Tapping wood

[John Paul Spiro-Colwell]

Hi,
I'm making some holes wood and was wondering what size bit I should use. They are #12 screws and the wood is maple. Is there somewhere where there is a chart for this? I found it for machine screws, but nothing for wood.

Thanks a lot
John Paul Spiro-Colwell

[karl in pa]

Look at Rockler catalog or Lowes, Home Depot for a tapered drill with countersink and adjustable depth stop for the size screw you are using.

[woodspinner]

For predrilling of screw holes in wood <which is different than TAPPING WOOD by the way....> be aware that you will need a slightly larger than regular drill size.

In other words, normal drill size could be considered the Shank Diameter of the screw.... Into Maple or other dense Hardwoods, try a drill a bit larger in diameter than the shank of the screw.

The reason for this is that the screw will be cutting the thread, as you insert it. With tight dense grain like Maple, you need not depend on the entire screws thread pattern to hold the screw in, the maple will do just fine with partial "thread cutting" of the screw.

In woods with lesser density of grain, say poplar, you should use the standard of drill size equals screw shank diameter, so that the grain of the wood is cut to the full potential of the thread pattern.

Also note, you can purchase screws meant for harder <dense> type grain OR softer grains from many stores both online and in larger cities with good hardware stores.... soft grain needs WIDER thread pattern, while harder <dense> grains can go with a smaller thread pattern OR finer thread pattern, if you will.

I hope that helps,

phil jaster