Building cabinets with MDF core plywood

[Wes Billups]

Sorry for the long post but I feel I needed to explain my reasoning for using the MDF prior to asking my question.

A couple of years ago I was at an auction for a cabinet shop. At the end the auctioneer asked for a $5 bid on a 6' tall stack of hardwood plywood. Thinking I couldn't let it go for that I became the happy owner of over 100 sheets of mixed MDF core sheets. There is cherry, walnut, maple, alder, and white oak. Since I have so much of this I want to use it for shop cabinets. My plan is to just build square boxes with rabbets in the sides for the top and bottom. I'll cut a 1/4" groove for the back. Then glue and screw the top and bottom on so no fasteners will show from the sides. My drawers will be full overlay so I'm not going to bother edge banding the MDF core. All of the boxes will set on a platform style toekick.

Is this an appropriate method for constructing the boxes?
What screws would work best for going into the edge of the MDF?
I will be predrilling.
I'm planning on using baltic birch for the drawers but thought I'd ask if there is a more cost effective material?
Some of them will be large (32" wide by 12" deep) so whatever I use needs to be strong.
Does anyone have recommendations on sources for full extension drawer slides?
I just saw Jon Bonham's posting on the Gliderite slides and their prices look like the best I've seen.

Thanks for everyone's help,
Wes Billups

P.S. If anyone in central Ohio needs some MDF core plywood let me know.

[Matt Meiser]

Confirmat screws (http://www.mcfeelys.com/confirmat-assembly) have worked well for me on a couple of particle board projects and they are supposed to work for MDF too. For them, I didn't even bother with rabbets, just screws about every 6 inches. One of those projects was a shop cabinet that has held up great even though its been moved around a number of times.

I got some full extension slides from Woodwerks in Columbus one time that were inexpensive and worked well. Woodworkers Hardware and Custom Service Hardware are the two mail order sources I've used.

[Jim Becker]

My friend Russ builds extensive cabinetry with MDF core sheet goods almost exclusively. Confirmat screws where possible/visible but also largely with just shallow grooves/dados/rebates and glue. I've used some of it. Heavy, but very stable and absolutely true in thickness.

[Wes Billups]

Matt, thanks for the info. I’m heading to Woodwerks on Saturday as the Woodworking Show is in town and they are offering 10% off everything in the store so I’m hoping to get some there.

As for the confirmat screws, I’ve got some and will try them. My problem is I want to cut rabbets which are ½” deep in the sides. I’ll then screw through the top and bottom into the side. This would put those screws pretty close to the ends of the top/bottom. Since I’m going to be using some nice plywood I was hoping to hide the screws from view on the finished product. I realize these are just for the shop but I like to practice on my shop projects and figured this would be a great way to try something new on cabinets.

Thanks,
Wes

[Rob Wright]

Matt, thanks for the info. I’m heading to Woodwerks on Saturday as the Woodworking Show is in town and they are offering 10% off everything in the store so I’m hoping to get some there.

As for the confirmat screws, I’ve got some and will try them. My problem is I want to cut rabbets which are ½” deep in the sides. I’ll then screw through the top and bottom into the side. This would put those screws pretty close to the ends of the top/bottom. Since I’m going to be using some nice plywood I was hoping to hide the screws from view on the finished product. I realize these are just for the shop but I like to practice on my shop projects and figured this would be a great way to try something new on cabinets.

Thanks,
Wes

Wes - 1/2" deep on the sides for the dado may be considered too deep. When building boxes with ply or mdf I usally go for a 1/4" deep dado in the sides and confirmat screw the SIDES and glue, or no dadoes at all and use glue and confirmat screws from the side. The confirmat screws work incredibly well in MDF/particle - I guess they should since they were deigned for that application. I would be hesitant to screw from the top and bottom insto the sides, although I do see your reasoning/thought process to be able to hide the fasteners - but you still leave the 1/8" lip of MDF that can be seen still.

If you screw from the side, remember that the fasteners will only shown in the 1 outside side of the box - the sides will be butted against other cabinet box sides hiding them.

$0.02

- Rob

[Matt Meiser]

You could use the Fastcap dots sold for covering the screw heads. They even make a bit which cuts a recess that holds them perfectly. Its a little pricey for shop cabinets for me though. I used a few of the dots to hide install screws in my bathroom cabinets--they stick incredibly well.

http://www.fastcap.com/products.aspx?id=412

[Howard Rosenberg]

I've built cainets in high-strees environments this way for YEARS with zero failures.

