b'\x1b\x1a\x19 \x1f\x18\x1d\x17\x16Shop OperationsMACHINING A HARDENED RING GEARBy John SaundersI ncorrect speeds and feeds are a surefire way to make terrible noises, break tools and scrap parts. Our initial attempts to machine a hardened ring gear made noises thatwouldmakeanymachinist shudder. Through experimentation, we optimized reliable recipes that result in an excellent surface finish and provide good tool life.These ProvenCut recipes were performed on a Tormach 1100, a 499-kg (1,100-lb.), 1.1-kW (1.5-hp) CNC mill. It has similar capabilities as a Bridgeport. Tormach machines target the prosumer market and often are found in garage shops and R&D departments.Although cutting tools designed specifically for hard milling are avail- RECIPE IDs: 502 and 505able, we chose a standard four-flute carbide endmill that many machin- Machine: Tormach 1100 series 3ists already have on hand. Our test- Tool: Lakeshore Carbide Inc. 6.35 ing focused on avoiding cutting toolmm(0.25")four-fluteendmill vibration and ensuring that excessive(1700014X-30R)heat was not created. We pushedMaterial: 8620 alloy steel hardened the tool and machine to achieve anto 55 HRCaggressive but sustainable rough-ing recipe and concentrated on theCut type: adaptive pocket clearing, surface finish of the workpiece forfinishingthe finishing recipe. Machining 8620Material removal rate: 655.5 mm3alloy steel hardened to 55 HRC can(0.04 in.3)leave an outstanding surface finish about the authorctemag.comJohn Saunders owns Saunders MachineTo view a video of the machining Works LLC, Zanesville, Ohio, and foundedoperation at www.ctemag.com, ProvenCut, a website with a videoscan the QR code with your library of speeds and feeds. For moresmartphone or enter this URL on information, visit www.provencut.com,your web browser: cteplus.delivr.www.saundersmachineworks.com orcom/29n2kwww.nyccnc.com.16APRIL 2020ShopOps.indd 16 3/16/20 11:25 AM'