MDF Span

[jmc]

I am currently building a CNC router, because it is a design as you go thing I have assembled some pieces and have laid them out in a configuration that I thought I would like.....after doing this It became aparent that my table span might be too much for MDF my question is, Does anyone have any idea how wide of span 3/4 in MDF can go without eventualy sagging in the center.
any suggestions would be good
thank you
Jim

[ger21]

Even small sections, maybe 12", will eventually sag. MDF is not made to span unsupported distances. If you want to make it much stiffer, you could glue plastic laminate (formica) to both sides. But it will still probably sag eventually. That's why most of the better designs around here use a torsion box construction.

[Zumba]

What kind of tolerances are you trying to achieve?

[jmc]

I imagine a torsion box is an angle frame around the MDF?
I am not crazy about just using MDF on its own but am considering somthing like this
with a 1/2 in sacrafitial (sp?) MDF on top.
thanks for your response
Jim

[jmc]

Well I never really considered tolerances I was just thinking that I should make the machine as rigid and robust as I can.
Jim

[ger21]

Torsion box constuction.
http://www.diynetwork.com/diy/shows_..._26946,00.html

[martinw]

Does anyone have any idea how wide of span 3/4 in MDF can go without eventualy sagging in the center.
any suggestions would be good
thank you
Jim

Dear Jim,

Although this is really for designing solid shelves, this rather wonderfully named site will give you a taste of the strength.


http://www.woodbin.com/calcs/sagulator.htm

Best Wishes

Martin

[jmc]

Both those sites are fantastic the help you people have given me is incredible
I changed my design on the fly theroy to accually making plans, I found I spent a lot of time in the shop staring at stuff tring to figure out the best angle of attack. anyway I plan to document the build and will post some drawings in the appropriate forum when I get them done.

thanks for your help
Jim