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How blades and saws work together to cut lead-free brass efficiently

A new sawing process for a new alloy family that pushes to reduce lead exposure

sawing process for a new alloy family

A modern push to reduce lead exposure from plumbing fittings has resulted in harder-to-cut alloys, which in turn led equipment manufacturers to develop new saws.

One of the earliest minerals exploited by mankind, lead has properties that make it a material of choice for a large number of applications. Abundant, inexpensive, and easily worked, it has been used for decorative and aesthetic purposes (glazing for pottery and leaded glass), utilitarian applications (letters for printing presses, batteries, and radiation shields), and weaponry (small missiles hurled from slings and bullets shot from firearms). Its ability to smooth the combustion process made it a helpful additive for gasoline.

In ancient Rome, lead’s use for water pipe was so pervasive that its Latin name, plumbum, is directly related to the modern English word plumbing. This is more than a historical tidbit; until recently lead was still used widely in making brass fittings for plumbing applications. Adding lead to brass alloys improved their machinability by providing lubrication for the machining process.

Although lead’s toxicity has been understood for hundreds of years, some of the more pernicious applications were barred only recently. Lead’s use in gasoline was phased out in the U.S. starting in 1976, and it was prohibited in household paint in 1978.

The state of California, often a leader in environmental, health, and safety issues, shook up the plumbing components manufacturing industry in 2006 when Assembly Bill 1953 became law. The bill would reduce the lead content of plumbing faucets and fittings sold in the state beginning in 2010; it stipulated that the maximum lead content would be 0.25%, a drastic drop from the 8% that had been allowed until that time.

In 2011 Congress passed the Reduction of Lead in Drinking Water Act, making the standard a national mandate effective in 2014.

Low-lead and Lead-free Brass Alloys

Around the time that Congress passed the bill, low-lead and lead-free brass alloys were gaining ground in Europe. These alloys go by two commonly used names: ECO BRASS (also spelled as one word, ECOBRASS) and dezincification-resistant brass, abbreviated DR or DZR. The former two are trademarked terms for specific alloys owned by Mitsubishi Shendoh. The latter two refer to copper-zinc alloys with a small amount of arsenic, up to 0.25%, which keeps the zinc component intact.

Regardless of what they are called, the reduced amount of lead, or absence of lead, makes these materials much more difficult to cut than their lead-containing counterparts. Lead provides a measure of lubricity, which assists chip-making processes, machining, and cutting. Cutting low-lead and lead-free alloys in the same manner as conventional brass alloys is inefficient at best and can lead to downstream problems at worst.

Developing an efficient cutting process was the outcome of rethinking the entire cutting process—getting the material into and out of the saw, cutting, and dealing with the chips.

Updating the Blade

sawing process for a new alloy family

As alloys become more advanced, metalworking applications become more specialized, and control technologies become more sophisticated, machines become more niche, such as a saw developed for cutting low-lead and lead-free brasses. Bundle loaders, inclined loaders, and step-by-step loaders are options for loading single tubes or bars. The touchscreen controller includes a cutting parameter database for standard brass, low-lead and lead-free brass, and copper alloys. A complete database includes a variety of blade styles for optimized cutting. For niche cutting applications such as low-lead and lead-free brass, the saw needs an appropriate amount of power and precision. BLM’s model CM602 has a 9.2-kW motor and a cutting head that moves on linear guides and is driven by a servo-controlled ballscrew for precise control.

Brass fittings are forgings made from brass billets, typically cut to length using a cold saw with a blade made from high-speed steel (HSS). Depending on the blade’s diameter, the cutting speed varies from around 600 revolutions per minute (RPM) to 800 RPM.

Such blades don’t last long when cutting the newer brasses. Where a typical blade would last typically one shift when cutting leaded brass alloys, a fabricator could expect a severe reduction in blade life when cutting low-lead and lead-free brass. Moreover, the downtime needed to swap out the blade and the cost of frequent sharpening make this process cost-prohibitive.

The upshot is that the first upgrade in converting a fittings operation concerns the blade. The substitute is a tungsten carbide-tipped (TCT) blade, which is much more durable than an HSS blade. While an HSS blade is made from a single piece of a steel alloy that resists wear at elevated temperatures, a TCT blade—sometimes known as a hard metal (HM) blade—has teeth made of tungsten carbide (or other hard metal) welded in place. Making such a blade is much more involved than making an HSS blade, and this is reflected in the cost—a TCT blade is much more expensive than an HSS blade. Another factor is reusing the blade. A TCT blade typically is disposable, so many fabricators are reluctant to adopt this technology.

