Problem:
My friend needs to carve solid blocks of oak into curved, twisting handrail sections in order to finish a staircase for a client. Ok. Here we go.
After slogging through a sixty year old handbook written by a master Italian rail carver from San Francisco, making extremely accurate measurements of the staircase, studying everything I could on the internet about his system (called the
tangent handrail method), brushing up on my plane and solid geometry, and drawing for four days straight, we ended up with this drawing on a full sheet of MDF (4 ft x 8 ft plus a little) which would (theoretically) accurately describe the three dimensional shape of a curved handrail if it were projected onto flat surface, like a block of wood.:
So, ok, next we glued up a big ol hunk of MDF to practice our carving and test our layout on. The THM gives you a big crescent shape, called the face mold, and some accurate angles that will eventually create the twist in the section, which you can see here on our practice block:
We make our first cuts with a big chop saw:
and proceed to laying out our guidelines on the actual block. This picture shows the first position of the face mold, the bevels (the profile of the handrail where it straightens out into a flat rake section instead of the curve), and the outside edge of the block that we will carve the section out of:
This picture shows the face mold slid into a position that describes the inside edge of the block, which is the top of the handrail projected onto the surface of our block. This part was really tricky, as there are different ways these angles can be transferred onto the block to give you steep rise/slow rise and L/R handrail shapes.
We square the edges of the pattern through the block and cut out this shape, called a "blank", with a bandsaw. We had to build tables and get a heavy duty blade to make the cut, the block probably weighed a hundred pounds to start. We realized at this point we were going to put a lot of thought into our tooling if we were going to get this thing to turn out right.
The following pictures shows the method we devised of roughing out the shape. Making it up as we went, we used a chainsaw to cut relief kerfs to our guide lines, working on what will be the sides of the handrail section first:
Then knocked the blocks out with a chisel and hammer:
And finish the shape with a right angle grinder with a very aggressive disc. Now we have a "plumb" section of handrail blank.
Then the same techniques to describe the third surface of the block, which is actually the bottom of the handrail when we put it over the staircase:
The MDF section was basically right but not perfect, so we made several models of the section, each time slightly adjusting our face mold shape and bevel angles, out of styrofoam to get it dialed in:
Once we got a model that sat perfectly over the center of the stringer cap (the curved outside edge of the staircase that we would be eventually using for a bottom rail) it was time to start on the actual oak handrail section. Our starting block needed to be 3.5 x 13 x 48 inches, and so we would have to glue many small boards together to make it. (This would also give us many slightly different grain directions, which would increase the strength and stability of the final piece.) After planing our stock planks of oak, we glued each layer laterally first:
..after the set up we ran the pieces through the planer again so we would have ultra flat boards, meaning no voids and excellent joints, and then did our final lay-up:
(thats sixty clamps and one STRONG oak block)
Final face mold and bevels on beautiful solid oak block:
Rough out "blank" with skill saw and band saw:
Drop pieces, might make fun sculptures someday:
Plumbed final handrail section, after lots and lots of chainsaw and chisel and grinding wheel action, its OAK, after all:
We join sections of the straight rake rail, called shanks, to the blank so we have sight lines to fair our bottom surface to as we carve:
And,
it fits!
and Hal's thinking, ok, now, how do we get it from looking like this:
To looking like this:
(railing we built at the top of the landing)
One day at a time, but we're glad to have made it this far. Stay tuned.
