Pilot hole...

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Old 04-23-13, 07:04 PM
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Pilot hole...

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?
 

Last edited by alesan; 04-23-13 at 07:42 PM.
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Old 04-23-13, 07:19 PM
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I would use a 1/8 or 5/32" bit. You want it not to split the wood, but leave enough bite to hold.
 
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Old 04-23-13, 07:48 PM
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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?
 
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Old 04-23-13, 08:04 PM
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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
 
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Old 04-23-13, 08:21 PM
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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.
 
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Old 04-23-13, 08:25 PM
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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!
 
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Old 04-24-13, 04:09 AM
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That's OK. I'm married. Good luck on the install, and welcome anytime!!
 
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Old 04-24-13, 07:02 AM
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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
 
 

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