Making an MDF Box

[Burt Alcantara]

I have a lot of MDF and I need some shop cabinets. My question is what is the best way to attach MDF to MDF? Most of the posts I've seen will have some saying this way works best followed by someone saying that particular method does not work.

I just want to put some simple storage cabinets together to hold finishing supplies, misc tools, all the shop junk that ends up on the floor, bench, under the bench, in bedroom closets, in the garage...you know, everything that you can't find because there's no place to put it.

I'm not concerned about nicks, gouges, scars and generally ugliness. I can always use the cabinets to practice veneering.

Thanks,
Burt

[Fred Hargis]

I prefer glue and biscuits, but screws and glue work very well if if the edge holding the screw doesn't split.

[Burt Alcantara]

Spax, Confirmat? Suggestions?

Thanks,
Burt

[Paul Redfern]

I would butt joint,glue and srew. You could use rabbets and dadoes for joinery, but MDF sawdust is bad stuff. That is why i would butt joint.Pre drill your srew holes

Paul

[Paul Redfern]

Confirmat are great screws if you have them lying around. On projects like this i try and use up what i have the most of. Gold diggers and sheet rock screws mostly.

Paul

[Burt Alcantara]

Woodcraft has HighPoint confirmat screws with bits and drills. They are very close by. Since I have a lot of MDF and want to build a bunch of things I'm willing to put the bucks up, unless there is a better cheaper option.

I also have a PC jointer with about 10k biscuits (well...seems like it).

Burt

[Joe Scharle]

Suggest you slightly countersink all holes before screwing down. Helps prevent puckering at the mating surface. I use a hand countersink tool and Woodcraft has them.

[Erech Myers]

I made a few of my shop cabinets out of MDF and I used pockets screws (kreg jig R3 - $39) & glue. It worked very well & no split edges.

If you use pocket screws though, I will give you a heads up. When putting in the screw, the piece has a tendency to slide out because the MDF has a hard shell and the screw does not penetrate right away. Since the screw does not penetrate right away, the piece will actually lift up slightly and slide out. You can try to pre-drill a starter hole in the piece you are screwing into, but I found it difficult to figure out exactly where to drill the hole. Instead I put my thumb on the outside of the piece and push against it to prevent it from sliding out. It takes a little getting used to, but once you get the hang of it, it works great.

The pocket screws are the easiest & quickest, but if you are looking for ultimate accuracy, I agree with Fred, use biscuits.

[Burt Alcantara]

I have the Kreg but it fools me often so I don't use it too much. Are biscuits better then screws, or at least, just as good/better?

[Cole Dunlay]

I've used biscuits in MDF with good success and since you seem to have plenty of them they seem like the way to go. MDF is inexpensive stuff and it doesn't seem to make much sense to spend a lot of money on fasteners for shop type projects in inexpensive material. Just my 2¢.

Cole

[Erech Myers]

I have the Kreg but it fools me often so I don't use it too much. Are biscuits better then screws, or at least, just as good/better?

The biscuits don't add much lateral strength, they just help with the alignment. You may want to use both, but since these are just shop cabinets, I agree with Cole, don't spend too much money or time. Screws and glue should be easy & cheap. Plus if you use screws, you won't have to use any clamps. If you only use biscuits & glue, you will need to use clamps until the glue dries.

What do you mean the Kreg jig fools you? I find the Kreg jig very easy for simple projects. I'm just curious.

[Jeff Monson]

I butt joint mine, glue them and use the mdf screws from mcfeely's, I have a kit that came with screws, bit driver and a drill bit that is designed for their screws, works really well.

[Don Morris]

I've been very happy with McFeely's screws and they usually give a good explanation of why each type of design is best for each application. I took this from their site for Confirmat screws: "If you assemble melamine cabinets or work with particle board or Medium Density Fiberboard (MDF), these unique fasteners have been specially designed to make your life easier. The 5mm dia.shoulder beneath the head acts much like a steel dowel pin and locks the shank in position to minimize the possibility of board failure. This creates a remarkably strong and stiff joint that generally does not require glue. Screws require a pilot hole through both pieces of material. Simply clamp the pieces together and drill with a specialized 3-step 7.62mm/5mm/3.5mm drill bit. These 5x40 screws are recommended for use with 1/2" materials and are ideal for constructing drawer boxes. If you are using 3/4" thick material, consider using the 7 x 50mm screws Confirmat Style Connecting screws."

[Burt Alcantara]

Erech,
When I use the Kreg, I loose alignment and squareness. I've tried clamping angles on to the joint but they still seem to slip or otherwise come out of alignment. I use them for non-important joints where I don't care if they are off.

I'm aware that the fault is with me and not the Kreg. I think it is a matter of compatibility. In this case I have filed for divorce.

Burt

[Myk Rian]

I use a locking rabbet joint to make MDF boxes.

[glenn bradley]

Spax, Confirmat? Suggestions?

Thanks,
Burt

I have several 3/4" MDF cabinets that are years old. One takes the stress of being rolled around the shop over the uneven surfaces. No joint failures. I make a 1/4" rabbet and then glue and screw with McFeely's (pick your brand) FHWS (not cheap soft or brittle screws). Center dividers are dado, glue and screw joints.

Confirmat and such are definitely a better fit for MDF but I have only used them occasionally for hanging cabinets. For me the trick is in the method for screwing MDF (more than the screw) which is no trick at all and has been widely published:

- Use straight shaft screws, not tapered.
- Drill the hole a bit deeper than the length of the screw.
- Drill the hole the diameter of the shaft so that only the screw threads bite into the material.
- Put a slight countersink at the hole on each of the mating surfaces to prevent the volcano effect.
- Use plenty of glue as MDF is fairly absorbant and starved joints can be a problem.
- Seal your cabinets to prevent structural breakdown from moisture, heat, whatever.

Others may add to this list but these points seem to be hit by most of the mags.

[Bill Huber]

With the glue, do just like wallpaper, sizing, put on a layer of glue and let is soak in a bit and then add another layer. MDF just soaks up the glue, mainly on the ends.

Then screws to hold it together, Mcfeelys has just what you need in that department.

[Angie Orfanedes]

I use butt joints with glue, further secured by deck screws from the blue borg (the kind with the #2 phillips head). I pre-drill a pilot hole/countersink, and I am careful not to overdrive them. I have a several roll around cabinets that I am sure will outlive me.

[Jerome Hanby]

So do I and Harbor Freight has them too. May not be the worlds greatest tool, but it's cheap and how good does it have to be :D


Suggest you slightly countersink all holes before screwing down. Helps prevent puckering at the mating surface. I use a hand countersink tool and Woodcraft has them.

[Jerome Hanby]

I'd be tempted to use "posts" in the corners on the inside, maybe an inch square, and screw/glue the MDF face to those. Maybe use biscuits to help with alignment. MDF is going to make some heavy cabinets...

[Stan Johnsey]

I did some foolin' around with the MDF makin' boxes and was surprised how much I didn't know. Found a website that covered using screws in MDF and took it to heart.

Drill the pilot hole full depth and 85-90% of root diameter of screw. Sheet metal screw work better than wood screws and the special MDF scews (folks call 'em cement board screws 'round here) work best. I was using #8 MDF screw with a 7/64" pilot hole. Chart called for a number bit I didn't have. Also had had better luck when I drilled the hole in the top piece oversize so that the two pieces pulled together better.

Here is a link to that data sheet: http://www.norbord.com/images/screws-MDF.pdf