Newbie- MDF cnc-vs- florida weather

[Blacksunshine]

how well willl a mdf table hold up to the humidity of florida's climat in a garage?

how long can I go on x or y before I get some kind of sag?

[LeeWay]

The cost and flatness of MDF is generally why I think people use it the most. I tried some for tooling plates and even the first sacrificial table on my router. It did not last very long. It's flatness and cost had completed reversed itself due to swelling and the remilling flat often. This after a coupe weeks in South Alabama.
I made no effort to seal it though. Sealing it will help, but again, there goes cost in time and materials. Baltic birch would likely be the best choice in sheet goods. I use a marine plastic called Star board for my table now. Rather than using baltic birch, I just use some cabinet grade plywood now for my tooling plate and jigs. It stays flat after the first leveling run. I have been able to use the same one for a couple years. I do replace them once they start showing any sign of warping though. 2 years is much better than 2 weeks.

[ger21]

Originally Posted by LeeWay outer. It did not last very long. It's flatness and cost had completed reversed itself due to swelling and the remilling flat often.

When you mill off one side of the MDF, the tension in the sheet will cause it to warp immediately. To use MDF as a spoilboard, it needs to be securely attached to the table so it's not allowed to warp.

[wcarrothers1]

I do 2 sheets of MFD. The first sheet is bolted down and milled flat then second sheet is bolted through the first to the table. Thus in theory when I'm done with the top one I can swap it for a new sheet. Long as you can live with the flatness over the piece within the tollerance of the second sheet it self. I have (2x2"square steel) support every 18" I think and between them I have welded in super strut support for the board

Seems to stay pretty darn flat. Course I'm in Michigan.

b.

[GaryV1959]

I built a router out of MDF and I live in Florida , I sealed the whole machine with a clear sealer , but my opinion is that there is too much flex in a MDF router for any type of close work, on a larger mill. My mill has a cutting area of 16" x 26" with 4" on the z..
I am getting ready to build a new one out of metal because now at least I have an idea of what I want and a little more knowledge of tha machine I will be using 2" square tubing and linear rails that I have been slowly picking up on ebay for the new build.
And like Gerry says afer you mill or cut the top finish off of the MDF it does tend to want to warp because the moister gets into the unfinished side ..
My 2 cents
Gary

[ger21]

Originally Posted by GaryV1959 And like Gerry says afer you mill or cut the top finish off of the MDF it does tend to want to warp because the moister gets into the unfinished side ..

Actually, that's not what I meant. MDF has internal stresses. If you take a new piece of MDF, and cut 1/16" off one face, it will warp instantly due to the stresses in the board, not from moisture. Moisture will just make it warp more over time.

Back to the original question, seal it and paint it with an oil based primer and you should have no problems at all. Just paint it as soon as possible.