Ever torque a chuck to 8 N·cm, zero the micrometer, and still chase 0.15 mm TIR — only to find a thin composite smear baked into the collet? I’ve started doing a Friday 4:30 ultrasonic-and-IPA collet soak with a backlight check, because nothing sabotages device accuracy faster than a “clean” handpiece telling jokes; anyone else on this preventative-maintenance comedy tour?
When I suspect a ‘thin composite smear’ I do a quick Sharpie test — mark the bur shank, light spin, check for a halo under 10×, then nylon-bristle scrub, 2 min in IPA, and a 60°C oil‑free air dry. Small caveat: long ultrasonic dips can tire the collet spring, so I keep it short and only oil after measuring so the film doesn’t nudge TIR like a tiny prankster; do you dry-bake or just air-blast after your Friday soak?
I’ve been there too — it’s amazing how something as simple as a collet can turn into a full-on comedy routine. I’ve started adding a couple of minutes for the heat check after the IPA soak; they’re like stubborn kids with those smears.