Making a straigtedge

[Robert Hazelwood]

The stick is 2-1/2" wide. On edge it should be stiff enough to get flat held in most any sort of vice. The last bit of fine tuning work should be done with very thin shavings and light pressure. The workmate is probably better at supporting this than most bench vises due to its length, and if you really want to be OCD you can shim the clamping boards with paper if they aren't perfectly straight.

[Aaron Rosenthal]

I want to thank everyone who pointed me in the right direction.
I came from Construction - string lines are part of my basic credo - and I forgot to see that way of truing the edge! Doh!
After all the instruction, I got out some fishing line (please don't ask me the strength) and a push pin, saw graphically where the concave section began and planed both ends until the line just kissed the wood along it's entire length.
Checked again with my little double square for the face for square.
For those who need to know, I used my Veritas #5 1/4 with the blade set for light shavings.
Again, thank you all.

[James Waldron]

I wont argue that Charlesworth begins with machined lumber but I will take issue with your conjecture that he relieves the woodworker of thought or judgement. If you watch him work an edge, you’ll see a carefully thought out and very efficient method of working it. It’s the opposite of an automatic or mindless procedure. In fact, the precision of his method is what I would use to make a straightedge hands down.

[snip]

I"ll go with Warren. I think you misunderstand his post. His point does not refer to "machined lumber" but rather to "machine tool thinking."

Machine tool thinking, i.e. Charlesworth, relys entirely on the sole of the plane to attain a straight and flat surface. In fact, it can get substantially there if sorting out a concave surface but it may take quite a while and shave off quite a lot of the workpiece to get there, as each full-length pass in a long piece cuts some in the center of the piece as well as the higher ends - because the plane can't span the entire length of the edge. Moreover, the Charlesworth technique will never flatten a convex workpiece because the plane will simply "roll" over the central hump and still be cutting the lower ends as well. Neither case is "efficient." Full length passes are inherently less effiicient than more targeted, short passes limited to the high spots.

It's important to keep in mind that full length shavings on long pieces do not equate to flat or straight surfaces. Woodworking would be a lot easier for all of us if that were true.

[Tony Wilkins]

I"ll go with Warren. I think you misunderstand his post. His point does not refer to "machined lumber" but rather to "machine tool thinking."

Machine tool thinking, i.e. Charlesworth, relys entirely on the sole of the plane to attain a straight and flat surface. In fact, it can get substantially there if sorting out a concave surface but it may take quite a while and shave off quite a lot of the workpiece to get there, as each full-length pass in a long piece cuts some in the center of the piece as well as the higher ends - because the plane can't span the entire length of the edge. Moreover, the Charlesworth technique will never flatten a convex workpiece because the plane will simply "roll" over the central hump and still be cutting the lower ends as well. Neither case is "efficient." Full length passes are inherently less effiicient than more targeted, short passes limited to the high spots.

It's important to keep in mind that full length shavings on long pieces do not equate to flat or straight surfaces. Woodworking would be a lot easier for all of us if that were true.

I understood. I mentioned machines in that his technique is based on starting with a machined board and getting to the last bit of flat. It isn’t a technique for taking lumber all the way from rough. Your points seem to suggest processing rough lumber. Your point on convex sides seems to suggest traversing, correct? I’ve never seen him traverse. In fact, his process is designed to turn convex into a minute concave.

eta: I use his method on rough lumber but only after I’ve used other techniques to get it close first.

[Robert Hazelwood]

I"ll go with Warren. I think you misunderstand his post. His point does not refer to "machined lumber" but rather to "machine tool thinking."

Machine tool thinking, i.e. Charlesworth, relys entirely on the sole of the plane to attain a straight and flat surface. In fact, it can get substantially there if sorting out a concave surface but it may take quite a while and shave off quite a lot of the workpiece to get there, as each full-length pass in a long piece cuts some in the center of the piece as well as the higher ends - because the plane can't span the entire length of the edge. Moreover, the Charlesworth technique will never flatten a convex workpiece because the plane will simply "roll" over the central hump and still be cutting the lower ends as well. Neither case is "efficient." Full length passes are inherently less effiicient than more targeted, short passes limited to the high spots.

It's important to keep in mind that full length shavings on long pieces do not equate to flat or straight surfaces. Woodworking would be a lot easier for all of us if that were true.

I'll argue that full length shavings do indicate that the surface is not significantly concave, unless the workpiece is very long relative to the plane.

You have the wrong idea of Charlesworth's technique. His idea is that taking continuous shavings along an edge will tend to produce a surface that is slightly convex- in fact I think he goes as far as to say it's impossible not to do this. I don't necessarily agree, but it's certainly easy to do and a very common issue. His remedy is to take stopped shavings until the plane stops cutting- in other words, planing only the central hump and not the low ends. When the plane stops cutting, you will have a slightly concave surface. Then you take one or two continuous shavings to diminish the concavity and clean up the surface, and you should have an edge that is perfectly straight or very minutely concave, which is usually acceptable.

When we're talking about planing an edge of a length typically encountered in furniture making, say 4' long or less, I would probably not take "targeted" shavings if the surface was concave (unless we are talking about something very rough). It seems more efficient to just plane straight through rather than picking the plane up twice every pass. If you're using a jointer plane, the length of sole *will* keep you from planing the bottom of the hollow until that hollow is very tiny- it's why they make them so long. On most panel glue-ups even a #4 will not permit much of a hollow to be planed in. So when working down a concave edge I would just take through strokes until I get a continuous shaving, and at that point it is going to be flat or extremely close. I don't know if this is machine-tool thinking, it just seems like utilizing the properties of the tool.

Of course if I am starting with a convex edge, I will just plane the center to start, as planing the ends will be counterproductive. When the plane can no longer cut in the middle, I know I am just a bit hollow now and can take a continuous shaving. It's a good way of knowing where to stop without having to pick up a straightedge every few passes.

The real trick is to keep a straight edge straight, such as when you need to fine tune the squareness of an edge you've already straightened. If you can't avoid making it convex while doing this, then you will have an annoying fit of back and forth to deal with. I believe you can keep an edge straight with good technique and proper tool setup.