|
|
 |
|
|
| |
 |
|
|
By
STEVEN MAXWELL
Illustrations PAUL PERREAULT |
THE NEW COMPOSITE |
| Coming
to grips with MDF and its benefits |
Although it’s never easy for me to admit this, new products
are sometimes better than older, more traditional ones—and
this is certainly true of building materials. Even though I
favour building out of solid wood, I approve of, albeit grudgingly,
a relatively new sheet material commonly known as MDF (medium
density fibreboard). This smooth, inexpensive, furniture-grade
composite has been sold commercially since
the 1960s but wasn’t widely available to the home workshopper
until the mid-1990s. It ranges between 1/4" to 3/4"
thick and is carried by most hardware stores. Unlike other composite
materials, such as plywood or particleboard, MDF machines well
and absorbs paint quickly and evenly. Unfortunately, it also
generates a large amount of fine dust, doesn’t resist water
well, has weak edges and holds a few other surprises I’ll
explain later. MDF isn’t the best choice for every project,
but once you understand its characteristics, you’ll soon
discover its many benefits.
Painting
 |
•
computer-generated paper carving template glued
to the work surface
• carve
right through the paper and then peel it off
• crisp
incised carving is easier than with solid wood
• finger
joints and dovetails work well with MDF |
|
The first
MDF project I saw was a set of frame-and-panel cabinet doors.
Several thick coats of catalyzed, sprayed-on lacquer left the
surface smooth and attractive. Visually, the doors looked almost
identical to natural wood. No other sheet material for indoor
projects takes paint as well as MDF; the consistency is so high
that it often looks like a plastic coating. And while that may
offend the wood purist in me, there’s no denying its applicability
in projects where a coloured, opaque appearance is what you’re
after. You can also stain and urethane MDF, although it dries
a darker tone than regular wood covered with the same stain.
Spray painting is the best method
for covering MDF surfaces. Even though I have an HVLP sprayer,
I still use spray cans for finishing small projects because
it’s convenient and easy to clean up. For an even smoother
finish, try sanding with 240-grit sandpaper between coats.
Cutting
Getting the most from your cuts depends on the blade; those
designed for veneered plywood or melamine garner the best results.
MDF routes well and holds crisper details better than either
plywood or particleboard. In fact it’s so consistent that
you can carve right into it. But that doesn’t mean it’s
tough; because MDF is soft, crisp outside corners don’t
last long on furniture destined to be bumped during daily usage.
In fact, MDF is often manufactured with an extra inch that acts
as a shipping bumper to be trimmed off in your workshop.
There are ways to add durability
though. Avoid intricate, delicate-edged profiles or crisp, square
corners. In most cases it’s best to round or chamfer the
corners. If you must use square corners, cap the edges with
a tight-grained hardwood, such as maple or birch.
Tricks and Techniques
If you’re going to have any trouble with MDF, it’ll
probably involve joinery. The main drawback of this material
is its tendency to split along the edges. Driving a screw or
nail into the face of MDF is easy, but try the same thing along
the edges and it will split. Connecting corners with biscuits,
dowels or rabbet joints is one way of avoiding this problem.
If you must use screws, use those designed for particleboard
and drive them into predrilled pilot holes. Half-inch-thick
MDF should be joined with nothing larger than #6 screws (into
3/32" pilots); #8 screws driven into 1/8" pilot holes
is fine for 5/8" boards.
| MDF
has a tendency to split along the edge, even with
screws designed for particleboard, but fixes are
relatively easy |
 |
LEFT:
inject glue into edge cracks with screw in place
RIGHT: remove screw, wipe away excess glue
and clamp tight |
|
If
you still end up with a crack, don’t throw the board away
yet. Instead, take the joint apart and put the screw back into
the hole to force the crack open. Before removing the screw
and applying a clamp, squeeze some glue into the gap. The screw
allows the glue to seep deeply into the crack before it closes
up. Wipe away any excess glue and leave to dry. Then, replace
the screw after drilling a slightly larger pilot hole. By leaving
the clamp in place during this second screw-driving attempt,
you’ll reduce the chance of creating another crack.
There’s another screwing
technique you should follow: when drilling pilot holes in the
face of MDF, prepare a small countersunk area around the hole.
This prevents a bump or pyramid that would otherwise rise around
the screw as it goes in.
Dangerous Dust
Last year, I received calls from two separate woodworkers who
had given up woodworking because of a heightened sensitivity
to wood dust that had slowly developed over several years. Dust
control is important when working with any wood—especially
MDF. The combination of minute wood particles and glue can cause
serious respiratory problems. Don’t cut MDF indoors without
equipment capable of filtering out the finest dust. Few workshop
vacuums or dust collectors are able to catch the smallest, deadliest
particles. In addition to collecting large dust particles at
source, use a whole-shop dust filter capable of removing particles
down to 0.5 microns. Anything smaller than this is harmless.
Painting
Since a sheet of 5/8" MDF costs less than $30, there’s
a tendency to only use it for simple, not-so-serious projects.
But you can do more with it. I’ve built toy boxes, utility
boxes and high-end kitchen cabinets out of MDF. Remember MDF’s
ability to accept fancy joinery; finger joints and even machine-cut
dovetails are possible. And unlike solid wood, MDF glue joints
are as strong on edges as they are on face surfaces. With the
right precautions and techniques, MDF is certainly worth considering,
even if it takes some effort to admit that new things are sometimes
better.
|
|
|
|
|
| FREE
NEWSLETTER |
Subscribe to our newsletter. Every few weeks, you'll get a behind-the-scenes
peek at the magazine, the web site and the folks who put it all together.
CLICK HERE |
|
|
PROJECTS
