Hardening MDF

[Jason Dreyer]

As I mentioned in a previous thread, I am currently building a router table. The top is made out of MDF and the plate sits right on "untreated" MDF. I'm a little concerned that over time the leveling screws for the router plate will dig into the MDF and make it increasingly difficult to level the plate.

I thought of routing the plate slot a little deep and maybe inserting some strips of laminate or something else in there where the leveling screws would make contact to beef it up, but I thought I read somewhere here a while ago about some type of epoxy or something that some people use on MDF to harden it and make it resistant to denting/chipping. Does this ring a bell with anyone, or maybe someone has a better idea?

Thanks!

[Prashun Patel]

You might be able to make the surface of MDF harder with epoxy, etc, but that won't necessarily increase it's ability to hold set screws through its cross section.

Your idea about strips of hardwood is the way I'd go. You might also consider threaded inserts.

[Michael W. Clark]

If you are putting set screws in the plate, then you could glue a thin piece of metal to the point where the screws rest.

I have an MDF top and I'm not a big fan of it. But one thing that has lasted is the router plate supports. I built the top before I knew a lot about the sag of MDF over time and laminating both sides. My top is 3/4" thick with laminate on the top side only. The plate is 1/4" thick and is recessed into the top leaving about 1/2" of MDF. The plate is leveled using four deep thread screws made for MDF that are screwed up through the 1/2" of MDF from the bottom (I forget the name of these screws). The top has sagged over time I think, but no complaints on the leveling mechanism. The fewer holes and slots on the top, the less places for pieces to catch as they slide through during a cut, IMO. My table top is about 7 years old and while it has sagged, it is still functional enough for most of what I've done. (One of my next purchases is going to be a shaper!)

If I were to build another router table, I would use 2 layers of 3/4" ply with laminant on top and bottom. I would also consider going the route of threaded inserts for leveling the plate as Prashun said with an all-thread and lock nut on the bottom. Minimal holes and slots on the top, just my preference.

You can also spray MDF with shellac and harden it some. I have it on a lazy susan finishing stand and that stuff seems hard as a rock after many coats of shellac and poly overspray!

Mike

[Andrew Pitonyak]

I placed an oak support system under my thick MDF, wihch was laminated on both sides.

To level the router place, I used blue painter's tape. More finicky, but fast and easy.

[Peter Kuhlman]

I have used shellac as well on MDF to toughen it up. Works well for bases on speakers that get hit by vacuums and such. Really helps prevent denting. I brushed it on heavy and let it absorb all it would take. Nice thing is the alcohol base for shellac does not make the MDF swell.

[glenn bradley]

I agree that small strips of metal may server your purpose. That being said I have had a PRL lift with a Milwaukee 5625 mounted in it (well over 15lbs) mounted in an MDF recess. It has seen almost daily service for years without ever requiring re-adjustment. The PRL lift uses eight set screws (about 1/4 x 20) that set directly on the MDF ledge. I always figured I would add small washers or metal strips if I ever had trouble. Non-issue so far.

[Jason Dreyer]

Michael - I made my top out of 2 layers of 3/4 MDF. The table will be supported very well underneath, so I'm not too terribly worried about it sagging.

I was wondering how much of an issue this would really be. The router table plans (Norm's router table, slightly modified) call for large leveling screws to be set underneath each corner of the plate, but my incra router plate has 10 separate leveling screws built in that I would rather use if I can. They are rather small diameter screws though, so I am just a bit concerned about them digging in to the MDF over time. I have a big Triton router I plan on mounting on there and it's a pretty heavy beast, to say the least.

Just throwing it out there for brainstorming or advice. After what Glenn said about not having any problems, maybe I'm just being paranoid for no reason. I suppose I could just use it for a while and see how it goes, and if need be, fix it up later.

I really appreciate the input, all.

[allan kuntz]

I also built a router table out of mdf i used a Jessem router lift that i tapped for leveling screw from the top and just drilled holes to match up with the leveling screws and inserted a dime in each hole. This has worked great and was a good way to save 60 cents
AL

[George Gyulatyan]

I think with 10 screws the load will be pretty spread around and after initial setup it's not something you'd be fiddling with all the time.

[Mikail Khan]

I bought an MLCS aluminium plate. The plate came with magnets to insert into holes in the mdf that are drilled under the levelling screws.

