Anybody else tried the Sunnen KG-9150 expandable mandrel for piston pin bore honing? We put it on the CV616 this morning and saw repeatability at 0.00015" across four LS rods with MB-30 at 70°F — seems to cut chatter and save a spark-out pass, but I’m wondering about stone life and glazing over a full set.
Ran the KG-9150 on our CV616 last week — 0.00015" held fine, but glaze crept in after 12–14 bores () until I dropped spindle about 10% and did a quick 2–3 sec dress with an alum-oxide stick between pairs. Keeping MB-30 locked at 70°F helped, and a light “pop dwell” in place of a full spark-out kept it cutting clean. @tinbake what RPM and stroke are you running, and are you indexing the mandrel a notch between rods?
If it’s bushed LS rods, swap to S‑series stones; they stay open in MB‑30 and cut cooler. We held “0.00015"” on a CV616 too, and life went from about 12 to about 30 bores per light dress after moving to S33 and swapping the felt wipers every 8 rods. Small caveat: ease the feed for the first 0.0002" so the bush doesn’t smear — @gradavi, that track with your setup?
I’ve stretched stone life on the KG‑9150 by easing the last.0001 with two tiny feed bumps and biasing flow to the exit side — keeps the smear down so it doesn’t glaze. On the CV616, a 1‑sec dwell at stroke reversal replaces a full spark‑out for me without drifting size. @james7622, have you tried backing the shoe preload a quarter turn once the MB‑30 is up to temp to keep it from tightening as the rod warms?
I only beat the glazing on LS bronze after we lightly chamfered the bushing oil holes and knocked the split‑line burr before honing; otherwise the stone smears and loads up fast. With MB‑30 at “70°F” we also saw fines hang around — adding a 5 µm bag filter and a 10‑second nylon‑brush flush between pairs bumped stone life about 25% (, fussy but worth it). If you try that, just watch for a hair more size growth as the oil runs cleaner — are your oil holes already broken?