Drilling 3/4" holes in MDF

[Victor Robinson]

I have an auxiliary worktable I'd like to drill 3/4" dog holes in. The top is 1.5" thick (2 layers 3/4" MDF). In total it's about 50 holes to drill. I've tried a few different methods and I'm thinking I'm not using the right bits or the right technique...in every case they have been relatively inexpensive but new bits:

1) 3/4" auger drill bit in corded hand drill - going nowhere
2) 3/4" forstner (carbon steel) in corded hand drill - better than the auger bit but still very very slow...worried about blueing the bit
3) 3/4" HSS spiral in router - seems to require too much pressure to plunge it...kind of a cheapie bit

Soooo, can anyone recommend a drill/router bit or technique that will handle this seemingly simple job?

[Larry Frank]

I have a 1-1/2" top on my workbench made out of MDF. I drilled the holes with an Irwin Auger bit in my electric drill. I made a 2" thick hardwood block with a 3/4" hole in it to use to keep my holes perpendicular. You need to be careful not to push to hard near the bottom to keep from blowing the bottom out. They came out very good. After drilling the holes, I used shellac on the inside of the holes. It gets soaked into the MDF and will harden given a stronger hole. After this dried, I ran the bit back down the holes carefully to get them back to the 3/4" as they MDF swelled with the shellac.

[Victor Robinson]

Thanks Larry. As it turned out, the reason why the MDF was being invincible was in fact, dull bits. I decided to chuck a more expensive/less used forstner and it made quick work of it. To save the good bit, I'm only doing the initial entry holes with the forstner, followed by a sacrificial 9/16" spade to clear out most of the hole, and the forstner to quickly do what's left. It's not really saving the edges of the forstner I suppose, but at least the bottom cleaning edges...

Great tip on the shellac for the inside of the holes.

[Leo Graywacz]

MDF will kill HSS pretty quick.

I might have used a paddle bit with spurs to cut the holes. It would have made quick work of it.

[Erik Christensen]

I like to use a 3/4" carbide plunge bit and router - it makes really smooth holes and if done over a sacrificial board there is little tearout. Only bad thing about a router & MDF is DUST - unless you have a Festool router I would do it outdoors and wear a dust mask for sure.