Machining For Dummies Cheat Sheet

A cutting tool primer

A computer numerical control (CNC) machine tool is an exciting, highly complex device, capable of great speed and accuracy. But like a car without tires, it would be naught but a big expensive paperweight (albeit with flashy lights and an advanced computer) without cutting tools.

• The cutting tools used on CNC lathes are generally “stationary,” meaning the tool holds still while the workpiece rotates beneath it. Machining centers, on the other hand, use cutting tools that are held in a rotating spindle.
• The centuries-old distinction between stationary and rotary tools and the machine tools they are used on is beginning to blur as multitasking and turn-mill centers grow in popularity.
• High-speed steel (HSS) was the first big advancement in cutting-tool technology, but has largely been replaced by tool bits made of tungsten carbide and other super-hard materials. HSS is still widely used, however, for drill bits, saw blades, and other cutting tools where a tough, wear-resistant, and low-cost metal is needed.
• One of the super-hard materials just mentioned is polycrystalline cubic boron nitride (PCBN), which is able to efficiently machine hardened steel, and in some cases, has eliminated secondary grinding operations.
• Most types of cutting tools, including drills, end mills, turning tools, and boring bars, are available in a solid, single-piece construction (the most expensive but also high-performance option) or with indexable “inserts” with multiple cutting edges, designed to be used up and recycled.
• Holemaking is the most common of all metalworking operations. Drilling, reaming, boring, trepanning—these are just a few of the dozen or so ways to either make holes or to improve their accuracy and surface finish.
• The majority of cutting tools today are coated with hard, lubricious materials applied in special vacuum chambers. Some examples include titanium aluminum nitride (TiAlN), zirconium nitride (ZrN), titanium carbon nitride (TiCN), and many others. All improve wear resistance and tool life.
• With the thousands of available cutting-tool styles, geometries, coatings, and brands, it’s important to develop a sound policy on their use, testing, and procurement, else “tool crib bloat” is sure to occur.

Why manufacturing is so cool

Whether it was Tinkertoys or mud pies, papier-mâché or a fort in the woods, all of us made things as kids. Somewhere along the way, most of us turned to less tangible pastimes and vocations, but think back wistfully now and then to the rocket you built with your brother, the triple-decker card house you and sis made over summer vacation.

Machinists, however, are lucky—they get to keep making things, all day every day, until the last day when they hang up their shop coats and spend what’s left of their time boring their grandkids with stories about lathes and mills and drill presses. Hopefully, these grandchildren listen, because there’s some really neat manufacturing technology coming down the pike, and all of us will depend on smart, qualified people to leverage it.

• Additive manufacturing (you probably know it as 3D printing) has been around for three decades, but it’s going through some dramatic changes right now. Chances are good that we will soon have the ability to print whatever we want, whenever we want, and in many cases cost-effectively and accurately enough to compete with traditional manufacturing methods.
• If you’re wondering why you should open a shop or pursue a career in manufacturing when we’ll soon be able to just print everything, don’t worry about it. Even while additive manufacturing grows more capable, so too does subtractive manufacturing (that is, machining). Machine tools get smarter, faster, and more accurate every year. They’re not going anywhere, at least not in our lifetime.
• As machine tools become more capable, the technologies that support and enhance them grow increasingly relevant. Robots are getting smarter and less expensive, freeing humans to do more important tasks than put chunks of metal into a machine all day. Cloud-based software tools help us humans manage the awesome complexity of our manufacturing processes and avoid expensive mistakes. And the Internet of Things—the same technology that gave us smart thermostats and (soon) self-driving cars—is playing a big role on the factory floor, spotting trends to help us improve our manufacturing processes and allowing us to go home at night while our smart systems keep an eye on things.

Checklist for a well-tooled shop

Good toolholders, workholding, and accessories are just as important as good machinery, but many shops invest heavily in their CNC machine tools only to skimp on the tooling. Doing so means losing out on the benefits of new technology and not taking full advantage of your machine potential.

