Te truth is, when axial feed rates are compared for both
operations in multiple materials, rough boring heads, such as the Kaiser SW Series 319, are faster for roughing operations. Two cutting edges are faster and less costly to index versus helical cutters with several inserts per cutting flute. Determining which operation you choose to use really
depends on the production requirements of the job. A lot of companies, when they start off doing it, look at their tooling costs, and one size helical mill can do an infinite size range, so they choose helical interpolation. But as production goes up, as it has been recently in the burgeoning energy industries (especially fracking), cycle time becomes an issue. In this case companies gradually turn to the boring tools because as you specialize in longer runs, and require repeatability, an operator generally will end up with diminishing returns for the versatil- ity milling can provide.
Fracking and Boring Many of BIG Kaiser’s customers had worked in oil & gas
for some time, but when fracking took off last summer job shops began to redouble their efforts in this area. Te indus- try that had started in Oklahoma and Texas quickly spread
feed of 0.020 ipr (0.51 mm/rev) and 1000 psi (6895 kPa) cool- ant through the tool. We always recommend coolant to help with chip evacuation. Usually, an operator is limited to what they have on the machine when it comes to through coolant. As for speed, 500 sfm is typically a safe starting point for P20 steel material. Tool lengths were a little bit long, but with BIG Kaiser’s
lineup of tooling, the operator was still able to run at a rea- sonable rate. Te feed rate of 0.020 ipr is a standard starting point, provided you have a rigid tool and a workpiece that’s rigidly fixtured.
Dealing with Chips My initial setup ran quietly without chatter, but I noticed
stringing chips in the bore that hadn’t been evacuated. Te spindle load was at around 40%, so I increased the feed to 0.024 ipr (0.61 mm/rev) on the next bore. Te chips were still a little long, but they were not nesting together, and the cool- ant supply was able to flush them from the bore. Te inserts needed to be indexed before we could run on the opposite side, where there is a heavy interruption. Te tool ran fine until the interruption—when we lost both cutting edges.
When axial feed rates are compared for both operations in multiple materials, rough-boring heads are faster for roughing operations.
as far north and east as Ohio, Michigan and Pennsylvania. Even more new gas deposits were discovered, and there was an arms race of sorts to equip these fracking operations with components to access the gas. One company, in particular, had the machining capacity to
meet the early stage demands of the fracking craze, but once their orders really began to spike, operators realized that they needed to change their process to keep up. Te operation involved starting bores of Ø3.625" (92.1
mm), which need to open to Ø4.100" (104.1 mm), boring from both sides at a depth of 9.5" (241.3 mm). Tis customer was interpolating, and had been using a competitor’s product to finish bore. Tis resulted in issues with holding size and chatter; luckily, the company had discovered BIG Kaiser while looking for finish boring alternatives. Te finish boring tools provided the capability to hold size consistently, so when the company realized that they needed to be roughing faster, operators naturally turned to BIG Kaiser for the rough-boring tools as well. Tey were using a Kaiser finish-bore regardless, adding a rough boring operation from Kaiser just helped to speed things up. I used the 319 SW twin cutting head in the balanced (RSS)
setting with CC12 inserts of grade TNP12 and started running at a speed of 500 sfm (152.4 surface meters/min [smpm]) and
I then decided to switch to the TNP14 inserts, which are
a tougher grade and have a flatter chip-breaking geometry and are similar to inserts the customer uses on other tools with much success in this material. We were able to get three bores with this insert, even in the heavily interrupted bores. And when we increased the speed to 600 sfm (182.88 smpm) and feed to 0.026 ipr, (0.6604 mm/rev) the chips were very short, which made the process highly repeatable, as the chips are easily evacuated from the bore. Te bore sizes will also be more repeatable versus the helical interpolation, which makes a more repeatable process for the BIG Kaiser 310 EWN heads they were already using for the finish boring. Both helical interpolation and rough boring have their
places in holemaking operations for oil & gas industry appli- cations, such as fracking. Each has its advantages and limita- tions. Te sheer flexibility of a mill in helical interpolation can make it a good solution for shallower holes or one-off projects that don’t merit a dedicated tool-up. But as these types of orders grow, the comparative speed, especially in deeper cuts, becomes magnified, and rough boring exponentially laps heli- cal interpolation in terms of production. Making the switch just requires the right tools with enough rigidity and repeat- ability to take on the large orders stemming from the rise of the fracking industry.
Energy Manufacturing 2013 47
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