What can I do to minimize TIR (Total Indicated Runout)?
Total Indicated Runout (TIR) is sensitive to a number of factors when using a nut type arbor. Minimize TIR by assuring that all blanks, spacers, arbor and nut faces are ground flat and parallel. A blank with faces out of parallel acts like a wedge when clamped under pressure, and the stoutest arbor will deflect. Tightening the nut should always abruptly stop, not slowly increase in resistance to the wrench. Increasing resistance (during, say, the last 1/4 turn of the wrench) usually means that the arbor is bending under clamping pressure. A spherical nut/washer combination can help to reduce clamping irregularities. These are usually available from suppliers of milling machine clamps and fixturing supplies. Michael also recommends limiting the arbor length to no more than 3 times the hole size of the gear blank. Thanks to Michael Kelly, Cardinal Engineering Company, for his suggestions. …and don’t use an arbor if possible. Use expanding mandrels between centers instead. This is proba