what size pilot for #6 coarse drywall screw into MDF?

[pierhogunn]

Hey, what size pilot should I drill to get the best hold w/out splitting the MDF pieces that I am joining together?

I am using #6 Coarse Thread Drywall Screws

[RodKirby]

Dan -

Edge or face, and what thickness? There's No "right" theoretical answer...

In my (extensive) experience with screws in MDF, the ONLY way to decide on a drill size is to "try it" on some MDF scrap

[otieo]

MDF and threaded fasteners

In a recent issue of Shop Notes magazine, the author of an article on the above subject recommends using straight shank machine screws instead of tapered screws of any type. Use a drill bit the same size as the minor diameter of the screw, drilling a bit deeper than the screw length. Countersink the top surface for the head and add a shallow countersink in the second surface you are screwing into.

The straight machine screw shank will not split or blow out the MDF, while the second countersink provides a space for the material drawn up by the threads. This allows the joint to pull tight without leaving a a gap.

Hope this helps.

[RayintheUK]

Make the pilot hole 1/4" deeper than the screw length. A dull bit or slow drill speed will burnish the hole, which can lead to crumbling. Use a sharp bit at high speed for a clean accurate pilot hole.

For a #6 screw, drill a 3/32" pilot (in a sheet no thinner than 1/2").

Do not overtighten the screws, or they will break away. 3/8ths of a turn past flush is maximum.

Ray.

[pierhogunn]

Awesome Guys, thanks

I am joining edge to face on 99% of the joints for these book cases