the board ft needed doesn't help that much since there may be a lot of waste if I don't plan carefully. If I know I can get 6" and 8" wide stock, for example, I like to figure how things are going to fit before buying the lumber. Sometimes I used CAD, especially good for sheet goods. (Or I used to. Since I took up woodturning I've built very little furniture or cabinets.)
JKJ
Contributor
If you used SketchUp to draw your projects, CutList would output a cut list with the dimensions and required number of every part, tell you how many BF of each thickness is needed, and even lay out the parts on the wood of your choice. Same for plywood. This is completely unnecessary for small projects but a huge help with large ones.
As far as how much extra lumber to buy, I usually buy about 25% more. It may go unused for awhile, but it never goes bad.
John
Contributor
Unless you have limited room or are on a tight budget I always buy plenty of extra. I'm always finding a small project that I'll do for fun with the wood I have laying around. Just last month I made a bunch of 1 1/2" buttons for my sister. Never would I have thought that about making a button until she asked but it was fun. She started making scarfs that used one large button so I got to use some of the very interesting but too small pieces of wood I just couldn't throw into the wood stove. Since there was only one needed per scarf I could use multiple species of wood and each one could be different. With a new lathe coming I'm going to revisit making buttons as I can do more to the face.
Moderator
I actually way-over-buy since I'm anal about matching grain and color and that sometimes means cutting a component out "not" parallel to the original board's edges. That's easy to do with a slider, but also doable with a track saw, at least for getting that first edge lined up the way one wants it. But one can, theoretically, do a rough calculation of board feet required, using whatever version of the formula is convenient for them, by doing take-offs from plans or from sketches on the back of napkins.And then add a good percentage for waste, mistakes and other things.
--
The most expensive tool is the one you buy "cheaply" and often...
Contributor
When I find really nice wood at a sensible price I buy all that I can, with "can" being defined by how big a check I can write without incurring seriously raised eyebrows, the size of my truck, or, most often, by what's available from the supplier. I have only ever regretted leaving nice boards behind, not buying too much. If you can buy the sequential boards from a log that is great for being able to bookmatch or do more subtle symmetry, as well as for consistency across larger projects. Pricing is often better as quantities go up as well.
I'd hate to be stuck with the vagaries of what happened to be available at the yard or mill on any given day I wanted to start a project. Having the wood well-equolibrated to the shop environment is also a benefit.
Most everything I do is maple and cherry, generally with lots of figure. If I had to stock 20 different kinds of wood the stockpile strategy wouldn't work so well.
[OP]
Contributor
Don't know why this is such a confusing thing to wrap my head around...the board feet thing. From what all you've said, it sounds like I should figure the BF for each part, then add up the parts BF, add some for waste and oopses, then buy that amount of BF?
(Length x Width x thickness)/144 inches per BF. Is that right?
So a board that is (2" x 25" x 3/4")/144 = .26BF? Why doesn't that look right to me?
Contributor
At the yard, BF is computed on rough dimensions. That 3/4 surfaced board started out as 4/4 stock, so that particular piece would be about .35 BF. However, as others have noted, you cannot base your purchases on cubic volume alone - any project will have length & width requirements as well.
-- Jim
Use the right tool for the job.
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