Bosch Keyhole router bit

Why I reached for this bit

Keyhole slots are one of those small operations that can make or break a project’s professionalism. I wanted a reliable way to hang floating shelves, plaques, and small cabinets without visible hardware, so I put the Bosch keyhole bit to work across several builds. After a few weeks in pine, poplar, white oak, and MDF—with both a compact trim router and a full-size plunge router—I have a clear sense of where this bit shines, and where you’ll want to pay attention.

Design and build

This is a 3/8-inch keyhole cutter on a 1/4-inch shank, made from high-speed steel. The geometry is classic: a plunge tip that bores the “head” recess and a trailing cutter that mills the narrow slot. Bosch’s control-cut profile is meant to minimize the grabby feeling some keyhole cutters have, and the asymmetrical flute pattern helps chip evacuation and reduces feed pressure. The overall package is compact and easy to balance in small routers.

High-speed steel has its place. It comes sharp and cuts sweetly at modest feed rates, but it won’t outlast carbide in abrasive materials. If you’re hanging a houseful of MDF shelves, you’ll notice wear sooner than with a carbide bit. For mixed woodwork and occasional ply, HSS is perfectly serviceable and more forgiving of heat than you’d think—as long as you don’t linger in the cut.

Setup and technique

Keyhole slots demand a repeatable routine more than brute power. Here’s what worked consistently for me:

• Mark a centerline and stop marks for each slot.
• Use a fence or an edge guide; freehand slots wander.
• Set depth stops carefully: one depth for the head pocket, one for the stem.
• Start at the closed end of the slot. Plunge to the full head depth, pause for a count to clear chips, then ease forward along the mark to your endpoint at the shallower slot depth.
• Lift straight out while the router is still moving slightly to avoid burn marks.

With smaller workpieces, I prefer a router table: flip the work, use a fence and a stop block, and feed right-to-left. On a handheld router, a plunge base is more controlled than a fixed base.

Cutting performance

• Softwoods (pine, radiata): Clean pockets and smooth stems at mid-high RPM with a modest feed rate. The plunge tip enters predictably with minimal kick, and the wide/narrow flute clears chips well enough that I didn’t feel the need for pecking plunges.
• Poplar and alder: Very tidy results. The slot walls came out crisp, and the bit felt stable. Minimal fuzzing at the exit, easily sanded off with a quick pass of 320-grit.
• White oak and maple: Still accurate, but the bit asked for a slower feed and slightly reduced RPM to avoid chatter. A backer block at the exit edge helps prevent any tear-out, especially if the grain transitions challenge the climb side of the cut.
• MDF and plywood: Acceptable but more sensitive to heat and dust packing. In MDF, I dropped the RPM a touch and vacuumed at the source. Plywood edges were clean when I used painter’s tape and a backer.

On a trim router, I found a sweet spot around mid-range speed. At full tilt, any small imbalance in a keyhole bit is amplified. With the speed dialed back one notch and the feed steady, the cut felt composed and predictable.

Fit and compatibility with screws

The head pocket this bit cuts mates nicely with typical #6 screws, including common drywall screws used for hanging light shelves and frames. The stem is narrow enough to hold the screw head securely without excessive slop. #8 screws will fit in the pocket, but you’ll want to test your exact hardware; heads vary, and a #8 with a large head may feel snug. As with any keyhole slot, set your wall screws so the head stands off the wall slightly—about a sixteenth of an inch usually does it—and test fit on scrap before committing to final pieces.

Control and safety

Bosch’s control-cut geometry does what it claims: the bit doesn’t feel grabby on the plunge, and lateral motion is manageable as long as you don’t force the feed. That said, the laws of physics still apply. Keep the work secured, use a firm two-handed grip, and avoid climb-cutting through the slot. I got the cleanest results with a consistent push past center and a straight lift-out, especially in hardwoods.

Chip evacuation is decent, but not magical. A shop vac at the router base improves cut quality and keeps the pocket from recutting debris, which can score the wall of the recess.

Durability and maintenance

After roughly 40–50 slots—half in hardwoods, half in MDF—the cutting edge showed the first signs of dulling: a faint darkening in the pocket after longer plunges and the need for a slightly heavier hand to maintain feed. That’s consistent with HSS. You can extend life by:

• Dropping RPM a touch on dense or abrasive stock.
• Using vacuum or compressed air to keep the pocket clear.
• Making sure you pause briefly at full depth to let chips clear during the plunge.

When it does dull, a light touch-up on the flat faces with a fine diamond paddle can bring it back for another round, though factory geometry is hard to replicate perfectly. If you expect hundreds of slots, I’d consider keeping a carbide keyhole bit as a companion for the high-volume days. For the typical shop, this HSS bit’s lifespan is reasonable.

Quirks you should know

• The bit is happiest at mid-range RPM. At max speed in a compact router, I felt a hint of high-frequency buzz in dense hardwood. It didn’t spoil the cut, but it’s a cue to lower speed a notch.
• Exit tear-out can happen if you don’t back up the exit point, especially across veneer plies. Tape and a backer board fix this instantly.
• The 1/4-inch shank is convenient for trim routers, but if your workpiece is heavy or awkward, a plunge router with more mass feels more planted and reduces user-induced wavering.

Practical tips for cleaner keyholes

• Score your slot endpoints with a marking knife when the face will be visible; it crisps the breakout.
• If you’re doing a run of identical parts, set up a stop block and a fence on the router table for repeatable length and straightness.
• Plunge, pause, move—then slow your feed as you approach the exit. That rhythm minimizes heat and breakout.
• Keep a scrap board with test screws at the bench so you can confirm slot fit before you cut into your project.

Where it lands

This bit delivers what I need for small to medium runs of keyhole slots: predictable plunges, respectable cut quality across common woods, and an easy fit with #6 screws. The control-cut design is not marketing fluff; it contributes to a tame plunge and steady slotting when paired with a sensible feed rate. The tradeoff is material life—HSS will ask for a touch-up or replacement sooner than carbide in abrasive sheet goods.

Recommendation

I recommend this Bosch keyhole bit for general shop use, especially if you work primarily in solid wood or do occasional runs in MDF and plywood. It’s easy to control, produces clean, repeatable slots, and plays nicely with compact routers thanks to its 1/4-inch shank. If you’re outfitting a production line of MDF shelving or expect to cut hundreds of slots per month, a carbide keyhole bit will be a better long-term value. For the rest of us building shelves, frames, and wall-hung fixtures, this bit strikes a good balance of cut quality, control, and convenience.