MLCS instructions can be found here:

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/graphics2/TM41-43routerplate0911.pdf

MK

[Larry Frank]

With MDF, I have used shellac to harden the surface and also for small areas, some super glue will work very well.

This may not be adequate for the leveling screws and insetting a piece of metal would probably be best.

[Larry Edgerton]

I use West System to treat my MDF patterns. Paint it on liberally and use a heat gun at that point to thin in and help it soak in. It soaks in about an 1/8 on the flat and about a 1/4" on the cuts. For threaded areas drill and tap the hole and apply epoxy, then thread in the same size screw coated with release agent of some kind. I use a liberal dose of TopCote and remove the screw when the epoxy is firm but not totally set.

For your application I would drill all the way down into the MDF through the plate and countersink allen heads into the mdf for the plate adjustment screws to ride on.

Larry

[Cyrus Brewster 7]

Jason,

My top is two layers of 3/4 MDF. In it is placed the PRL with the 3hp PC. I coated the top and the ledge the lift sits in with poly then waxed the top.

I too had the same concern as you about the possible denting of the MDF. I figured if the poly was not strong enough and the lift sunk into the top, at least the leveling screws would leave a mark. If this happened I planned on coutersinking some screws into the indents from the leveling screws.

However, after 3 years the top of the lift is still level with the table top. (the lift and motor weigh over 15lbs.)

[Richard Dragin]

I made my router table top out of two layers of 3/4" MDF glued together and then laminated the top and bottom with Formica. I use confirmat screws from below to level the plate. No hardening needed. Once you rabbet to fit the plate in a single layer of MDF you don't have much material supporting the plate,lift and router.

[Carl Beckett]

My router top is two layers MDF. Then several layers of shellac. The shellac penetrates and hardens the surface

It has leveling screws and I haven't noticed any issue at all. About 6 years old now. Although I haven't had to change the leveling settings much at all

[Mike Heidrick]

On the Joes CNC parts man MDf edges are treated with 50% water 50% wood glue mixture. Works awesome. Try it if you doubt it :)

http://i39.photobucket.com/albums/e169/BloomingtonMike/CNC%20Router%20Build/green.jpg

[Leo Graywacz]

Get some thin 2p10 from Fast Cap or others and squirt it on the softer MDF and let it sink in. Put on as much as will sink in and then spray the activator on it and it will become very hard.

[Michael W. Clark]

I made my router table top out of two layers of 3/4" MDF glued together and then laminated the top and bottom with Formica. I use confirmat screws from below to level the plate. No hardening needed. Once you rabbet to fit the plate in a single layer of MDF you don't have much material supporting the plate,lift and router.

"Confirmat", that's the screws I used and was trying to think of in my earlier post. Like I said, I only had one layer of MDF, so about 1/2" of thickness for screws to grab and no problems with the plate. The sagging issue is my fault for not knowing any better when I built the table out of one layer MDF and laminant only on top. It wasn't sagged immediately, but now after a move and 6 or 7 years, it has sagged to the point that it can affect performance for some cuts. With two layers of MDF and laminant top/bottom you'll probably be fine. My next major purchase is a shaper, then I'll move my router to the tablesaw wing. I'm buildign the table saw wing either torsion box or plywood.

Mike

[Thomas Canfield]

I use a thin shellac (cut 50%) to harden MDF for threads on jam chucks and different fixture and jigs used in the shop. The good thing about using shellac like that is that I have not cleaned the brush for over 5 years but just wrap it up in paper towel soaked in DNA and put in plastic bag. The next time I use it, the thin shellac will soften the bristles if they have hardened, and the shellac is very self leveling and not a problem getting a good coat. You can sand between coats to gain a smoother surface and even do a light sand on the final coat for supe smooth surface.

[Keith Westfall]

Saw a tip in the "Best ever - 300 + Shop Tips" magazine I just picked up, where they said to put a flat top screw in the bottom support where your leveling screws hit. Seems like that would work.

[Myk Rian]

Michael - I made my top out of 2 layers of 3/4 MDF. The table will be supported very well underneath, so I'm not too terribly worried about it sagging.

I was wondering how much of an issue this would really be.
I also used 2 sheets of 3/4". The cutout hasn't been a problem the last 6+ years.
I did nothing special to it.