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Hole sizes

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JohnMD
Navigator

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USA
207 Posts

Initially Posted - 03/03/2008 : 12:28:37

Hi all. I'm going to be drilling some holes inside the boat to hang some curtains. What size drill bit should I use for a #8 screw? 9/64, 1/8??? Thanks. Wish me luck.

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Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 03/03/2008 : 13:37:49

#8 Screw
Soft wood - use 5/64"
Hard Wood - use 3/32"

If in doubt start with the 5/64" or 1/16". You can always drill a hole larger if the screw is to tight. Fiberglass is hard so 3/32" might be closer to what you need.

http://www.santafefasteners.com/fasteners/technical/proper.htm

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britinusa
Web Editor

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USA
5404 Posts

Response Posted - 03/03/2008 : 21:19:01

Here's a trick you can use to ease the spliting of FB when driving a screw into a pilot hole:

Use a dremmel with a disc cutter (they are about 1/32" thick) to cut a grove along the thread from the screw tip towards the head of the screw, but not going all the way to the screw head.

It will act like a self tapping screw and drastically reduce the tendency of the screw to crack it's way into the fiberglass.

Paul

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lewalskim
1st Mate

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USA
70 Posts

Response Posted - 03/04/2008 : 06:29:18

What size would I use to drill a hole in the mast in order to tap it for a #10 machine screw? What about a #8?

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welshoff
Captain

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USA
253 Posts

Response Posted - 03/05/2008 : 13:29:10

I bought a small drill/tap kit that included the drill bit to go with each tap. Takes the thought process out of tapping for fasteners.

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sterngucker
Navigator

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USA
169 Posts

Response Posted - 03/05/2008 : 16:19:25

Here is a handy web site for determining tap and clearance holes.

http://www.marfas.com/machinescrewtapping.shtml

Enjoy!

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Al
Captain

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USA
269 Posts

Response Posted - 03/05/2008 : 19:45:08

I'm no expert, but I don't think you'd want to tap a thread into material as thin as I assume our masts are. To make up for the thinness of the material, you need thread depth and I think the thread depth of a sheet metal screw is much deeper than even a coarse thread machine screw in an equivalent size.

I've only heard of using sheet metal screws or rivets on a mast...

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.