# Kerf width

I’m looking at the possibilities of using the Forge to cut strips of 1/8" ply 40" x !.5" with box joints along the long edge. Then 'engraving a series of parallel cuts across the width, in order to facilitate the bending around a 12" radius. I’d assume that I’d make the cut through to the inner face of the outer ply, rather than producing a living hinge cut, for appearance’s sake
My calculations are that I need to lose about 3/4" around the inner surface, so how many cuts do I need to make for the total kerf width to add up to 3/4" ?

If I assume 0.008" for the width, then OK that’s only about 100, one every 1/2" or so, but that doesn’t seem very likely. I’m sure I’d need a lot more.
Has any laser owner here ever done anything like this ?
I’d be glad to have their input.
John

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This is relevant to my interests

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I’ve been thinking about it for future products but haven’t gotten around to testing it. I think the ply is basically MDF with whatever veneer over it. I’m thinking if you can get most of the way through the MDF it will work fairly well.

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John, a couple more things you need to consider. Your calculations about the total kerf being .75" seem to be if your kerf goes through the entire material. 3.1416 * 12 *2 = 75.3984 inner and 3.1416 x 12.125 * 2 = 76.184.
The difference is .786.
In no situation would you kerf completely through the material. You only want to add enough kerf cuts to allow you to easily bend the ply without having facets, or breaking the ply.
You will have to do some trials, but I would suggest .008" kerfs every 1.5" at a depth of half the ply.

Good luck

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Hi takitus, another difference in nomenclature across the pond, I’m afraid.
In UK plywood is always just that, three plies(or more) of wood. Often in cheaper grades the middle one will be thicker, of an inferior quality, and the outer layers little more than veneers, but it will still be all wood.
MDF in the centre is not a material that I’m familiar with, but sounds interesting, and potentially useful to me in this particular job.

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Yes, it looks like a trial and error approach will be the best way, but I just wondered if anyone had already ‘been there, done that’

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well here most plywoods you get have inner material that is very inconsistent in density, so having an mdf center that is designed to work well with lasers is really nice. all of the results Ive gotten from it so far have been pretty great.

Here’s a really crappy ply that I definitely can’t use for engraving lol

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Does this type have a particular name to distinguish it from ordinary ply ?
EDIT Just googled veneered mdf. Is this it ?

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Yes, been there, done that. It is trial and error after you calculate your best attempt.

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TECHNICALLY according to the wood working standards up here(Canada, and I’m trying to remember this paraphrase, so not 100% accurate), plywood is any 2 or more ply sheet good. So technically melamine on particleboard and veneer on MDF core are plywoods. TYPICALLY most people think of plywood as wood only , cross grain layered. This is technically called “veneer core plywood”.

What I think your describing in your OP is a kerf bend. I tend to do this on a table saw and leave more or less a 1/16"(1.5 mm) from the good face. And leave about 1/8 to 1/4 between kerfs, depending on radius. But that is with a 1/8 table saw blade. With such a thin kerf, I am truly not sure how many kerfs, and how often. But I think a depth of about 1/16" to 1/8" or so from surface should be sufficient.

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This may all now become academic.