Stainless steel is best known for its strength and ability to withstand corrosion. These properties quickly become the greatest foes when drilling stainless steel. Unlike most materials, this hardens when heated and without accurate information, trying to drill stainless steel can be frustrating and often ends in extensive damage to tools.

That covers hole deburring, but what about smoothing the sharp, often ragged edges found on pockets, bosses, ribs and other machined features? Mike Shappell, senior application engineer at Norton | Saint-Gobain Abrasives, Worcester, Massachusetts, said programming the toolpaths needed for a chamfer mill or radius cutter isn’t terribly difficult, eliminating some if not all manual deburring. What’s more, some shops are morphing those toolpaths for use with one of the company’s nonwoven, unified or convolute abrasive wheels.

However, these traditional deburring methods are slow. Features that can’t be reached while in a machine — which is often much of a part — must be manually scraped, buffed and chamfered. If an operator isn’t paying attention, a machine tool might sit idly while he or she is busy deburring parts. And a bit too much pressure with a grinding wheel or blade could mean the inadvertent scrapping of a completed, possibly very expensive machined component.

“There are still an awful lot of people out there doing it by hand,” Baumet said. “Sometimes it’s because that’s all they know, other times because they don’t want to spend the money on a dedicated deburring tool. Either way, there’s plenty of room for improvement.”

Although relatively new, such systems are becoming popular, Suica said. As alluded to earlier, automated deburring raises fewer health and safety issues than manual deburring. Part quality is similarly improved, with no worries over an expensive machine tool sitting idly while the operator tends to a drill press or buffing wheel. And because the robot acts as a hardworking assistant to the CNC machine tool — or flexible manufacturing system — more machine uptime is possible.

Bruno Boutantin, global marketing director for Extrude Hone LLC, Irwin, Pennsylvania, said suitable TEM applications include die castings and machined parts of all shapes and sizes, but the approach is popular in the heavy equipment industry. This popularity is due to TEM’s fast cycle times, consistency and cost-effectiveness. The method is often ideal for deburring manifolds and other large, high-volume components.

“The Cofa and Cofa-X are specifically designed for irregular surfaces,” Baumet said. “Let’s say you’re deburring a hole drilled on an angled surface or a cross-hole in a piece of tubing. Here, the blade actually pivots in and out of the holder for continuous engagement. You get a nice, even chamfer all around the hole instead of the football shape you’d see using a standard chamfer tool.”

Your best chance at successfully drilling stainless steel lies with choosing the right drill bits. Although there are different types of reamers and drill bits that are suitable for drilling stainless steel, going for the best will improve your chances of getting good results and ease the process.

“It depends on the hole size and material,” he said, “but you could expect to hold plus or minus a couple thousandths on a chamfer.”

Kip Hanson is a contributing editor for Cutting Tool Engineering magazine. Contact him by phone at (520) 548-7328 or via e-mail at kip@kahmco.net.

Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.

Carriage or drum attached to a machining center that holds tools until needed; when a tool is needed, the toolchanger inserts the tool into the machine spindle. See automatic toolchanger.

Operation in which electrical current flows between a workpiece and conductive tool through an electrolyte. Initiates a chemical reaction that dissolves metal from the workpiece at a controlled rate. Unlike with traditional cutting methods, workpiece hardness is not a factor, making ECM suitable for difficult-to-machine materials. Takes such forms as electrochemical grinding, electrochemical honing and electrochemical turning.

The easiest way to tell if the speed, feed and temperature of the drill are within parameters is to check the swarf. They should be helix-shaped with the same colour as the workpiece or with a slight yellow tint.

As you drill, keep the drill bit cool and well lubricated. A cutting and tapping fluid should help to reduce friction and keep things moving along. If you have the setup, it’s best to keep a constant supply of coolant and lubricant to the workpiece and bit throughout the drilling operation. If not, you can stop to apply the fluid.

David Suica offers a novel though unsurprising approach to deburring, one that often trumps in-machine and manual processes alike. The president of automation systems provider Fastems LLC, West Chester, Ohio, said the company’s self-contained robotized finishing cell comes equipped with an industrial robot and gripper system, an automatic toolchanger and a servo-powered rotary workholding table and can have electric or pneumatic spindles. The RFC is easy enough to set up that it’s suitable for low-volume, high-mix work.

With the right drill bits, an average metal work drill should get the job done. But before you get started, it's crucial to observe the correct safety measures, including eyewear. With the intense pressure and heat involved in the process, it's easy for the drill bits to snap.

“AFM uses a puttylike abrasive media that is forced under pressure through or around a workpiece, removing burrs and smoothing surfaces as it passes,” Boutantin said, “while ECM employs a shaped cathode and electrolytic fluid to quickly erode even stubborn burrs.”

CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

“Considering the difficulty that everyone faces in finding qualified people,” he said, “plus the call for unattended machining in an environment that’s increasingly demanding, the need for this level of automated deburring is clear.”

The first parameter you will need to configure is the speed of the drill. If the drill speed is too low, the drill bit will rub on the surface of the material, eventually creating a work-handed zone, resulting in drill failure.

Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.

Once you start drilling, you will quickly run into work hardening. This will increase the wear and tear of your drill bits and the time it takes to complete the drilling. The best way to manage work hardening is through patience and a few handy tips.

Both processes are scalable, accommodating large parts, such as crankshafts, and relatively small parts, such as turbine blades and fuel nozzles.

“You don’t want to pay CNC machinists to deburr holes,” said Samuel Dean, director of sales and marketing at Whitney Tool Co. Inc., Bedford, Indiana. “You want to pay them to program and set up and maintain machinery, which means that the deburring — or as much of it as possible — is done inside the machining center where consistency is assured and there’s no chance of missing a hole. This is why it’s so important to convert manual deburring operations into automated ones so that shops can more efficiently utilize their production floor staff.”

Worker health and safety are also a consideration. As machinists would attest, cuts, scrapes and repetitive stress injuries are common during manual deburring, never mind the potential inhalation of abrasive grit. Surely safer, more productive methods are available?

If you use a conical punch to mark the positions of the holes to be drilled, you could increase the chances of work hardening. Instead, use a 3-corner pyramid punch to reduce this risk.

Using an automated deburring tool like the Cofa, tedious deburring of small parts by hand can be eliminated for maximum efficiency and burr-free parts. Image courtesy of Heule Tool

“They’re also scalable in the sense that we have customers with multimillion-dollar equipment installations to those with fewer than 20 employees who process lot sizes of 400 to 1,000 pieces per production run,” Boutantin said. “Between TEM, AFM, ECM and their variants, we have solutions for practically any deburring need.”

Any manufacturing process in which metal is processed or machined such that the workpiece is given a new shape. Broadly defined, the term includes processes such as design and layout, heat-treating, material handling and inspection.

If the drill speed is too fast, it will generate too much heat. This will also lead to the failure of the drill. Identifying the right feed control is going to be critical, particularly in breaking the chip. Ensure the speed is high enough for the cutting edge to enter into the workpiece.

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.

Dean said Handi-Burr typically is reserved for manual deburring operations in a drill press or power tool while Burr-Zit is suitable for CNC and manual equipment. He also said both tool types are only for deburring, in that they produce a rounded edge. If a qualified, dimensionally accurate chamfer is needed, it should be machined using an actual milling cutter.

When working with metals, deflection is a real challenge, especially for a metal with a high tensile strength like stainless steel.

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Operation in which electrical current flows between a workpiece and conductive tool through an electrolyte. Initiates a chemical reaction that dissolves metal from the workpiece at a controlled rate. Unlike with traditional cutting methods, workpiece hardness is not a factor, making ECM suitable for difficult-to-machine materials. Takes such forms as electrochemical grinding, electrochemical honing and electrochemical turning.

The ability to deburr both sides of a hole (above) in a single operation is a huge timesaver. Image courtesy of Whitney Tool

Imagine a process that can completely deburr a part in less time than it took to read this sentence — much less time. The thermal energy method removes burrs, flashing and trapped particles from practically any workpiece in just a few milliseconds. TEM works by placing a workpiece — or hundreds of workpieces — in a sealed, pressurized chamber, filling it with a mixture of methane gas and oxygen and then introducing a spark. The resultant explosion generates a 3,316° C (6,000° F) heat wave that instantaneously vaporizes burrs and loose matter but leaves the workpiece undamaged.

Automated manufacturing system designed to machine a variety of similar parts. System is designed to minimize production changeover time. Computers link machine tools with the workhandling system and peripherals. Also associated with machine tools grouped in cells for efficient production. See cell manufacturing.

One step in this conversion process is the use of Burr-Zit and Handi-Burr deburring systems from Whitney Tool, he said. Often referred to as clothespin tools, Burr-Zit deburrs the front and back of hole diameters from 1.98 mm to 25.4 mm (0.078" to 1") in a single in-and-out pass. The Handi-Burr line of spring-loaded deburring tools extends that diameter range to 50.8 mm (2"). Multiple lengths, geometries and coatings are available, and the Burr-Zit series can be purchased in kit form to cover a range of hole sizes.

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This self-contained robotized finishing cell boasts an industrial robot and gripper system and is suitable even for low-volume, high-mix work. Image courtesy of Fastems

Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.

Use of rapidly spinning wires or fibers to effectively and economically remove burrs, scratches and similar mechanical imperfections from precision and highly stressed components. The greatest application is in the manufacture of gears and bearing races where the removal of sharp edges and stress risers by power methods has increased the speed of the operation.

