Pilot Hole Size for Self Tappers

[imroberts]

I'm fixing some blinds into a window recess.

There is a metal lintel above the opening and I intend to screw into that with stainless self tapping screws.

I think size 8 screws will be ideal for the brackets or maybe size 10. What size pilot hole should I drill?

 

[Deleted member 174758]

How thick is the metal you are screwing into? The thicker the metal, the bigger the hole you need.

According to my tables a stainless steel #8 self tapper (4.2mm diameter) requires 3.0 to 3.4mm pilot drills (the former for 0.75mm metal, the latter for 1.6mm or thicker metal) while for a #10 self tapper (4.8mm diameter) the pilot size range is 3.5 to 3.8mm. That's assuming that you are screwing into stainless steel or mild steel. Steel lintels may well be harder. There's always a bit of trial and error with this, so start with a smaller drill and enlarge as necessary

 

[imroberts]

I can't be sure exactly how thick the metal is but I'd guess 3-4mm from drilling through with a small pilot hole.

I have 3.0, 3.2 and 3.5mm drill bits so I'll see how I get on with some #8 self tappers once I've picked some up!

 

[foxhole]

No pilot needed with these .
https://www.toolstation.com/techfas...MI-IC-9MCr5QIVDVPTCh0NBwEgEAQYAyABEgJdCfD_BwE

 

[Deleted member 174758]

You'd have thought so, Foxhole, but I've had quite a few situations where the steel we were going into was pretty thick (4 to 12mm) and even with winged fasteners it was still necessary to drill a pilot hole. Otherwise the point on the fastener would simply burn out before the threaded bit could get into the steel

 

[foxhole]

You'd have thought so, Foxhole, but I've had quite a few situations where the steel we were going into was pretty thick (4 to 12mm) and even with winged fasteners it was still necessary to drill a pilot hole. Otherwise the point on the fastener would simply burn out before the threaded bit could get into the steel

Secured my patio frame with them into 10mm steel .No problem .