Best way to remove MDF fuzzies

[contoursvt]

Well I was using a router bit that was probably a bit dull so the result is that my MDF is fuzzy or furry looking. LOL. Well anyway I've tried very lightly sanding it with high grit sand paper (400) to see if some of it comes off and it seems like its going to be tough.

Whats the best way to smooth this out? I'm thinking that maybe once I prime, I can sand that area and prime again and it should be better right? Is there something I can do before priming?

[NickS]

Try 120 grit sandpaper.

[jerryanderson]

100/120 grit sandpaper & elbow grease! Your getting there

[contoursvt]

Thanks guys. I was afraid to go too rough on sandpaper but maybe I'll go ahead and try that. i'll start with very light pressure and see how it goes I think I have 220 and 150 here that I can go down to.

[tubetrek]

OR before primer you can paint on diluted Titebond (to seal the MDF), allow to dry then sand.

T

[domwilson]

Flapper wheel.

[carlspeak]

If you're planning to veneer (it will hide what I'm about to propose), you might try the 'high' setting on a hot air gun held up close. It should singe the fuzzies but will also darken the MDF. Some light sanding after that should do the trick.

[contoursvt]

Hmm both the watered down glue and heat gun options sound quite interesting. I think I'm going to do a quick test on a scrap piece of wood and see which of those I like better Thanks friends for some options.

[augerpro]

I apply a coat of Minwax Wood Hardener (from any HD or Lowe's) then sand with 220 grit.

[arlis_1957@yahoo.com]

in the future, make your last pass very light and slow. btw sharpen your roundover bit first

[PassingInterest]

I apply a coat of Minwax Wood Hardener (from any HD or Lowe's) then sand with 220 grit.

This is what I do.

Also, in the future, you might consider experimenting with a compression bit. If you're not already familiar, it combines an up-cut and down-cut on the same shaft.

[lunchmoney]

OR before primer you can paint on diluted Titebond (to seal the MDF), allow to dry then sand.

T

+1

I always use a 50/50 water/wood glue solution prior to primer.

This will tame the fuzzies nicely.

[Bob Brines]

Shellac is your friend.

Bob

[jonpike]

Shellac is my friend, too...

It may not matter as much which kind, but things that soak into the surface then dry hard will make the MDF harder and sand smooth. I like shellac, (particularly the "Seal Coat" dewaxed sealing version) 'cause it's solvent is alcohol. Makes it soak in well, and evaporate fast. For this, even cutting it 50:50 with alcohol works great. Couple of well soaked coats, 15-30 min apart, dry for 1-2 hrs... sand away.

Another thing, some have noticed that all MDF isn't created equal... there seem to be "softer" and "denser" cored types. Softer ones are fuzzier. Going to a professional/woodworking supply store rather than a big box home repair place might find you higher grade stuff in the future.

Hope that helps...

BTW, what's going in the boxes?

[Bob Brines]

Shellac:

I know that the overwhelming choice of surface prep for MDF is diluted PVA glue. This makes absolutely no sense to me since absolutely worse thing that can happen to MDF is to have water applied. Dilute PVA is going to expand the end "grain" of MDF. Has to happen. Alcohol based shellac will not. Advantage #2: Shellac is far easier to sand than PVA.

Bob

[edlafontaine]

I agree with Bob. Water and mdf is just bad juju.

also, any effort removing the "fuzzies" before treatment will reduce your time spent by ~half. They are much easier to remove before they become part of a "matrix".

[contoursvt]

Well I applied just a very tiny amount of diluted wood glue with a brush and sanded lightly. Its resolved the issue. Thanks everyone for the help

[lunchmoney]

I know that the overwhelming choice of surface prep for MDF is diluted PVA glue. This makes absolutely no sense to me since absolutely worse thing that can happen to MDF is to have water applied.
Bob

There's a lot of theory about how this technique will cause problems, and it's simply not true.

Every speaker I've ever made has been sealed with wood glue/water, and I dare say that says a lot. Never had a problem.

I've achieved very nice paint finishes that still look great 2+ years later.

It's cheap, non-toxic, and sands FAR better than shellac.

You're not "applying water". You're applying a mixture. The 50/50 mixture is still fairly thick, like whole milk. It doesn't penetrate very deep, and the water completely evaporates. What's left behind is rock hard dried glue. It does NOT swell up, warp, etc.

Come look at my speakers and tell me I'm wrong.

[davepellegrene]

Here we go again!

[lunchmoney]

Yup.

I keep waiting for someone to present some actual evidence that 50/50 damages mdf.

Until they do, I will continue to bust this false assertion.

Anyone?