Novice needs help with MDF boards

Hi,
I am totally new to woodworking and I am thinking of building an inexpensive wall cabinet out of cheap MDF boards. My questions are:
1. Is MDF boards strong enough to be used in a wall cabinet ? Can it even hold it's own weight ? Or should I add some real lumbar as reinforcements ?
2. What is a easy way to join boards at right angle ? Can I simply use screws / gule and wood filler to patch the hole ?
3. When you paint the boards, do you need to use a primer first ?
Thanks in advance for your advise.
JW
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JW wrote: >Hi,

Hi, JW. Check out FINE WOODWORKING's recent issue(June 04 #170) for joining MDF. Plus, there're some good tips on finishing the stuff. Tom
Work at your leisure!
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MDF is reasonably strong if it's reasonably well supported. What are you planning on holding up? Try loading a length with the kind of loads you anticipate. Is the deflection acceptable? If not, add a support to the middle.

Ty and Wynn use glue and a brad nailer, iirc. I think if they had a more reasonable timeframe, glue would be sufficient with a decent clamp time.
I would try to arrange things so that all my load-bearing was done under compression, rather than tension.

In general, primer is MUCH cheaper than paint, so that's a resounding YES.
I'd use oil-based primer, but check the paint manufacturer's recommendations for their product. Makers of quality paint want you to feel happy with their products, so they tend towards conservative recommendations, application-wise.
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MDF is strong enough for a wall cabinet, but it wouldn't be my first choice. I'm working on some face frame shop cabinets right now made from 1/2" meranti. 1/2" meranti runs about $22.50 per 4x8 sheet here and 1/2" MDF (regular weight) gets $15. For me, I'm able to get 5 18x30x12 wall cabinets out of two sheets of ply, so the difference in material cost is not that great. Unless you make the lengthwise cut 1/2" too narrow and have to go back and get another piece. DAMHIKT. With that said, here is the gist of a paragraph on the subject from "Building Your Own Kitchen Cabinetry", by John Paquay. MDF is stable, uniform, and very smooth-surfaced. It's inexpensive, paints well, and makes strong glue joints. The downside is that MDF can be damaged easily, particularly at corners and edges.
todd
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Say no more; find your way over to uk.d-i-y. Anal retention is not rquired there. Also the chat is actual hands on stuff not stuff on hands.

Any shelf needs support at 3 foot intervals for a section 1" thick. MDF has been used for a long time now. It is common on stair risers for example and the beloved media of house make-over programmes on the TV over here

Space some strips on each side piece to set the shelves on. Put them tight to the back and stop them short of the front and cut the front edges of them at an angle. MDF has to be pre-drilled for screws and a countersunk bit used to bury the head of the screws. Over here in the UK the trade named filler is Pollyfilla. Any wood filler will do. Follow the instructionson the packet.

Yes. Acrylic then undercoat then gloss if that is what you want for a finish. It will look OK with 2 or 3 coats of acrylic.
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Thanks to everyone who have responded to my questions. You guys are very helpful.
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On 23 Jun 2004 10:07:07 -0700, snipped-for-privacy@hotmail.com (JW) wrote:

MDF is strong enough for almost anything. However it's not very stiff. It won't break, but it'll sag like crazy if you're not careful.
I like it for built-ins and kid's furniture, but I'd not use it for bookshelves.

Just choose the right thicknesses and get the design right. 1/2" thick is OK for shelving and put a back on it, screwed from the back. You can go to 3/8" thick if they're not too deep and you know what you're doing.
Another tip is to saw the front edge into a gentle curve. If it does sag, it makes it much less obvious.

Biscuit jointer. If you're in the UK, try Screwfix's Ferm cheapie.
Avoid screws for the carcase. Getting them to hold edge-on to a board is a thankless task. If you must do this, use the right screws - parallel shanks, with narrow thread ridges and a fairly big spacing between them. You can find these as MDF, chipboard or even drywall screws.

Yes, and it needs to be MDF primer. Anything with water in it raises fibres and
--
Smert' spamionam

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snipped-for-privacy@hotmail.com (JW) wrote in message

Depends on the width of the cabinet and how much weight you anticpate loading.I prefer Plywood myself , but I have a tip or two if you do use mdf. Several joints will work, biscuits, loose tenons , simple butt glue and screw. Dado or rabbet joints, shallow about 1/4" or less deep help line up your parts. When you drill mdf , drill thru the center line of the rabbet or dado, use a bit that is about 3/4 the diameter of the screw. Countersink slightly on the dado or rabbet INSIDE. This is very important for mdf, mdf when screwed leaves a little hill, the slight counter sink gives the broken fibers a place to go without pushing the board away. Naturally you want to countersink or counterbore the face side too. A coarse thread drywall screw is well suited for this work. There are special screws for mdf and hardboard, can't comment on them because I've never used them. I have found that bondo or water putty is the best filler for nail or screwheads in mdf. Both can be sanded when hard, bondo is best , invisible under a coat of paint. I believe Rockhard Water Putty is the other fillers name,works good but not always invisible.When I paint mdf I spray a primer then two coats of finish. Brushing takes too many coats , at least four including primer to cover. Other posts make help more on the painting aspect, I never liked brushing paint on mdf, maybe it's my technique. As far as the other questions, you do not need to reinforce mdf with lumber.Last thing,remember if you need full sheets , have the yard rip or crosscut them for you to a rough dimension. Full sheets are very heavy.
mike
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JW wrote:

If your concerned about shelving, the maximum length for droop-free shelves is about 32". If you add a 1"x2" wood banding to the front, that will extend to about 40". This per "Trim Carpentry and Built-Ins" by Clayton DeKorne.

If you're making shelving/carcasses, you can dado the vertical pieces and then glue and screw the pieces together.

Yes, but if you've milled any of the MDF (e.g. edged it with a router) *don't* use a latex primer. You'll raise the fiber something fierce and spend hours sanding it down. On unmilled, flat surfaces, any primer should work fine. I learned this the hard way with some raised panel wainscoting I made from MDF. Spent 3 days sanding down the routed edges of the panels, rails and stiles.

As an aside, veneered MDF (e.g cherry, maple, etc.) is becoming increasingly popular as material for cabinets and shelving, so it must be okay.
~Mark.
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On 23 Jun 2004 10:07:07 -0700, snipped-for-privacy@hotmail.com (JW) wrote:

Hello JW,
MDF is a fine substrate for most low to mid range cabinets. It takes paint very well, machines nicely and will accept veneers of wood and metal . Exposed edges do not paint very well so be cautious in your design details. But above all, please wear a back brace cause that stuff luvs gravity!
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