Dado 25mm router bit with 25mm thick MDF

[Ringus]

The numbers match up, but what's the chances of them actually fitting snug?

Also not sure how deep of a dado to make in MDF?

many thanks

 

[Rorton]

try on a test piece and see? You may be better off getting a19mm router bit and making 2 passes on the width, one at the full width, and then ease over the bit to get a snug fit?

Depth wise, usually no more than half the thickness of the material, suggested 1/3, so prob 8mm deep

 

[JobandKnock]

Zero?

 

[Sgian Dubh]

The numbers match up, but what's the chances of them actually fitting snug?

It's possible, but not overly likely. You might consider doing a tongue and groove/housing. For 25 mm thick MDF cut a groove up to ~12 mm deep using any convenient router bit with a diameter between, say, 9 mm and 16 mm. Then work a tongue on the mating piece using a ±16 mm router bit and cut the tongue length 0.25 - 0.5 mm shorter than the groove/housing depth with the tongue thicknessed to suit the groove or housing width, which means the tongue slips in with a gentle push fit, i.e., it doesn't need forcing in with a hammer or clamps. Slainte.

 

[stuart little]

Mitre lock joint, if a router table is available?

 

[Sgian Dubh]

Mitre lock joint, if a router table is available?

I suspect the question by Ringus was focused more towards jointing shelves or vertical dividers into a cabinet or a similar joinery task. Mitre lock joints are primarily useful for creating corner joints, although they could be pressed into service as an alternative to a panel edge joint, so outside that (those?) applications I can't really see a role for the joint. Slainte.