SHOP THINKS OUTSIDE THE CUTTING TOOL BOX
Use a cutting tool only for its intended machining operation? No way.
Bradley’s Inc. (Gregory, TX) is an 81-year-old company in its sixth generation of family ownership, one of the largest electric motor machine shops in the U.S., and a plant that always thinks outside the box when it comes to tooling. Started by James Bradley, this shop refuses to limit its part processing capabilities by using a cutting tool only for its intended machining operation without considering how it might apply to other cutting procedures.
Plunge cutting with a face mill or slotting with an inserted drill are typical examples of how Bradley’s always strives to get the most out of its tooling. The shop manufacturing manager believes there is always more than one way to get a job done and will push tooling to its maximum potential. And quite often the shop itself determines that ultimate level of performance by running cutters until they break, then backing off on the machine speeds and feeds by 10 percent. Needless to say, this no-holds-barred approach has paid off for the company.
With its unique ingenuity and the right tooling in place, much of which comes from Seco Tools (Troy, MI), this plant has reduced several part processing times from days to hours, brought jobs back in house, and improved overall part quality as it delivers jobs quicker, saves its customers money and continues to grow.
Most of the electric motors produced here are used in the oil industry. The shop is the largest in its vacuum pressure impregnation (VPI) capabilities of insulation materials used to lock in electric motor windings – a capability that allows Bradley’s to repair big motors up to 25,000 hp. However, the shop also offers general machining services to customers in other industries, including the capability to process parts up to 5 ft x 6 ft on its mills and as big as 50 in diameter and 25 ft long on its turning machines. A CMM is used to inspect these large workpieces at accuracies down to increments in the millionths of an inch. Manual and CNC machining operations in the plant have both incorporated Seco tooling into their processes.
One of the first applications where the shop experienced machining improvements because of the tooling involved a shaft that is used to connect two 2,500 hp DC motors running in tandem. The shafts were brought back in-house after being farmed out in the past to a manual shop that took seven to ten days to complete just one. Having recently installed a new CNC turning machine, Bradley’s decided to try making the shafts in house because it realized there had to be a more efficient way to machine them. By switching from standard inserts to Seco inserts, the shop was able to complete a shaft in only four hours.
“We weren’t using the right inserts at first, so we ran the shafts slow at low speeds and feeds,” explains Bryan Faircloth, the manufacturing manager at Bradley’s. “Machining time was reduced significantly when we began using Seco inserts, but we knew we could do even better so we called in their application specialist. He recommended some pretty aggressive speeds, feeds, and depths of cut that further reduced machining time.” Back then, according to Faircloth, the shop would “just grab any old insert off the shelf.” But now, with Seco helping them match insert to application, Faircloth notes that the shop now carefully considers what insert hardness the part material requires, proper insert radii, and the speeds and feeds that match that insert.
For example, in 2009 the shop installed a huge CNC horizontal mill and needed tooling for the specific parts that it would run. Rather than risking a waste of money on the wrong tooling, the shop contacted Seco. “Every tool they suggested back then we still use today. We improved our efficiency because we didn’t have to waste time and effort figuring out the tooling ourselves,” smiles Faircloth.
As a result, Bradley’s is one of the few shops that run the Jumbo Bridge Boring Bar, which it uses for 30.313 in diameters on electric motor frames. Jumbo Bridge Boring Bars are made of high tensile aluminum with steel interfaces and span a range of diameters from 25.75 in to 84.84 in. They also allow the plant to do symmetrical or staggered boring for roughing and for large OD overturning, while providing the capability to rough and finish with the same insert holder.
The Jumbo Bridge Boring Bar, along with a 10 in diameter Double Octomill face mill with 16 inserts used for plunge milling, has drastically reduced processing time for this particular motor frame style from two weeks to just five hours. This also enabled the company to eliminate the need to farm out the frames to various other contractors for completing certain required operations. Those suppliers typically bored the big ID on the parts by using manual vertical turning lathes that involved extremely time consuming setups and long boring cycles where the tool ran slowly down through the center of the frame ID.
