What type of stainless steel self-drilling screws are there?
There are two main types of Stainless Steel Self-Drilling Screws:
1. Self Drilling Screws for Timber, which as the name suggests drill into wood or timber, usually with a Type 17 style cutting flute:
2. Self Drilling Screws for Metal often called a Stainless Tek Screw. These are screws designed to self-drill into metal without needing a pilot hole.
What type of Tek Screws are there?
Here we are talking about the Self Drilling Screw for Metal often called a Stainless Tek Screw.
The Tek Screw or Self Drilling Screw for Metal is generally available in 4 material types within the Stainless range, they are:
- Bi-Metal Self Drilling Screws – a 304 Stainless Steel body with a Carbon Steel tip. Because of the Carbon Steel tip they are very hard and good for drilling but they are not 100% Stainless. They have a 500hrs Salt Spray Protective Ruspert Coating on them to increase corrosion resistance somewhat.
- 410 Stainless Self Drilling Screws – These are completely Stainless Steel. 410 is a Martensitic Stainless Steel and so can be hardened by heat treatment (which Austenitic types 304 and 316 cannot be). For this reason it has excellent drilling properties, however 410 has lower corrosion resistance than grade 304 and should not be used in highly or even moderately corrosive environments or tea-staining will result.
- 304 and 316 Stainless Self Drilling Screws – Because the 300 series of Stainless Steels are of an Austenitic crystal structure, hardening by heat treatment is not possible. These screws provide excellent corrosion resistance but are really only good for self-drilling through thin aluminium due to the softness of the material.
- Hardtec Stainless – ‘Hardtec’ Stainless Steel is a propriety grade made specifically for Stainless Self Drilling Screws, it is the best performing stainless self drilling screw. It is hardened by heat treatment and so have excellent drilling performance into metals like grade 410 BUT unlike grade 410, it has Molybdenum added to it and has corrosion resistant properties in line with the 300 series Stainless Steel grades. Salt Spray tests show corrosion equal or better to that of 304 Stainless and not far behind 316 Stainless Steel.
Click here for more information about the different types of Stainless Steel.
NB: Always select which grade of stainless steel is appropriate for the application and be sure to follow good stainless steel guidelines. For help and advice on stainless steel grade selection, please contact the Nickel Institute or the Australian Stainless Steel Development Association.