Stair Treads
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This page documents the construction of the extremely custom birdseye maple "rounded" stair treads

Here is the objective:  Create stair treads that integrate with the birdseye maple flooring and deliver the contemporary, curvy, underwater feel that goes with the theme.  No classical architecture allowed!  Since these would no doubt be a focal point, the glue line between the tread and the mitered return (The side of the tread where you would otherwise see end grain) must be perfect.  The usual ways of doing this are extremely inaccurate, so I decided to devise my own using a router and jig.
First, each tread was glued up from a single board that was purchased "in the raw".  By milling and jointing the boards myself, I could control how the grain was matched and where on the finished tread the natural variations in the wood would show up.  I don't have any pictures of that, but here's one of the enormous pile of shavings that was created by taking the 1" wood down to the 3/4" after gluing.
Next, the tread was mitered to receive the "return" on the side so that no end grain is seen.  Obviously, doing these two cuts on a tablesaw is dicey since the circular saw blade cuts further into the wood near the table than at the top.  The standard way around this is to cut as much as possible on a table saw and then finish the cut by hand.  the result is usually less than perfect, and for this reason the modern stair parts mills use routers (or shapers).  You can spot this in a stair tread by examining how "sharp" the two cuts intersect.  Is there a radius to the intersection?  I decided that a tight joint with a small radius is better than the classical - but sloppy - sharply intersecting cuts done with a handsaw.
Not having the computer controlled routing machines that the factories have, I used instead a router "collar" (it's that brass ring mounted in the base around the shank of the bit.  Click to enlarge the picture if you need to)  This particular one is perfectly matched to the router bit.  The collar rubs on a pattern clamped to a piece of wood, and the bit cuts the wood to match perfectly.  All that's needed to make two perfectly joining pieces of wood are two perfectly joining jigs to act as patterns: 
Here's the first one, laying on top of a tread that is already glued.
And here's the jig for the mating returns.  These two boards are used to create all of the treads and returns ready for gluing 
Here is a tread and return clamped up while the glue sets.  You can clearly see (because of the glue) the mitered piece on even the back of the tread return.  What a detail!
When the tread is sanded the glue line disappears.  This is the general shape that almost all treads have before they get rounded over on the front and side (called "nosing")
Instead, I created an ellipse to treat the end with.  The really, really astute reader would notice that my returns looked way too wide - this was on purpose to accommodate the curve.
A couple of passes with the router and we have a pretty nicely shaped tread.
I had a single casualty with the router when I hit a weak spot on the wood.  It broke so cleanly that the line was completely invisible when the two halves were pressed lightly together.  I glued and clamped it back together and I can't find the line today.
After rounding over top and bottom to create the nosing, this is the result.
Indecently, we nicknamed this controversial tread the "Swordfish Step" because of the twin dark streaks running across.  Do you know that dark area that you sometimes get in swordfish steaks...?.  The board that we used had a boring light side, but I thought this side was far more interesting
Here's the swordfish step as it is today.


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