Edge Banding Plywood with MDF Core

[George Bokros]

I need to make a shelf 5" long which will be well supported across the back and have some support for the middle 15" so I am not afraid of sagging. The shelf will 3/4" thick and I need to face the front edge with oak and plan to glue a 3/4" x 3/4" piece of oak to the front for the edge band.

How well will glue hold the oak edge to the MDF?

Thanks

[Steve Jenkins]

Whenever I edgband mdf I always use biscuits ever 10-12 inches.

[Robert Engel]

MDF edges can be sized with glue first, the apply edge band when tacky.

Other options: contact cement or epoxy.

I think the iron on edge banding would probably work you have to try it first.

[Larry Browning]

+1 to Steve's idea of using biscuits. Have you considered a wider banding? Like maybe 3/4 X 1 1/4. You could cut a 3/8 X 3/4 rabbet in it which looks really nice and adds stiffness to the front edge. Regular Titebond works great for gluing hardwood to mdf.

[Steve Jenkins]

I'd go with Larry's suggestion on the width and make it either 1-1/4 or1-1/2. I think that a shelf that long 3/4 would look kind of skinny. I usually use 3/4 thick by 1" tall on my book shelves but usually keep them less than 36" long. I've made thousands of shelves over the years just using a square joint and biscuits and have never had any problems.

[George Bokros]

This is a shelf in a closet with a clothes hanging rod underneath it. I did that in one other closet and used wider baseboard as the cleat on the wall but it looks to massive, so in this closet I am using narrower baseboard as the cleat and with a 1 1/2" wide edge on the shelf it is difficult to get the hangers on to the rod because you cannot lower the rod enough to compensate. Most of the old time closets, when they did not use the dumb wire shelves, the shelves were only 3/4" thick and looked fine to me.

[Larry Browning]

This is a shelf in a closet with a clothes hanging rod underneath it. I did that in one other closet and used wider baseboard as the cleat on the wall but it looks to massive, so in this closet I am using narrower baseboard as the cleat and with a 1 1/2" wide edge on the shelf it is difficult to get the hangers on to the rod because you cannot lower the rod enough to compensate. Most of the old time closets, when they did not use the dumb wire shelves, the shelves were only 3/4" thick and looked fine to me.
George,
MDF has a real bad habit of sagging without good support. The main reason I suggested a wider banding was to add stiffness and support to the front edge. If you think you will have enough support on the front edge, then go for it. Keep in mind too, 1-1/4" edging is only going to be 1/2" below the bottom edge of the shelf.
You can also add width to the cleat only at the place where you mount the rod, so you could lower the rod as much as you want. But I don't think that extra 1/2" is going to interfere with hanging clothes on the rod at all.

[Peter Aeschliman]

What do you mean by "some support for the middle 15"?

Is that a measurement across its depth, or width? If depth, are you saying that you'll have some kind of 90 degree bracket supporting the shelf every few feet? If so, then yeah, sagging won't be an issue. If there is no support in the middle of the shelf, then even with the wall cleat, you're going to have a lot of sagging. So I have to agree with others that the edge banding should be around 1.5" tall for support.

Biscuits + glue size would be my approach.

[Larry Browning]

Biscuits + glue size would be my approach.

Ok, call me ignorant, but what do you mean by glue "size"? That term was used in an earlier post as well. So I am thinking it must be a pretty common term, but I have no idea as to what it means.

[George Bokros]

What do you mean by "some support for the middle 15"?

Is that a measurement across its depth, or width? .

It is a shelf 60" long with 15" in the middle supported.

[George Bokros]

Thanks for all the suggestions. Here is more detail. The span will be 23" then support then 15" then support then 23" for a total of ~60", don't believe sagging would be an issue. This will be of course supported on both ends and along the entire back edge.

The only reason I have considered MDF core is because it is so flat compared to cabinet grade ply, which on some sheets I have purchased have had some warp to them.

[Larry Browning]

It is a shelf 60" long with 15" in the middle supported.

With 1 15" L bracket support in the middle of the 60" span? That means there will be ~30" on either side of the support.
I am thinking that will give it ample opportunity to sag without some additional support. The 3/4 oak edging will help, but the thicker the better.

