Formula or unwritten rule for pilot hole size?

[Phatsub]

Is there a set percentage of screw diameter to use when pre-drilling MDF?
Also, does anybody drop any wood glue down the hole before putting the screw in?
(I'm making my own cabinets)

[Phatsub]

Nevermind...I found this chart.

http://www.diydata.com/information/screwholes/screwholes.php

[tanky321]

I just usually try to match the inner diameter of the screw ( not counting the threads) and drill away.

[trushelrl]

I drill at about 1/2 the diameter up to 1/4" hole in MDF when making speaker enclosures (using drywall screws to secure). I do not put glue in the hole...the glue between the wood surfaces is what hold the structure together - all that the screws really do is just hold it together temporarily while the glue is dryin.