How to Work With Purpleheart Wood

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Purpleheart is a hardwood from Central and South America. Similar to mahogany, purpleheart trees are big and straight-grained, yielding wide, clear boards with few defects. Due to its strength and resiliency, purpleheart is often used as construction lumber in the Southern Hemisphere. In the United States, purpleheart is prized by woodworkers and craftsmen for its color. Issues with purpleheart include its high density and reactivity to light.

Density Compared

  • The Janka scale ranks wood for hardness and density. Purpleheart ranks 1860 on the scale, making it harder and heavier than most other domestic hardwoods such as oak, ash and maple. For comparison, Brazilian walnut is the hardest with a rating of 3684 while white pine is the softest with a 380 rating. Red oak, a common furniture wood, ranks toward the middle at 1290 on the scale.

Sharp Tools

  • The above-average hardness of purpleheart requires sharp woodworking equipment. Carbide-tipped blades and tools are recommended. High-speed steel blades cut purpleheart with some efficiency, but purpleheart dulls steel blades, which in turns increases blade friction and surface burning during cuts. Burning can be controlled to a certain extent by heeding the burning odor while cutting purpleheart on a table saw. Adjust the feed rate when pushing purpleheart over the blade; slow down or speed up until the wood runs through the saw without smoking. If you get burning no matter what you do, remove the blade and get it sharpened or replace it with a new carbide-tipped blade. Another issue involves resin: When dull blades heat up, purpleheart emits resin. The gummy substance sticks to blades, lumber and other woodworking tools and can also cause burning.

Feed Rate

  • Machines with power-feed rollers such as a straight-line ripping machines, shapers and sanders typically require slower than normal speeds when milling purpleheart. Common issues with too high a feed rate include burning, chipping and blow-out -- which is when grain lifts up or chips off at the cut edge. If purpleheart chatters inside the machine, or you see or smell smoke, slow the automatic feed rate down. If it continues to burn, chip or blow out, turn off the machine and spin the lumber 180 degrees and feed it into the machine from the opposite end. Grain is directional; it lays down flat in one direction, and chips up from the opposite direction. The simple procedure of reversing the board can make all the difference.

Hand Tools

  • The density of purpleheart can cause router bits to burn and splinter. Use carbide-tipped router bits for best results. Make incremental passes when cutting with a router bit, taking off small amounts with each pass until the bit glides smoothly. Purpleheart may also be brittle, causing cracks and splits when nailing or driving screws. Refrain from using fasteners within 1 inch of the edges. Pilot holes are almost always necessary when using screws to fasten purpleheart, or when nailing by hand. Pneumatic nail guns should be adjusted to full capacity, and tested on scrap purpleheart to make sure they penetrate. If nails bend consistently, drill pilot holes as needed.

Sanding

  • Use 100-grit sandpaper to smooth purpleheart. Use short strokes parallel with the grain until smooth. Purpleheart can be finished at this point. A subsequent sanding with 120-grit may make the finish glassier, but it's not necessary. Due to the density of purpleheart, sanding with sandpaper finer than 120-grit sometimes polishes the surface, making the application of stain or dye appear blotchy, because stain doesn't absorb evenly into polished surfaces.

UV Protection

  • Purpleheart reacts to light. Without protection, the purple color fades to brown. There are two ways to preserve the color; by adding dye, and or finishing it with a topcoat that contains UV protection. Lacquer is better than other finishing products because it won't yellow like other clear coats. Lacquer is sufficient to seal in the color for many years, but to ensure it doesn't fade you may wish to apply a bit of purple dye to the wood before sealing it with lacquer.

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  • Photo Credit ColorBlind Images/Blend Images/Getty Images
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