Tapers and how to figure them
Bill a friend of mine who is now retired, but when he was working was an expert in optics and actually helped fix the Hubble space telescope. He was employed by 3M Company and was sent out on loan to NASA to fix the Hubble space telescope. Now after his retirement he has decided to get involved in scissor and clipper blade sharpening. He bought a new blade each from Andis, Oster, and Wahl and measured the hollow in each blade and found there is no measurable difference between the three companies they all use the exact same hollow of 57 microns. He then set out to learn what taper it would take to get 57 microns and he found that in all tapers at some point you will get 57 microns if the wheel is big enough. He then made a chart for tapers from .001 all the way up to .031 mapping out how many microns there are in every inch of the clipper wheel and what he found was pretty amazing. It all boils down to a very simple formula which took a lot of heavy duty math to discover, but here it is in a nut shell.
If you put a .011 taper on a wheel you will find that the 57 micron sweet spot will be located at the 11” diameter of the wheel, if you put a .009 taper on a wheel the sweet spot will be located exactly at the 9 inch diameter of the wheel, and this applies to all tapers. The sweet spot will always be located at the inch value of the corresponding taper so then a taper of let’s say .008 will yield a sweet spot at the 8” diameter and so on and so on for all tapers. What that does is allow you to place the 57 micron taper anywhere on the wheel you want it, and the very best place to put this sweet spot is in the center of the sharpening band. The sharpening band is (if you are right handed) on the left the side of the wheel that you sharpen on (to be more specific) on the part that holds the grit. The reason I say to place the sweet spot in the center of the sharpening band is because of how it affects spring tension. If you sharpen too much on the inside of the sweet spot next to the center of the wheel you will end up with way too much hollow in the cutters. The closer you get to the center of the wheel the hollow gets steeper and steeper. The closer you get to the outside edge of the wheel the hollow gets flatter and flatter. So to get the right mix placing the sweet spot in the center of the band that you sharpen on will do the job.
If you have too much hollow from sharpening too close to the center of the wheel you will need more spring tension to get the blade to cut as much as 3 to 5 pounds, but if you are close to 57 microns the same blade will cut with only 2 to 2 ½ pounds of spring tension causing way less friction and less wear on the clippers. Personally I am very happy with anything between 2 to 2 ½ pounds of spring tension. Before I learned this I had to use 3 ½ to 4 pounds of spring tension and some of my customers were complaining about it. I sharpen on a 24” clipper wheel with the sweet spot in the center of the sharpening band, I start near the center of the wheel right next to the hub area as a place to set the cutter down on then I move all the way out to the outer rim of the wheel, I then do all of my sharpening moving back and forth from the outer rim of the wheel to just on the far side of the sweet spot, then I move directly over the sweet spot to do my finish sharpening at exactly 57 microns by moving the cutter back and forth over the sweet spot about ¼” in each direction several times then I lift the cutter straight up and I am done.
I use a dial gauge (that I make and sell for this purpose) to measure how much metal I have removed and I only do as many passes to remove between 1½ to 2 thousandths of metal. To give you an idea of how much metal that is a human hair is about 3 thousandths diameter so it is not a lot, but you need at least that much metal removed to get a good full sharpening that will work as it should.
To figure what taper you need all you have to do is measure the width of the sharpening band and divide it by 2 then mark the center of the band onto the clipper wheel using a pencil or marker. Then measure from the center of the clipper wheel out to the mark you made. Let’s say it measures 5 ½” so multiply that by 2 and you will get 11” which of course means you will need a .011 taper in order to place the sweet spot in the center of that particular sharpening band. So whatever diameter wheel you have you can figure exactly what taper you need using this same method. Every diameter will need a different taper to place the sweet spot where you want it.
Any taper, let’s say in this case a .011 taper the taper is measured for every inch across the face of the wheel, or to put it another way every inch no matter where you measure it on the face of the wheel will always measure .011 per inch. If you were to measure 2” instead of 1” the measurement will read.022. If you measure 3” then the dial indicator will read .033 and so on so each inch from the center of the wheel out to the edge of the wheel will always measure .011 per inch if you put a .011 taper on it. This applies to any taper you pick.
If you have any questions please let me know!
Ace Sharpening & Co