Hi, I want to screw an antenna mount in the attic. The mount comes with hex-head screws that have a "root" of slightly less than 3/16 of an inch. Including the thread, the size is 1/4 of an inch. The head fits in a 3/8 hex socket.

What is the size of the pilot hole I must drill in the wood to properly torque the screw in the wood?

 

I would use a 1/8 or 5/32" bit. You want it not to split the wood, but leave enough bite to hold.

 

So small??? Will I be able to actually screw it in without breaking it? It sounds like I will have to put a lot of force... Should I lubricate the screw?

 

So according to this table, a screw that has a thread diameter of about 1/4" is a #14:

Bolt Depot - Wood Screw Diameter and Number Table

And according to this other table, a tapered #14 screw on softwood would need a 15/64" hole, that is more than 3/8"... I am thoroughly confused!

Bolt Depot - Pilot Hole Sizes for Wood Screws

 

Right.... a 1/4" is roughly a # 14

For a # 10 screw I would use a 1/8" bit
For a # 12 screw I would use a 3/32" bit
For a # 14 screw I would use a 3/32" bit

Usually my 3/32" is broken and I use 1/8" for everything.
I buy 1/8" bits by the box of 100.

Technically putting that screw into the center of a 2x4 shouldn't split it without pre-drilling.

So if you use either of the two sizes we mentioned you'll be in good shape. If you are really concerned about binding......use a little soap or candle wax.

 

Oh wait, these are the screws I have:

[ATTACH=CONFIG]11870[/ATTACH]

And it seems they are NOT tapered... so the table I linked suggests a 5/32" like you said, chandler. Thank you and sorry to have doubted your expertize!

 

That's OK. I'm married. Good luck on the install, and welcome anytime!!

 

Just a correction, 15/64 is less than 1/4, not more than 3/8. Moot point as you have the correct advice.
I know I'm too picky .

Bud