Pilot hole size?

Re: Pilot hole size?

Kevin French, Antrim, NH

>davidewhiting WROTE:

What Pilot hole size for a 5/16-18 thread in wood

Are you using a lag screw?

My chart only goes to #14 which is 1/4"-BUT a #8 has a shank hole of 5/32, with a pilot hole in hardwood of 7/64 and a softwood pilot hole of 3/32. SO your 5/16 SHOULD have a HW pilot hole of 7/32 and a SW of 3/16

YES?

Re: Pilot hole size? *LINK*

Bill Houghton, Sebastopol, CA

>If you're threading hardwood to insert a machine screw, why not use the standard pilot hole size, which is an "F" letter drill?

There's only one reason to undersize the hole, because the tap's going to cut out what it doesn't need for threads: if you don't have a set of number drills, I would think (think: I've never experimented) that you could use an undersized drill in making a pilot hole in wood, because the tap should be able to handle removing extra material better in wood than in metal. So, if you don't have an F, try the next smaller size, which is 1/4". Work slowly and back up the tap a lot to clear swarf, aka sawdust.


One tap drill table