May 2018 Issue
Toc

Stainless steel is a highly multifunctional material. It’s resistant to corrosion and adds a high-end appeal to many of the products in which it is found. Not only are its aesthetics attractive to manufacturers, it’s also widely used thanks to its hygienic properties and resistance to germs. From its use in food service and medical products to its prevalence in modern architectural design, it’s truly a diverse material.

There is an art to processing and finishing stainless steel, however. Its special properties require special tools, accessories, techniques and handling. Finishing by hand, as just one example, can be a complicated and time-consuming process, and there are many factors that can affect the outcome of the finish.

Before getting started with the finishing process required for stainless steel, it’s important to understand that abrasive accessories made from aluminum oxide or zirconia alumina can be used for steels and stainless steels.

It’s also important to understand that when working with carbon steels and stainless steels, they be kept apart from one another. That’s because the dust generated from grinding carbon steels can transfer through the air to the stainless steel and contaminate it. Likewise, when using wire brushes, only use brushes made of stainless steel wire to prevent contamination.

First Steps

When dealing with stainless steel, pre-finishing is the first step to conquer. This is the process of working out all of the kinks, scratches or burrs in the material to begin working with a clean slate. Knowing the condition of the stainless steel before starting a job will greatly save time and money in the finishing process.

And then there is the issue of dealing with deep scratches. The deeper the scratch, the more steps involved. For some scratches, fabricators will need to go through a series of progressive grit levels before achieving a good finish.

Lastly, the physical shape of the stainless steel will determine what tool and accessory is needed to accomplish the final finish.

In addition to the pre-finishing process, fabricators will learn that it’s crucial to choose the grit specification, abrasive accessory and appropriate tool for the actual finishing job.

The grit specification depends on what finish the user is trying to achieve. Whether it’s a No. 4 finish for an appliance or a No. 8 mirror finish for artwork, there are multiple possible outcomes. A different process is required for achieving the desired finish, whether it is a rough matte surface, a satin sheen or a bright mirror finish.

The No. 4 finish is the most common and can range from a rough to a fine No. 4 finish. Stainless steel that is in the 2B condition (mill finish) requires first working with traditional abrasives of aluminum oxide or zirconia alumina using coarse grits, 60 or 80 grit, to open the surface. This is then followed by 120 grit, then 150 to 180 grit for a rough No. 4 finish. A fine No. 4 finish requires an additional step, finishing to 280 grit.

Abrasive Accessories

The more carefully the prep work for stainless steel is handled prior to the finishing stage, the better the end result will be. Those results will also come quicker with the latest abrasive technologies.

That’s because Metabo’s Pyramid abrasives shorten the time required to get to the final finish. The structured geometric placement of the grains on the abrasive paper allows finer grit sizes to remove more material while providing a consistent finish.

The Pyramid abrasives allow for fewer steps to achieve a desired finish, depending on the condition of the initial surface. For example, starting with the 2B mill finish, a fine No. 4 finish can be obtained in two steps: first working with A160 (120 grit) then finishing with A65 (280 grit).

Playing It Safe

In addition to speed and quality, the operator’s safety is also a top priority. Therefore, it is to the operator’s advantage to use a tool that protects them and their work in the process. With that in mind, Metabo developed a range of safety mechanisms for its handheld tools.

For example, Metabo offers tools that switch off if the motor or battery becomes too hot or if the tool is overloaded. The company also delivers a restart protection feature on its equipment that prevents the tool from starting up unintentionally after the operator changes the battery pack.

This feature reduces the risk of accidents in case of a power cut or if somebody removes then reinserts the plug into the power supply with the switch still on. If the power supply is interrupted and restored, an angle grinder, for example, has to be manually switched off and switched on again to prevent the unintentional restart.

Furthermore, a soft start function also helps ensure safe operation by reducing the amount of kickback experienced when a tool is turned on. Similarly, many Metabo tools have electronics that aid the operator in maintaining speed under load, which is critical for improving productivity and for creating consistent finishes.

Choosing The Right Tool

In addition to choosing the right tool based on its safety features, selecting the proper tool can make a stainless steel finishing job a lot easier to accomplish while also saving time and money. Metabo offers a variety of handheld tools to get the finishing job done in both corded and cordless versions.

The cordless versions allow for work in any area where power is inaccessible. Advanced LiHD (lithium high density) batteries offer maximum power and runtime, delivering corded-like processing.

Metabo’s burnishers, the SE 17-200 corded and S 18 LTX 115 cordless, are well suited for heavy material removal or producing fine finishes on large, flat stainless steel surfaces and are capable of polishing to a mirror finish. The standard kit is designed to take stainless steel from a 2B mill finish to a No. 4 fine finish. For the full mirror finish, additional abrasive accessories are available. With their high-torque, variable-speed range, the burnishers are designed to prevent the “bluing” of the stainless steel.

For sanding tube and pipe, Metabo’s RBE 15-180 270-degree wrap angle grinder is suited for handrail fabrication or for finishing or repairing pipes and tubes up to 7 in. in diameter. Its cordless cousin, the RB 18 LTX 60, is equally equipped for handrail fabrication, rework or cleaning. Ideal for use with Metabo’s Pyramid abrasives, operators can quickly remove welds and reach desired finishes.

Metabo’s KNSE 9-150 corded and KNS 18 LTX 150 cordless fillet weld grinders are ideal for reaching welds at interior angles of handrails or other similar hard-to-reach locations. After two pieces of stainless steel have been welded together, it can be difficult getting into tight spots or insides welds. Discoloration from the weld’s heat-affected zone can also be a challenge to remedy. The weld grinders, however, can be a good solution. Their flat construction and rotating arms allow them to get into these areas without damaging neighboring surfaces.

Also helpful in difficult-to-reach areas, the BFE 9-20 corded and BF 18 LTX 90 cordless band files are versatile tools for external and internal work. They can be used to sand pipes and profiles as well as deburr and burnish surfaces in hard-to-reach places. The band arms can swivel up to 270 degrees for easy work in these confined areas.

The high-torque, variable-speed angle grinder, the corded WEV 15-125 Quick Inox, is another useful tool to rough grind, fine grind, cool finish and clean stainless steel. For those unfamiliar, Inox steel is simply another name for stainless steel derived from the French word inoxydable, meaning inoxidizable or incapable of rusting. The abrasive accessory for the angle grinder can be changed quickly and easily without the need for tools, and additionally, its guard can be rotated.

Also available is the 4 1/2-in./5-in. flat-head electronic high-torque, variable-speed angle grinder, the WEVF 10-125 Quick Inox, which can be used to rough grind, fine grind, polish and clean stainless steel. Due to the low-profile design of the gear head, this tool is also particularly suited for work in confined areas.

For fine grinding and high-gloss polishing of stainless steel, the corded PE 15-30 high-torque, variable-speed dry polisher is available. Its extreme torque is produced by the unique planetary gear system that drives the accessory between 800 and 3,800 rpms.

Although the choices in pre-finishing and final finishing tools and accessories seem to be vast, taking the time to make the right selections will pay off in the long run. And for any questions along the way, qualified hand tool manufacturers can help potential users make heads or tails of the available options based on the application at hand.