New Method Proves Successful For Sheet Metal Hole Making

Modern Machine Shop, Jan, 2001 by John M. Jordan, Katherine A. Kelley

As an electrical contractor, Cincinnati Electric (Cincinnati, Ohio) installs power distribution systems throughout industrial and commercial buildings, and as an OEM manufacturer, it fabricates control panels, junction boxes, drive units, housings and enclosures for machine tools, material handling systems and pumping stations, among many others. The company uses a lot of sheet metal, and in both the shop and in the field, it has to make a lot of holes. Unfortunately, sheet metal and holemaking are not always harmonious operations.

"In the past, Cincinnati Electric used standard hole saws, carbide tipped hole saws and hydraulic knock-out punches, all with meager to moderate success," says George Blanchett, purchasing agent at Cincinnati Electric. "Either they were too slow, as with the knock out process, or the saws produced poor quality holes--dimpling and deforming the surrounding material and leaving jagged, sharp burrs--or they became dull and didn't last very long. The traditional tools were not getting the job done to our satisfaction."

At the Cincinnati Electric shop, most of the holes are produced on drill presses, reports Mr. Blanchett, while field work and installations use hand-held electric drills or the knock-outs. "The control panels and enclosures are made from 12 to 22 gauge steels and require holes for installing push buttons, cycle and warning lights, and conduit and cord grip connectors. They are most frequently 7/8 inch to 1 1/8 inch diameters, but other sizes as well," notes Mr. Blanchett. "The sharp, jagged edges resulting from hole saw use easily cut fingers as connectors and lock nuts were assembled. The knock-outs usually produced a better hole, but, considering the time to drill a pilot hole and attach the unit, the entire process took too long." Cincinnati Electric decided to look for a single tooling system that could be used in both environments. What the company found were tools from Hougen Manufacturing (Flint, Michigan).

Hougen's 14,000-Series Holcutter annular cutting tools are designed to make drilling holes in sheet metal (for example, electrical boxes) and other thin materials (rubber, gasket and fiber materials and some plastics) up to 1/8 inch thick easier and faster than with twist drills, hole saws or knock-out punches. The tools' cutting tooth geometry cuts clean, round, accurate and virtually burr-free holes faster than twist drills or hole saws, and it cuts much faster than knock-out punches--without damaging or deforming the surrounding material.

The cutters are hardened and precision ground M2 H.S.S. with sizes developed for producing large diameter holes--11/16 inch up to 3 inches.

"We've found that the smooth cutting action of the Holcutters means there's less force or pressure required behind the tool," Mr. Blanchett says. "This added level of control not only helps to reduce burrs at breakthrough, but also, when using hand drills, reduces the risk of penetrating the interior of the enclosures too deeply and possibly damaging wiring or other components."

For convenience, Cincinnati Electric has been purchasing the cutters in a packaged unit Hougen refers to as its Electrician's & Fabricator's Kit, an HDPE tool box that holds and protects six cutters (7/8-, 1 1/8-, 1 3/8-, 1 3/4-, 2- and 2 1/2- inch diameters), the two arbor sizes, three pilot points, attachment fasteners and instructions.

"We've only been using the Hougen tools for a few months but have experienced immediate improvement in hole quality and have had fewer injuries," Mr. Blanchett reports. "In the shop, they're faster than the conventional hole saws we used in the past, and early results show we are producing holes at job sites a minimum of 30 percent faster than with knock-outs. And, preliminaly data show that the cutters are lasting longer, but it's still too soon for an exact comparison. Based on their successes so far, however, we'll be using the Holcutters for a long time and have plenty of opportunity to make that determination."