Using Marine Grade Plywood

[Barry Anderson]

Good morning. I have someone that wants letters cut out of exterior, treated plywood. Being treated, the wood is wet to some degree when purchased. Any comments and/or advice on how this will affect the cutting capability of a 1/4" end mill?
Thank you,
Barry

[carbidetooth]

I can guess at the results, but it's unclear what material you're actually going to use.

Marine plywood is typically a better grade of fir plywood with exterior glue. Thought by many to be waterproof, but not really true. It should cut fine but edges will have a little tear out and checking as is typical of softwood plywood.

Treated plywood refers to "pressure treated". A process where preservative chemicals, usually in water base, are imbued into plywood under pressure. Often colored to identify as such. Because it has so much added moisture, the wood fibers are going to be more pliable. I would expect to see a more "hairy" edge, but have never cut it on router. Because it often starts with a lesser grade of plywood, possibility of voids on inner plys is greater.

[Rcnewcomb]

Might it be better to use Extira or sign foam for this application?

[GeneMpls]

Or exterior pvc- usually anything over 1/4" is exterior.

[Wayne Locke]

You can get marine plywood in different hardwood species but it is expensive and difficult to find. If it is not to be submerged or on water, marine grade is probably expensive overkill. The letters will most likely be painted so an exterior ply will probably be fine. I am pretty sure that Baltic birch uses an exterior glue and would work fine.

Maybe go on a sign forum and see what they say.

The treated that I have seen all seems to be not very high quality, from a furniture maker’s perspective, construction material.

[Barry Anderson]

Thank you for your replies. The concerns posted are things I have thought about, and wanted other opinions. I will check into the other material suggestions.

Barry

[jerry carney]

My material of choice for out door work is HDU cuts beautiful and lasts a long time . Paints well. IMHO

[adze_cnc]

I have someone that wants letters cut out of exterior, treated plywood.

As in "letter shapes" and not carved into the material? How about "medium density overlay" otherwise known as sign-board? https://www.windsorplywood.com/product/ ... o-plywood/ Each face has a phenolic coating. You'd just need to seal the cut edges.

Steven

[Barry Anderson]

Yes sir, letter shapes.
Barry

[martin54]

What sort of thickness & what is the intended use?
If these are for something like a shop front then wood is very rarely used because it requires to much maintenance, depenting on thickness then Acrylic, foamex or ACM would all be better choices. If they are thick letters then Randall's suggestion would be better, Channel letters are often used for thicker letters but you wouldn't be able to produce those without special software/hardware or a lot of mucking about/trial & error

[Barry Anderson]

The customer wants 3/4" thick letters to put on an existing sign. In the past she has furnished cedar, but asked about the treated plywood. The cedar she furnished was dry and brittle. Sharp corners easily broken. So I want to use something different. I checked into the costs of some of the other suggestions, and think they will be cost prohibitive for her. She changes the words every year or so, depending on what new venture she is promoting. With this, a long service life is not a requirement.

Barry