Once I've jointed an edge, I'd like to know that there are no hills or
valleys in the edge over the length of the board. For example, it's
hard for me to know if there's a concavity a 16th deep if it's spread
out over half of an 8' board. How can I tell how straight an 8' edge is
without an 8' straightedge?
Buy a long straight edge, but then you are subject to the slave labor in
china that makes the straight edge. Or do as the rest of us do, sight down
your jointed edge to check. Also place against the other piece to be joined
and you'll see any problems.
Radial Arm Saw Forum: http://forums.delphiforums.com/woodbutcher/start
Often, you can just sight down it with a practiced eye, Or, lacking that,
there is generally a surface in your shop that is "flat" (a relative term),
i.e, your table saw top, a bench top made "flat" (a relative term) for the
purpose, a wing of a jointer, a factory cut plywood edge, etc, that can be
used for comparison.
Flat enough is relative, and generally perfect enough for woodworking.
Sighting down the board is probably the easiest method, although not
quantitative. Winding sticks are also useful. You could also use a
laser. A board can be out-of-whack in other ways too: cup, bow,
crook, and twist. A well-tuned long-bed jointer should give you a
: Once I've jointed an edge, I'd like to know that there are no hills or
: valleys in the edge over the length of the board. For example, it's
: hard for me to know if there's a concavity a 16th deep if it's spread
: out over half of an 8' board. How can I tell how straight an 8' edge is
: without an 8' straightedge?
A very sensitive spirit level will do the trick.
Jeff Gorman, West Yorkshire, UK
Email: username is amgron
On Sun, 12 Dec 2004 07:55:33 -0000, "POP_Server=pop.clara.net"
That is the most accurate. This is how they make those huge machines
flat. It takes longer than other methods, but works. Just use a level
that is calibrated and write down the numbers as you move it along.
Once you have a good straight board, keep it upright in a dry area to
use as your standard. Check it once in awhile.
BTW, you can also plot a large panel this way.
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