Screws add needless complexity.

My 2C.
Howard

[Wes Billups]

Thanks for everyone's response. I think I'll just use the confirmat screws through the face of the side. If it bothers me I'll put a faux rail and stile on the end cabinets at a later date. One more question on this subject.

Is it worth my time to cut a 1/8" deep rabbet to help align the pieces?

Still looking for opinions on the best drawer materials. Baltic birch is great to work with but pretty expensive. Does anyone have better options? I've heard of appleply but never seen it. If I can find this would it work just as well.

Wes

[Chuck Burns]

Confirmat screws (http://www.mcfeelys.com/confirmat-assembly) have worked well for me on a couple of particle board projects and they are supposed to work for MDF too. For them, I didn't even bother with rabbets, just screws about every 6 inches. One of those projects was a shop cabinet that has held up great even though its been moved around a number of times.

I am building some book cases using 3/4 MDF Plywood. As I like things to be reasonably strong I decided to acquire some screws and experiment. I bought some of the 7x50mm Confirmat screws from McFeelys plus some of their standard square drive screws. I also used fine and course drywall screws, fine and course Kreg screws and some #9 x 3" Particle Board screws I go at a local lumber yard.

For each screw I drilled a hole equal to the root dimeter of the screw as measured by a vernier caliper. As I have numbered and lettered drill bit sets in addition to the standard fractional set I was able to get very close in all cases. For the Cofirmat screws I used the bit supplied by McFeelys. The holes were drilled 2 1/2" in from the edge of the MDF (I read that the screws should be in by that amount somewhere).

There were some screws that stripped when run in using my DW power screwdriver set on it's lowest torque setting and then finishing snugging up by hand. For the ones that snugged up nicely by hand I put a bit on
my 1/4" SanpOn torque wrench (inch/pound) and proceeded to tighten them until they failed.

The Confirmats did the best: they started to strip out at 55 in/pd but didn't fail catastrophically. After the torque stopped building I could continue to tighten at about the same torque for a few turns. After a few turns I could see the MDF swell and after a few more it split.

Next best were the #9 x 3" PB screws that tightened to 40 in/pd before failing; but when the failed they failed completely.

Fine and course thread DW screws or std McFeelys sq dr screws only went to about 30 in/pd.

So I'd use the 7x50mm Confirmat screws if going into 3/4 MDF and stay 2 - 2 1/2 inch in from the edges. If going into 1/2 MDF McFeelys sells a 5mm Confirmat screw. In both cases I'd use McFeelys specialty bit. There really is no other way to do it as it's got two diameters and two tapers.

My only question is on a 10 1/2" width (not counting 3/4" edge banding) should I run two screws or could I use three. That would be one 2 1/2" in from each edge and then one in between spaced at 2 3/4" on center.

At any rate, I hope that helps.

[Chuck Burns]

So I take it that MDF takes glue well. What type of glue do you recomend? I've got TB II and III on hand but if something else works better I'm willing to buy it.

As for the added complexity of the screws I guess it would make me feel better so I'm willing to do it.

[Matt Meiser]

Is it worth my time to cut a 1/8" deep rabbet to help align the pieces?

If you are using screws, I'd vote no. They go together quick enough without. If anything, use a biscuit jointer and cut two biscuit slots. You wouldn't even need to glue them.


My only question is on a 10 1/2" width (not counting 3/4" edge banding) should I run two screws or could I use three. That would be one 2 1/2" in from each edge and then one in between spaced at 2 3/4" on center.

I was told to put them about 6" apart, so 2 would be fine in that case.

[Grant Charlick]

I noticed you said that you were concerned about seeing the screws and it got me thinking. Have you thought about using a pocket hole screw. A good jig can be bought easily for under 100$.( I have a Kreg) You are already going to be investing the time to predrill and all, you might as well just use pocket hole screws. the srews will be hidden under the countertop and the bottom will be hidden under the toekick lip. The joint is super strong and really easy.By the way Hi fellow michigander, I'm from Oakland county.

