MDF wood working advice

[Negativecreep0]

I'm about to start a showcase cab and am new to wood working so here is what I have gathered from this message board on working with mdf board

use a circular saw blade with smaller teeth, this is good for smoother cuts and will help avoid tearouts. Also put a piece of scrap wood under the piece your cutting to help avoid tearouts. Whats the deal with using tape on the good side? what kind of tape is good to put on the line where you cut (this avoids tearouts Im told)

Also i have seen an example of how to make a ripper board for your circular saw. This helps keep every cut straight. much faster and reliable than clamping a straight board down on your line.

In terms of jointing the mdf boards I plan on reinforcing them with 2x4's my question is what do you think is the best thickness to use for this as I will be using a very heavy 33" wg d9200 monitor? Also what type of screw is best for 3/4" mdf, length? brand?. I have seen these screws online
http://www.mcfeelys.com/multiple.asp?productID=7050-CSP
wanna know what people use and think. As far as making joints with mdf I would also like to know what glue people use and how deep they countersink. Do you guys screw right into the edge of the mdf or into some sort of support .

Thanks for any help you guys can give me.

[Taborious]

    I completed my cab about 3 months ago and I used 3/4 MDF and NO support beams inside; ie 2x4 framing. I screwed right into the side of the MDF and right into the other piece of MDF. I used no glue but I would recommend if you paranoid. I have moved my cab several time (UAII) and have had no problems with the joints. I used drywall screws and just countersinked enough to get the screw head flush.
    For the circular saw I had 2 blades a 150 tooth non offset blade and that sucked. I went and bought a 40-50 tooth carbide blade and that was PERFECT. Nice and smooth no tape needed.
    For the formica I cut with a razor knife with tape along the lines; to prevent chipping. You have to cut your formica larger than you will use and then glue to the surface. After dry you can then fine cut to fit with a router.

I have some pictures of my project on my site if it helps http://www.taborious.com

good luck...

[wintermute]

I used Deckmate #8x2.5" screws and they worked well.  These are available at home deopt.  You definitely want something pretty long with an aggressive thread, MDF doesn't hold screws half as well as normal wood will.

  In my circular saw I use a Freud thin-kerf combination blade.  (The blade is red).  It works pretty well, cuts like butter although my tablesaw still is cleaner, but that might just be the nature of the saw.

To tape over the cut, I've used blue masking tape in the past with good results.  Make sure you put the tape down, THEN draw the line on top of the tape.  It's hard to see your cut line with tape over it

wm

[rdagger]

Another option to secure the MDF to the 2x4's is to use T-nuts.  On my cab, I flush mounted T-nuts in the MDF panels and then used bolts to fasten them to a 2x4 frame.  This allows me to easily remove the panels with a socket wrench.  It is also very strong.

[prOk]

Use 1x1 blocking on the inside.. arcade cabinets from the early 70's to current day use this same method as it's cheap, small and strong.   Screws or staples and glue from the inside.

/brian

http://www.rgvac.com

[Bones]

I mounted a 27" D9200 on 18mm MDF which spanned 700mm. This was supported by two pieces of 2X4 on each sides.

Initially it seemed solid as a rock and could hold my own weight, but after a week or two there was some bowing of the shelf. Only very slight but there was a visible gap between the bottom of the monitor frame and the shelf.

Since then I have reinforced the shelf with some framework and I doubt I will have anymore problems. I would suggest something similar considering the extra weight of a 33" screen.

[Tailgunner]

Something else no one has mentioned, get yourself a box of dust masks. MDF contains formaldehyde, and produces a fine sawdust when you cut it. Inhaling it is hard on your lungs, and enough of it can make you rather ill.

[elvis]

Something else no one has mentioned, get yourself a box of dust masks. MDF contains formaldehyde, and produces a fine sawdust when you cut it. Inhaling it is hard on your lungs, and enough of it can make you rather ill.

I'm glad this was mentioned.  I was going to say the same.

Even worse than making you "rather ill" the longterm effects of the carcinogenic dust/glue particles are emphysema and/or lung cancer:
http://en.wikipedia.org/wiki/Emphysema

If you're working with this stuff, use a good dust mask that will filter fine particles.  And not some cheapy $2 face mask either, for the sake of your health.

[RandyT]

To augment what has been said,  faster feeds and speeds are usually a good idea with this stuff if your equipment can take it.  You want to make little chips, not dust.  Even when cut on a tablesaw with a coarse blade, the finish is quite good compared to other materials.  A little coarse sandpaper will shape it right up.

It's a fairly free-cutting material and slow speeds and feeds can make dust so fine that it will float around the room and cover everything.  One time I forgot to turn on the dust collector for the CNC router and when I cam back 10 minutes later, there was literally 1/16" of fine MDF powder on everything in the room.     2 hours of cleaning time later I was back cutting, but I never made that mistake again.

RandyT

[Negativecreep0]

thanks for all the replies. What type of wood is best for the supports inside? looking for something that can support the 33" monitor. Also what type of sandpaper is good for the mdf.

[AceTKK]

With a monitor that big I would really consider a 2x4 frame to support it.  I wouldn't trust an MDF shelf to support that kind of weight over time.

-Ace-

[dema]

Use drywall screws. They won't strip when you're screwing them in.

[SpeedyR]

I"m surprised more folks don't use glue... I would use the screws but a good woodworking glue will help a lot with the overall stability of the setup. If you need it fixed that is...

but you could use soemthing like Gorilla glue, and Titebond are all good.

[Ed_McCarron]

RE:  Glue.

I tried using plain old Elmer's white glue on MDF... The surface was so smooth, that once the glue had set, the block I had glued on sheared right off - it seemed like the glue had no grip on the MDF.

It did leave a nice, clean spot where the glue was, tho.

Is there a better glue/way to prep the MDF for glueing?

Also, when sanding down my nicely filled screwholes, the MDF seemed to shred a bit - if it were real wood, I'd say the grain got raised.  Took a bit more work in paint to make it nice again.

Any thoughts?  I'm planning to go to all interior screws on the next few cabs I've got to build, which makes the glue/block question even more critical.

I guess the easy way would be to learn to tell my friends "no".

[elvis]

I"m surprised more folks don't use glue

All my cabinets are screwed and glued.  MDF doesn't have the 'pull apart' strength of natural timber fibres like pine or the hardwoods for just screwing alone.  You MUST use glue if you want your cabinet to last a couple of years, especially if it takes absue from friends and/or kids.

I use Selly's Aquadhere (available in every single hardware store and/or supermarket in Australia).  Cheap stuff, but it works a treat on porous timber materials.

That's for raw non-coated MDF of course (I always paint AFTER building).  If I was using pre-laminated stuff, I'd use something that will hold onto that a bit better.  But my carpentry is not good enough to use pre-laminated stuff.  I need plenty of putty for my cabs to cover all the oopsies.

[flyguy1821]

I used Gorilla Glue.  The stuff is ridiculously strong.  I would caution to get it off your fingers quickly as it will stick to them.  You can get this at any home improvement store for a few dollars.  It does expand a little but easy to scrape off.