I’ve been building some shop jigs and a router table from MDF, using just dados and glue to hold the latter together – i’m just wondering if anyone knows what the glue holding properties of MDF are. I know that with a good edge grain glue joint with most woods is supposed to be stronger than the wood itself; is the same true for MDF? Does glue hold on the face of MDF better than the “end grain” (so to speak)?
Jesse David
Replies
If you're going to join an edge to a face, either dado the face and insert the edge or glue/nail/gusset or screw the pieces together. If you want to make something that creats a right angle, like a fence, just the two pieces alone won't be terribly strong. You can do a lot with MDF, but no, it's not like wood. Boxes can be very strong, angled pieces with gussets can be strong, but unless the piece is for light duty, I would glue/screw the parts together.
I did one of my 'scientific tests?' once. Used Elmers Probond on MDF edge to edge, face to face, face to edge and also MDF to oak. Nothing fancy, just a nice clean cut right from the saw. Smear glue on both pieces, clamp, next day...
Not sure why I do it, but any smooth face I will sand just for some tooth. I just have some little 'L' blocks.. 1/4, 1/2, 3/4 etc. with used 80 grit paper stuck on. Just run it along the edge of the surface to be glued. The L shape makes a stop block so I don't wander onto the non-glued surface.
I used my old roofing hammer (30 Ounce about) and my bench vice. Well, lets just say, my bench moved about a foot before the stuff broke. Bench must be about 300 pounds. I did not see that much difference between edge to edge, face to face, face to edge except how it tore out. As I remember, face to face pulled chunks out of each side and edge to edge broke cleaner (smaller chunks?).
Well, anyway.. Dosen't hurt to biscuit, nail, screw, peg, whatever... for backup.
By the way.. the oak just split!
Another thing that matters is the quality of the MDF. It's not all the same. You can get it from a place that sells specifically to cabinet shops, from lumber yards and big box stores. Particle board is the same, in that there are varying levels of quality. If you need particle board that's really stable and even, get the stuff with paintable surfaces. The face is darker brown(has some kind of coating on it) and the density is higher at the surfaces, then slightly lower in the center. It holds screws better, it's straighter, cuts cleaner. More money, but for something that's important, it's worth it.
"I cut this piece four times and it's still too short."
Stuff with paintable surfaces... Is that the stuff good old 'NORM' uses. I forgot the name but I can't find local. Shipping on those 100 lb sheets kind of expensive.
Local Home Depot I go to has some stuff about 5X5? (there abouts) sheets of MDF that dot bad.. I get most of my MDF from a local hardwood place, Owl Hardwoods (Chicago). Not a expert but the stuff from the big box works about the same. Could be I'm not smart enough to know the difference?? LOL...
I think I like the low weight MDF Owl has is pretty good but not quite as stiff...
Edited 1/28/2005 11:59 am ET by Will George
No, Norm uses MDO(medium density overlay), same as what's used for highway signs. The stuff I'm talking about is used by cabinet shops that do high dollar and retail cabinetry. I should have thought back to when I used it for the cabinet doors in my rental unit. It's paintable on one side, melamine of the other. Pretty dense stuff but is nice to work with. The paintable side is for keeping the contact cement from soaking in(saves material and time, since it doesn't need to be applied twice) and is smooth.
"I cut this piece four times and it's still too short."
Does it have a Brand name?
One thing to remember about MDF, especially if you are working on edges, is to pre drill screw holes. MDF is quite prone to edge splitting.
Alan & Lynette Mikkelsen, Mountain View Farm, est. 1934, Gardens & Fine Woodworking, St. Ignatius, MT
Good point. Particle board splits too, especially if the screw is too large or the material isn't good quality. Coarse thread works best- fine strip out too easily.
"I cut this piece four times and it's still too short."
Biscuit joinery was developed in Europe to assemble casegoods. Biscuits will make the strongest joint in particleboard and MDF. Both particleboard and MDF glue fairly well but MDF is better. Biscuits will make a stronger joint than screws.
The glue bond will be stronger than the material itself.
Mike
MDF will glue much better face to face than edge to edge. I've recently started using polyurethane construction adhesive for gluing mdf. It seems to work quite well for gluing edges as the stuff is thick enough that it doesn't all soak into the fibers and makes a much stronger bond. I think the name of the glue is PL3000 or something like that.
Andrew
PL-3000 oughta hold it! PL-400 or 600 ought to work, as well. I just saw a link to FastCap this AM and they have a glue bottle cap that's made for laying a bead of wood glue along the edge of sheet goods. It was in a thread for hanging kitchen cabinets and I'll edit this reply with the link. They have other tools and accessories for this kind of thing. I don't know if the guy I got the material from still works there but Alpine Plywood may sell it. They have a site, too. Or it can be googled.The website is http://www.fastcap.com"I cut this piece four times and it's still too short."
Edited 1/28/2005 4:19 pm ET by highfigh
highfigh,
That's a great link. Thanks!
Rich
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