#14 x 1-1/2" Button Head Sheet Metal Screw, Resist Torx Buy  As low as $0.59

Attaching Toilet Partition Screws into Metal Backing

When attaching toilet partitions and the related toilet partition hardware, there are many special challenges when you have steel backing in the walls. This is becoming the standard for commercial construction and the old practice of placing wood blocking in walls is fading as more carpenters become familiar with working with steel for their wall structures.

Compounding the challenges are the need to use the screws provided by the toilet partition manufacture. A quality installation calls for a uniform look of the screw heads and often stainless steel screws are called out as part of the solid plastic toilet partitions. You cannot simply substitute a self drilling screw.

My article here tries to document the special considerations to install the screws into steel blocking. You obviously will have drilled a pilot hole through the tile and sheet rock that sits over the backing. The drilling through tile is not part of this article and will be addressed separately.

Fastener:
#14 x 2-1/4” Stainless Steel sheet metal screw. Tamper Resistant Torx head.

Steel backing as tested:
16 and 14 guage steel. I used steel straps for the test, since they are piloted and easy to work with.

Tools:

Measure the Fastener for drill bit size

The idea is to use the drill bit size that is the same size or only slightly larger than the screw body - the solid section in the middle that the "flutes" spiral around . This way the screw has maximum "bite" of the flutes. In this picture, I use a dial caliper to measure the screw body. In this case, my #14 screw has a .195 diameter, so I choose the 13/64" drill bit. I then will proceed to drill a "test pilot hole" so that I can verify my choice. (more on this later)

If you have 16 gauge  (or thinner) backing : This will drive easily into the backing. You should be able to drive it in with your hand screw driver. This is what I do on my first screw, so that I get a good feel for the thickness of the steel.

If you have thicker that 16 gauge:  On my tests with 14 gauge steel, I was not able to drive the screw into the 13/64th pilot hole. (The screw would not get started. I then went up to the next largest 64th and tried again. I arrived at the 7/32 drill bit size for this thicker material.

Drill the pilot hole into the steel backing

Here you see my piece of cardboard in action. I have placed a few drops of cutting oil onto it and then daub the drill bit onto the oil each time I drill. My drill bits last at least 10 times longer verses no oil!

If going into the 16 gauge or thinner steel: just the tip is good.

 

The screw on the left was "jammed" into 14 gauge steel, causing excess friction that produced galling that strips the flutes off the screw and has caused it to fail - it does not hold.

Thicker than 14 gauge (.083) thick

This will be unusual, but some times there will be a thick metal place placed as backing. (beware that you are not trying to drill into a pipe!) Unfortunately, you are now beyond the capacity of a sheet metal screw. Your options are to drill and tap, using a machine screw or to use a special self drilling and tapping screw that are available from an industrial hardware dealer.