Finishing routed MDF doors

Dealing with sealing and finishing routed Medium Density Fiberboard doors. April 11, 2000

I have been outsourcing my MDF doors for some time now, and find that the area that has been routed for the raised panel effect needs to be sanded.

Any suggestions for a quicker, more effective way to sand that part of the door and not lose the detail of the routed edges before or after they get primed? Currently I do it all by hand, and that takes forever on a large job.

There are a few things you can do here.

One, purchase an abrasive wheel. It looks something like a grinding wheel, with the same contour as the profile of your routed area.

Another option is, I believe, called a fladder sander. It has strips of sandpaper on a wheel, kinda like a balloon sander does, and you brush the profile. The problem is that it can take away your profile if you are too aggressive with it.

I know hand sanding is a time-consuming process. You won't be able to eliminate all of it, but can reduce the time spent hand sanding with these tools.

Another thing you may want to consider is using a filler in the places where the primer is being soaked up. If you are using a conventional, solvent-based system you can fill the edges, dry either overnight or in an oven at 130-150 degrees for about 30 minutes (depending on the filler), then allow the substrate to cool down before priming, sanding and topcoating.

Are you paying good bucks or discount prices for your doors? Anyway, sanding by hand is quite tedious, but there is no better way to get the best result.

The routered spot on the doors you speak of is a very tricky area to sand without taking all the edge, or worse yet, completely rounding off the edge. With power tools, this becomes especially likely.

All I can say is, CHARGE FOR SANDING -- it's just the way it is. Top quality comes at a PRICE.

I use Kilz primer, thinned (three cups mineral spirits to one gallon primer), and spray it with an HVLP turbine, applying it semi-heavy.

This may cause some orange peel, but it's easly sanded smooth with very little effort thanks to those guys at 3M - their fine sanding pads work best. But be careful on the edges with a new pad!

There are few solutions for edge and internal profile sanding of MDF cabinet doors:

1. Use an abrasive alumimum head with rechangeable and rejectable profiled inserts in your router or point-to-point machine.

2. To sand the internal door profile you can use also use an OMNIA 90 PLUS sanding machine system, a semi-automatic machine that will solve your tedious manual sanding.

The easiest and most efficent way to form open grain on MDF or HDF is to seal it with lacquer with conventional spray or brush, then sand with 320. Then prime.