Kerf bending masonite

[Patrick Nailon]

I'm currently building a tambour clock from a Woodsmith plan, and it calls for the technique of kerf- bending masonite. I made up two masonite boards of the required size and cut kerfs most of the way thru the masonite, each 1/4" apart. When I gently tried to bend the first board over the curve of the clock, it broke. I found the kerf wasnt quite cut deep enough, and did better on the second one, but I think it's still a bit low.

Anyone use this technique before? I think that my combo blade isn't the right blade, as the bottom of the kerf has a raised middle, as opposed to a flat bottom, and I think this would make the middle of the kerf stronger, and the edges weak, possibly causing the fracture. Also, does masonite age and get more brittle? I'm using some pretty old masonite for this.

Any thoughts would be appreciated.

[Jamie Buxton]

I never had much luck kerf-bending stuff. It breaks and/or the kerf locations telegraph through to the finished surface. My go-to material is bending plywood. This is plywood specifically made for bending. (It is three-layer plywood, and the middle ply is very thin.) It is eerie stuff. You can easily bend 1/8" bending plywood into a 4" radius. In your neighborhood, Anderson International stocks the stuff. http://www.aitwood.com/default.asp

[Patrick Nailon]

Thanks for the tip! I didn't know about them. Too bad it's Saturday and they're closed. I'll check them out asap.

But this weekend, I'll keep experimenting. I have a lot of masonite and some 1/4" ply of various types, maybe I'll get one decent bend this weekend.

[Charles Lent]

We've had good luck bending (no kerfs) untempered 1/4" masonite by spraying water on both sides of it. This softens it significantly and allows the bending, but you will need a form and lots of clamps or some way of holding it's shape until it dries. We bent several 4' X 4' pieces into half round shapes on a form, held in place with clamps, and let them dry overnight. It wasn't easy, but was very successful. Both sides of each piece had to be sprayed several times before they got flexible enough to fit to the form. A light sanding will be required to restore the smooth surface.

Charley

[Patrick Nailon]

Thanks Charley, I was wondering if some water would soften it up. It should work very well with masonite that's been cut halfway thru as mine has. I'll give that a test too.