For medium roughing applications, Bokram recommends a double-sided insert with Ceratizit USA’s -M70 chipbreaker, which is available in three grades: CTCP115-P, CTCP125-P and CTCP135-P. CTCP115-P is for continuous turning at elevated surface speeds, CTCP125-P is a universal grade that covers a broad range of machining conditions, including slight interruptions, and CTCP135-P is for challenging conditions, such as interrupted cutting or turning surfaces with scale or welds. All the grades enable wear detection so an operator can visually determine which edges are used and the level of tool wear.

“The critical performance characteristic is to be able to curl and break the chips across the entire application range of that chipbreaker design,” he said.

“Machining of steels is quite common,” said Sarang Garud, product manager for turning, drilling and boring at Walter USA LLC in Greer, South Carolina. “However, many well-known challenges exist.”

Enlarging a hole that already has been drilled or cored. Generally, it is an operation of truing the previously drilled hole with a single-point, lathe-type tool. Boring is essentially internal turning, in that usually a single-point cutting tool forms the internal shape. Some tools are available with two cutting edges to balance cutting forces.

Carbide saws are more robust and can withstand higher temperatures, making them suitable for use on heavy-duty materials like stainless steel. Diamond-tipped hole saws are also available for use with ceramics, glass, and stone.

Image

Alex Rennie is a freelance writer who specializes in the Home Improvement, DIY, and Tool space. As a former residential and commercial carpenter, Alex uses his hands-on experience to write practical buying guides, how-to articles, and product reviews. His work has also appeared in Business Insider's Insider Picks, and before his writing career, he was a full-time carpenter living in New York City. There, he worked as part of a team designing, building, and installing large furniture pieces, as well as performing a variety of home repair and maintenance projects. Alex currently lives in Los Angeles, CA, and spends his free time exploring the beaches and mountains with his fiancé and their dog Louie.

“Wavy cutting edges and higher rake angles make the same geometries shear the material better,” Garud said, “thus reducing cutting forces and allowing a weaker machine tool to perform heavier-duty cuts for the same horsepower.”

It’s important to stabilize the cutting edge during interrupted cutting. Therefore, Bokram recommends using an insert with a corner radius that is as large as possible.

Alan holds a bachelor’s degree in journalism from Southern Illinois University Carbondale. Including his 20 years at CTE, Alan has more than 30 years of trade journalism experience.

If you don’t already have an arbor on hand, make sure you choose a saw or kit that includes one. If you do have an arbor already, you can usually get more bang for your buck by going with a saw that doesn’t include one.

Despite the budget-friendly price, this Bosch kit still packs a ton of value. In addition to the high-quality construction found in Bosch products, you’re also getting two universal arbors and a steel pilot bit for maximum control and stability.

I used hole saws extensively when working as a commercial carpenter, and have cut hundreds of holes in office desks, doors, and drywall. I kept this experience in mind when assembling this list, making sure to include brands that I’ve come to trust over the years, as well as avoiding frustrating design components and brands with poor quality control reputations.

Stainless steels possess high strength, heat resistance, excellent workability and erosion resistance. Four general classes have been developed to cover a range of mechanical and physical properties for particular applications. The four classes are: the austenitic types of the chromium-nickel-manganese 200 series and the chromium-nickel 300 series; the martensitic types of the chromium, hardenable 400 series; the chromium, nonhardenable 400-series ferritic types; and the precipitation-hardening type of chromium-nickel alloys with additional elements that are hardenable by solution treating and aging.

Dillaman said in addition to using an insert with a tough substrate, reducing the speed and feed through the interruptions is helpful. Also, taking a maximum DOC and having rigid workholding help reduce vibration.

Although the Saegertown, Pennsylvania-based company is traditionally known for its ceramic grades, Dillaman said Greenleaf recommends its GA5035 and G5125+ carbide grades as the primary choices for rough turning steel. When better wear resistance is required, the toolmaker offers its GA5025, GA5026 and G-9230 grades. For enhanced toughness, G-5135, GA5125 and G-915 grades are available.

“Chip formation is also heavily influenced by the chipbreaker design behind the land,” he said, “and much time is spent optimizing these designs based on the range of materials that might be machined and the range of feeds and speeds that are desired for that design.”

For CVD-coated inserts turning conventional steel, Garud said Walter USA labels the geometries RP (R for roughing and P for the ISO P material group, which is steel). HU geometries (H for heavy duty and U for universal ISO P and M material groups, in which M is stainless steel) are suitable for turning stainless as well. Turning stainless, however, might require a PVD coating, and the HU5 geometry is available in both CVD and PVD grades.

In addition, Garud noted that steel workpieces tend to be abrasive, and a hard insert grade, such as WPP10G, can resist the resultant flank wear. Crater wear is another possible pitfall, especially when a parts manufacturer turns at a high cutting speed to boost productivity.

