I've been asked to glue up a maple handrail using bending rail for a prefab metal spiral staircase. I have a shop full of machines, hand tools, clamps, etc. and some experience with bent laminations, but not with this application. Looking for any advice. Build a form in the shop? Try to use the staircase rail (1 1/4" square steel) to clamp to? I 'm thinking West Systems epoxy for open time and glue line. I don't think this is beyond me and I'd like to give it a go. Am I missing something, before I commit?
(Architectural Woodworking Forum)
From contributor R:
You can use the metal handrail as a guide to clamp up the bending rail. The bending rail supplier can provide you with two matching profiles (the handrail profile on the inside, flat on the outside) for clamping. Basically, you will need to clamp the rail to the inside or outside of the existing steel rail. I know of no practical way of clamping the rail to the top of the steel, which would be ideal.
Yes, clamping it to the outside is a different diameter, but the finished rail will be flexible enough to fit onto the rail. There will be considerable cleanup of glue squeeze out all over the rail, and you will then need to plow the bottom of the rail to fit over the steel. It is not complex, but there are some tricks to it.
Second, what happens with the railing at the top and bottom? That's a minefield in itself.
Third, have you worked with West before? If not, there's another very real learning curve.
Fourth, is contributor R's suggestion workable? Is this job across town from your shop? Is there even enough clearance to clamp to the existing steel railing? (Sometimes these stairs are in a very small well.) If that doesn't work out, are you prepared to build a bending form in your shop?
Fifth, with a couple of hundred railing bends under my belt, I usually pass on bending wood rails for steel stairs, spiral or otherwise. By now, can you guess why?
The problem with prefab bending rail is the slices are too thick to conform to such a tight radius, but if you steam them the keys swell and won't fit together and the outer slices will cup.
Contributor R, I don't know if you've tried this, but it works pretty slick on most railings (just generally not spirals). On prefab bending rail, take the center five slices out and rip off the thickness of the steel. Then after you glue them up and stick them back together, your plow is already made and you can form the rail right over the top of the steel. You have to clamp pretty close together to keep the shape and also clamp from the underside of the steel to the top of the railing to control the twist. Also make sure to rub some paste wax on the steel prior to make it easier to take the rail off to clean it.
I like contributor N's notion of welding the brackets on. That ought to work fine.
As for steaming and having the tongue swell on the bending rail pieces, I run them through the planer and remove the tongue. To keep them together I use vertical clamps with contoured blocks. (I cover the blocks with the cellophane tape also.) With a radius this tight, I would steam the rail first, bend it on the form, let it sit there for a few days, then glue it.
What I think we're all saying is the learning curve is pretty steep. I suspect we all learned this stuff the hard way, and at least in my case, I lost my butt on the first few jobs. The good news is I finally have enough clamps.