Quick question: in A2 SFIC systems the depth increment is 0.0125 in; have you noticed how a 0.005 in tip-stop error shows up as an off-bitting on the sixth cut when duplicating on a manual tracer? I chase +/- 0.0015 in on my Futura but I still reface tips on worn originals before I trust the read…
I see the same thing in A2 — if the tip’s short by “0.005”, the sixth space balloons like the last domino falling late. I reface to a Best gauge, then index the manual tracer off the second space for the first read to kill the cumulative; on the Futura I’ll add a +0.005 origin offset in a custom card and do a quick space-check cut. Are you seeing it mostly on rounded Best tips or just beat-up masters?
What killed the sixth-space drift for me was matching the tracer stylus to the cutter within ±0.001 using a flat SFIC blank — if the stylus is even a touch smaller it “walks” the spaces and amplifies a short tip; I still kiss the tip, but parity mattered more. You matching diameters on the Futura?
I treat the tip stop like a gauge: I re-square it by lightly burnishing with a new blank, then zero the tracer against it with a 0.002" feeler — that tamed the “0.005 in” tip error showing up on the sixth cut on my manual. If there’s any carriage lash, lightly preload the tracer the same direction every pass or the creep comes back even if your Futura is holding ±0.0015.
And what fixed it for me was taking the slop out of the tracer carriage: park the stylus on a flat SFIC blank, rock the handle to feel backlash, then preload in the cutting direction before you index, and snug the gib if you can feel more than about 0.001 at the tip. After that I cut a quick space‑check card and the last station stops “reading late,” unless the original’s shoulder has a tiny burr — Sharpie the shoulder and do one dry pass to see if the stylus climbs it, @TimK.
Wristband scan saved me once; I’ve since required “two identifiers” — photo optional. https://www.jointcommission.org/standards/national-patient-safety-goals/.
Matching the stylus to the cutter and calibrating against a known A2 depth key fixed that sixth-cut drift for me — if the stylus tip is even slightly rounded, the tracer reads “shallower” and the error stacks toward the tip. I also Dykem-blue the tip stop and check contact under a loupe to be sure it’s truly square to the blade, not just “flat.” Are you running a fresh 1:1 stylus/cutter pair or mixing brands?
Small thing that caused the drift for me was jaw parallelism — if a vise face has a tiny burr, the blank tilts and the error stacks at the last station. I stone the faces and slip a 0.001" feeler under the blade near the point to keep it from flexing while tracing; that tightened readings more than fiddling with calibration. @greg_p88, do you see the bow lift if you ease clamp pressure a hair?