Router bit for dado

[mastercabman]

What router bit do you use to make dado for 1/4" mdf core melamine?
I have been using a down cut spiral bit(1/4")but i need to replace it.I've had it for a long time and it's getting dull.
Also,i'm having a hard time inserting the 1/4" panel into the groove.Should i get a step up in size?

 

[tiralie]

Vortex makes an 8mm with an 8mm shank which might be better.
I have found the straight bits give me as clean a cut as the down cut bits with less heat and chance of breaking off...but that's 'cause I would want to plunge a down cut which is a no no.
Tim

 

[mastercabman]

Is the 8mm not too big for 1/4" mdf melamine?

 

[tiralie]

Is the 8mm not too big for 1/4" mdf melamine?

1/4" = approx. 6.5mm. With an 8mm bit you have 1.5mm play. Not a lot if the board is really thicker than 1/4".  If you are finding the 1/4" bit you are using is too tight, caliper your board and your bit and check the thickness. The board may be thicker by the coating amount which makes it slightly thicker than 1/4".

 

[mastercabman]

Thanks Tim,i will look into it.
I still need to get a replacement 1/4" for other application too.