b'increase quill diameter (DIA), re- always bounces at least a little.) Wepends on DIA 4 . And length? Reduc-ducequilllength(L),decreasewant it to bounce up and down at aing it actually decreases mass and wheel width (w), or increase quillhigh frequency to put those chatterincreases stiffness. Both of those in-stiffness (E). Pay attention to ex- marks closer together. Carbide hascrease the natural frequency.ponents to see which one has theabout double the density of steel.Now its getting messywhat to most effect. (Dont forget that cool- Unfortunately, that extra mass willprioritize? I tend to prioritize diam-ant hydroplaning can play a largedecrease its natural frequency (seeeter (particularly near the bearings roll in F , even during spark-out.) the equation)not a huge amountwhere its more important than near NFinally, heres another reason Ibut enough to counter at least somethe wheel), then length, then normal dont immediately jump into switch- of the benefit of the increased stiff- force, then quill stiffness. Mostly. ing from steel to carbide: chatter.ness. Yes, increasing the quill diam- But not always. It depends on whats That spindle is going to bounce upeter will do the samebut onlyeasiest to change and whether Im and down at its natural frequency. (Itas DIA 2 , whereas the stiffness de- battling deflection or chatter.Thats the simplified version. It becomesmorecomplicatedas about the authorstiffness and natural frequencies Jeffrey Badger, Ph.D., is an independent grinding consultantdepend on numerous factors, not who has resumed his popular three-day High Intensity Grind- just whats happening in the quill. ing Course. For more information, visit www.TheGrindingBut as far as simplified concepts go, Doc.com. it works.CTEU L T R A E F F I C I E N T L E A N G R I N D I N G P R O C E S Sctemag.com/cteguide.com13GrindingDoc.indd 13 12/15/22 11:40 AM'