# What depth and offset from edge my dado / groove in particle board should be?

This is a follow-up on this question (How to make bottom for a big drawer)?
I have also read this one (What are the minimum, maximum, and optimal depths for dadoes, grooves, and rabbets) and I'm not entirely convinced it can be applid to particle boards "as is".

I'm making a large drawer - 130 x 60 x 18cm (on the inside) with 3-4 muntins (cross beams) in the middle. Sides and muntins are planned to be made out of 16mm particle board, bottom - out of 4-5 disconnected (by beams) sheets of 6mm plywood.

|     |
|    _|
|   |_   grooves on walls where 6mm plywood slides into
|_____|

I have got two questions:

• What is the rule of thumb for depth of grooves in particle board of given thickness? Should it be still 1/2 of the thickness (8mm) or less, given particle-y nature of the material?

• How far should I offset from the bottom edge? I reckon 1/2 of the thickness (8mm) should be minimum as well, does it need to be even more than that?

Sidenote: I'll be using a router table with 6mm bit to cut the dados / grooves, if that is any relevance.

• Safety note: many people will exclusively use the router on top (with the fence obviously) for this kind of operation. You can watch what you're doing as well as control the router more easily than you can the piece of wood, and the potential for kickback is much less. – Graphus Jun 8 '17 at 12:54
• @Graphus Thanks for safety warning. Just did ~8 meters of cut on a table - didn't got any kickback at all. Visibility and control was also much better than with the router facing down. I was using two straight bits - R6mm (for grooves) and R20mm (to trim straights). – Kromster Jun 8 '17 at 17:00
• Two very different operations for the 6mm and 20mm bits. Trimming (jointing) edges with the 20mm it's standard practice to use a router table. – Graphus Jun 9 '17 at 6:46

I'll share my own experienсe

Particle board is quite isotropic in all directions (unlike typical wood with directed grain). Sharp router bit spinning at 28k rpm produces very clean cut, without any tearouts. So there's nothing special to take into consideration.

Dado depth and offset should be around 1/2 of the material's thickness. So that the remaining material has enough strength to support the slided insert.

|      |
|    __|
|   |                 <-- depth is 1/2 of thickness
|   |__
|      |              <-- offset is 1/2 of thickness
|______|

Though it seems, that a little less depth and bigger offset is better, due to insert acting more as a lever than a straight force directed down.

In my case - 1/2 worked just fine.

P.S. Take into account, that some particle boards have more densely compressed particles near the outside, which means they have weaker insides, which means they are easier to fracture under stress and might need more offset from the bottom edge.