What the 6" Bayonet Ring Does and When to Replace It
By Zygo | Published: 2026-11-02
Category: Tips & Care
Learn how the 6" bayonet ring secures optics on Verifire interferometers, spot wear and seating problems, and decide when replacement is the right fix.
Quick answer
Replace the 6" bayonet ring when you can see or feel damage on its seating surfaces, when optics no longer lock repeatably, or when cleaning and reseating do not restore stable measurements. If the ring looks clean and undamaged, diagnose alignment and mounting first—replacement will not fix a bent mount or a dirty optic.
What the ring actually does in the optical path
The 6" bayonet ring is the interface that holds a compatible optic—typically a transmission sphere—square and secure against the interferometer's bayonet mount. Its job is repeatability: the optic should seat in the same position every time you install it. Any burr, contamination, or deformation on the mating surfaces changes that position and shows up as tilt or focus error in the measurement.
Because the ring is a passive mechanical part, it does not wear out on a schedule. Wear comes from handling, dropped optics, cross-threading, or grit trapped between mating surfaces. That is why the diagnosis below starts with inspection rather than replacement.
When cleaning and reseating is the better first move
Many apparent ring failures are really contamination or installation errors. Before ordering a replacement, clean the bayonet surfaces with a lint-free wipe and approved optical cleaner, inspect for burrs under magnification, and reinstall the optic with the ring fully seated and the bayonet locked. If the measurement stabilizes, the ring is probably fine.
Also check the optic itself. A transmission sphere with a damaged reference surface or a loose retaining feature can mimic ring seating problems. Swap in a known-good optic to isolate whether the ring or the optic is at fault.
The trade-off: replacement vs. sending the mount for service
A new 6" bayonet ring is a straightforward spare-part swap, but it only addresses the ring. If the interferometer's bayonet receiver is bent, corroded, or out of tolerance, a new ring will seat no better than the old one. In that case, stop and arrange service for the mount rather than buying a part that cannot fix the root cause.
Conversely, if the ring is visibly damaged and the receiver is clean and true, replacement is usually faster and less disruptive than a full service visit. Keep the old ring labeled as a known-bad reference so you can compare seating feel after the swap.
Diagnose the ring before you replace it
- Symptom: optic rocks or locks inconsistently: Inspect the bayonet lugs and the ring's seating face for burrs, dings, or embedded grit. Clean and reseat the optic. If the lock still feels vague or the optic moves, the ring or receiver is damaged. A repeatable lock should feel firm with no perceptible rock; if it does not after cleaning, move to the next check.
- Symptom: tilt or focus error changes each time you reinstall the same optic: Mark the optic's orientation, remove and reinstall it three times, and compare the fringe pattern or wavefront error. Variation that follows the ring—not the optic—points to a worn or deformed seating surface. If the error follows the optic when you swap it into another mount, the optic needs service, not the ring.
- Symptom: visible damage on the ring: Look for gouges, corrosion, or a bent lug on the ring's mating surfaces. If damage is present and the receiver is clean and undamaged, replace the ring with the 6" Bayonet Ring (SKU 6500-1077-01, Standard). Photograph the damage before swapping so you can confirm the new ring seats differently.
- Stop point: receiver damage or uncertain fit: If the interferometer's bayonet receiver shows damage, or you cannot confirm your model is a Verifire, do not order the ring as a fix. Arrange service or confirm compatibility first. Replacement is the right call only when the ring is the damaged part and the mount is known-good.
Product facts
- 6" Bayonet Ring: The 6" Bayonet Ring is a ZYGO spare part intended for use with Verifires and is available in a Standard option. Confirm your interferometer model is a Verifire before ordering, because this ring is not a universal fit.
6" Bayonet Ring
