Bookcase back panel opinions

[ars_lurker]

I am building a set of barrister bookcases off the plans in one of my old Wood magazines. The main parts are all QSWO and the back of each case is spec'd as 1/4" oak plywood. There lies the problem. I can only find QSWO 1/4" veneer over mdf core instead of actual plywood.

It fits into a rabbet so you cant see the edge but these are going to be used for hopefully a couple generations. Using MDF anything on this just feels wrong.

Any suggestions?

http://woodstore.net/babo.html

Mike

[LarryG]

Option A: If you're concerned about the strength of the MDF core, you could sandwich it with another 1/4" layer of lesser plywood. Obviously this would result in a minor dimensional change to either the gross or net depth of the units.

Option B: If you're opposed to MDF on principle, increase the back thickness to whatever minimum you can find. Again, you'll either lose a bit of inside depth or will need to adjust the overall depth to compensate.

Option C: Mill up some individual boards with a shiplap or T&G edge detail. You'd need to allow some room for expansion across the width of the bookcases.

[LCHIEN]

I'm not sure what your objection to MDF is.
The back of such bookcase has two purposes, one to present the Oak veneer for appearance sake and that is done quite well. The other very important reason it to prevent racking of the carcass and give it lateral strength across the back which MDF will do quite well. I doubt that the MDF strength is an issue. I suppose that the nails that hold it to the rabbeted back could split and the MDF pull loose, ply might be better at that. For racking strength the ply should be just as good and lie flatter and be heavier to the thump test. Since it won't be visible in any way there's no points lost there.

An option is to use 3/16 veneer ply (if you can get it), a little thinner but I'm sure strong enough to do the job, there may be some visible ripple in the back if you go too thin.

I really don't see any serious negatives to using MDF-core veneered backing.

[ars_lurker]

MDF it is then.

I have never used MDF on any project outside of jigs and fixtures. I was curious about it's longterm durability mainly.

Thanks for the help. This site is great!

[jking]

I could see a problem if you were talking about the back of a cabinet that hangs on the wall, but, since it's sitting on the ground it shouldn't be an issue.

FWIW, I built my wife a nightstand out of 3/4" oak veneer mdf core material. I wrapped all exposed edges with solid 3/4" oak. It does get much abuse, but, it's several years old & hasn't had any problems.

[RodKirby]

What Loring said and...

This has a 1/4" MDF back that I painted first (front and back), and then glued/nailed into rebates - hasn't moved in 4 years

[cabinetman]

I agree with Loring. You didn't say how large a panel it would be. If you're really concerned, you could buy 1/4" plywood, and veneer it with QSWO veneer. The panel you found you said it was a MDF core. Was it all MDF with a QSWO face, or was it 1/4" ply with a MDF core and QSWO face?

MDF cored hardwood plywoods are fairly common among hardwood plywood suppliers.
.

[LCHIEN]

MDF it is then.

I have never used MDF on any project outside of jigs and fixtures. I was curious about it's longterm durability mainly.

Thanks for the help. This site is great!

as long as it doesn't get soaked with water, it's going to be pretty durable.

[ars_lurker]

I agree with Loring. You didn't say how large a panel it would be. If you're really concerned, you could buy 1/4" plywood, and veneer it with QSWO veneer. The panel you found you said it was a MDF core. Was it all MDF with a QSWO face, or was it 1/4" ply with a MDF core and QSWO face?

MDF cored hardwood plywoods are fairly common among hardwood plywood suppliers.
.

This is why I come to this forum. You all have lots more experience than I and the advice is very helpful.

Each panel will be 15" x 35". The plywood at the mill is 1/4" QSWO A2 MDF core. It is going to cost about $68 for the 4x8 sheet. The 3/4" QSWO A2 MDF for the top and bottom of each case is $82. Expensive but cheaper than solid QSWO.

[jackellis]

I used to be a snob about materials and workmanship (this is before I attempted to build anything from wood). Dovetail joints in drawers, solid wood, etc.

I've since learned that since I can't afford to be a snob about these things and pay extra for appearances sake, engineered materials and simpler joints work quite well, thank you.

Based on the price, it seems you're using good quality materials for the back. The only suggestion I'd have if you're worried at all about moisture is to seal the edges of the MDF ply.

[ars_lurker]

Thanks Jackellis. I haven't made too many projects since high-school shop class 15 years back so I am sure I am being a little too snobbish about the materials. MDF was either really new or non-existant back then.
I could afford solid material all around if I was only building one case but I plan to build 4. Solid QSWO all around becomes cost prohibitive for me at that point. The last project I made I posted here so I will make sure I do the same for this one.

Thanks everyone! I am sure I will need help again sometime in the future.

[Carlos]

MDF lasts forever or until water soaks into it, whichever comes first. It really does soak up water though, so I always put some Kilz primer on any edges that are not glued, just in case. You figure water will never get near your furniture, but then we had a pipe issue recently and lost two pieces of simple particle board furniture because of it.