2 Questions on Cabinet assembly (using Saint's/Lusid's Plans)

[shredso]

I have most of my pieces cut, control panel done, I'm about ready for assembly.  My questions:

Is it necessary to use 2x2's inside the corners?  The book says to use them.  I don't mind filling a few countersunk holes.  It seems like with the L brackets it should be plenty sturdy.  I'm also weary about using glue because it would make disassembly impossible.  SO the question is, do you think the cab will be sturdy enough with only a srew every 4-6 inches and L brackets?

The second question is how do you mount an arcade monitor instead of the TV?  should I put in the monitor shelf anyway for sturdiness?  I planned on just copying however it's mounted in the cab I have it in now ( the monitor).  Any tips or suggestions?

[sstorkel]

How long do you want your cabinet to last? L-brackets don't provide a whole lot of holding power and definitely seem to loosen over time, especially if the cabinet gets moved frequently. Glue adds a lot of strength to a cabinet! Today's wood glues are so strong that in many cases the wood around the glue will fail before the glue does...

If you're using an arcade monitor, you probably don't need a shelf. Unless your cabinet is already wobbly to begin with. In that case, a shelf might help stiffen it up, even if it isn't used by the monitor.

[Kirth]

The first time I made my cabinet (Lusid design) I just used screws and 2x2s to hold the mdf piece together.  It wasn't very sturdy and creaked a lot.  There were no back panels so the entire top half had no way to handle the shear stress of rocking the cabinet side to side.  After a year I moved to new place and had to cut my cabinet in half to get it upstairs.

I decided to use the opportunity to take it apart and reassemble it.  Here are the changes I made:
1. I got rid of the 2x2s and screwed directly into the mdf edges instead.  I drilled all the pilot holes before disassembly so this was easy.
2. I used glue.
3. Took the tv tube out of its shell and mounted it to the cabinet at its four corners.  This added a lot of stability and I could get rid of the monitor shelf.

Things I would do differently:
I would assemble the mdf carcass using only glue with no screws (maybe biscuit join it).  The screw holes are a real pain if you're going to paint it.  Basically, the mdf will absorb the water from anything water based and swell up.  It will eventually contract back but long after you've finished painting.  This means you'll end up with slight bumps or depressions where the hole was, even if you feathered the patch properly.  I started with a wall spackling compound but I finished with bondo.  If you do patch the holes, use something like bondo.  It still sands fairly easy and won't make the mdf swell.  The bondo patches on my cabinet are hardly noticable while the some of the others are easily seen.

I might use vinyl on the sides of the cab instead of painting it.  I would definitely use an oil paint if I could.  I was painting in a spare room so I had to use latex.  The latex isn't a big deal though, you can just sand it flat after each coat.  What made it a big pain was the screw holes.

[Blanka]

Good glue is stronger than wood, so I did the whole cabinet by just glueing. I did previous MDF furniture, and the covering of screws is always a real pain. But with wood on the inside, you can also choose to screw from the inside and thus leaving the exterior surface untouched.
100% screwing is not recommended because edges are not connected over the full length and cracks is finishing can occur.
If you decide to go 100% glueing, make sure there are enough supports inside to keep the shape sturdy.

[CommonDenominator13]

If there was more material than just 5/8 to 3/4" and if it wasn't MDF, I'd say you could probably get away with screws.

However, MDF (and even plywood) doesn't hold screws that well, especially not at this scale.  And there isn't nearly enough depth for the screws to really hold on to.  It may hold for a while, but as others have mentioned, it will gradually work lose over time.

Definitely don't skip the glue.

[sstorkel]

Good glue is stronger than wood, so I did the whole cabinet by just glueing.

This is true... but not the whole story. If you try to edge glue two piece of plywood together, for example, the glue joint will be very fragile. Similarly if you attempt to glue an end-grain piece of solid wood to another piece of wood, the joint will be be delicate. This is one of the reasons that people still make mortise and tenon joints, dovetails, etc.: because they allow face-to-face gluing, where the glue is strongest, rather than end-to-end or end-to-face gluing.

