Dry, tight fluid connectors require the right tool

Whether you’re a truck driver, a commercial airline pilot or a snowmobiler, a leaky hydraulic system or fuel line can spell big trouble. A little fluid in the wrong place on these and a host of other vehicles and machinery might create a life-or-death situation for operators and passengers alike.

That’s why organizations like SAE (Society of Automotive Engineers) and ISO (International Standards Organization) have developed a series of standards that make even the highest-pressure, most-demanding fluid connection leak-free. These include SAE J1926, SAE J514, MS 33649/SAE AS5202, ISO 6149 and other technical documents that describe threaded connections.

Some fluid connectors come with O-rings, others with metal-on-metal seals, but all rely on a complex shape that is usually machined with a port tool.

Port tools can be resharpened many times and, according to Wetmore Tool, may last decades. Photo courtesy of Wetmore Tool and Engineering.

It’s Scientific

Dale Christopher, president of Scientific Cutting Tools Inc. (SCT), Simi Valley, Calif., said his father built the business on port tools. Even though that source of revenue has fallen relative to the other types of cutting tools the company now offers, there’s still plenty of demand from hydraulic-manifold manufacturers, automotive and aerospace customers, and electromechanical equipment suppliers.

For those scratching their heads over the bewildering array of port specifications, the situation’s not as complicated as it first seems. “The military came up with a standard hydraulic connector many years ago for connecting hose lines to hydraulic fittings,” Christopher said. “That was the start of the MS (mil-spec) standards. Some are still the
original Army or Navy design, but quite a few have been replaced by SAE numbers.”

Nor are ports as complex as they initially appear. “It’s really just a series of diameters and angles,” he said. “Sometimes you’ll have radii callouts and sealing surfaces with tight finish requirements. Because ports are used with a connector, there’s a thread somewhere, usually at the bottom, that can be tapped, thread-milled or single-pointed if you’re turning the part on a lathe.”

Porting is not rocket science. However, the configurations are sufficiently complex that they would be extremely challenging to make on most machines without what is essentially a big form tool. CNC lathes make it possible to shelve port tools in favor of a boring bar and CAM-generated toolpath. Still, port tools remain commonplace on machining centers, mechanical screw machines and even drill presses, where profiling the port shape is impossible.

Port Popularity

“Porting on a drill press or transfer line requires a tool with a ground body so it can slide into a bushing mounted in a drill plate to guide the tool into the workpiece,” said Phil Kurtz, vice chairman of the board at Wetmore Tool and Engineering Co., Chino, Calif. “But those tools are rarely used anymore because hardly anyone uses drill presses. Virtually everything is made on CNC machines today.”

Other port tools have also seen a decline in popularity. Kurtz said the company has a long history of manufacturing port tools, but much of the work has dried up as aircraft designers move away from specifying hydraulic control systems in favor of electronic ones. As a result, Wetmore has redirected most of its development efforts into aircraft assembly tools, such as extension and core drills.

A mock-up of a ported agricultural valve body for a trade show presentation. Image courtesy of New Dimensions Precision Machining.

“We still see a fair amount of activity with standard brazed porting tools, but it’s not like it once was,” Kurtz said. He added that cartridge cavity tools remain fairly strong. “These are quite similar to port tools but larger, to accommodate a two-, three- or four-way hydraulic valve body that might be used to control a backhoe, for example.”

Keep Quiet

One of the biggest challenges with any porting operation is chatter. SCT’s Christopher said a 3-flute port tool is often effective in combating chatter. However, the feed rate is sacrificed because there’s one less edge in the cut compared to the more-common 4-flute port tool. “That’s why we take a diamond brush hone to all our tools,” he said. “This puts a microscopic edge break on the sharp edges. [It is] a little like rubbing a penny or a Scotch-Brite pad on the tool’s spot face, a trick that many veteran machinists are familiar with.”