“The ease of setup is largely due to our Fastsimu programming and simulation software,” he said. “It allows you to import the CAD model and generate the toolpaths, the inspection points, check for collisions — all offline. There’s no more standing on the shop floor with a teach controller nudging the head this way and that or trying to figure out how much wheel pressure to apply. And because there’s a toolchanger and the option for a tool magazine, you can easily switch to whatever deburring tool or abrasive wheel is most appropriate for the application. There are very few parts that the RFC can’t complete in a single deburring operation, with changeover often taking just a few minutes.”

Machine designed to rotate end-cutting tools. Can also be used for reaming, tapping, countersinking, counterboring, spotfacing and boring.

Cobalt drill bits – Cobalt drill bits are designed to work on high tensile and heavy-duty performance metals. Using cobalt as an alloy increases the strength of the parent metal and boosts its heat resistance properties, both of which are vital when drilling stainless steel.

Wheel formed from abrasive material mixed in a suitable matrix. Takes a variety of shapes but falls into two basic categories: one that cuts on its periphery, as in reciprocating grinding, and one that cuts on its side or face, as in tool and cutter grinding.

Once you have all the tools you need to start drilling, including the pilot hole (where required), it's time to get started. It's always a good idea to have the metal firmly clamped to the working table to reduce movement and deflection.

“The wheels wear well, are coolant-proof, and most CNC machine tools these days have some level of cutting fluid filtration, lowering concerns over grit and contaminants getting into the way surfaces,” he said. “So with that in mind, it’s not a huge leap to mount a nonwoven wheel in a CNC machining center and use it for part deburring and finishing operations. Whether you’re using these products in an automated environment or a manual one, however, I strongly advise that shops review their abrasive wheel and disc selections every few years because we’re constantly improving both.”

The T350 and T450 (pictured) thermal deburring machines offer a fast, cost-effective way to remove burrs and loose material. Image courtesy of Extrude Hone

You will also need coolant for heat management, both on the metal surface as well as the drill bits and some tools for chip evacuation.

High-Speed steel drill bits – This type of bits are specifically designed for drilling stainless steel. The best HSS drill bits to use for this application are those with a Titanium Nitride tip to help reduce friction and heat.

Matt Baumet, technical sales engineer at Heule Tool Corp., Loveland, Ohio, suggested several similar alternatives. The company’s Snap front and back chamfering tools, for example, feature a replaceable, spring-loaded blade and are intended for use with CNC machine tools while providing more accurate chamfering than tools for only deburring.

Mechanism typically included in a machining center that, on the appropriate command, removes one cutting tool from the spindle nose and replaces it with another. The changer restores the used tool to the magazine and selects and withdraws the next desired tool from the storage magazine. The changer is controlled by a set of prerecorded/predetermined instructions associated with the part(s) to be produced.

Also available are the Cofa “universal deburring tool” for elliptical or contoured surfaces, the Defa adjustable chamfering tool and the X versions of Snap and Cofa for deburring cross-holes and intersecting bores.

Robot designed for industrial use. Primarily used as a material-handling device but also used for changing tools, assembling parts, and manipulating special tools and measuring devices. Depending on design, an industrial robot can be programmed to perform a task by means of a controller, or it can be “walked” through the required movements by utilizing a digitizing system that translates movements into commands that the robot can be “taught.” See robot; teaching pendant.

Rotary tool that removes hard or soft materials similar to a rotary file. A bur’s teeth, or flutes, have a negative rake.

Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

Liquid used to improve workpiece machinability, enhance tool life, flush out chips and machining debris, and cool the workpiece and tool. Three basic types are: straight oils; soluble oils, which emulsify in water; and synthetic fluids, which are water-based chemical solutions having no oil. See coolant; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

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Just as holemaking is common in metalworking, so is deburring the tops and bottoms of produced holes. Chamfering tools are effective, as are the familiar Rotoburr-style scraper blades. These tools also deburr machined edges fairly well and, given the right extension or blade geometry, can access hard-to-reach areas deep inside parts. Add a few Scotch-Brite pads, a drill press and a bench grinder to the mix, and there’s little that any skilled machine operator can’t deburr.

Here again, multiple grades, geometries, diameters and lengths are offered, and both companies provide application and programming advice to those getting started. While Dean and Baumet might not agree on which brand of deburring tools a shop should buy, they do agree that deburring is a machining process that bears lots of low-hanging fruit.

For deep drills, the workpiece can be annealed before drilling to soften the material and improve machinability. It will help reduce the risk of work hardening.

Finishing and deburring operation for holes, inaccessible areas or restricted passages. Done by clamping the workpiece in a fixture, then extruding semisolid abrasive media through the passage. Often, multiple parts are loaded into a single fixture and finished simultaneously.

Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

One of the best ways to keep the tools from deflecting on contact is by using a pilot hole. The pilot hole is essential for deep drills to ensure the stability of the drill bit and accuracy.