Everyone Needs a CNC Mill

I am currently trying to solve a problem of failure to clamp tightly on a tripod leg, and my solution is to make a donut of acetal just small enough to slip inside the sleeve that goes over the tripod leg, with a hole through the center of the donut slightly smaler than the tripod leg.  Then slice it in half, so that when drooped into sleeve, the bolts that currently fail to lock onto the tripod leg with enough force will press the two half donuts on to the leg with considerable force.  Perhaps attach some sandpaper to inside of donut to increase friction.  But how to slice donut in half?  The chop saw has no easy way to hold donut firmly while slicing a diameter.  Solution: put donut in mill vise, flat, then run a 1/16" end mill along a diameter parallel to vise jaws.  Do it slowly (perhaps 1 in/min).  But this requires a 1.25" cutting length end mill.  Maybe a slightly larger diameter.  That diameter has short cutting lengths.  Competition matters: I found a 1/4" diameter end mill with a 4" cutting length--for $228.  But in 9/32" diameter, 1 3/8" cutting length, $22.84.