Materials & wear
Choosing the right steel and hard-facing decides how long a screw lasts. Knowing how it wears tells you when to act.
Steel
Our standard new screws are machined from EN41B (905M39) nitriding steel. Each one is then nitrided for more than 80 hours to give it a hard, wear-resistant surface.
Hard-facing
Filled, abrasive or high-output work wears flight tips quickly. For this kind of work we hard-face the flight tips to produce a bimetallic screw, using Stellite 6, 12 or 1, or Colmonoy 56.
Hastelloy screws are rebuilt with C276 alloy so they keep their corrosion resistance.
We also apply hard chrome plating, Armoloy and tungsten carbide coatings. They can go on a new screw or be renewed during a refurb.
Wear
Most of the wear happens on the flight tips. As the gap between flight and barrel grows, material slips back over the flights. Output drops, melt temperature creeps up and the process gets harder to hold. The barrel wears too, and matching the screw to the bore is what brings the clearance back.
On smaller screws the root wears as well, and that is usually what ends a screw’s life (see Refurbish or replace).
Warning signs
Measurement
Wear has to be measured with the screw out of the barrel and cold, and with the barrel cold and clean. Once your screw has been pulled, we can measure it at your works or in our workshop, and we give you a written report. With regular checks you can see how fast each line is wearing and plan around it.
A barrel out of line with its gearbox can wear a screw or seize it. We laser-align barrels and gearboxes on site.
Get in touch
Mon–Thu 07:30–16:15 · Fri 07:30–15:00
Want your screws and barrels measured? Call the workshop or send an enquiry through tws-ltd.com.
Call +44 (0) 1706 655402 Send an enquiry