"Smitty Two" wrote in message
news
In article ,
"Jon Danniken" wrote:

Smitty Two wrote:
But a 1/8"
pilot is too small for a 1/4" screw. The pilot should be the diameter
of the shank. Hold the screw and the drill up to the light together,
with the drill in front of the screw. Only the threads of the screw
should be unobscured by the drill.

No, an 1/8" is actually too small for a 1/4" (size 14) screw:

http://www.engineershandbook.com/Tab...pilotholes.htm

Jon

I thought I said that. I guess I haven't had enough coffee yet. BTW,
that table is for tapered wood screws. I didn't think lag screws were
tapered.

You are right -- they are not tapered. Heh, you just may grasp climb
cutting sooner than I predicted!

The root diameter on a 1/4" lag is almost exactly 3/16.
A 1/8" pilot would cause about 1/32" (.032) compression, "on the radius" --
which, if too much, is a whole lot better than *no pilot*, which is what
proly 95% of people do.

Proly the pilot size would depend on the wood and on the grain orientation,
as well.
But as I think about it, and look at a lag bolt, mebbe a pilot closer to
3/16 than 1/8 IS appropriate, esp. for long lag bolts. Mebbe 11/64.
--
EA