Stainless Steel CD Weld Studs M4 x 25mm Length (A2 spec.)

60 Reviews
£31.12 per hundred
Weld Stud Material:select Copper Flashed Mild Steel A2 Stainless Steel Aluminium Alloy Exotic Materials  inc. Brass, Bronze and 316s/s below to switch product or see our range
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4 - 6 days
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Immediate in-store pickup near you. We can take payment immediately and have your studs waiting for you at one of our preferred welding supply re-sellers
Our network of independent welding suppliers are all stocked with Studfast's superior stringently quality controlled studs. Look for the Studfast Quality assurance label on the bag. That way you can be assured of producing quality welds on your job, every time, but collect immediately from a store near you. We always send out a re-supply too, so in the unlikely event that THEY are out of stock, we will notify you immediately and rest assured your studs will be immediately on their way to your local welding supplier, reserved only for you.
Thumbnail image of Stainless Steel CD Weld Studs M4 x 25mm Length (A2 spec.)
Stainless Steel CD Weld Studs M4 x 25mm Length (A2 spec.)

General specs

  • Material:Mild Steel Copper Coated
  • Manufacturing Certification:ISO 13918
  • Threading Spec.:M4
  • Threading compatibility:Metric Standard

Pip Length Specifications

  • The pip on the end of the stud is the timing mechanism for the entire weld. As such we are militant about testing all our studs to ensure not only apparent physical consistency, but also consistency in the welds they produce.
  • Length of Pip:1mm target length (We determine accepted variance by testing)
  • Pip Diameter:0.5mm with 0.012mm variance - (between 0.588 and 0.612mm)

The Studfast ISO 13918 Capacitor Discharge Studwelding Stud Specification Drawing

Our drawing available below clearly illustrates the key dimensions essential for consistent, quality welds. Our drawing is created with clarity in mind overviewing the key factors in the ISO specification. Should you require an exhaustive CAD drawing of the exact spec, just fire us an email and we will provide one for you.

iso 13918 spec for cd weld stud available for download
Download the ISO 13918 Drawing

Download the The Studfast ISO 13918 Capacitor Discharge Studwelding Stud Specification Drawing here. Just click the button above. Should you require an alternative format, please don't hesitate to send us an email.

Stud Length Characteristics

  • Our stud length specifications are measured as LAW meaning 'Length after Weld'. This is because during the weld process some of the parent material is blown away as weld spatter, (albeit minimal for the CD process.) Also some of the material is turned to plasma and a further volume of the material is liquified, filling the weld cavity and moving to the edges of the stud. What we are looking for in a good quality weld is a uniform 'witness' of a minimal solidified molten metal ring around the edges of the stud flange. Later we will discuss cone angle which is there to help this process.
  • Stud Length: 25mm LAW (Length After Weld)
  • Accepted VariancePlus or minus 0.6mm
  • Should you be getting LAW Length After Weld measurements exceeding this variance then that would indicate a problem in setup. Call our experienced team and we will be there to help you rectify any issues, free of charge. Calibrate customers also benefit from unlimited preferential 24/7 support, on site visits or virtual troubleshooting over Zoom (preferred), Skype or Facetime

Weld Specific Attributes (as detailed on our ISO 13918 drawing)

  • The Studfast ISO 13918 Capacitor Discharge Studwelding Stud Specification Drawing illustrates some design features that must be stringently controlled to ensure quality welds. Firstly, while the end of the stud may look flat to the naked eye, there is in fact a shallow angle causing the pip to protrude further out, giving a conical end. This design feature is essential to ensure the weld pool that begins vaporising and liquifying at the centre, is evenly worked outward during the weld, aided by the spring pressure in the weld head or hand tool.
  • Angle Marked 'ΘCA' (for Cone Angle):2.2 degrees to 3.8 degrees
  • N.B.// This Cone Angle is greatly exaggerated in our drawing to illustrate its existence and make it clear what the 'ΘCA' placeholder is referring to

Certificate of Conformity

  • Your online purchase includes a Certificate of conformity. This will be emailed to you immediately upon your purchase. Metallurgy certificates and other supporting documentation is available upon request. Ideally shoot us an email, (received directly by our technical team,) or call our main line and speak to a human immediately, (no frustrating voice menus,) who will be able to deal with your request 24/7.
Product thumbnail image of Stainless Steel CD Weld Studs M4 x 25mm Length (A2 spec.)
Stainless Steel CD Weld Studs M4 x 25mm Length (A2 spec.)

