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Pre-treatment of MDF?

183 Views 4 Replies 4 Participants Last post by  BigCountry79
Greetings! New to group and not really a precision woodworker, but love to 'do it myself' whenever I can.

I'm planning a new project, a bit off-beat, in which I'd like to use CNC-routed MDF parts in place of machined metal ones. I chose MDF because of its density and durability; actual strength isn't a primary concern because very low forces are involved. However, dimensional stability could be an issue, although the final home for this project will be indoors and climate-controlled.

The Web gave me some info on MDF stability, recommending covering the surfaces with high-pressure laminate, which I was planning to do anyway. However, there will be back-door access to the raw material here and there, so I was wondering if any sort of brush-on sealer might help protect these areas. My dad swore by Rez Sealer back in the day, but like a lot of good old standbys it's now a known carcinogen and no longer sold. Some of the available sealers are water-based, which seems wrong to me, so I wondered if someone here might have suggestions.

Also, I welcome any comments on CNC-routing of MDF in general, whether it's a customary practice in furniture-making, etc., and what sort of tolerances can be expected to be held. I don't own or have access to CNC gear and would appreciate any tips on where I might go to get one-off parts made. Many thanks in advance!
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Welcome to the forum, Jim - we're glad to have you here with us.
As for any project that is "off the beaten path", drawings, sketches and sample photos will get you the best suggestions. Other than that, we are just throwing rice on the wall to see what will stick.

I'm planning a new project, a bit off-beat, in which I'd like to use CNC-routed MDF parts in place of machined metal ones. I chose MDF
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Hi, John,

Thanks for the welcome and quick reply.

Rice-on-the-wall is all I'm looking for at the moment. The final decision between using MDF and having parts machined from aluminum (doubtless at show-stopping expense) depends on garnering some facts about MDF in general. I can certainly be more specific, with laughable sketches that may or may not be decipherable, once there's confidence in the direction I'm heading.
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There are numerous grades of MDF ultralight, lightweight, and standard. Masonite used to make a higher density MDF called Baraboard which was a popular product when HPL was in vogue. I do not know if it is still made or not. The higher the density, the heavier the weight, the greater the glue to pulp ratio, the greater the strength, the greater the water resistance. No MDF is water resistant, but Baraboard was as close as it gets. As for primers Mohawks Clawlock is great for MDF and is solvent based. Zinnser Bin, shellac based is also good as is water based Insl-X Stix.
CA glue actually seals the edges of MDF very well.
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