Are there any drawbacks to using MDF?

While MDF has been in use for almost 30 years, it is only now becoming available to the general public. Finding MDF may end up being the single toughest part of using it. As its density implies, MDF is very heavy and thus potentially difficult to handle. See the safety issues below.

What are the safety issues to consider when working with MDF?

MDF is typically made with urea-formaldehyde resin totaling 9% by weight. While most people will not be affected by this, people sensitive to formaldehyde emissions should consider low formaldehyde or formaldehyde-free MDF, or consider methods of controlling these emissions through proper finishing. Finishes that work best at controlling formaldehyde emissions are solid add-on surfaces such as high pressure laminates, vinyl covering, and finished wood veneers. Less effective at controlling emissions are simple seal coats, oil and latex paints, danish oil, and wax. Plum Creek makes low-formaldehyde MDF, while Medite II and Medex from Medite Corp. are formaldehyde-free MDF.

Dust is another MDF hazard. The large amount of dust released when working MDF makes proper respiratory and eye protection mandatory. At a minimum use a dust mask. A respirator is preferable. Shop dust collection (or even a ShopVac) would greatly help the removal of dust from not only the air but also the working surfaces, making them easier to see. Goggles should always be worn while using tools.

Is all MDF the same?

No. MDF from different sources will vary in texture, density, color, etc.

How is MDF sold?

MDF is manufactured in sheets up to 8ft x 25ft. Typical consumer level sheets are 2×2, 2×4, or 4×8 and 1/2 inch, 5/8 inch, 3/4 inch and 1 inch in thickness. Thicknesses can also be metric – an important consideration for the use of English system tools (such as router bits). MDF is also available with a variety of veneers and laminates pre-applied, which may affect its actual thickness.

What about MDO, particle board, hardboard, void-free plywood?

Medium Density Overlay and High Density Overlay are plywood products with a resin impregnated paper coating. They are often used for exterior painted surfaces. These are not fiber based products.

Likewise, particle board is not fiber based; it is a solid wood composite product. Along with flakeboard and other engineered lumbers, composite products are made from wood flakes, chips, splinters, etc., formed into layers and held together by resin glues and heated under pressure. Being layered and consisting of larger chunks, particle board does not have the uniform texture of MDF.

While MDF is a hardboard, the term hardboard is often used to refer to 1/8 or 1/4 inch thick HDF, usually containing a screen pattern on one surface. As previously mentioned, this is commonly referred to as Masonite.

Plywood is made from an odd number of lumber plies, each layer having a grain direction at right angles to the previous layer. This arrangement provides a dimensionally stable product. Void-free plywood uses plies with supposedly no holes, thus the completed plywood has in theory no voids. Baltic birch plywood is often sold as void-free plywood though some users have encountered small voids in these products. Be sure to ask specifically for void-free plywood if this is what you are looking for.

Can I build speakers with {MDF | particle board | plywood | solid wood}?

You can build speakers with whatever you like. However, MDF is often the material of choice. Its stiffness and density yield good acoustical damping properties. Particle board and plywood are cheaper and can still be used if cost is an issue. Plywood (especially if void free) can be used in the main baffle as a sandwich material to better hold fasteners. Plywood is also a good material for making braces inside speaker boxes. Solid wood (lumber) suffers from movement – the swelling and shrinking of wood due to environmental changes such as humidity – and is therefore not a good material for speaker enclosures. Lumber is also not as acoustically dead as MDF.

What should I use to cut and mill MDF?

MDF can be treated much like a fine grained hardwood. Its high glue content means that steel cutting tools will dull VERY quickly; thus the use of carbide tools is highly recommended. Always keep your tools sharp for efficiency and safety.

The following recommendations are from The National Particleboard Association publication:

• For general shop or table saw use with decent cut and good blade life, a 50 tooth, 10 inch combination blade may be used.
• For those demanding a better cut, consider a 60 tooth, 10 inch blade with alternate top bevel (ATB) teeth at 15 degrees, 10 degree positive hook, 5 degree side clearance, 10 degree outside diameter clearance, and low approach angle (blade projecting no more than 0.5 inch through top of material).
• For an even smoother cut, consider an 80 tooth, 10 inch blade with 15 degree ATB, 10 degree alternate face bevel, 15 degree positive hook, and 7 degrees side clearance. This is costlier and may result in a shorter blade life.

Where can I find MDF?

Availability varies geographically so there is no simple answer to this question. Hobbyists have found MDF from a wide variety of sources including, but not limited to :

• large warehouse style supply dealers (Home Depot, Lowes, etc)
• small local lumber yards
• cabinet shops who buy in large quantities and are willing to part with some
• surplus building supply dealers

As MDF becomes more popular you will see it more and more in your local hardware stores. Sometimes, they will only have smaller 2×4 pieces or 1×4 pieces designed for use as shelving, so be sure to look around or ask.

Beware of clueless store clerks trying to pass plywood, particle board or MDO as MDF ! Note that many lumber yards can special order MDF but may not realize this, so it never hurts to ask. Ask them to check their price book for availability.