60 Reviews

4.2 Overall rating

51 out of 60 (85%)
Customers recommended this product


Rafael Marquez
Review from Our Customer by L Clarkson
83% of users found this review helpful

Studfast are the sort of supplier I like - the parts just arrive when they are supposed to without any issues ,

  • Pros: Speedy delivery, always accurate
  • Cons: None that I can think of
Review from Our Customer by S Rigler,
97% of users found this review helpful

We have used Studfast for over 12 years and have always found them to be extremely helpful and very knowledgeable; I would not hesitate to recommend them.

  • Pros: Real people, who care about customer service
  • Cons: n/a
Review from Our Customer by D Ridgwell,
75% of users found this review helpful

Fantastic quality, expert advice and speedy delivery. Our precision applications demand all these three and in nine years Studfast have never disappointed

  • Pros: Product Consistency... this is KEY for us. My previous supplier provided studs with intermittent reliability
  • Cons: Did not initially mention ability to schedule orders for volume discount, but that is a minor minor point 🙃

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You can quickly place your Stainless Steel Weld Stud Order Online

Buy Online Stainless Steel CD Weld Studs from our extensive range of welding products. Either metric threaded or unthreaded studs which are also called plain pins. Stainless Steel Stud welding supplies, including capacitor discharge weld studs, A2 Stainless Steel Capacitor Discharge weld studs, low carbon steel studs. We stock regular stainless steel cd studs, the metal composition of which conforms to the Stainless Steel A2 specification. We can also supple 316 stainless steel weld studs where extreme corrosion resistance is required. Our metric 'M Threaded' cd studs in stainless or mild steel are specially calibrated for use with our capacitor discharge cd stud welding equipment for welding to mild steel sheet metal or to stainless steel metal sheet, depending on your application. We also supply Aluminium Alloy CD Weld Studs for welding to aluminium sheet, as is used extensively in the signage industry and on jobs like building cladding. Small aluminium components require small diameter aluminium alloy studs for CD welding at low power, where the pip consistency stud-to-stud is imperative, while some of the more heavy aluminium structures use thicker, sturdier aluminium alloy studs at diameters of 6mm (M6 threaded), and we even sell up to M10 aluminium threaded studs which are still suitable for welding with the CD process, necessitating a wide range of aluminium threaded studs kept in stock on the shelf, all quality checked and ready for immediate dispatch. Keep your stud welding production line stocked, as recent trading issues have sometimes created longer lead times. Use high quality Stainless Steel CD Weld Studs to ensure consistent quality in your welding application. Always test destructively on a spare piece of metal sheet material, while welding under identical conditions to be sure that your welds are meeting your torque tolerances under test conditions.

And if you don't require the corrosion resistant properties of stainless steel in your application, you can make a considerable cost saving by considering our product range of Mild Steel CD Weld Studs, also available threaded M3 to M10 or unthreaded diameters 3mm to 10mm.

Why choose a2 stainless steel weld studs for capacitor discharge welding applications?

Choosing A2 stainless steel weld studs for capacitor discharge welding applications can have several advantages. First off let us clarify which variant of S/S we're looking at. First off the most popular by far is 'A2' stainless steel. You will also hear people referring to this material as AISI 304 or 18-8 stainless steel... but it's all the same stuff. Same metallurgical make-up and composition. It is this specific high-chromium content in the alloy that lends A2 its famed properties of resistance to corrosion, preventing oxidisation in the presence of moisture. And the exact balance of the elemental proportions in the alloy also prevent the layers of iron atoms rolling over each other giving it a rigidity and strength that makes for a reliable and durable material.

The other prevalent element in the 304 / A2 Stainless Steel Alloy is nickel. This type of steel is referred to as Austenitic due to its microstructure, comprising of cubic crystal structure that is entered to a face. The density of this A2 / 304 ASTM Grade steel is fairly low, (for steel,) coming in at 7930 kg/m3.

Even More Corrosion Resistant, Stronger CD Weld Studs... introducing 316 Stainless

There is another 'upgrade' austenitic stainless steel known as type 316 which is created by adding two percent molybdenum to its chemical alloy make-up. By adjusting the crystalline lattice structure of the material in this way we find improved performance where usual chloride ions may have otherwise allowed acid corrosion '316 Stainless Steel' is able to further weather and even out perform standard A2. However, in order to weld effectively there is a low carbon version called 316L, (this is the material we use in all our 316 stainless steel studs.) To get a decent weld you really need the carbon contents of the steel as low as possible, (below 0.03% ideally.) Adding carbon adds massive strength, but you are also dramatically reducing the material's ability to liquify and re-set, because carbon and iron have drastically different melting points, (iron being the lion's share of the elemental makeup of any steel, obviously,) and so by liquifying and vaporising at different rates, we are prohibiting the formation of a decent weld-pool in a uniform manner.

