Tips on Steam Bending 12' x 1-3/4" Round KD Mahogany Handrail

[Robert Ellenwood]

Next weekend I will attempt to steam and bend a 12' x 1-3/4" Round KD Mahogany Hand Rail that was laminated from two half round stocks. Based on everything I am reading, the odds are against me on a successful bend. This weekend I will be building the 14' Steam Box and ordering the Rockler Steam Bending kit and setting up the clamp form jig. Any tips from any steam bending experience (especially with Mahogany) would be greatly appreciated. Attached pics are of rail and located of stairs.

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[Mel Fulks]

I don't think there is a chance of that working. Steam is used by chair makers,but on smaller pieces made from wood that has some water in it ,once their supply of wood air dries too much most turn it into firewood and get new material. Unless you have other routine uses for a steam box I would make a form and glue up another piece from dry lams,
round rail is pretty easy to shape after gluing.

[Mark Bolton]

Remeber too that that is compound curve.

I'd say depending on your desired end product you'r in for a challenge.

[Michael Kellough]

Remeber too that that is compound curve.

I'd say depending on your desired end product you'r in for a challenge.

also, so, it would have to be bent beyond the finished curve to account for spring-back.

[Eduard Nemirovsky]

I did some steam bending, and from my experience you have a high risk for failure. First - your round piece made from two, risk for separation and braking not on the glueline. Second as Mark said - it is compound curve. I think better and higher chance for success - lamination from thin wood.

But again - I have just a short experience.
Ed.

[Mel Fulks]

Well, now that we are all in agreement...Start by determining radius of stair by determining radius of that wall add enuf to where rail will be AT LEAST 1and 1/2 inches from that bottom square, make a form from 2x 4s nailed to plywood segments, edge of each 2x4 (or every other one) should be spaced the dim. Of riser faces and at same height attach blocks onto form at riser points for the glue up to rest on. Experiment with scraps of same wood species to determine how many lams you need to bend smoothly and evenly,springback can be a problem but in this case you need such small segment that I don't think
that will be a problem .glue up at least a foot longer than you need on EACH END. Remove and shape with router, spoke shave etc. Offer to teach a friend to sand stuff in return for his help sanding the rail.

[ray hampton]

I do not steam bend BUT it is my understanding that the time that the wood need to stay in the steam chamber will depend on the thickness of the wood[ it will take longer for the steam to reach the center of thick wood ] while thin wood can be steam and add to the bending form and allow to cool

[Jerry Thompson]

I am following this thread. I want to do some steam bending but I have read in several places that one cannot steam bend kiln dried wood. Does anyone have any first hand knowledge?

[Robert LaPlaca]

I am following this thread. I want to do some steam bending but I have read in several places that one cannot steam bend kiln dried wood. Does anyone have any first hand knowledge?

Link to a pretty nice guide on steam bending that the folks from Lee Valley Tools has written that is free.. Seems as though the answer to your question is yes only use air dried material. http://www.leevalley.com/us/wood/page.aspx?p=31161&cat=1,46096,46123

[Bill Orbine]

I am following this thread. I want to do some steam bending but I have read in several places that one cannot steam bend kiln dried wood. Does anyone have any first hand knowledge?


Much more difficult, if not impossible. It has been advised to use air dried material. The heat in the KD "sets" the lignum within the material. The lignum, I believe, is the binder for which holds the cellulose material together. I've been into very little steam bending, but that's my understanding of steam bending KD lumber. Doesn't hurt to try (except the wallet) and I see the bend is rather gentle base on the pics of the stairs.

[Jamie Buxton]

There are tables of how well various species steam bend. Mahogany is one of the worst.

And do you know that the glue used in the lamination is waterproof? Good ol' yellow carpenters glue would dissolve in a steam chamber.

[Jamie Buxton]

You might consider bending handrail. This is stock intended exactly for what you're doing. It consists of nesting stacks of thin laminates which can be bent (cold) and glued together to make a curved handrail. Each laminate has a tongue and a groove that register it to the neighboring laminates. Here's a link to one source, but most any stair parts company can supply this stuff ---http://www.allstairs.net/handrail/bending-handrail .

(The pics for this material usually show red oak. However, red oak is not particularly durable outdoors. White oak is much better.)

[Jamie Buxton]

And one more alternative is PVC water pipe. It is much less expensive and much easier than any of the wood or metal approaches. You bolt the rail-hanging brackets to the wall, and then screw the PVC pipe to them. 2" or 1 1/2" pipe certainly is strong enough to provide assistance to folks who are climbing the stairs, but it still can be easily bent to the curve you need. PVC stands up to the elements better than wood. You can paint the pipe if you don't like white. I worked on a house ten years ago where the homeowner put up white PVC pipe as a temporary measure, and it is still there. The staircase leads to the front entrance, so every visitor walks past it, but nobody every notices it is plastic.

[Robert Ellenwood]

Thank you all for a speedy response, I have decided to "save" this rail for another project, on to plan B. thanks again!