[CommonDenominator13]

Good glue is stronger than wood, so I did the whole cabinet by just glueing.

This is true... but not the whole story. If you try to edge glue two piece of plywood together, for example, the glue joint will be very fragile. Similarly if you attempt to glue an end-grain piece of solid wood to another piece of wood, the joint will be be delicate. This is one of the reasons that people still make mortise and tenon joints, dovetails, etc.: because they allow face-to-face gluing, where the glue is strongest, rather than end-to-end or end-to-face gluing.

True.  Although it's my understanding that end to end isn't as much the problem, as much as not having enough surface area or structural support to support the joint.

Dovetails, mortise/tenons, etc. add not only surface area for the glue, but also additional structural support (a good dovetail doesn't even need glue).

But that's neither here nor there.  Use glue in this case, especially with MDF, plywood, or even regular softwood.  They typically aren't 'solid' (too soft) enough for holding such shallow screws.

If you were to do a bolt clean through both pieces, then it'd be a different story and you could probably get away with not using glue for the shelf brackets, but then your machine would start to look like Frankenstein.... Hmmm.... that's an interesting idea....

[sstorkel]

True.  Although it's my understanding that end to end isn't as much the problem, as much as not having enough surface area or structural support to support the joint.

The glue tests I've seen in Wood and Fine Woodworking would seem to indicate that end-grain to end-grain (or edge-to-edge joint in plywood) are physically weaker even when surface area is the same.

Obviously, I would recommend using glue in this situation. But to think that a glue joint is always stronger than the surrounding wood may lead someone into trouble in the future...

[CommonDenominator13]

True.  Although it's my understanding that end to end isn't as much the problem, as much as not having enough surface area or structural support to support the joint.

The glue tests I've seen in Wood and Fine Woodworking would seem to indicate that end-grain to end-grain (or edge-to-edge joint in plywood) are physically weaker even when surface area is the same.

Interesting.  I wonder if it has to do with porousness of the wood.  I'm guessing that two smooth surfaces will likely create a more uniform (and smaller?) glue plane than between the relatively porous surfaces of end grains, as well as the end grain absorbing more glue.  I'm curious if that's what it is or there's more to it.  I'm also curious about finely finished hardwoods, do they have the same problems?

Do you have a link to any of the articles?  I'm curious to read more about it, if only for trivia.

Edit:  Just in case I sounded sarcastic, I'm not asking for proof, I'm legitimately interested in reading the article.

[sstorkel]

Interesting.  I wonder if it has to do with porousness of the wood.  I'm guessing that two smooth surfaces will likely create a more uniform (and smaller?) glue plane than between the relatively porous surfaces of end grains, as well as the end grain absorbing more glue.  I'm curious if that's what it is or there's more to it.  I'm also curious about finely finished hardwoods, do they have the same problems?

I'm not sure either of the articles had a definitive explanation. I think there are at least two factors at work. One is that end-grain tends to soak up glue and pull it along the wood fibers and away from the joint, just like it does with finish. I also think that there's something about the way the glue chemically bonds wit the wood fibers. For yellow glues, at least, long-grain to long-grain bonds have higher strength than end-grain bonds. Heck, it might just be a surface area thing: the glue creates bonds between glue fibers. If you think of the fibers as cylinders, you obviously get much more surface area along the length of a long cylinder than across the diameter.

Do you have a link to any of the articles?  I'm curious to read more about it, if only for trivia.

Unfortunately, I don't. I subscribe to the print magazines, so I have no idea if the articles are available on-line. If I get a chance, I'll see if I can dig up issue numbers and post them.

[CommonDenominator13]

Unfortunately, I don't. I subscribe to the print magazines, so I have no idea if the articles are available on-line. If I get a chance, I'll see if I can dig up issue numbers and post them.

That'd be awesome.  Thank you!