Bending Forms - sizing and construction

[ken cierp]

We use a pipe bender similar to this:
viewtopic.php?f=8&t=794

leaving sides too thick is the "number one bending mistake" -- Martin sides are .078" or less! the drawings I have seen always have this dimension wrong -- I think they pull it out of their butts.

[Jim Ball]

How are you handling the exact placement/marking of the narrow point on the waist?

I laid tape along one edge of my Plantilla, trimming it to the centerline on each end, then marked the waist location. I removed the tape and laid it down on a 40" steel ruler and noted the distance from the end. (you could just as easily lay it on your bench and measure with a tape measure.) It's then simple to mark the waist location on the sides to be bent. Be sure to offset enough to allow material to be trimmed from the end to square it up and trim to exact length.

[ken cierp]

Our sides are pre-profile to exact size and the waist curve apex is a line drawn on both sides of the blank

[Daniel P]

Getting closer

[Daniel P]

It works!

I fired up the new side bender last night to bend some ebony bindings. For this I just did a pair of bindings, taped side by side, wiped with water, and wrapped in blank newsprint.

My stack order, bottom to top

Steel - Wood (wrapped in paper) - Silicone Heating Blanket - Steel

I ran the temperature up to 285 degrees and the bending went pretty well. I see one area where it almost looks like it wanted to crack, just the slightest hint of separation. I'm wondering if a slightly higher temperature would have been beneficial.

[Kevin in California]

Congrats. Always fun to fire up a tool we made ourselves. I love the bending process.