Studfast · Putting Product Quality First and Foremost : Quality Weld Studs and CD Welding Support When You Need It

At Studfast we have a mantra, "Our Studs, Our Machine, Our Problem"... this means that if you are using our CD weld studs and a machine supplied by us, (either purchase or rental,) if you should encounter any problems in production then we will make it our problem too. We can solve most problems either over the phone or by hopping on a quick zoom so we can see your setup. But we have also been known to travel the length and breadth of the country visiting our customers to make sure they get their welding application set up right. If you're interested in learning more, there's a great set of articles here on applications and structural properties of various Stainless Steel grades and also understanding corrosion by WorldStainless , and I've also included one of WorldStainless Secretary-General Tim Collins' lectures further down the page too as a YouTube embed on corrosion.

Balancing Stainless Steel CD Weld Stud Performance

When looking at weld stud materials, while the compatibility of A2 stainless steel weld studs is second to none and can form a decent weld with various base materials. They are used by people manufacturing electrical products, along with automotive and the food industry particularly likes the clean finish provided by the CD weld process (say, versus drilling and tapping, which leaves grooves that bacteria can live in.) Capacitor discharge welding is a clean process... and Stainless Steel is one of the cleanest most corrosion resistant and durable materials available. If you're in need of some truly heavy-duty corrosion resistance, or creating something that's liable to be exposed to saltwater, then we do have a range of 316 stainless weld studs too. I'm not sure we've thrown them up on the Studfast e-commerce site as of yet though, so you might need to give us a call or alternatively drop us a line with your enquiry / requirements / brief description of what you're trying to achieve. I'm sure our team will be able to get straight back to you and advise or quote on one of our stock items we haven't got around to uploading to the Studfast online studwelding shop yet.

A Weld Stud in Stainless Steel vs. A Mild Steel Weld Stud

When stud welding capacitor discharge stainless studs... one thing you'll notice about A2 Stainless vs. Mild Steel is that it is not 'ferrous' i.e. it has very little magnetic properties, whereas you'd be able to pick up a whole bag of mild steel studs with a magnet... the stainless steel material doesn't transmit electro-magnetic fields. This may or may not be as you desire in your application, so its important to be aware. While the 316 varient of Stainless Steel is a little more expensive, the A2 standard of Stainless Steel strikes a great balance between durability, strength and affordability. Talk to us about your job and we will be happy to advise.


The Lecture above was by WorldStainless Secretary-General Tim Collins, in my opinion a great bit of content on understanding corrosion.

Let's re cap some of those advantages we've been discussing for A2 stainless steel weld studs or even the epic corrosion resistance of 316 stainless steel weld studs and why we will need to use the 316L varient in our capacitor discharge welding applications. The advantages and plus-points of stainless over regular ole copper-flashed mild steel are numerous, so lets run down the top points as they pertain to the cd weld studs themselves and the capacitor discharge process in particular;

  1. Corrosion resistance: A2 stainless steel, also known as AISI 304 or 18-8 stainless steel, offers excellent corrosion resistance. This is particularly important in capacitor discharge welding applications where the studs may be exposed to harsh environments or corrosive substances. The resistance to corrosion helps ensure the longevity and durability of the weld studs.
  2. Strength and durability:: A2 stainless steel is a high-strength material that can withstand the stresses and forces involved in welding applications. It provides good mechanical properties, including high tensile strength and toughness, making it suitable for capacitor discharge welding.
  3. Compatibility: A2 stainless steel weld studs are compatible with a wide range of base materials and can be used in various applications. They are commonly used in industries such as automotive, construction, and electrical, where capacitor discharge welding is frequently employed.
  4. Non-magnetic properties: A2 stainless steel is non-magnetic, which can be advantageous in certain applications where magnetic interference is a concern. This property can help ensure that the weld studs do not affect nearby sensitive electronic components or devices.
  5. Cost-effectiveness: Compared to some other stainless steel grades, A2 stainless steel is relatively affordable. It provides a good balance between performance and cost, making it a cost-effective choice for capacitor discharge welding applications.

In choosing the right CD weld studs for your job, its a good idea to consider all the options. Think about which parts of the finished job are liable to be facing the elements. What environment will it live in after it's been put together with CD welding studs. It's important to note that the specific requirements of your welding application may vary, and it's always recommended to consult with welding experts or suppliers to determine the most suitable material for your specific needs. As always you can talk to us about your studwelding job and we will be happy to advise.

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