[Wes Billups]

I noticed you said that you were concerned about seeing the screws and it got me thinking. Have you thought about using a pocket hole screw. A good jig can be bought easily for under 100$.( I have a Kreg) You are already going to be investing the time to predrill and all, you might as well just use pocket hole screws. the srews will be hidden under the countertop and the bottom will be hidden under the toekick lip. The joint is super strong and really easy.By the way Hi fellow michigander, I'm from Oakland county.

Grant, I don't like the way pocket holes hold in MDF. Their thread depth doesn't provide much grip.

Thanks,
Wes

[Doug Jones from Oregon]

Titebond II is sufficient. I've built a lot of case goods with mdf and it is my experience that if the glue joint fails, the screw will too, and therefore, I would vote for no screw at all...glue well and clamp. And, I would vote for a dado, I like the lip for the bottom shelf and the ease of alignment.

[Blake Holton]

Still looking for opinions on the best drawer materials. Baltic birch is great to work with but pretty expensive. Does anyone have better options? I've heard of appleply but never seen it. If I can find this would it work just as well.


Wes:

I've used ApplePly for drawer sides with good success / look in the past. I just finish the edges and leave the plies visable. It is a product manufactured by States Industries and sold through distributors across the country. You usually see it with maple face and back, but it is available in other species. If you dovetail the drawers make sure you use backer boards to reduce chip out.

Blake

[Joe Chritz]

I lost the link but somewhere I had read about an informal test between confirmats and zip-r screw construction just with a buttjoint.

The strength to failure was nearly always the same and the strength of the material is always the deciding factor.

Some people swear by #8 zip-r's some #9's some confirmats, all work well.

For drawers I have used scrap pieces of regular 1/2 maple or birch plywood for shop drawers or pocket screwed scrap 3/4". For show drawers it is either solid wood or BB ply 1/2 blind dovetailed. At the price I pay for BB($1.5 +/- per sq/ft last time) I don't think you could find anything cheaper that looks good.

Joe

[Wes Billups]

I wanted to update everyone here on the shop cabinets. I finally got a start on them today and ended up using some Spax screws I'd bought a few years ago. They work amazingly well. I ran some trials to see how close I could get them to the edge before causing the MDF to separate. With a pilot hole they never split the MDF even to 1/4" from the edge. Without a pilot hole they split the MDF at 1-1/2". I'm going to complete the assembly with these screws and will definetly use them again.

I have some of the Confirmat screws from Mcfeely's and will try those at a later date. For now the Spax screws are working great. I also found this link which shows a Spax screw specifically made for MDF. Spax link (http://www.ultimategarage.com/shop/part.php?products_id=267) I may have to try those if I get into a really big project with all of this MDF I have.

Thanks,
Wes

[Art Mann]

I hesitate to make this recommendation because it is not the recommendation of the manufacturers. However, I will do it anyway because I have had some measure of success. I have used pocket screws in this situation. They obviously don't hold like Conformat screws that are made for the purpose, but if you use enough of them, you may find them strong enough and they won't show. Strong clamping is required to avoid "mushrooming" the material being penetrated without a pilot hole when you drive the screw. I would strongly advise experimenting with scrap material before relying on this type fastener.

[Wes Billups]

I forgot to add the pictures of what I accomplished today. I'm happy as I only got about 1-1/2 hours in my shop tonight as my wife is out of town and my 4 and 2 year old can't seem to play for 5 minutes without someone ending up crying.

I decided to screw the top on from above as it will be hidden by the counter top. My construction method was to cut a 3/4" wide by 1/2" deep rabbet in the sides to receive the top and bottom. This is shown in the first picture.

I then screwed down from the top into the side doing my best to keep the Spax screw centered in the side panels. Second picture

The center divider isn't sitting in any dado as I just screwed through the top and bottom panel. The last two pictures are just to show where I ended tonight. I'll cut and install the backs tomorrow night as well as get a frame/toe kick built underneath this thing.

For those that are really observant the top is quarter sawn red oak, bottom is white oak, and the ends are maple. The future cherry counter top is leaning against the jointer. I'm thinking of using walnut for the drawer fronts.

Thanks for looking.

[Jim Broestler]

Glue and biscuits are a great way to join sheet goods. It's what they're made for. While the glue should be enough, the biscuits give you that extra bit of mechanical strength, and help align things too.

For drawers, I'm thinking 1/2" ply is your cheapest option, unless you want to try making them with 1/2" MDF, but they might not stand up to hard use.