Angle of inclination between the face of the cutting tool and the workpiece. If the face of the tool lies in a plane through the axis of the workpiece, the tool is said to have a neutral, or zero, rake. If the inclination of the tool face makes the cutting edge more acute than when the rake angle is zero, the rake is positive. If the inclination of the tool face makes the cutting edge less acute or more blunt than when the rake angle is zero, the rake is negative.

High-temperature (1,000° C or higher), atmosphere-controlled process in which a chemical reaction is induced for the purpose of depositing a coating 2µm to 12µm thick on a tool’s surface. See coated tools; PVD, physical vapor deposition.

Garud said those grades for thermal shock are also suitable for interrupted turning, in which an insert is hammered and punished. When faced with exceptionally interrupted cuts, end users should consider single-sided negative inserts.

Ability of the tool to withstand stresses that cause it to wear during cutting; an attribute linked to alloy composition, base material, thermal conditions, type of tooling and operation and other variables.

Tool-coating process performed at low temperature (500° C), compared to chemical vapor deposition (1,000° C). Employs electric field to generate necessary heat for depositing coating on a tool’s surface. See CVD, chemical vapor deposition.

Whether for automotive, aerospace, railroad, mold and die or a host of other applications, heavy rough turning of steel will continue to be commonly performed and manufacturers with properly designed carbide inserts in their toolrooms will continue to reap the rewards.

Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).

Another common issue when rough turning steel is notching at the depth of cut when a workpiece has a poor surface condition because of the presence of scale, contaminants or welds, said Robert Bokram, product manager of cutting tools for Schaumburg, Illinois-based Ceratizit USA Inc., who’s based in Warren, Michigan.

“Typically, stainless steels need sharper geometries to shear the metal better and also higher positive rakes,” he said. “Both of these functions are complemented by PVD grades.”

“These geometries offer the capabilities of a larger depth of cut while still providing relief along the face and turned diameters when machining to square shoulders,” he said.

If you want to create perfectly round holes in wood, metal, or plastic, you’re going to need a hole saw. These cylindrical saws are powered by any corded or cordless drill, and their hollow shape allows you to remove the waste material in a single piece, or “plug,” which drastically cuts down on sawdust cleanup.

An effective rake angle is also required, which Bokram said should range from 12 degrees to 20 degrees depending on the size of the insert and chipbreaker and the application.

Dillaman added that if the rake is not steep enough or the chipbreaker groove is too shallow or wide, the workpiece material will not break and may create long, stringy chips.

Distance between the bottom of the cut and the uncut surface of the workpiece, measured in a direction at right angles to the machined surface of the workpiece.

A quick-change arbor sleeve quickly releases the saw after drilling, and their open-end design allows you to ram it backwards against the base to eject the plug in seconds. This arbor design also makes it easy to switch between saw sizes as you go, saving even more time.

“If chips are not evacuated properly,” he said, “they can end up being re-cut, fracturing the cutting edge and causing shortened tool life.”

Its carbide teeth are strong enough to be safely and efficiently used on metal surfaces, and their ejection springs easily pop out plugs when you’re finished with a cut. A raised shoulder prevents you from over-drilling too, which is always a nice perk.

These features make the Disston QuickCore saws especially useful for those who use hole saws frequently, since that extra time per plug can really add up over the course of a workday.

A pilot drill bit ensures that the saw is perfectly centered before it makes contact, reducing the chances of the blade skipping or walking across your workpiece. Hole saws come in a wide range of diameters, too, so whether you’re cutting a ¾-inch hole for conduit or a six-inch hole for can lights, you can find one that suits your needs.

Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.

To ensure that you choose the most effective hole saw for you and your projects, keep these factors in mind before purchasing.

For example, he said steel with a low carbon content, such as AISI 1018 carbon steel, often produces long, stringy chips that are difficult to control when turned. To overcome that, Walter USA offers a variety of chipbreaker options like FP5 and MP3.

Image

Hole saws are typically made with either bimetal or carbide blades. Bimetal saws are more popular because they’re compatible with a variety of materials and cut quickly while resisting wear and tear.

If you’re primarily using your hole saw to create holes for door locks or knobs, and don’t need the variety of a large kit, this Lenox Tools model is a great choice.

Groove or other tool geometry that breaks chips into small fragments as they come off the workpiece. Designed to prevent chips from becoming so long that they are difficult to control, catch in turning parts and cause safety problems.

Its 2⅛-inch diameter has you covered for the majority of lock sizes, and the included arbor means you’ll be able to get to work right away. The large, staircase-style speed slot allows you to quickly remove plugs too.

Dislodging the plug inside the saw after cutting can be a frustrating and time-consuming task, so look for a saw that allows you to clear it quickly—some saws have large cutout slots that you can poke a screwdriver through, and others even feature spring-loaded ejection mechanisms.

