garch 22:
Reamers are not designed to cut quickly thru much materal they should just shave a little off with each pass.
The fast cutting action on the drill is what causes inaccuracy.
If you tried to sharpen the reamer by hand it is most likely no good any more. Sometimes cutters aren't ground correctly in a mass production process. The solution is to find someone with the knowlege and equipment to sharpen it correctly. A correctly sharpened and cared for reamer should last thru 100s of props.
I use reamers daily in toughened steel and they do wear out. Usually they can be touched up on just the cutting face and used some more. Plastic and wood will not wear the reamer as fast as steel nor will the size be as critical as I need.
A tapered reamer will leave a tapered hole not a pilot hole. The small surface will wear quickly and is a product of trial and error, not accuracy of tooling. The hole should be sized correctly as close to the propface as possible; usually in the sholder of the shaft not the threads.