Dear Doc: I grind bearing steel and am trying to increase feed rates without getting grinding burn. I got a new wheel salesman and he suggested a new—and rather pricey—wheel with “cool-cutting characteristics.” When pressed for more details he just repeated the term “cool cutting” over and over. What exactly does that mean? Does my wheel salesman know what he’s talking about?
The Doc Replies: I’d give 10-to-one odds that your wheel salesman’s previous job was selling toothpaste and, instead of saying he doesn’t know the details, is trying to bluff his way through.
There are definitely cool-cutting wheels, and there’s no shame in using that term. But your wheel salesman has to do a better job describing why it’s cool cutting.
A wheel can be cool cutting in many ways: It has high porosity and therefore can carry more coolant to the hot spot. It uses a friable grit instead of a tough grit, so the wheel self-sharpens better via grit fracture. It has a softer grade, so it self-sharpens better via bond fracture. It grinds with an angular instead of a blocky grit, so the grits attack more aggressively (which reduces rubbing) and fracture more easily (which improves the wheel’s self-sharpening ability).
I work with wheel salespeople all the time. Some are very well educated and experienced in grinding—and some are absolutely clueless. The following are some of the telltale clues of a clueless wheel salesman:
- He says “cool-cutting characteristics” without telling you what makes it cool cutting or what characteristics he’s talking about.
- He repeatedly says the term “high performance,” such as “It’s a high-performance wheel,” without telling you specifically what makes it so.
- He says “It’s the latest technology from Europe” without explaining what that technology is.
- He says the term “performance increase” without defining how he measures performance.
- He makes outrageous yet vague claims with specific numbers, such as “This wheel will give you a 250 percent performance increase.”
This last one drives me crazy, and I want to ask, “From where did you pull that number?” Assuming no adverse side-effects, a 250 percent increase in wheel life is impressive but achievable; a 250 percent increase in feed rate is nearly impossible without sacrificing somewhere else. Which one is he talking about?
The following is a conversation I recently had with a wheel salesman.
Salesman: “It’s a cool-cutting wheel.”
The Doc: “Why is it cool-cutting?”
Salesman: “Because it generates less heat.”
The Doc: “Why does the wheel generate less heat?”
Salesman: “Because it’s a cool-cutting wheel.”
Of course, if a salesman works at an industrial distributor selling everything from grinding wheels to air compressors to toilet cleaner, cut him some slack. But if he works for a grinding wheel company, he should know this stuff.
Here’s the final litmus test. Grinding is complex, and there are no guarantees. So when asking a wheel salesman if his wheel works better and he answers “absolutely,” you’ve got yourself a clueless wheel salesman. But if he says: “I’m not sure. Here’s what I know. Here’s what’s worked before and here’s why I think it’ll work for you, but I can’t be sure until we try it,” then he’s a keeper. CTE
About the Author: Dr. Jeffrey Badger is an independent grinding consultant. His Web site is www.TheGrindingDoc.com.
Related Glossary Terms
Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.
- grinding wheel
Wheel formed from abrasive material mixed in a suitable matrix. Takes a variety of shapes but falls into two basic categories: one that cuts on its periphery, as in reciprocating grinding, and one that cuts on its side or face, as in tool and cutter grinding.
On a rotating tool, the portion of the tool body that joins the lands. Web is thicker at the shank end, relative to the point end, providing maximum torsional strength.