hey bubba,IDON'T KNOW THE BLADE TIP SPEED ON THE GRAVELY,BUT ON MY DIXIE I USE TWO SETS ON EACH SPINDLE,ONE MED. LIFT UNDER A GATORBLADE.WORKS GOOD FOR ME BUT IF GRAVELY HASN'T CHANGED SPINDLES LATELY(2YEARS)YOU MIGHT WANT TO GO WITH A HIGHLIFT BLADE ONLY AND SHARPEN THEM EVERY6-8 HOURS.FROM WHAT I'VE HEARD.<p>----------<br>DON<br>LIANNES' MOWING