Indexable Drill Heads Double Profitability

Part production is often hampered by a single operation — often a single critical feature that, for whatever reason, creates a bottleneck that dramatically alters the profitability of a job. For example, one machine shop was struggling with hole-making. Specifically, the shop’s drills were unable to handle the cutting forces generated by aggressive drilling cycles, and this slowed down production. Investing in more robust drills with indexable cutting tips enabled the shop to dramatically improve productivity, doubling the job’s profitability.

Rethinking Process to Boost Profits

Columbus Machine Works, a job shop located in Columbus, Ohio, serves multiple end markets to avoid being hit by cyclical slowdowns in any one industry. The company produces a wide variety of parts on both traditional and CNC machine tools, with one of its two buildings having three VMCs and seven lathes. Roughly three-quarters of the job shop work is in contract manufacturing for other Central Ohio businesses, which means a lot of short-run parts with fast turnarounds.

For some time, the company had been struggling with the profitability of a high-production part with a hollow interior. Initially, Columbus Machine had made it using steel DOM tubing — a kind of hollow tubing formed through cold-drawing over a mandrel and through a die to get a precise ID and OD. The part required some turning and drilling operations, but automating it was difficult because the bar feeder attached to the lathe pushes from the center of the workpiece — something that does not work with hollow tubing. Additionally, the drilling operations were slowing down the process, as the company’s drills were unable to handle aggressive cutting forces, creating a bottleneck on a job that was already moving slower than desired.

The company decided to switch from DOM tubing to bar stock, as it was both less expensive and worked with the company’s bar feeders. “Once we decided to replace the tubing with bar stock, we had to find a drill that could handle aggressively cutting through the center of the bar stock,” Colopy says.

Colopy’s search for the right drill involved many considerations. First and foremost, it had to be a flexible system that could perform roughing operations on a variety of hole sizes in a variety of materials to cover the high mix of parts the company produces. Secondly, the drills had to handle the cutting conditions needed to reliably produce holes fast enough to eliminate the production bottleneck. Finally, they had to be easy to work with one-handed, as machinist Jim Larimer — the machinist handling this part — only has one hand to work with. “Jim uses the drills more than just about anyone,” Colopy says, “so it just makes sense to get drills he can use. There’s no point in buying something that he physically can’t install.”

Drilling Down to Basics

Eventually, Colopy landed on indexable drills with carbide inserts from Allied Machine & Engineering — the T-A line with “shovel-tip” inserts for roughing and the XT Pro line for finishing. Testing found that the combination of the drill and inserts met the company’s requirements in flexibility, speed and ease-of-use.

Flexibility: When using the T-A and XT Pro, one drill body can take a range of tips — with 20 drill bodies, the company can fit inserts for drilling any hole size from 0.5 to 4 inches in diameter. These 20 drill bodies and inserts replaced drawers full of solid-carbide drills.  Additionally, the drill works with a variety of materials, including tool steels, stainless, aluminum, plastics and even superalloys. Some materials, like aluminum, use specialized inserts for improved chip evacuation, but the standard carbide insert with a cobalt-based coating can handle most materials as long as the operator dials in the cutting parameters.

Speed: According to Colopy, the steel drill body enables the drill to have the flexibility of steel with the cutting edge of the carbide inserts, making the combination well suited for roughing under intense cutting conditions. “Solid carbide drills can snap or need regrinding,” Colopy says, “but these can handle almost anything. We have modern machines that can’t handle the load these drills are designed for.”

Machinist Mike Cargioli agrees. “The Allied drills are good for getting as much material out as quickly as possible,” he says. “Drilling just takes up so much time, so I’ll take any chance to speed it up.” Additionally, the Allied drills center very well, Cargioli says, making it even easier to drill holes quickly.

“A lot of the time, we use the Allied drills to quickly get the holes where we need them, then finish with another drill, or even a mill or a bore,” Colopy says. Finally, both drill lines are usable with through-tool coolant systems, which improve chip evacuation and reduce heating, enabling more aggressive machining.

Ease of Use: Finally, the Allied drills passed the one-handed test with flying colors, according to Colopy. “The inserts slot right in, so you can’t load them incorrectly,” he explains. “And it uses a Torx screw at the top so the insert won’t fall off while you’re trying to secure it. It’s honestly harder to get it wrong than get it right.”

Of course, the drills are not perfect fits for every job. “The four-inch drill only works on our most powerful lathes,” Colopy explains. “Allied makes larger drills, but they were too big for our machines’ horsepower to push through the part.” Additionally, the company opts for solid-carbide drills for holes under 0.5 inch. “Underneath a half-inch, chip buildup can twist the drill body right off.”

Despite these limitations, the Allied drills cover the majority of hole-drilling applications at the shop, and they paid off big on the high-production part that set off this search.

Building Profits out of Process

While replacing the DOM tubing with barstock added an operation to the machining process, the new drills performed it quickly and the ability to use the bar feeder made the process more efficient. Additionally, switching to Allied drills on other operations increased overall production speed, reducing the time needed to machine each part. In final analysis, the savings gained by moving to bar stock combined with the reduced machining time and automation to dramatically improve the job’s financial outlook. “Switching over to Allied drills on this job doubled its profitability,” Colopy says.

Of course, it was more than simply pivoting to a new drill that made this part profitable. From the moment they began researching new drills, the team at Columbus Machine focused on how to adjust the process to be more efficient. The new drills may be a key part of the new approach’s success, but the team’s ingenuity in putting that technology to work ultimately led to a more efficient and less costly process.