[johngalt47]

I am having the worst trouble using mdf with my cnc router. I realize part of the problem is the swelling due to humidity but there must be something else that keeps the cuts from being exact.

[keebler303]

The rest of the problem is your machine.

Thanks for providing so much information, it would be hard to help if you did not provide information about the machine you are using, the tool, the depth and width of cut, the speed and feed.....

[salzburg]

Make all your cuts and drill all your holes as quick as possible and right away put a coating on the mdf, like epoxy.

[zool]

1. Does your machine move as the controller says it is moving; i.e., is the machine calibrated to the software?

2. Are you using old or new MDF? I found some of the veneer-covered MDF that I'd been saving for that perfect project for it, had swollen and gotten soft over the years. [Yes years...it was just too good to toss..though finally did toss a lot.]

3. I found that using a down-cut spiral bit got better results.

4. As salzburg suggested, cut the MDF, and assemble and finish quickly.