• Setup time is a killer and quick-change tooling is one of the best ways to avoid it. This begins with an organized approach to workholding, using zero-point or ball-lock clamping systems, or a quick-change chuck on a lathe.
• Quick-change toolholders are also important, especially on CNC lathes, where easily five minutes per turret position can be spent changing tools. Quick-change holders turn minutes into seconds.
• Another way to reduce setup time and in-process disruption due to tool replacement is with offline presetting. Break out your crystal ball and be sure to purchase a system that addresses future needs as well as the current ones.
• Shrink-fit tooling is one of the best ways to hold solid carbide drills and end mills.
• Hydraulic toolholders and mechanical milling chucks are a good alternative to shrink fit, but are somewhat less “balanceable” than shrink fit.
• Did someone mention balance? Balanced toolholders aren’t just for high-speed machining. In fact, most industry experts suggest spindle speeds greater than 8,000 rpm require balancing the entire toolholder assembly.
• Never buy bargain toolholders, and always go for the best retention knobs you can find.
• If the majority of your turned parts are under a couple inches in diameter and can fit through the lathe spindle, invest in a bar feeder. If you routinely have thousands of these parts to make, invest in a magazine-style bar feeder.
• Robots are good for lots more than deep space navigation on starships. They’re also great at loading and unloading parts from machine tools.
• As with a bar-fed lathe, a palletized machining center suffers less downtime and is far more flexible than the traditional, “two-vises bolted to the table” approach taken in many shops.
• The next time your tooling rep buddy drops in with some carbide inserts or a new toolholder for you to try, consider how these additions will fit into your overall tooling strategy. Standardization is key to a manageable tool crib.
• Don’t have a tool crib? Better set one up. Tooling is expensive and downtime even more so, and without an establish tool crib and tooling policy, you’re wasting money.
• Now that your tool crib is in place, it’s time for a maintenance plan. Tooling should be routinely disassembled, cleaned, and checked for wear.

Finding (and keeping) new machine shop customers

As with many businesses, one of the most challenging aspects to launching a machine shop is finding enough work to stay afloat. Making your customers happy will keep them coming back, but it’s important to maintain a disparate customer base to get you through the lean times and grow the company when times are good. Here are a few ideas to point you in the right direction.

• If you can run a computer numerical control (CNC) machine, you can set up a corporate website. And if you’re too busy making parts to do so, then hire someone to take care of it for you. Even a single web page telling potential customers what you do and how to find you is a good start.
• Similarly, Facebook is becoming a great way to share photos of your shop and its employees and get the word out about the vibrant, customer-focused company you’re operating.
• If a trade magazine calls and wants to write a profile on your business, or asks you to participate in a case study, by all means say “Yes, how can we help?”
• Do you, a family member, or one of your employees like to write? Start a blog as part of your website. It’s a great way to boast about your machining capabilities and get others interested in what you do there.
• YouTube videos are also a necessary part of social media. Showing off your new CNC lathe installation or recording a part being machined using a special cutter (or maybe even starting your own YouTube channel) is an increasingly popular way to share information.
• Make sure you and your business are on LinkedIn, then connect with customers and suppliers.
• Too busy to take on more work? It’s tough to say no to customers, especially when you’re just getting started. Be prepared for some long nights. If you decide to subcontract some of your work, that’s fine, but be sure your supplier has been well-vetted and can deliver as promised.
• A number of online part brokers and manufacturer representatives are out there and capable of bringing in all the work you can handle. Tread carefully so that you don’t take on so much that your existing customers suffer.
• One of the cardinal sins in any manufacturing business is becoming married to a single customer. It’s really easy to take the ball and run with your first big-break aerospace or medical company and let them become your sole source of work. Don’t be a captive supplier, or risk going out of business when your customer is acquired by a giant European conglomerate.