When work in the oil field dried up due to poor economic conditions, Knust-Godwin LLC, a Texas oil & gas supplier, faced new challenges following transitioning into small parts machining. Rather than hunker down and wait out the cyclical downturn as many shops would do, David Prickett, sales manager, and Knust-Godwin management agreed they should work to diversify the company’s customer base. This would keep the doors open during lean times and keep the business primed for an oil & gas resurgence.
Located in Katy, TX, a small town 30 miles west of Houston, this precision machining company specializes in large, complex parts for oil field instrumentation. Typical workpieces include flow diverters, electronics and manifold chassis, measurement and logging tools for directional drilling used in downhole oil and gas applications.
Machine tools in its 238,000 ft2 (22,111-m2) facility are able to drill holes up to 31′ (9.5-m) deep, turn shafts nearly 21′ (6.4 m) long, and mill parts 36′ (11 m) across. An average workpiece measures 5′ (1.5-m) long and 6″ (152 mm) in diameter, is made of Inconel, Hastelloy, or a similar tough material, and might require 50–60 hours of machining. Up to several hundred hours of machine time per part is not uncommon.
Knust-Godwin, however, doesn’t limit itself to manufacturing parts for the oil industry. The company also services the semiconductor, medical, seismic and geophysical industries. Its capabilities range from five-axis CNC machining and mill/turning to gundrilling, laser and electron beam welding, EDM, and even additive manufacturing.
So it’s somewhat ironic that when the opportunity to machine wristwatch parts came along—some smaller than 0.40″ (10 mm) in diameter—Knust-Godwin management asked, “Why not?”
And there was some precedent. Knust-Godwin LLC resulted from a merger of two Houston-area machine shops. Knust began as a precision watchmaker more than 50 years ago. Godwin opened its doors around the same time, and was focused on general machining. Both came to be experts in oil & gas machining and were eventually acquired by Schoeller Bleckmann Oilfield (SBO), which merged the two into a single company during the recent oil & gas slump.
Programmer Cameron Birse learned of a Portland, OR, startup—VERO Watches—offering a new line of high-end timepieces. The fledgling watch company was struggling with fit and finish problems on prototypes from a local machine shop, and was looking for an alternate source. Birse alerted Prickett of the opportunity, the quote package was delivered, and Knust-Godwin soon found itself back in the watchmaking business.
“Many of us were unaware of our roots,” said programmer Chris Hurst. “Then one of the old-timers from Knust saw the drawings. ‘We used to make parts like that,’ he said. It turns out we came full circle.”
Needless to say, machining technology has changed substantially over the past 50 years. Knust-Godwin quickly learned that what works for large parts is less effective on very small ones. Even though Hurst and his team were quite familiar with the difficulties of titanium and high-nickel alloy machining, the far more machinable 316 stainless steel watch bodies were destroying tools quickly enough that acceptance of future orders was in question.
“We started with an order for two sets of prototype parts,” said Hurst. “This includes the watch case itself, plus the back piece, the bezel, the crown, and a few other pieces. The biggest is around 1.2″ [32 mm] across, while the smallest is a washer just 0.178″ [4.5 mm] in diameter.”
Most of the parts were machined on one of Knust-Godwin’s DMU 125 monoBLOCK universal machining centers from DMG Mori (Hoffman Estates, IL). With a large work volume and table load capacity of over 13,228 lb (6000 kg), the DMU was obviously overkill for the small parts, but the machine’s superb accuracy and 10,000-rpm spindle made it the logical choice for the project.
Despite the high level of machining technology, Hurst said they soon found themselves in trouble, “I don’t mind challenges. Some of our large Inconel parts sell for over $100,000, so we’re used to high-stakes machining. But our tool life on the prototypes run was so poor, we knew the production order would be miserable. Most of the tools couldn’t complete a single part without needing to replace it. We had to do something different,” said Hurst.
VERO Watches enthusiastically accepted the prototypes. Knust-Godwin was soon facing an order for 105 complete watch sets, so they called Grant Gregory, south central productivity engineer for Sandvik Coromant (Fair Lawn, NJ).
Gregory said the problem of poor tool life during prototyping could be solved for production orders by switching to hydraulic toolholders and high-quality cutting tools. Gregory’s recommendations included replacing the ER-style collet holders used to hold the various end mills and drills with CoroChuck 930 high-precision hydraulic chucks, greatly improving tool runout and security. Instead of a 0.50″ (12.7-mm) diameter solid carbide end mill, roughing was done with a CoroMill 390-07 indexable cutter with GC1130 grade carbide inserts. And the 0.0625″ (1.5-mm) ballnose “import” end mills were replaced with CoroMill Plura 1630 grade cutters.
The results were dramatic. Hurst said he was previously using two ballnose end mills—a regular length and a stub—to semifinish and finish machine each watch body. By switching to a Plura ballnose end mill held in a hydraulic CoroChuck, tool life increased to 80 parts per end mill. “It was an unbelievable improvement,” Hurst said. “Feeds and speeds, depth of cut—everything was the same, except the one Plura end mill was actually doing 90% of the finishing work on the outside of the part. It came out to an 8000% productivity increase per tool.”
The CoroMill indexable cutter produced similar results, roughing out the entire 105-piece order on a single set of inserts. Tool life improved even with the legacy tooling. In one case in which a 0.032″ (0.8-mm) square nose end mill was responsible for cutting a groove on the crown interior, tool life improved by 400% by switching to the CoroChuck. “That was the smallest improvement we saw with any of the tools,” said Hurst. “We’d long suspected that better tooling would make a difference, but never had this sort of head-to-head comparison.”
Granted, the Sandvik end mills cost substantially more than the legacy tooling, but the cost per part still came in at roughly one sixteenth that of the less-expensive cutters, Hurst said, not counting the disruption and downtime of frequent tool changes due to dull cutters.
“Tool life was definitely an issue,” Cameron Birse said. “We had all these three-dimensional surfaces blending into other three-dimensional surfaces, so any time you had to change tools it was a big deal. I think much of the improvement came from the carbide, but those hydraulic pencil-style holders definitely helped as well. It was a massive benefit.”
Knust-Godwin delivered the watch parts as promised. And because of the greater tool life and surface finish achieved with the Sandvik Coromant tooling, Hurst and others there are looking forward to the next order. “The Houston machining industry has never been very good about diversification,” said Hurst. “It has always been about the oil field, so when things slow down it’s tough to transition into different markets and actually make it successful. We’ve learned some things from this job and that’s always a good thing. And I can honestly say, even if we never make another watch body again, we’re going to be reevaluating our cutting tools, and how we’re holding them.”
For more information from Sandvik Coromant, go to www.sandvik.coromant.com/us, or phone 800-726-3845; for more information on Knust Godwin, go to www.knust-godwin.com; for more information on VERO watches, go to www.vero-watch.com.
This article was first published in the December 2016 edition of Manufacturing Engineering magazine.