Screw sizes?

[William Frederick]

Just trying to get ready to start to make some items after the new year and was looking at getting a few different screw sizes. I noticed some listed by length, coarse or fine, then #8, #7, #2. I understand the length as difined by Kreg. To use course on soft woods and fine on hardwoods. Is the # size the square drive size or is this in reference to the diameter of the screw or what? I hope this is not a silly question.

[William Frederick]

Thanks for the help.

[Mark Quo]

Screws are categorized in 3 main ways - the type an size of the driver, the diameter (of the shank) and the length. The numbering system is similar and that may be causing the confusion.

First, is the size and style of the driver used for the screw. In case of Kreg screws, they are Square Head size #2. Square head drivers are available commonly in #1, #2 or #3 with #1 being the smallest. Phillips heads are specified the same way, #1, #2, #3. You can look at a kit of screwdrivers and see that the drivers are marked with a #1, #2, or #3 to indicate the size of the driver.

Next is the diameter of the screw itself - the diameter of the shank.. Typical sizes for drywall, pocket hole screws, machine screws, etc are #6, #7, #8, etc with larger numbers indicating larger diameters. Here's a link to a chart of wood screw diameters : www.mypianoshop.com/Screw_Chart.pdf

Last is the length of the screw as measured in inches, ie 1 1/4" screw.

For Kreg screws, most sizes are also available in either coarse or fine thread.

So for example, the most popular screw sold by Kreg for 3/4" wood is the 1 1/4" inch length, #2 square head drive, and #7 shank diameter. It is available in either coarse or fine thread.

You can go to the hardware store and look at drywall screws, and see how they are marked the same way, except that they typically use #2 phillips head drivers.

hope this helps

[John Laing]

Diameter of the screw. Kind of like the penney size of nails.

[William Frederick]

Very nice description, this is very helpful.

They are similar to machine screws then having their diameters being called out by number sizes until they reach I believe 3/16" or 1/4". I should have known since I have worked with metal fasteners like socket head cap screws. Mostly work with metric fasteners now (European company). They are called out by their metric diameter and length.
Thanks again and the link is helpful. I will save it to my documents and print it off.

Mark Quo said:

Screws are categorized in 3 main ways - the type an size of the driver, the diameter (of the shank) and the length. The numbering system is similar and that may be causing the confusion.

First, is the size and style of the driver used for the screw. In case of Kreg screws, they are Square Head size #2. Square head drivers are available commonly in #1, #2 or #3 with #1 being the smallest. Phillips heads are specified the same way, #1, #2, #3. You can look at a kit of screwdrivers and see that the drivers are marked with a #1, #2, or #3 to indicate the size of the driver.

Next is the diameter of the screw itself - the diameter of the shank.. Typical sizes for drywall, pocket hole screws, machine screws, etc are #6, #7, #8, etc with larger numbers indicating larger diameters. Here's a link to a chart of wood screw diameters : www.mypianoshop.com/Screw_Chart.pdf

Last is the length of the screw as measured in inches, ie 1 1/4" screw.

For Kreg screws, most sizes are also available in either coarse or fine thread.

So for example, the most popular screw sold by Kreg for 3/4" wood is the 1 1/4" inch length, #2 square head drive, and #7 shank diameter. It is available in either coarse or fine thread.

You can go to the hardware store and look at drywall screws, and see how they are marked the same way, except that they typically use #2 phillips head drivers.

hope this helps