Bending a Handrail in one plane.
I have a 6″X 2″ hand rail that I cut into 3/8″ strips 15′ long. My question is: If I steam them one at a time and form them, will they hold the shape for gluing?
I have a 6″X 2″ hand rail that I cut into 3/8″ strips 15′ long. My question is: If I steam them one at a time and form them, will they hold the shape for gluing?
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Replies
May not even need steam. Is it a constant radius? Can you bend one piece to the desired shape? More info will get you more help.
PJ
Everything will be okay in the end. If it's not okay, it's not the end.
The radius is 48"'s. I can bend the inside pieces to form, but am afraid of the 3/8" front and back.
Intuitively, I'd say 8' diameter is doable without steam. Lay out and build a rock solid form full height of rail...I'd probably use a router on a trammel and stack up 2x lumber or perhaps MDF or chipboard. You're gonna need around 20-30 clamps and some clamp blocks so you don't damage the outer strip. Minimum 3" throat on clamps, 6" would be better.
Use two part urethane glue to prevent creep...need a ridgid glue line and lots of open time. Lay out parts, roll or brush generous coats on both sides of all except inner and outer. Start at one end and clamp all layers to form...if you've applied enough glue, you should get squeeze-out between layers. Work your way around form, clamping as you go.
24 hrs. later unclamp, scrape and cleanup. Lots of belt sanding top and bottom.
The weird thing is, the actual clamping process is probably one of the least time consuming parts of the whole operation. PJ
Everything will be okay in the end. If it's not okay, it's not the end.
Thanks for the information. I was going to build forms out of 2x6 and screw them to template on the floor.
That'll work. Here's a bent lamination I did. Used the same frame for the 3 different ellipses the door needed. These were 2x6 Ls, screwed to a sheet of plywood. You can get incredibly tight radii if you slice thin enough.
Yellow glues creep. I like resorcinol. Don't forget the waxed paper (paste wax, whatever) to keep the glue from attaching your work to the form. PAHS Designer/Builder- Bury it!
I mispoke on the glue. Urea resin, not urethane....duh. Gettin' my U's confused...
http://www.vacupress.com/veneerglue.htm
Resorcinol will certainly work, too.
Might want to dry run, so you see any problems before they're...well...problems!PJ
Everything will be okay in the end. If it's not okay, it's not the end.
Save the steam for making artichokes.
I just made a form for bending walnut for a handrail and moldings. The overall diameter was 62 inches. I took a sheet of beaver board (anyone still use that term?) and made a jig with my router to a radius of 30 ". I made 5 layers of the board trimming each time with a 1/2 inch straight router bit. to yield a 2 inch curved curb.
Take the 1/4 inch x 2" by 40" nominal walnut strips and butter them up with Titebond III in my case. Use a paint roller for speed. Start to clamp in the middle and work to the ends.
I waxed the form with candlewax and scraped off the excess. sort of a poor man's mold release.
It took about 12 hours to set up. (inner boards don't get much ventilation) I just did one a day. If you can let it sit for longer ... like 24 hours the better. At the least the exterior slobbered glue needs to be dead dry. That is a climate issue (heat humidity) 20 hrs on a 2 inch cross section will at least let you get it out of the mold. Maybe wait until they are all made before you start the machineing.
After I removed the wood from the form, I used an old innertube stretched like a bow string to take the stress off the lamination until the glue was dead dry. If you have bikes just start saving the tubes or hit a bike shop and ask for the cast offs. I find them so much more useful than band clamps.
Make it larger than you need in length and height as you'll have to machine off the excess with the table saw to make it consistent in cross-section. after that you can machine in the finger groove and the top can be rounded with a shaper pretty safely.
I'll look for pictures. It turned out better than fine.... Oh yes make sure they are long enough. I made and machined a rail only to find it 1/2 " short. It is the prettiest piece in my scrap bin.
PS reading on the 48 inch radius you ought to be fine. Even putting glue on the boards will make them more flexible. PS avoid knots and deteriorated grain. They don't bend well and machine worse on this wild stuff.
Edited 3/7/2006 7:29 pm by booch
Everyone has been great in their responses. Thank you all. Do you think one person can do this alone ?
Sure. Preparation is the key, as is the setup of the roller for the glue. I just bought a 4 inch cheapie from a box store. something like 1.29 each. plastic handle and included plastic "paint tray" It is good for about 4 applications (wash in water after use) then the handle breaks.
Try a dry clamp first. it will give you a good indication of wether the jig you made is user friendly. I can't stress enough the jig strength. You'll be looking for more hands unless you get a jig that doesn't move around. The Particle board (beaver) jig is pretty cheap and dead solid.
The laminations will walk a bit. so the pic that someone included about clamps holding the wood around the curve is pretty accurate but.. try using 2 paralel jaw wooden clamps on the ends to keep things in a singular plane. Even those you need to release to accomidate the sliding of laminations.
Unless you are using perfect wood / clamps it will try to walk in a helix rather than a flat curve. That is why I suggest a slightly wider strip to laminate. I had to trim off about 3/8" on top and bottom. Probably less but allow yourself the ability to cut it true.
Last thoughts.
voids. if you make any don't worry. Just carve a thin piece to fit the void and glue/pound it in place. Not too hard but enough to minimize the void. After machining the area will look fine.
Keep your rippings (laminations) in order. Less visual incongruity allows the eye to assume it is one piece. Unless that is the effect you wish.
Figure you'll create a bad one so buy enough wood to allow for a mistake.
Boldly go where you've never gone before.
Jack of all trades and master of none - you got a problem with that?