b'\x1b\x1a\x19 \x1f\x18\x1d\x17\x16Ask the Grinding DocEXPONENTIAL CHANGEBy Jeffrey Badger But switching to carbide is not al- steel to carbide.ways my first choice. Why is that? ItLook at diameter. It has an expo-D earDoc: Were ID grindinghas to do with exponents. Deflec- nent of 4. Lets say you have a quill di-and suffering from deflection,tion depends on E 1(quill stiffness), L 3 ameter of 30 mm. If you can increase taper and chatter. Were thinking(quill length) and DIA 4(quill diameter).it to 40 mm, youll get about one-of switching to a carbide quill. WillWhere will you get the most bang forthird the deflection: (30/40) 4= 0.316. that help? your buck? Quill diameter (exponentYour diameter is only a third bigger, The Doc replies: Yes, it will help.4), then quill length (exponent 3), thenbut you get three times the benefit. Carbide has about three times thequill stiffness (exponent 1). Thats the power of exponents.Youngs Modulus, E, or stiffness,Lets say youve got a quill lengthThat spindle deflection is what of steel. Therefore, you can expectof 50 mm. If you can get that downcausestaper,h ,andthebell wabout one-third the spindle deflec- to 35 mm, thatll give you one-thirdmouth shape that we see in cy-tion as shown in the figure for thethe deflection: (35/50) 3= 0.343.lindrical ID grinding. How to deal formula for h , spindle deflection. Thats the same as switching fromwith it? Reduce normal force (F ), s NDeflection is shown in the quill in cylindrical ID grinding. Exponents matter.J. Badger12JANUARY 2023 GrindingDoc.indd 12 12/15/22 11:40 AM'