FSW Tools: FAQs

Frequently Asked Questions on FSW & FSSW Tools

Carbide or Tool Steel?

The choice of the right material for the manufacture of friction stir welding tools requires great attention. In many cases, the pin and shoulder are made of different materials, because they have different functions. The pins are usually made of one of the following materials:

  • S = Steel (1.234/MP159) 
  • H = HSS-E 
  • V = Tungsten Carbide
  • B = Cubic Boron Nitride
  • D = Polycrystalline Diamond

The main advantage of carbide pins is their long service life. Carbide tools with the same dimensions have significantly less abrasive wear and a longer service life than hardened tool steel.


What are the Benefits of Carbide?

One of the most important benefits of carbide pins is their advantageous length-to-diameter ratio. A long, slimmer pin requires only a smaller shoulder diameter. Thus the following goals are achieved:

  • High welding speeds, e.g. on CNC-controlled FSW machines
  • Low process forces, e.g. in robot welding
  • Less space required and therefore better accessibility due to smaller shoulder

Make or Buy?

For laboratory investigations and preliminary tests, many FSW tools have already been produced worldwide on existing manually operated lathes and milling machines. An experienced toolmaker needs about half a day to a full day to manufacture three simple tools according to an existing drawing. With a CNC machine it is a little faster. 


However, for industrial high-volume production, the tools are usually not manufactured in-house, but purchased from a tool supplier who is specialised in tool manufacture, as the demands on the tools are increasing and the tool geometries are becoming more and more complex.


How to Specify and Order FSW Tools?

AluStir provides technical consultancy on friction stir welding tools. In close cooperation with leading tool makers, we can supply you with standardised tools as listed in the catalogue or a tailor-made customer-specific complete package for your needs. In many cases we supply special tools with standardized pins and shoulders adapted to your tool holder. 


We can help you, to specify and order your tools, if you describe your application to us with the help of a sketch, a drawing, a CAD file or a photo as well as the material specification of your workpieces.


CNC Pins or Robo Pins?

The geometry depends mainly on the desired welding depth and the work piece material. Depending on the spindle bearing and the compliance of the FSW robot or CNC machine, different concepts are used, colloquially called "CNC Pins" and "Robo Pins", depending on whether the work is carried out with rotating or stationary shoulder. AluStir will be happy to advise you on the tool specification.


Standard Tools or Bespoke Tools?

A mutually acceptable minimum quantity is required for the procurement of special tools, so that the design and set-up costs are in balance with the manufacturing costs. In most cases, it is therefore advantageous to select as many standard components as possible from the catalog and adapt them to the specific application. Due to our experience with friction stir welding and tool manufacture, we can supply you with standardized individual components or customized complete solutions at attractive conditions. 


Turning, Milling or Grinding?

Ground carbide pins have a much smoother surface than milled or turned tool steels. The aerospace industry in particular prefers ground carbide pins because the tool steel abrasion of turned FSW tools, especially new FSW tools that have not yet been run in, often contaminates the weld metal. Tool steel particles embedded in aluminium can cause local corrosion (pitting corrosion) in a moist environment and are therefore undesirable, especially near the root or surface of the weld. 


The ‚3 × 3‘ of FSW Tools for High-Volume Production

The quality of friction stir welds depends mainly on three factors, of which the FSW tool plays an often underestimated important role: 

(1) Friction stir welding tool

(2) Friction stir welding machine with fixture

(3) Friction stir welding personnel


The most important factors in FSW tools are:

(1) Tool geometry

(2) Tool material

(3) Tool surface finish


The costs caused by the tools depend mainly on the following cost factors:

(1) Tool procurement costs

(2) Tool life

(3) Tool availability