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Thanks for that, just sharing my professional experience!
No probs, just calling it as I see it!
Thanks for the further tips. Re. sanding and putting a radius on MDF edges, since I've worked mainly in 18mm MDF my approach (in the absence of a good sander) has been to glue on D-profile softwood mouldings. Obviously that take the paint well and seems to be fairly durable.
That Festool looks interesting. As you say though, it's pretty pricey. I went to a window-makers recently and the owner was banging on about how great rounded tenons are, so I can believe it makes for pretty strong joints. What's your opinion of Kreg jigs or similar for pocket-hole joinery? Apparently they make very strong butt joints, but I guess for the kind of cupboard you're describing here the backboard takes care of most of the shearing force that would push the box into a parallelogram shape.
Edit: Can you post some more details/links of the sound-dampening material please. That might come in handy very soon!
ffm-
The wood moulding edges on mdf is a good approach in lots of circumstances, it's way more durable than bare mdf so it works well for desk edges etc. Going back 15 years I would do that on most things too. It just adds to the cost for pro work. I make them in any size I need from soft or hardwood with a table saw. Usually a little oversized, glued and pinned on then planed and sanded to disguise the joint. Sometimes needs a little filler, it's all a time-consuming.
The domino is the one that most diyers dream of, I have the smaller one they released 10 years ago and it's paid for itself over and over. They make a larger one which I've not had enough call for yet, I still make mortice and tenons for windows and doors by hand, it's easier than it seems if you have a good mortice chisel, japanese pull saw and accurate mortice marking tool. The domino spreads the force of the dowel on mdf too as the mdf is quite weak on the edges and force applied to a large box before it's installed can be enough to split it.
I think the Kreg gets used by a lot of guys but I've never used it. I used to use doweling by putting the boards together and drilling a tiny pilot hole through from the outside edge then drilling from the inside part way through following the pilot and into the edge of the other board again following the pilot hole. It's surprisingly easy to get it right. The jigs you can buy for dowelling work on a similar principle but guide the drill bit at 90 degrees.
The backboard does save you from a lot of issues with strength in the joints, sometimes I rebate the back edge of the box and use a thinner panel or tack the rear panel on because I'm sure the box is square.
I'll look for links on the sound deadening material but I get it from a mate who has a load of offcuts from the work he does. If you search for van acoustic deadening it's a very similar material. I can usually find offcuts of different materials when I need that kind of thing.
Airhead
Thanks for that, just sharing my professional experience! In fairness I have a few advantages that I use to help my projects along. Although they're not really affordable for diy.
Festool domino - use it to join boards, it's a type of biscuit joiner where the biscuits are more like tenons. The furniture stands up on it's own before you glue it.
Spray shop quality sander. You can polish the edges of mdf boards to 400 grit through 4 grits. The edge then takes paint as well as the face. Spray painters have huge machines that can swallow a whole board just to do this one job to it. They usually put a small radius on the edges too. You should consider a radius on the edges of your mdf boards as they hold the paint better, there are aesthetic reasons you wouldn't do that from time to time.
Rafix/minifix connectors - like Ikea connectors, it's a pin screwed in one board/ ratchet thing in the other. You tighten the boards together and it saves gluing up on site which requires clamping or you can make furniture that can be dismantled and moved/sprayed. I've moved one of my freestanding pieces 3 times for the owner, it's huge and fills a transit broken down but it's been able to travel with them. Also no screws to split the mdf or require filling. Can also be used for shelves you want fixed in place.
18 gauge air powered nail gun, invisible nailing for trim. The nail heads are tiny and basically disappear.
Plastic screw caps. It's not invisible but if you need 2 or 4 screws on the inside of a cabinet to fasten it to the walls then at least the next guy can find them and remove them easily! With filler on top of these nails a change in loading/tension on the outer walls can make the filler pop. Also useful for bath boards and panels that should be removable in bathrooms and battening under shelves. They can be painted and virtually disappear.
32mm system plastic jig. Its a little plate that shows you where to drill the holes for mounting plates and holes of the hinges. It's affordable if you can find them outside of trade suppliers.
A bag of plastic wedges, you will probably need more than one wedge size every day you work on these types of projects. Saves improvising them from wood stock.
These sort of tools can save having to use filler, fill screw holes or use clamps and screws and make the preparation easier. Also useful when you are working with veneered mdf and can't use filler.