Related Glossary Terms
Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
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.
Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.
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.
Space provided behind the cutting edges to prevent rubbing. Sometimes called primary relief. Secondary relief provides additional space behind primary relief. Relief on end teeth is axial relief; relief on side teeth is peripheral relief.
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.
Just how big is the change that has come to tool-sharpening equipment? To get an idea, consider the increasingly small size of up-to-date sharpening operations.
“Today, companies don’t have whole tool-grinding departments,” said Jeff Toycen, president of Cuttermasters, an Ottawa, Ontario, maker of drill and endmill grinders. “In a toolroom we just set up, we replaced a room half the size of my house full of old tool grinders with some machines on a benchtop that do the same work.”
Tool-grinding options cover a wide range of sharpening needs. “We have sharpeners for shops that need to handle 20 drills a week all the way up to thousands of drills a week,” said Jim Wiltrout, operations and engineering manager for drill grinder manufacturer Darex LLC, Ashland, Ore.
Designed to sharpen drills and endmills, the CS320 from Cuttermasters features a small footprint and heavy-duty construction. Image courtesy of Cuttermasters.
To reduce the cost of its light- and intermittent-duty sharpeners, Darex installs some nylon parts in the units’ drill-holding chucks. Sharpeners with these nylon parts offer good value to small machine shops that need to sharpen five to 50 drills a week, according to Matthew Prell, Darex’s industrial sales lead.
However, heat generated by continuous sharpening may eventually deform nylon parts, adversely affecting the results of the process. So for shops that are constantly sharpening tools, Prell recommends a continuous-duty sharpener with all stainless parts.
Darex’s light-duty manual sharpeners start at about $1,500. At the other end of the spectrum are the company’s fully automated, 4-axis CNC drill sharpeners for high-volume applications. Starting at $33,000, these machines allow operators to enter desired tool attributes, such as web thickness, relief angle and facet overlap. Prell said, “All the user has to do is chuck the drill in, select the program and hit a button, and the sharpener will do everything from alignment to grinding and honing.”
Based on the speed of the grinding wheel and the amount of current going to the motor, these CNC machines can tell when a drill has reached maximum sharpness, according to Prell. The machines can complete the sharpening process in as little as a minute, Wiltrout said, adding that “our precision is usually beyond what the [tool] manufacturer offers.”
The XPS-16+ CNC drill sharpener is for shops that demand military-spec precision, simplicity and productivity with the touch of a button, according to Darex. Image courtesy of Darex.
How often do tools need to be sharpened? According to Cuttermasters’ Toycen, the answer depends on a number of factors, including the workpiece material, tool substrate, machining parameters for the tool and whether or not coolant is being used in the machining process. Generally speaking, however, “I would say that in the average shop with 10 to 20 machines, you could keep somebody busy all day sharpening drills and endmills, if you were doing it right,” he said.
As for the results of the process, “with the new machines, you don’t have to measure anything,” Toycen said. “They are accurate enough that if you run them through their steps, the tool that comes out should look and feel sharp.”
For the most part, Toycen said, drill grinders cost about $500 for smaller drill diameters to $2,500 for larger ones. The latest models eliminate the need to buy expensive drills for specific jobs. Instead, shop personnel can simply get a drill from the toolroom and put the required tip on it. “By taking control of the tip of the tool, you can use the drills you have in stock,” he said.
Top-notch drill sharpeners can produce tip angles from 90° to 140° and offer excellent repeatability, according to Toycen. What’s more, getting the desired results is fast and easy.