43 - Build Your Own Dovetail Jig, страница 31
LUMBERYARD cost. The thing to be aware of is that "Select" pine is considerably more expensive than "Common." So if you want to build a project out of clear pine, you may be surprised to find that it ends up costing as much as one made of oak or walnut. The solution is simple. For the short pieces of a project, buy "Common" boards and cut around the knots. Buy "Select" only when you need long pieces. DEFECTS Besides working around the knots, there are also some defects that you'll want to avoid. loose knots. Loose knots are easy to recognize, see photo 'A' below. They slide back and forth in the knothole. And in time they're likely to fall out, leaving a hole in your project. If the loose knots fly out when you're cutting or routing a |board, they can be dangerous as well. A. Loose Knots. A black ring around a knot is a sign that a knot will loosen up over time. B. Pitch Pockets. These slits ooze sap which gums up saw blades and creates finishing problems. 'C. Pith. It's the very core of the tree. But you'll find it much too soft to sand and finish. D. Wide Growth Rings. It means a tree has grown fast. But at the cost of strength and appearance. < Common. A board that has one of the common grades has more knots, but it still has plenty of usable lumber. ■< Select. Expect to find clear-grained lumber with few (if any) knots on a board assigned one of the Select grades. pitch pockets. Another defect to steer clear of is pitch pockets, see photo 'B.' These are slits in the board that ooze sap. The sap gums up saw blades and router bits. And it can bleed through a finish long after the project is completed. pith. On some boards, the pith (core) of the tree runs lengthwise down the center, see photo 'C.' It's so soft you can dig it out with your fingernail — too soft to sand or finish. But there's usually straight-grained wood on each side of the pith. So if you're making narrow rails or stiles, cut out the pith to get the usable lumber. wide growth rings. One final note. Some boards have growth rings that are extremely far apart, see photo 'D.' This is the result of a tree that has grown too rapidly. These boards tend to be a bit punky, so they're not as strong. And I find the grain pattern is less desirable. & Tips on Selecting PineIBuy Common. For small projects, buy common boards and cut around the knots. Buy select only if you need long, clear pieces. 2 Avoid Loose Knots. A saw blade can fling loose knots out of the board. And they may fall out of a project after assembly. 3 Pitch Pockets. The oozing sap in pitch pockets will gum up blades and bits. And it can bleed through a finish long after it dries. 4 Pith. Cut out the pith that runs lengthwise down the center of a board to take advantage of straight-grained wood on each side. 5 Wide Growth Rings. Steer clear of wide growth rings produced by fast growing trees. It reduces the strength of the lumber. 6 Check Grade Stamps. If it's difficult to identify the type of pine by the grain, the grade stamps provide useful clues. - r No. 43 ShopNotes 31 |
