What size pilot holes do I need to drill?

[dingy]

Hi,

I am making a basic cubby unit for my little boys bedroom using MDF I have everything ready but want to make sure I am making the correct size pilot holes to avoid any splitting. I am using "MDF-Tite" screws at 3.9 x 45mm.

I am making more than one unit and stacking them on top of each other, all very basic. I will be using 18mm for the base 18mm for the uprights and 9mm for the top plank (as I will be stacking them I will use 9mm on the next base to give an even finish of 18mm throughout the whole unit)

I will be joining them together with simple butt joints, again nothing fancy.

I was wondering if anyone had a good guide or tips when deciding what size drill piece to using when making the pilot holes, as I am trying to waste as little MDF as possible. Also any info on depth would be good.

Any other hints or tips are also welcome.

Many thanks!

 

[big-all]

0-0.5 mm less than the shank size on 12mm full depth pilot i
use no6x2" on 12mm mdf 3.2 pilot or 3.5 pilot no8 in 18mm


do not attempt to end drill any smaller size than 12mm

i personally would forget the 9mm it will just complicate things and reduce the strength

go for 12mm throught with 6mm for the backs
join the sides to the top and bottom to keep the external lines clean
also by using 12mm all round you can separate the sections

what size are you planning the boxes ??

 

[foxhole]

45m is a bit short , would use 50mm at least, 12mm mdf splits very easily and is usually more expensive than the popular 18mm so stick with that.Use a single sheet of mdf, 6mm would be ok, to back the assembled units which will tie it all together and add strength.Use a combined countersink and pilot hole bit, saves a bit of time.