[Larry Browning]

Thanks for all the suggestions. Here is more detail. The span will be 23" then support then 15" then support then 23" for a total of ~60", don't believe sagging would be an issue. This will be of course supported on both ends and along the entire back edge.

Ahh! That's different. Then the 3/4 edging should be fine, as long as the supports extend to the front edge of the shelf (or at least to within and inch or 2 of the front edge)
BTW: most of the closet shelves in my house are 2 1x6 solid pine or fir boards edge joined or even a 1x12 mounted on 1x4 cleats on 3 sides. The rod is just mounted on the 1x4 cleats at each end of the shelf. This just seems to be a lot of extra work for a simple closet shelf.

[George Bokros]

The closet shelf runs across the top of the closet organizer that is being installed in the center of the closet.

[Larry Browning]

The closet shelf runs across the top of the closet organizer that is being installed in the center of the closet.
I was beginning to suspect as much. So your are going to have 2 rods spanning the 23" on either side of the organizer? Maybe even 4, 2 up high, and 2 in the middle somewhere. I am beginning to see it a little clearer now. Are you going to stain and urethane, or just paint it all?

Also, can someone please explain to me what glue size is?

[George Bokros]

You are on to it Larry. It will four rods two up and two lower. It will all be stained and urethane to match the existing woodwork in the house.

Guess I should have given more project details but I was only really interested in how others have applied edge banding to MDF core ply. The edge banding will be 3/4' thick and 1 1/2" to 2" wide.

[Charles Taylor]

Can someone please explain to me what glue size is?


It's a thin wash of glue applied to the bare edges of (in this case) MDF and allowed to dry a little so that the next application of glue, intended to do the bonding, won't just get soaked up by the material. It also helps when gluing miter joints in wood.

[Larry Browning]

It's a thin wash of glue applied to the bare edges of (in this case) MDF and allowed to dry a little so that the next application of glue, intended to do the bonding, won't just get soaked up by the material. It also helps when gluing miter joints in wood.
Well that makes sense...(NOT)! I mean the name. I suppose there is some ancient meaning to the word "size" that I am not familiar with.

[Charles Taylor]

Well that makes sense...(NOT)! I mean the name. I suppose there is some ancient meaning to the word "size" that I am not familiar with.

I've heard it used in reference to preparing a canvas for painting, or preparing a wall for wallpaper, and it means a similar thing: applying a thin film of something to either improve adhesion, protect the substrate, or both.

[Steve Jenkins]

It also works well to seal the edges of mdf prior to painting. Glue size,sand,sealer,paint.
Mix about 3 parts wTer to 1 part pva glue

[jack duren]

You don't need biscuits for this application...

[Brian Tymchak]

Ok, call me ignorant, but what do you mean by glue "size"? That term was used in an earlier post as well. So I am thinking it must be a pretty common term, but I have no idea as to what it means.

Sizing the joint (usually end grain to end grain) means to apply a thinned mixture of glue to the end grain a few minutes prior to using full strength glue on the joint as normal. It helps to keep the end grain from sucking up all the glue and starving the joint of glue.

MDF edges are worse than any end grain I've encountered for sucking up the glue, finish, etc. Just like a dry sponge.. I don't use a water thinned glue on MDF though. I'm too worried it will separate and be worthless. I use full strength glue to size mdf edges if I have to. Usually I find a different method to attach to mdf edges than relying on glue.

[Andre Blanchard]

Ok, call me ignorant, but what do you mean by glue "size"? That term was used in an earlier post as well. So I am thinking it must be a pretty common term, but I have no idea as to what it means.

In weaving the warp threads are under tension and pass the length of the loom thru some eyelets that pull the thread up and down between passes of the filler threads. The raw threads have fiber ends sticking out which can hangup on the holes in the eyelets. So the thread is treated (sized) with a starch (glue) to keep the fiber ends flat to the thread so that it is smoother and more uniform in size.

[johnny means]

Good glue coverage and clamps will do. A few micro pins will help keeping things aligned. Not sure what these guys think is going to rip that edge off, but you'd be hard pressed to pull it off five minutes after glue up.

[Larry Browning]

The biscuits are for alignment without nail holes, not strength. Of course if there is no issue with nail holes, then I would just brad nail it every 6-8 inches and call it good. Might not even clamp it.