The upside is that tungsten carbide is so much more wear-resistant than HSS that it’s a much better value. The increased service life of a TCT blade often is proportionally greater than the increased cost. In other words, in terms of purchasing cuts, TCT is a better value than HSS.

A second factor is cutting speed. A TCT blade runs quite a bit faster than a comparably sized HSS blade, so it cuts faster.

A third concern is the blade’s thickness. Brass is pricey, and every cut wastes one blade thickness of raw material. Around the time the new brass alloys were introduced, a typical TCT blade was around 2.5 mm thick, whereas HSS blades averaged 1.8 mm thick. Some blade manufacturers have worked diligently to bring down the thickness, and TCT blades now are much thinner than before, often 1.5 mm thick.

Finally, a TCT blade is versatile. Among many companies that make brass forgings, low-lead and lead-free brass alloys comprise just part of their production, perhaps 20% to 30%; conventional brasses make up the balance. A TCT blade is a good candidate for cutting both families of brass.

Updating the Saw

While the blade handles the cutting process, the saw’s construction and features affect the other aspects of processing lead-free and low-lead brass efficiently.

Cutting with Precision. Every application in every industry has its own standards for precision. For example, a length tolerance for an aircraft component typically is far more exacting than that needed for a table leg. It depends on the demands of the industry, the specifics of the application, and of course subsequent manufacturing processes.

sawing process for a new alloy family

A relatively new development in the plumbing industry, a family of low-lead brass alloys, spurred a new saw design, including feeding two workpieces at a time to double productivity.

For making plumbing fittings, the governing subsequent process is forging. The forging process needs constant inputs—that is to say, workpiece lengths that don’t vary—for constant outputs. If a length of raw material is too short, the piece doesn’t have enough volume to fill the mold, resulting in scrap. If the incoming piece is too long, it overfills the mold. If the excess is minor, some amount of brass seeps out of the mold and creates a burr; if the excess is major, the stroke of the forging press can break the mold.

For making the most precise cuts possible, the saw frame must be more rigid than the frame of a saw for cutting softer metals. Rigidity also protects the blade from shocks and vibrations, which can knock the teeth off.

Furthermore, the blade must be contained with a guidance system. A saw created for making brass fittings has a cutting head with guides to keep the blade from wandering more than 0.1 mm (0.004 in.) during the cut to ensure every length meets the dimensional requirements of the forging industry.

Infeeding and Outfeeding. A saw does more than cut parts; it has an infeed system, bundle loader, step-by-step, or inclined for raw material and an outfeeding system for handling cut-to-length parts. These are two areas where good design concepts contribute to process efficiency. A basic saw that cuts just one length repeatedly doesn’t maximize yield. A saw designed and programmed to cut a variety of part lengths, and divert them into separate bins, optimizes nesting and maximizes the yield.

In some cases, a fabricator can nearly eliminate scrap. Depending on the length of the raw material, the condition of the leading end, the lengths to be cut, and the kerf, a saw that is extremely precise in feeding and cutting doesn’t need to make an initial (trim) cut and the scrap at the end can be as little as 5 mm. This means that the yield is close to 100%. For fabricators accustomed to dealing in steel, this doesn’t sound like a big deal, but brass isn’t steel. Steel is priced in dollars per ton; brass alloys are bought and sold in dollars per pound.

On the output side, a saw built to handle large volumes of parts typically deposits parts into a collection bin that is changed out automatically after it reaches a preset level. The saw doesn’t come to a stop to wait for an operator to empty the bin, maximizing machine uptime.

Market Size

It’s difficult to estimate the size of the market for brass fittings, but some proxy metrics illustrate market trends. For example, using the number of residential construction permits as a benchmark illustrates the current status of this portion of the plumbing market. The number of such permits peaked in 2005 when 2.2 million were issued. It fell to about 583,000 in 2009, and by 2019 was closing in on 1.4 million. In other words, it’s growing, but it has a long way to go.

A look at the entire construction market provides a different picture, but one that also illustrates growth. In 2005, the total spent in the U.S. on construction was $1.120 trillion, which fell to $814 billion in 2010. It climbed to $1.1 trillion in 2015 and hit $1.3 trillion in 2019, for an average growth rate of 4.5%.

Certainly these growth trends were interrupted by the COVID-19 pandemic during 2020, but the long-term prospects are good. The residential construction market has plenty of room to grow until it gets anywhere near its previous peak, and the entire construction market has been growing nicely over the last few years. For fabricators considering entering the plumbing fittings market, now might be as good a time as any.

About the Author

Tim Robbins

Business Development Manager, Sawing & Production Turning Division

BLM Group USA

46850 Cartier Drive

Novi, MI 48377

248-560-0080