Joining MDF?

[Deb]

Have a project to build a small set of tables. For cost AND ease of purchase the Beach Vainered MDF 19mm seems the best buy for this work. Not having used this for any lasting work, only backing, or shelving, so the fitting was not of any real concern as it did not matter if it was visible, how should I fix these MDF parts together?

I need fixings for strength, durability, and Cosmetic appearances.

The idea is to have 4 legs made from 2 pieces of material joined along their longest edge, making a 90 degree angled section. The corners of these will be facing outwards, lining up with the table tops, and their inner faces will have a small pieces of material to make a box frame, along these lines:

Table top ******************************* ************************* ******* piece for ******* * boxing/fill in * * * * * * * * * * * * * * * * * * * * *

Legs from top:

****** join here ****** ** ** **

For the legs I would normally use either a dowel or biscuit, and then a Mortice, and tenon for the frame to support the table, but not sure if this material is up to this amount of machining.

The top could be fitted using buttons, or small fill in piece screwed, and glued to both the frame and the top, but the frame and legs I'm really not sure of how to joint them.

Any help here will be most greatfully received

Cheers Deb

[Mike Marlow]

If you need strength and durability in a table, MDF is an oxymoron. How much more could pine or poplar cost?

[Deb]

Got to be of a beach finish, but I cannot get the sections large enough to do the job.

Totally agree Pine would be better, but just not the same look or grain structure.

Any idea on how to overcome this MDF problem?

Cheers Deb

[Deb]

Got to be of a beach finish, but I cannot get the sections large enough to do the job.

Totally agree Pine would be better, but just not the same look or grain structure.

Any idea on how to overcome this MDF problem?

Cheers Deb

[Guess who]

I've used MDF for a large table top, but any part requiring any strength was still solid oak. The only way the MDF was used was as a flat panel surrounded by oak for the top ...biscuit joinery, good glue and clamps, and lots of varnish to waterproof. To try to use it for legs etc, he might as well use papier mache.

i won't do it again for a large project, but might for a small one. Still ...surround by oak for adjoining parts and so on.

[Jim]

Yes, replace the MDF with plywood. MDF compensates for its heavy weight with its low strength. Jim

[John B]

G'day Deb, There are lots MDFobia's out there, but used properly it is a great material that can do a lot of things that solid timber can't. I'm not quite sure what you are trying to do ??? Biscuits join MDF well so do screws and glue. If using it for legs or other parts of furniture that touches the floor put glides on the bottom of the legs. This allows the object to be moved easily and stops water damage when the floors are mopped. If using it in damp areas such as bathrooms, laundry etc. use HMR. Perhaps if you can post a sketch I may be able to be of more assistance. regards John

[Peter Huebner]

I am afraid I cannot make anything out of your sketch, esp. the top view.

So I'll just sling some thoughts your way and hope you can use them.

Best way by far of joining MDF in my opinion are bisquits. If the loading is high, every 6-8 inches. In addition, painting the edge of mdf with pva where it joins on to a flat surface WILL provide extra strength, unlike endgrain in timber. Round dowels tear out, ordinary woodscrews seem to become slack - I believe that there are MDF screws available.

For cosmetics, and extra strength, I tend to join real wood to the edge of the veneered mdf -- you can have an l-shaped leg, for instance, where two strips of MDF join on to 1 bit of 3/4" square beech from two sides. If you glue a veneer or ~1/8" thin strip of beech on to the other edge of the MDF, nobody will ever know what it is, and it will look really nice. Quite a bit of work though, and the question is if the extra labour won't upset the savings on timber equation :-)

You'll definitely need rails, and extra rails under your table top, depending on size. A table 6' long I'd use 3@5" or 4@4" rails. (extras under the centre of the table). MDF on the flat sags badly, but on edge it's not bad at all.

Be aware also that the pre-veneered MDF veneer tends to be VERY thin. It's awfully easy to cut through that with a bit of sandpaper. I've done it a couple of times, fortunately I was able to turn those bits to the inside of a cabinet, or use them for the underside of a drawer - the latter was done after sanding off some spider-crap and light damage :-(

-P.

[Prometheus]

How are you planning on finishing it? If you're going to paint, pocket screws work well, and you can fill them with bondo. This would still work fine if you plan on laminating or veneering it.

Crappy stuff, but surprisingly forgiving and fun to work with.

[tom]

[Deb]

Did try to send a full plan but this group would not let me use attachments, so did the every poor sketch found in the first post. :-(

Can post to alt.binaries.pictures.woodworking, with a picture, or plan, would that be ok or may I email you direct?

Thanks for the help so far Deb

[Bill B]

CLIP

I built a 4'x8' model train table out of 1/2" MDF and it is holding up well. It is on casters in a carpeted room. I pull it out to work on and push it back in the corner when I'm done. The legs are 3" wide, two pieces in a L shape. #10 Biscuits every 6", lots of glue, and coarse thread screws. Four years old and hasn't loosened at all.

[Deb]

Have posted a very simple design on alt.binaries.pictures.woodworking, under Joining MDF Help please.

Hope this helps you see what I am trying to achieve.

Thanks Deb

[John B]

Yep, no probs emailing me I'm sure you can decipher the address, just leave out the NOTTHIS ;) More than pleased to help if I can. regards John

[Pat Barber]

He is talking about VENEERED mdf, which is used in the U.K. and all over europe because of cost. It is also used extensivly here in the USA by a LOT of furniture manufactures.

Many folks have no idea they are looking at MDF when they see the finished product.

He is NOT talking about raw mdf sold in home centers.

Prometheus wrote:

[Prometheus]

Sure man, I got it- no need for the excessive emphesis. We use veneered MDF at work, I just didn't catch it in the original post the first time through.

In that case, it's pretty simple to countersink and screw it together, and then make a nice frame to cover the edges and screw holes.

Alternately, it seems to hold together ok with simple miters with or without biscuts, especially if there is some other internal structure with better joinery to re-enforce it.

[Peter Huebner]

LOL - my newsserver does not carry any binaries. Unfortunately more and more nntp operators are adopting that policy. As has Google (dejanews) ages ago.

Good luck with your project

-Peter

[Pat Barber]

I have seen these threads on MDF for years on this group.

The amount of bad information here can be really incredible at times.

Did not mean to over emphasize.

Since you have some background in it's use, you can write a short version of how to use the product in more practical situations.

MDF is a great product if used in a correct and planned manner. Raw mdf is great for jigs, braces and many other uses that plywood often gets cut up for.

It can not be beat for prototypes and patterns.

MDF is also MUCH cheaper to purchase than plywood.

Prometheus wrote:

[tom]

D.J. Delorie's got a place for you:

Huebner wrote: >

[Prometheus]

Not sure what you're looking for, but I gave the OP some suggestions on ABPW, after seeing the plan.

Sure, I like MDF- I've even come around to preferring it over standard plywood because of the lack of voids. I wonder (though have no real idea) how many folks confuse it with particle board, especially when I hear people say that it's weak. Particle board, I can break on the edge of a plastic garbage can with no effort- MDF is kind of like trying to bust a hunk of pine, sometimes even stronger than that, because of the lack of knots to weaken the structure.

Only reason I said it was crappy is the horrendous dust- other than that, it's great. Made a box jointing jig out of the stuff a few hours ago, and it worked a whole lot nicer than the one made of solid pine that it was replacing. At work, all the cabinets are made of it- as long as the cherry, maple, or oak is what the customer sees, they're happy as can be.