Ream a ‘hole’ lot better with replaceable heads

Do you still use that old standby, the HSS chucking reamer, for hole-finishing operations? There are excellent reasons to do so. HSS chucking reamers are inexpensive, dependable, readily available and forgiving of misalignment and misuse. For example, one catalog house lists more than 5,000 HSS reamers on its website, most of them in stock. But if you decided a long time ago to ditch HSS hand-ground tool bits for carbide ones, it might be time to question why you haven’t taken the same route for reamers.

For many shops, the move to solid-carbide reamers is a no-brainer. Yes, the price may be several times that of their HSS equivalent, but the higher productivity and hole quality are enough to win over even the most frugal shop owners and purchasing managers — that is, until reaching hole sizes of 12.7 mm (0.5″) and larger, at which point a solid-carbide reamer becomes increasingly hard to justify. What then?

Brazed carbide reamers are one option, but a better alternative dates back a century. On Dec. 27, 1920, inventor Torsten A. Gyllsdorff of Detroit-based Standard Reamer & Tool Co. applied for a patent for a two-piece reamer, one “wherein the cutting end can be replaced at low cost when worn.” His “new and improved reamer” unfortunately used an HSS head, which minimized improvements to productivity, but hats off to his forward thinking regardless.

Old Dog, New Tricks

A number of cutting tool manufacturers have resurrected Gyllsdorff’s idea and made it better. Peter Gennuso, sales engineering manager for OSG USA Inc., Irving, Texas, said the company’s PXM endmill platform can be equipped with a variety of heads, including special form tools, chamfer and radius cutters or exchangeable-head reamers.

“Because only the head of the tool is made of carbide, it’s a much more cost-effective solution for large-diameter reaming applications,” he said.

The Bayo T-Ream reamer from Iscar is equipped with a bayonet screw and special wrench for rapid changeovers. Image courtesy of Iscar Metals

What defines large? Depending on the style of head, the PXM system covers diameters from 10 mm to 32 mm (0.39″ to 1.26″), a range that Gennuso said complements OSG USA’s solid-carbide reamer line.

“The vast majority of machined holes are 9⁄16″ (14.29 mm) in diameter or smaller,” he said, “and for most of these, solid reamers are the best choice. For larger diameters, however, the PXM lineup provides the advantages of a solid cutting tool with the flexibility and cost benefit of an indexable platform.”

These reamers are also quite accurate. In OSG USA’s case, the PXM offers 0.015 mm (0.0006″) or less of radial runout and axial repeatability within ±0.03 mm (0.0012″). This is accomplished via a buttress-style, screw-on carbide head whose face and taper mate with a cylindrical steel shank, similar to an HSK spindle or a comparable dual-contact mount.

Gennuso said a general rule is to leave 1% of a hole’s finished diameter for reaming. For a 12.7 mm hole, that would mean drilling to 12.57 mm (0.495″). Check any drill chart, however, and you’ll find that the nearest drill size is 12.3 mm (0.484″), roughly three times his recommendation. So what do you do?

“Reamers are designed to remove a relatively small amount of material,” he said. “But with the larger diameters like those discussed here, your drilling options are more limited. So it might be necessary to drill as close as you can, semifinish with a boring tool and then ream to size. Without that three-step process, it can be tough to guarantee the proper amount of finishing stock and avoid problems with chip evacuation.”

Hello, Alvan

What if you need to go even larger? Talk to Ben Morrett, senior product manager for the Alvan reamer line at Allied Machine & Engineering Corp., Dover, Ohio. Since the early 2000s, the company has partnered with S.C.A.M.I. snc, a family-owned reamer manufacturer in Italy that produces modular reamers up to nearly 203.2 mm (8″) in
diameter.

Since the early 2000s, Allied Machine & Engineering has partnered with S.C.A.M.I., a manufacturer of modular reamers. Image courtesy of Allied Machine & Engineering

The reamer line’s monoblock style covers hole diameters from 5.8 mm to 32.1 mm (0.228″ to 1.264″) while the replaceable-head series is slightly larger at 11.8 mm to 60.6 mm (0.465″ to 2.386″). Both kinds are available in fixed or expandable models. There’s also a ring-style reamer that ranges from 17.6 mm to 200.6 mm (0.693″ to 7.898″).