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How Does a Keyhole Drill Mount Work?
A keyhole rim drill mount is a rimless mounting style where the lens is drilled with a keyhole-shaped opening so the frame hardware can lock into place. The wider part of the hole lets a post or bushing pass through, then the mount slides into the narrower section to sit securely. It is common in three-piece rimless glasses because it keeps the lens edge clean with no full rim.
Pros and Cons of Keyhole Drill Mounts
Rimless mounts rely on precise holes or slots in the lens so screws, bushings, or compression parts line up with the bridge and temples. With a keyhole opening, the hardware can be inserted through the larger round section, then seated into the narrower slot so it is less likely to rotate.
This design still depends on correct hole size, placement, and lens thickness around the mount. If the lens is too thin near the slot, the area can chip or crack.
Best Lens Materials for Rimless Drill Mounts
Pros include a minimal look, easier lens changes on some chassis, and less visible hardware from the front. When drilled cleanly, the slot can reduce spinning at the mount compared with a simple round hole.
Cons include sensitivity to loose screws, worn bushings, and small cracks that can start at the drill area. Any mismatch between the mount and the hole shape can put extra pressure on the lens.
What to Know Moving Forward
For drill-mounted rimless glasses, labs often recommend tougher plastics that resist chipping around holes. Trivex and polycarbonate are widely used, and Trivex is often favored for rimless drilling because it is light and impact resistant.
Some high-index plastics are less friendly for drilled rimless mounting, so the lab may suggest an alternative if the prescription is strong. An optician can also request extra thickness near the mount so the hardware sits more safely.
Frequently Asked Questions about Keyhole Rim Drill Mount
Is a keyhole drill mount different from a screw mount?
Check your rimless mounts for wiggle at the lens, a shifting bridge, or a temple that feels loose. Small issues can be tightened before they turn into a cracked drill hole.
If you see white stress marks, tiny chips, or a hairline crack near the keyhole slot, stop wearing the glasses and have the mount inspected. Rimless repairs often need specialty tools and replacement bushings fitted to the lens.
Can a cracked drill hole be fixed?
It describes the hole shape in the lens. The mount can still use screws or compression parts, but the keyhole opening helps the hardware seat into a slot.
Do high prescriptions work in keyhole rimless mounts?
Minor chips can sometimes be stabilized by replacing bushings and relieving pressure, but a true crack often means the lens needs to be replaced.
How do you keep rimless drill mounts from loosening?
Often yes, but the lens material and thickness around the mount matter a lot. An optician can advise if a different frame style will hold up better.