Interior design : What is MDF-Medium Density Fiberboard. ?

Main Article page | Beauty articles | Health page | Computers| Diseases | Education | Entertainment | Family
Business |Fitness|  Fruits and Vegetables | Jobs | General | Personality| Technology | Tourism | Sports
 House Plans | House Loans | Real Estate| Vaasthu Shastra| Construction Tips
 Engineering page | Interior Design | Property Buying Tips | Renting Tips | Journals / Magazines
Education | List of Colleges | Entrance

MDF belongs to the hardboard family of products which are made from wood fibers glued under heat and pressure. Medium Density Fiberboard typically has densities between 33 and 50 pounds per cubic feet while High Density Fiberboard (HDF) ranges between 50 and 80 pounds per cubic feet.

Medium Density Fibreboard (MDF) is an engineered wood-based sheet material made by bonding together wood fibres with a synthetic resin adhesive.  MDF is extremely versatile and can be machined and finished to a high standard.  As a result, MDF has replaced solid timber as a low-cost alternative in a wide range of applications across industry. 

The majority of MDF is mainly composed of softwood, although some brands may contain a higher percentage of temperate hardwood if this is locally available to the manufacturer.  High levels of hardwood can be found in MDF board from outside the UK and Ireland.

The most common binder for boards intended for dry environments is urea-formaldehyde.  Other binders may be used depending on the grade of board and its intended end-use.  For example, melamine urea-formaldehyde, phenolic resins and polymeric diphenylmethane diisocyanate (PMDI) are generally used in boards that require an improved moisture resistance.  PMDI binder is not formaldehyde-based and consequently does not emit any formaldehyde.  The exact constituents of an MDF board will vary from product to product.

A: MDF has many qualities that make it an ideal replacement for plywood or particle board. It is dense, flat, stiff, has no knots and is easily machined. Its fine particles provide dimensional stability without a predominant "grain" (as is the case with lumber). Unlike most plywoods, MDF contains no voids, and will deliver sharp edges with no tearout.

Below are some metrics for MDF and other types of wood. Ex: Weight of MDF board. As you can see, MDF is very dense and heavy, but is not as stiff as other types of wood which is why bracing is suggested.

The modulus of elasticity (MOE), also called Young's modulus, is the ratio of stress to strain, where stress is the force per unit area placed on the item and strain is the deformation caused by the stress. The MOE is therefore a measure of stiffness.

Q: What does MDF look like?

A: Here is an image of a birch veneered MDF board on top and for contrast an image of veneered particle board below. Notice the much larger and obvious particles.

A: 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.

A: 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.

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

A: MDF is manufactured in sheets up to 8ft x 25ft. Typical consumer level sheets are 4x8 or 5x8 and 1/2 inch, 3/4 inch and 1 inch in thickness. Thicknesses can also be metric - an important consideration when considering 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.

A: 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.

A: 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 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.

A: 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 2x4 pieces or 1x4 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.

A: Because MDF can be milled to just about any profile, there are many possible joints. However, not all make sense in the context of speaker building.

• butt - this simplest of joints may not be ideal for furniture but works very well for building speakers, especially when combined with biscuits (for alignment) and screws (for holding strength while the glue dries).
• miter - works well when using pre-finished MDF (veneered or laminated) thus leaving no exposed unfinished surfaces.
• lock-miter, dovetail and other routered joints - works just like lumber. These joints have limited use in most speaker enclosures.
• rabbets, dadoes, grooves and other saw cut joints - same as with hardwood. Note that these can also be cut with a router. These joints may be useful, depending on the design of the speaker.
• spline, biscuit, dowel - as with lumber, the glue joint is stronger than the MDF. Dowel holes should be 0.002 to 0.003 inch larger than the average dowel diameter, and 1/32 to 1/16 inch deeper than the actual depth used. Plain or spiral grooved dowels are preferred over fluted or multigrooved dowels. Biscuits are very handy for alignment of parts in addition to the additional gluing surface provided.

MDF can also be edge glued to make larger surfaces, although this is not likely to happen except with exceptionally large speakers. Panels can be scarfed, doweled, tongue & grooved and finger jointed.

A: Some typical fasteners and their uses follow :

• staples - Do not staple within 3/4 inch of any corner. Coated staples hold better than smooth staples. Use a finer wire staple if splitting is a problem. Drive at right angle to the surface to avoid bending.
• nails - The same rules apply to nails as they apply to staples. Use ring-shank nails to avoid fiber raising around the nail head; do not use smooth nails.
• screws - Drill pilot holes between 85 % and 90 % of the root diameter of the screw used and at least as deep as the screw. Untapered sheet metal screws with constant size shank are good, as are some untapered wood screws. Pilot hole sizes and minimum edge distances for common screw sizes are :
  • #6 screw - 3/32 inch pilot - 1/2 inch edge distance
  • #8 screw - 7/64 inch pilot - 5/8 inch edge distance
  • #10 screw - 1/8 inch pilot - 1 inch edge distance

Do not rely solely on the above fasteners for building speaker enclosures. This is especially true for butt joints. Combine glue with screws for a simple and strong joint.

A: Good glues to use are gap-filling glues such as polyvinyl acetate (PVA) typically known as yellow glue, modified PVA glues like Titebond II or white glues. Epoxy, urea and hot melt glues may also be used.

A: For that finished look, there are many options requiring different levels of woodworking skills.

•  May be painted. Be sure to seal and prime the surface before painting to ensure even absorption on all surfaces. A high gloss piano finish can be made with combinations of spray enamel, spray lacquer or other topcoats. A little experimentation at this juncture can be very rewarding.
• May be laminated. Options include melamine, Formica, or even contact paper. Be sure the surface is clear of dust before applying any laminate.
• May be veneered. Carried out properly, veneering can yield a very professional looking  Refer to the references below for veneering info. A veneered surface can be finished with lacquer, varnish, oil or wax depending on individual taste. Stains and dyes may be used to modify the color as desired.

Note that raw MDF is very porous. Use a generous amount of glue to ensure a proper bond.

Veneered MDF

In modern construction, spurred by the spiralling costs of hardwoods manufacturers have been engineering new and better ways to achieve a high quality finishing wrap covering over a standard MDF board. This is known as a Wood veneer. The most common type of Veneered MDF is by using Oak.[11] This is a highly complex procedure which involved taking an extremely thin slice of hardwood (approx 1-2mm thick) and then through high pressure and stretching methods they are wrapped around the profiled MDF boards. This is only possible with very simple profiles because otherwise when the thin wood layer has dried out, it will break at the point of bends and angles.

Pre-Laminated MDF is a Medium Density Fibre Board, laminated on both surfaces by synthetic resin-impregnated base papers under the influence of heat pressure. Pre-laminated MDF boards are available in Interior and Exterior Grades, in both One side Laminated (OSL)  and Both Side Laminated (BSL)  varieties.

Pre-laminated MDF can be used for Modular Furniture, Computer Table, Office Furniture, Dressing Table, TV Trolley, Pre-laminated Doors etc.

( Reference : www.diyaudioandvideo.com/, www.hse.gov.uk )

• More information about MDF-Medium Density Fiberboard

Articles: