Thread: Pilot hole size for screws

I just measure the shank with my dial callipers and drill that size. Same for all woods.

Try these - https://www.bunnings.com.au/frost-ga...chart_p6270572

https://www.suttontools.com/products...zi-sizer-m810/

https://s3-ap-southeast-2.amazonaws....izer_Gauge.jpg

Thanks guys.

I'm looking at self tapping screws online. What is the difference between 14G-10 and 14G-20?

About 10

Sorry, I'll see myself out...

For wood screws I use this reference guide: Wood Screw Pilot Hole Size Table - Engineer's Handbook

Brian

Originally Posted by qwertyu

Thanks guys.

I'm looking at self tapping screws online. What is the difference between 14G-10 and 14G-20?

Screw Size Identification The description of the size of the screw is usually listed as three figures:

1. The first figure indicates the gauge of the screw (g),
2. The second figure indicates the threads per inch (T.P.I.),
3. The third figure indicates the length of the screw - mm or inches (”).

e.g. 14-10 x 20mm = 14 gauge, 10 threads per inch, 20mm in length.

Often the second figure is not listed, particularly in timber screws, etc., e.g: 10 x 2-1/2” = 10 gauge, 2-1/2 inches in length.

From page 3.004 - https://www.hvaceducationaustralia.c...ew%20Types.pdf

I see.
If they dont list the second figure - is there a standard TPI which we assume it is?

OK. If you are talking about true "Wood" screws, then a tapered bit should be used. The bit would be specified by the drill bit manufacturer according to the diameter of the screw.

If you are talking about sheet rock screws or sheet metal screws (non tapered threads) like we all use, it is a bit more complicated.

There are two diameters of the screw that are important, shank and thread. The easiest way to determine the appropriate screw size is to hold the screw up to a light area with the drill bit behind it. The pilot drill bit should be hidden behind the screw including both sides of the threads. The body drill would not stick out beyond the threads of the screw.

Food for thought department.
You are using a screw to hold two pieces together, the top and the bottom. The threads of the screw should pass through the top piece freely and only engage the bottom piece.

Originally Posted by rrich

Food for thought department.
You are using a screw to hold two pieces together, the top and the bottom. The threads of the screw should pass through the top piece freely and only engage the bottom piece.

Second course:
drill through both pieces together with the pilot first before enlarging the top hole, so that both holes line up.

For me, pilot hole size varies with the timber density. The pilot hole I use in Ironbark is larger than in pine and different again in MDF
If they were the same size hole you would find one screw stripping the hole and the other screw snapping off with different timbers

Hey Qwertyu, going on the basis that a picture is worth a thousand words - I found this video some time ago, and it seemed to cover most aspects of this (that I didn't know)

https://www.youtube.com/watch?v=Ne69SeQ1b7w

Originally Posted by Beardy

For me, pilot hole size varies with the timber density. The pilot hole I use in Ironbark is larger than in pine and different again in MDF
If they were the same size hole you would find one screw stripping the hole and the other screw snapping off with different timbers

Agreed, same as metal screws have a smaller thread than wood screws due to density of the product. Same principle, aluminium screws have a lager thread than ones for steel.

Originally Posted by rrich

.......Food for thought department.
You are using a screw to hold two pieces together, the top and the bottom. The threads of the screw should pass through the top piece freely and only engage the bottom piece.

Indeed, so how come it's so damned difficult to find wood screws that are not threaded all the way to the head, these days? And when I do at last locate some 'real' wood screws on the racks at my local Big Green Shed, there are only two or three sizes and none in the gauge or length I'm after.....

Cheers,

Originally Posted by IanW

Indeed, so how come it's so damned difficult to find wood screws that are not threaded all the way to the head, these days? And when I do at last locate some 'real' wood screws on the racks at my local Big Green Shed, there are only two or three sizes and none in the gauge or length I'm after.....

Cheers,

Ah, the wonderful benefits of competition and a global market!