18th November 2024
Introduction to Fettling
In the world of metalwork and coatings, fettling is a term that is often thrown around but not always fully understood. It’s a crucial part of ensuring that metal components are clean, smooth, and ready for further processes like powder coating, painting, or plating. For those involved in any kind of metal fabrication, fettling is essential, especially when preparing metal for long-lasting finishes. But what exactly is fettling and why is it so important? This blog will delve deep into the fettling meaning, the processes involved, and how newer technologies, like hot zinc spray, eliminate the need for fettling in many cases.
Fettling is the process of cleaning, smoothing, or trimming the surface of a cast or forged metal component. It’s most commonly used in foundries, where rough metal parts come out of the casting mould or forging process with imperfections such as sharp edges, excess material, or rough surfaces. This process ensures that the part is ready for subsequent finishing processes, whether it’s painting, powder coating, or another method of protection and aesthetic improvement.
In essence, fettling refers to removing unwanted material, often using tools like grinding wheels, files, or pneumatic burrs. The goal is to smooth out imperfections, prepare surfaces, and ensure a polished finish. Without fettling, parts can suffer from poor adhesion when powder coating or painting, as any excess material can prevent the coating from bonding properly to the metal surface.
The Origins of Fettling
The word “fettling” itself has old roots in the English language, originally used to describe making something tidy or putting it in order. This older meaning aligns perfectly with its current usage in manufacturing, where fettling involves making a rough metal object smoother and more presentable.
In traditional foundries, fettling was a manual, labour-intensive process. Workers would spend hours grinding down metal edges, removing burrs, and making sure the cast or forged part was ready for its next steps. Today, fettling is still used, but new methods such as shot blasting and hot zinc spray can eliminate the need for extensive fettling in certain cases.
This image of an Elcometer shows the reading before fettling of 104 microns.
Why is Fettling Important in Metalwork?
Fettling serves two main purposes: it improves the aesthetic quality of metal parts, and it ensures proper adhesion for subsequent coatings. For example, if a metal part is going to be powder coated, any rough edges or excess material can interfere with the coating process. The coating may not adhere properly, leading to imperfections that will compromise both the appearance and the durability of the final product.
In the case of structural steel, architectural coatings, and other industrial applications, the aesthetic quality and durability are paramount. No one wants to see rough patches, sharp edges, or discolouration on what should be a sleek, smooth, and protected surface.
Fettling in Different Industries
Fettling plays an essential role in multiple industries, such as:
- Automotive: Fettling ensures that car parts have a smooth, polished surface before being painted or coated.
- Construction: Metal frames and supports need to be fettled to prevent sharp edges and achieve a professional finish.
- Aerospace: In an industry where precision is vital, fettling ensures that components meet the exacting standards required for safety and functionality.
Common Methods and Tools for Fettling
In modern metalworking, fettling can involve a range of techniques and tools, including:
- Hand Tools: Files, chisels, and sandpaper are often used for minor fettling work, especially when precision is required.
- Grinding Wheels: For larger jobs, a grinding wheel can quickly smooth out a surface or remove unwanted material.
- Pneumatic Burrs: High-speed rotary tools can be used to remove rough edges and clean up intricate areas on metal components.
- Shot Blasting: This process uses high-velocity abrasives to clean the surface, effectively “fettling” it before coating.
Fettling vs Grinding: Is There a Difference?
Many people confuse fettling with grinding, but while they are similar, they have distinct purposes. Fettling is typically a finishing process focused on removing imperfections, while grinding often refers to reshaping or resizing a metal part. In essence, fettling is the finer, more detailed cousin of grinding, focusing on surface quality rather than form.
this picture shows the Elcometer reading after fettling and its down from 104 to 76.5, so nearly a quarter of the protective zinc has been taken off.
Hot Zinc Spray: No Need for Fettling
One of the most significant advancements in metal coating is the introduction of hot zinc spray, also known as arc spray or thermal zinc spray. Unlike hot-dip galvanising, which leaves a thick, uneven zinc layer that often requires fettling to smooth out, hot zinc spray applies a thin, even layer of zinc without the need for further fettling.
When a metal part is hot-dip galvanised, it is submerged in molten zinc, resulting in an uneven coating that often needs to be fettled afterward. This process is time-consuming and can even remove some of the protective zinc layer during fettling, reducing the effectiveness of the coating.
In contrast, hot zinc spray applies the zinc layer evenly and smoothly. This means that once the zinc spray is applied, there’s no need for fettling, and the part is ready for additional coatings, such as powder coating or paint.
At NSP Coatings, we exclusively offer hot zinc spray because we believe it provides superior protection while eliminating the need for fettling. This ensures the zinc layer remains intact, offering long-lasting durability without the additional time and cost associated with fettling after hot-dip galvanising.
Why Choose NSP Coatings?
At NSP Coatings, we specialise in providing high-quality coatings for industrial and architectural steelwork. Our services include powder coating, hot zinc spray, and shot blasting, all performed in our state-of-the-art facility. With our in-house quality assurance team, you can be sure that every part we process is meticulously checked to meet the highest standards. Contact us today to get your job priced up.