With the ample part machining capacity of its recently installed horizontal machining center, Bradley’s decided to tackle the frames itself completely in house by thinking outside the box on how to more efficiently machine the motor frame ID. The Jumbo Bridge Boring Bar performs the finishing cut of the ID, but to save time the shop first rough cuts the ID. This reduces the amount of material the boring bar has to remove and speeds the finishing operation.
But the real challenge is the inside surface of the ID: one continuous interrupted cut caused by numerous 1in thick x 2 in wide flat A36 carbon steel bars evenly spaced and secured to the surface. After finish machining, these bar surfaces form a picket fence-like ID that secures the motor’s stator inside the frame with a precision fit to within ± 0.002 in.
For the roughing operation, the shop first tried circular interpolation half-way to the other end of the frame ID by using various sizes of roughing mills. To complete the roughing operation, the part was then turned around and the same approach was repeated from the opposite side to meet in the middle. Unfortunately, according to Faircloth, a 2 in diameter inserted cutter simply wasn’t strong enough to handle the cut. A 4 in diameter tool generated too much chatter, and the operation still took way too long to complete.
“Now what we do is program the machine to run the Double Octomill as if it were a 10 in diameter drill bit and then plunge cut using the side cutting edges of the tool’s inserts,” explained Faircloth. “It’s nothing but a drilling process, but not many people would think to use a face mill in such a way. We also use the same Double Octomill tool to face cut and chamfer the outside lip of the frame ID. This doubles our use of the tool and consolidates the amount of tooling required for the job.”
Double Octomill face milling cutters are highly versatile, economical and productive tools that can be used for both roughing and finishing. Hardened 65 Rc HSS pins position its inserts in place securely, accurately and repeatably within the cutter body. Using 16 insert cutting edges with positive insert geometry significantly increases the milling performance of the cutter – and stands up to Bradley’s other unique uses of the face mill.
Another example of Faircloth and his team using tools beyond their intended purposes happened when trying to improve a drilling operation. The shop was using standard jobber drill bits to drill 2 in diameter holes in 2 in thick steel plate. Having to run at 400 rpm, the drills took all day to complete the part’s holes, so a Perfomax drill was applied to the process. Speeds and feeds were upped to 3,000 rpm and about 30 ipm to slash drilling time down to around 20 seconds per hole. The surface finishes were much smoother and straighter than ones produced with the jobber drills.
Unlike standard drills, Perfomax tools are indexable insert drills with strong, square inserts that offer four cutting edges per insert and allow Bradley’s to use the most advanced Seco insert grades. Perfomax low-friction coated drill bodies also deliver operation stability paired with low-noise optimized chip flute designs for running the tools at extremely high feeds and speeds.
Faced with another challenging workpiece in a rush job that required a slotting operation, the shop searched for a tool that would get the job done in the most efficient manner, but at the time had nothing that would. The shop couldn’t waste time waiting on an ordered tool, so Faircloth thought about how the Perfomax drill works. “We realized that it cuts on its OD and on its face,” he says. “It’s a drill that acts more like a mill, so we tried it for side cutting the slots and they were perfect. We finished the job on time and gained a second use out of the Perfomax.”
Faircloth says he honestly believes that shops fall into the habit of using tools only for their designed purposes. That is not the case at Bradley’s. “It comes down to just really watching how a tool works, then thinking about ways it could apply to other operations,” states Faircloth. “Having an expert tooling supply company like Seco also helps. Working with them is nothing like dealing with a typical vendor because they are truly concerned about improving my processes and helping me any way it can.”
Bradley’s Inc., 600 East Highway 35, PO Box 308, Gregory, TX 78359, 361-643-0100, Fax: 361-643-9160, www.bradleysmotors.com.
Seco Tools Inc., 2805 Bellingham Drive, Troy, MI 48083, 248-528-5200, Fax: 248-528-5250, www.secotools.com.