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Hello,
is there an easy way to figure out how many BF you will need to buy if the plans only give you finished dimension? The obvious answer is to add up all the length, widths and thickness.... and a little for kerf, jointing, planing etc....
best regards,
patrick
On the thickness, I usually round up to 4/4 or 8/4. At first I used to try to calculate the BF as close as possible to the actual dimensions. However, I usually now want flexibility on grain selection and extra stock for mistakes - er - design changes midstream; so I just ball park it and add another 10-25%.
A lot depends upon the lumber you buy. If you need 7" wide pieces, but buy 12" wide stock then your yield will be terrible unless you are OK with the look of gluing up some narrower widths. I try to find stock about 1" wider than the widths I need, up to the 10" width of my jointer, or stock that is 1" wider than some multiple of narrower widths. It's flatness dependent, but you will almost always lose at least 1/8" on thickness, often double that. All said and done, I plan on at least 20% extra if I can match the boards to the project, otherwise I figure at least 25% extra.
John
I think that the 25% extra is a good starting point. I always plan for extra due to "design changes", grain issues and warpage. It also depends on the source of your wood. I typically buy a couple hundred board feet of red oak at a time. When I have a project, I lay out the boards and mark with chalk what I can get out of the boards and where there are defects. Of course, it is a little different if you are buying clear wood at a big box store.
I was absolutely amazed at the big box store as they had a couple of pieces of red oak that were 12" wide and 16 feet long that were absolutely clear. They must have come from one amazing tree. Yes, it was priced over $100 but was pretty.
If I am cutting narrow pieces rail and stile doors, I plan extra because as I cut some pieces from larger ones, you can always get some pieces that suddenly are twisted or bowed.