When driving nails into hard dense recycled
wood there are a number of techniques to help you avoid splitting the wood or bending the nails.
The single most important part of driving any nail is to use a suitable hammer. The hammer must be properly beveled since those that are flat ground will bend nails more frequently. Use a hammer that is comfortable for you and concentrate on your aim. Sometimes the head of the hammer becomes quite slippery particularly if you're using galvanized nails. Rubbing the hammer briskly on rough
concrete produces many tiny scratches which reduces this slipperiness. A hammer treated in this way will bend fewer nails. I like to hammer straight down onto rough concrete so that my hammer picks up a million little pock marks.
SPLIT PREVENTION
Drilling pilot holes is one obvious
answer but not something I do on every old 2x4 since it's time-consuming.
Dulling the end of the nail works well in some situations. A nail which has been hammered slightly on the point will tend to punch its own pilot hole. This isn't as effective as drilling but it's much faster and for softer woods it's quite effective. Sometimes when using this method I will also use dip galvanized nails. These nails often have a chunky and somewhat abrasive surface which tends to open up a path for the nail.
Keep your nails as far as possible from the end of the board since splitting is more likely the closer you get to the end.
Use skinny nails. Quite often nails of a given length are available with a smaller cross-sectional area. Provided you can drive these nails without bending you will produce less splits with a skinny nail.
Use ardox nails. These nails have a twisty spiral profile like a barber pole. As the nail is driven it rotates which presents a different section of nail head pointing at your hammer for each strike. Generally these nails will not bend quite as often as common smooth nails.
Nail into existing holes. If I am reapplying ship lap boards or plywood I'll often nail through the old hole but with a slightly larger nail so that everything fits tightly.
Does anyone have other little tricks to aid in reusing lumber?