The topic of drill sharpening gets brought up here in RCM on a fairly
regular basis, when cheap and expensive drill sharpening fixtures or
dedicated drill sharpening machines often get discussed, but I don't recall
the TDR SRD machines being mentioned any time recently.
I'd watched a couple of these sell on eBay over the last several months, and
I was outbid twice, but I wasn't trying very aggressively to get one.
The unique "chuck" used to hold the drills keeps drills of various sizes
centered so that no adjustments need to be made when changing to another
size (1/16" to 13/16" according to the manufacturer's claim, larger sizes
with optional accessories).
The "chuck" that's used to hold the drills is unique square block that
consists of two halves, which are two mating segmented V blocks which
mesh/interlace to form a square opening where the drills are secured,
essentially making a self-centering 4-jaw chuck.
The centering aspect of the V blocks maintain the correct center height.
The square outside dimension ensures that the two grinding positions are
oriented 180 degrees apart.
Another part to be noticed is the small, straight cup wheel. A chamfered or
beveled face on the *inside* edge of the wheel is where the drill point
contacts the wheel. No separate additional motion is required to crown the
cutting face of the drill flute.
The precise orientation of the drill's centerline, in relation to the
centerline of the cup wheel, and the feed angle of the sliding assembly,
determine the relief angle of the drill point.
A separate adjustment sets the overall inluded angle of the drill point.
The motor travel remains stationary for the most part, and the chuck holding
the drill moves the drill point across the inside beveled face of the wheel
on a lubricated, free-moving slide assembly (motion supplied by operator's
There is an adjustment screw in the wedge-shaped control block/chuck holder
for setting the drill cutting edge relief angle.
Most of the motion during resharpening is the slide. When one side of the
drill is completed, the chuck is rotated (rolled over) 180 degrees, and the
other side of the drill is ground. The unique chuck maintains the proper
center height to grind the second cutting edge.
The motor may require a slight amount of inward adjustment during the
resharpening, but otherwise it doesn't travel during sharpening. Unless the
drill point is badly damaged, the motor probably won't need to be
repositioned repeatedly to complete the resharpening of both drill cutting
It appears that there would be a little difficulty at first, in getting
familiar with the proper positioning of the web and cutting edge. The manual
describes how the cutting edge is lined up with a scribed mark on the chuck,
but some experience will be required to get the rotational position
consistently correct, it seems.
One noticeable advantage would be that the drill point is facing the
operator, so examining the drill point geometry while resharpening is fairly
13 years ago