Proper shank/clearance hole size?

[Frank Gallagher]

Can anybody out there point me a chart for the proper size
shank/clearance , pilot hole size for a variety of standard wood
screws ?

[Doug Shepard]

I've got a small folder of saved links

http://www.boatbuilding.net/article.pl?sid=06/05/08/1333208
http://www.mcfeelys.com/tech/drill-size-recs.htm
http://www.ibiblio.org/twa/info/screwChart.pdf
http://www.sawdustmaking.com/Free%20Charts/Pilot%20Hole.pdf
http://www.hingedummy.info/screwinfopage2.htm
http://www.wlfuller.com/html/wood_screw_chart.html
http://www.internetwoodworking.com/w5/screws.html

[Tom Veatch]

Frank, it's no help for pilot hole sizes, but a simple relationship for the shank diameter of numbered screws is:

Diameter = .060 + .013 x Number

Example: A #6 shank = .060 + .013 x 6 = .138

[Chris Friesen]

Different types of screws vary...your best bet may be to simply hold up the screw to the drills.

Generally in softwood the pilot should be slightly smaller than the root, while in hardwood the pilot should be slightly larger. The clearance hole should be big enough that the shank passes loosely, and if the threaded part of the screw extends back up into the top piece the clearance hole should be big enough that the threads don't grab.