The Tube & Pipe Journal

The most important question still wasn’t answered. Would the three critical bending elements—the machine, tooling, and material—interact in such a way that the finished parts would be accurate and consistent?

Material. “Bob Want, the sales engineer for Tools For Bending, was ready to design the tooling around normal ASTM tolerances,” Kuhn said. “That’s fine, but tolerances are a worst-case scenario, and people don’t want to deal with the worst-case scenario. I told him that GL Precision Tube could provide material at half the standard wall tolerances, gauge-restricted steel, chemistry-restrict-ed steel, and specific weld locations.

“In a common steel such as 1008 or 1010, the carbon content can vary from virtually none to 13 points; that will significantly affect the way the tube forms,” Kuhn said. “We can do better than that, but we have to know upfront if that’s what’s needed. The mill can do it and it doesn’t add cost.”

Tooling. “We had the steel guy and the tooling guy at the first meeting,” said Chuck Schooley of KCS Industrial Sales, referring to Chuck Kuhn and Bob Want. KCS is a sales representative for both Tools For Bending and SMT Industries Inc., the bending machine manufacturer for this project.

“Getting them together was crucial
because they were able to discuss the
details,” Schooley said. “They were able
to haggle back and forth to determine the
specifications, the tolerances, the amount
of elongation, and all that good stuff
regarding the steel. There was no time to
produce samples of tubing before making
the tooling, so we had to agree to it on
paper. That’s a recipe for disaster because
you can spend several thousand dollars
on tools and it could turn out that they
don’t fit.”
Want concurred. “We didn’t have
time to wait for the mill to make some
samples, so we worked back and forth to
come up with an appropriate compro-
mise on the tolerances and built the tool-
ing without a physical material sample.”
Ultimately it worked, because GL
Precision Tube was able to hold toler-
ances that were approximately half of
ASTM tolerances. According to Want,
ASTM tolerances for nonround tubing
are too loose to be practical for modern
manufacturing requirements.