Hello All, long time lurker, rare poster with a question:
I like to build my own designs and so consequently don’t often have a pre-made estimate of how much stock I’ll need for a given project. Since money for wood is always a little tight, I’m curious how others determine how many boards of a certain width, thickness, etc, are needed to complete the project. Since I don’t know in advance what width boards I’ll find at the hardwood store, it’s difficult to do some kind of layout like you can do with sheet goods. Is there some kind of estimation trick that can be used with the finished sizes of the project parts or ?
Any suggestions much appreciated.
Replies
Hi JKling , Typically hardwood is ordered by the board foot , not by the piece . Much hardwood comes in random widths and sometimes random lengths. Figure your square footage of stock based on the job at hand . The species you are using will have a varying waste factor of perhaps 10 to 35 % based on the grade you buy and the cuts you need . It is very challenging to try and only buy exactly what you need , having a little cushion is a good idea , just in case the waste runs higher or you make some mistakes .
good luck dusty
Thanks Dusty,I understand I'm not going to be able to make it exact for the reasons you listed. I am fortunate in that I've got a pretty good hardwood store in town and can go there and pick through their stock to buy what I need, so I don't have to just order so many board feet from a supplier sight unseen. What I guess I'm getting at is, what's the formula, if there is one, for making a 'reasonable' estimate on how many boards to purchase. If I'm understanding you correctly the idea is to figure out the board feet needed based the dimensions of the various pieces and then add a 20 - 30% margin to that for waste and needing a 30" piece and having only two 15" pieces left over from the boards. I would assume that if the stock is shorter (8' lengths vs 12' lengths) that I'd need to err more on the liberal side. Thanks again for the info.
JKling ,
Maybe you could actually make a cut list and try to select the width boards that will give you the best yield . For example if you need some boards 4 1/2" wide , 5 " plus up to say 10" you would have less waste then say an 8" board . By all means if they let you select based on yield . You may end up needing 4 - 4 1/2" X 10' and say 8 pieces 2 1/2" X 10' . These will be the net sizes needed for your job , you will need a bit wider pieces to start with or a combination that will work .
Take your cutlist to the supplier and they may help you select the right amount . But yes I calculate the square footage and add the waste to the total tally based on the specie you are using .
good luck dusty
Here's an extract from one of my scribblings that might help. Slainte.
Timber Buying.
Waste allowance varies from species to species, and the form in which the timber is sold is also a factor. Waney edged boards are always more wasteful than square edged stock, and there are always faults in timber that can’t be used It’s also necessary to cut pieces about 100 mm longer than required to allow for planer snipe and other machining faults at the beginning and end of each board.
I usually calculate the volume of timber required for a job as follows.
Estimate the rough sawn board requirement that will yield the finished dimensions. For example, ten pieces at a finished size of 800 mm X 44 X 18 (31-1/2" X 1- 3/4" X 3/4") will come out of ten pieces of rough timber 36” X 2” X 1” = ~0.42 cubic feet (5 BF in US). Using this method you allow an additional waste factor even though you've calculated using rough sawn board sizes. Waney edged English oak has an additional waste factor of about 100%, so price for 0.8 cubic feet (US 10 BF). As examples of typical additional waste factors use 50% for walnut, cherry 30%, and poplar 20%.
A second method people use is to calculate exact finished sizes with a percentage added for waste, but it can be seen that the waste factor allowance must be higher-- in my experience about double the factors suggested in the first method.
Richard Jones Furniture
The tough part is estimating the waste or the amount of extra material you will need to purchase. In my experience I might have 10% waste if the material is plywood or similar sheet material or if the product is utility grade such as rough shelves in a shed. For furniture in hardwood I typically see 50% to 100% waste, toward the higher end if figure is important and it often is.
When milling, first get out the larger pieces and the parts that must look good. To get more yield from a rough board, rip with a bandsaw or jigsaw instead of a table saw.
Ed
All of the above are good ideas, but it also depends on the project, the wood type, the effect you are looking for and your lumber supplier. If the project is not too involved or big, and your supplier is indulgent, you could make full size patterns of the parts out of craft paper or cardboard and then lay them out on the boards for best yield or figure or match, allowing 1" on all sides for cutting and trimming. Few of us have that option though. the most you can do normally is to work up a cut list of all pieces and maybe note any special pieces that need to match or have some intersting figure ( like drawer fronts), again, allow a minimum of 1" on all sides, and then go down to the lumber yard with the list and a tape measure and go thru the boards and see what you can come up with.
This method may require you to go back and get more lumber, if you find faults in the boards when milling, make a mistake in cutting or just plain forgot something. If you know what widths and lengths he generally stocks, you could do some layouts on paper to come up with the least waste before going down also.
start building it on paper, labelling parts, determining pieces at sizes. Then go shopping. Then update the cutting list to reflect what you have and where you are going to cut it out of hte planks you've got.
THis helps you determine the order of operatons as well, so that you can streamline and speed up the roughing aspects of the work to be more efficient. (I mean, really, who actually enjoys using the planer for 8 hours?)
The older I get, the better I was....
This forum post is now archived. Commenting has been disabled