A handy quick-change arbor allows you to easily switch between sizes, and the split-point bit keeps it from walking as you start to drill. We’re also big fans of the flange stops on each cutter, so you don’t have to worry about over-drilling.

To resist heat deformation when turning at high cutting speeds, Garud said Walter USA’s WPP05S grade has a coating with a high aluminum-oxide content and a TigerTec Silver coating.

In addition, a roughing insert tends to run at a moderate surface speed, which he said doesn’t generate enough heat to oxidize a PVD coating and activate its wear- and heat-resistant configurations.

Despite a growing trend of lightweighting vehicles, as well as products produced by other industries, steel parts still represent a sizable share of the market, and a large percentage of those parts must be turned.

When it comes to carbide insert designation, Dillaman said the 80-degree insert, CNMG, is the most common, followed by the trigon style, WNMG.

The staircase-style speed slot will help cut down on plug removal time too. It’s not cheap, and you’ll need to supply your own arbor, but if you have the need, this saw could be a great investment.

The proprietary tooth design uses alternating tooth sizes, and claims to increase both performance and durability. Made with an 8 percent cobalt alloy, these saws are a great choice for those who prioritize durability and extended blade life.

Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.

If you need to make large holes for vents or can lights, consider this six-inch Lenox saw. The large teeth and thick walls maximize durability and efficiency, allowing you to confidently use it on both wood and metal applications.

“With a possible application range from P05 to P40, the P05 grade would be ideal,” he said. “However, in the real world machining conditions rarely allow for this ideal. P15 to P35 is a more typical range for steel roughing applications.”

Image

Three arbors and three bits make this kit even more functional, and ensure that regardless of the size you’re using, you won't have to sacrifice control as you operate.

Greenlee has been a favorite of professional tradespeople for years, and these carbide-tipped saws are a great example of why they’re so popular. This carbide construction allows them to power through metal, and also cuts down on annoying squealing and saw chatter.

He concurred that CVD coatings, which are usually 10-µm-to-20-µm thick (0.0004" to 0.0008"), are more effective for rough turning steel than PVD coatings, which are limited to about 10-µm thick.

Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

If you don’t have the need or budget for commercial-quality carbide hole saws, this three-piece DeWalt kit could be exactly what you’re looking for.

If you’re tired of wasting time and energy removing stubborn plugs from your saws after drilling, you’ll appreciate the user-friendly design of these Disston saws.

However, Martin Dillaman, global manager of engineering/applications and project manager for Greenleaf Corp., emphasized that chip control is the biggest challenge when turning steel.

“There is a commitment to continually developing our carbide grades using the latest technology to help advance the capabilities of our customers,” he said. “Depending on the alloy of steel, requirements of the application and machine capabilities, we have many options available to help find the best solution for the customer.”

For abrasion resistance, Garud said grades with hard and refined substrates, such as WPP10G with the latest TigerTec Gold coating, are suitable. For thermal shock resistance, a tough grade with a relatively large-grain substrate and a high cobalt content, such as WPP30G or WKP30S, works best.

Bokram added that grade selection is driven by machining parameters and part configuration, and the goal is to select the hardest grade that can be used without experiencing edge breakage or other premature failure mechanisms that shorten tool life.

Although uncoated insert grades are still widely applied to machine heat-resistant superalloys and titanium alloys, Garud said uncoated grades are not recommended for cutting steel. Typically, CVD-coated grades are most effective for steel, such as Walter USA’s WPP20G.

“They provide (a) robust and high-precision seating surface, along with a wide-open chip groove and robust cutting edge,” he said “This combination tends to withstand the interrupted cuts very well.”

Space provided behind the cutting edges to prevent rubbing. Sometimes called primary relief. Secondary relief provides additional space behind primary relief. Relief on end teeth is axial relief; relief on side teeth is peripheral relief.

Garud said another HU geometry that’s effective is the HU7, which has a varying thickness of the protective chamfer to not only reinforce the cutting edge but help control chips and reduce cutting forces.

Boasting 28 individual saw sizes, this Milwaukee kit is prepared for a wide range of projects and tasks. A sturdy molded case keeps your saws protected when not in use, and their nested design allows the kit to take up minimal space in your toolbox or on your workbench.

Instead of a hard grade, Garud said a tough grade can do the trick when turning steel with a potentially problematic forging skin or casting scale. He recommends WPP30G or WKP30S grades for those applications.

Advances in coating technologies have enabled coated carbide to be nearly as smooth as uncoated polished carbide, Bokram said, so there are very few cases in which it is not beneficial to use coatings to extend tool life.

Typically, a flat or slightly positive land provides that protection, which can range from 0.254-mm-to-0.356-mm wide (0.01" to 0.014") for medium roughing and 0.356-mm-to-0.508-mm wide (0.014" to 0.02") for heavy roughing.

“Proper insert edge design is critical to help mitigate this,” he said, “but a common strategy is to vary the depth of cut over time to disperse the effect across the cutting edge.”