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View Full Version : Bending 2" flat bar, the hard way



Evan
07-16-2007, 07:23 AM
I am making a handrail for the spiral staircase I built. According to code the railing must be continuous with no interuptions along it's length. I don't have the facility to bend tubing in the required manner but I can manage a piece of 2" x 1/4" flat bar stock. This will serve as the base for a bent wood handrail attached to the flat bar top rail and gives a solid railing. I could have approached this problem by cutting and welding together short pieces but decided to try bending instead.

The force required to bend stock cold "the hard way" is considerably higher than bending it with the flat instead of against it. I welded up a bending jig from scraps and clamped it on the corner of my welding table. Nothing special about the jig except one feature. The center piece that covers the bar and prevents it from twisting is "hinged" by welding it at one end only. A piece of scrap round stock is welded to it to serve as a "bash button" for a sledge. This serves to flatten the stock being bent if it takes a bit of a twist during bending.

http://vts.bc.ca/pics2/barbend1.jpg

The stock is inserted and clamped securely to a BFH, the H standing for Handle in this case.

http://vts.bc.ca/pics2/barbend3.jpg

Brute force is applied and the required bends produced. Fortunately when I built the garage over twenty years ago I had the foresight to place a door exactly where it was needed for this job.

http://vts.bc.ca/pics2/barbend4.jpg

The final bent part. This is more complex than it appears. It is bent to a specific angle at each point that is in part a function of the helix angle of the stairs. It also must be twisted a certain amount along the length of the piece, in this case 32 degrees of twist.

http://vts.bc.ca/pics2/barbend5.jpg

Your Old Dog
07-16-2007, 07:52 AM
That worked out ok. Couldn't you have used a conventional BFH on the outside of the bend and a little bit of heat to achieve that amount of bend with a smoother arc? It would have made the outside of the bend a little thinner but I expect the outside of your bend is a little thinner then the inside. Just wondering?

On the other hand, us Philistines would have hired out the job :D

Evan
07-16-2007, 08:10 AM
I wasn't trying for a smoother arc. It is bent the correct amount for each step to transition to the next on a tangent.

Sure I could have used heat. Where's the challenge in that? :D

Also, we have more than enough heat here already.


http://vts.bc.ca/pics2/hot070712.jpg

I know it is in the direct sun but I have never, not ever, seen it read that high. That was a couple of days ago and all time records for absolute max temp were broken in a number of places.

Doc Nickel
07-16-2007, 09:13 AM
That worked out ok. Couldn't you have used a conventional BFH on the outside of the bend and a little bit of heat to achieve that amount of bend with a smoother arc?

-2" by 1/4" flatbar, however many feet long? That'd be a bloody great deal of heat... Like two or three full sets of oxyacetylene and a big rosebud at least, or three or four 20-lb propane tanks and a blacksmiths' forge.

I wouldn't have wanted that job even if I had an air hammer to do the pounding.

No, mild steel bends fairly easy- if you have the leverage, and something hefty to bolt your pivot to. :D

As for the smoothness, keep in mind the stairs themselves aren't a smooth outside radius- the rail should match the "faceted" look nicely.

Doc.