1. Removal of dull cutting radius on tooth edge.
2. Even tooth contact on every tooth.

All other considerations, though important, are secondary.

1. Insufficient amount of metal removed to fully sharpen cutting edge
2. Uneven metal removal, resulting in uneven tooth contact pattern

To remove the dull tooth radius .001" or more of metal removal is necessary. Consistent metal removal of .001" or more requires knowing your grinding rate on fresh and ending charge. Inspection of cutting edge and teeth tips will determine if more than .001" of metal has to be removed to fully sharpen blade.

To know if you have achieved even and equal tooth contact the blade must be rubbed on an accurate test plate after grinding to display the areas of contact. Visual inspection of a freshly ground surface without rubbing on a test block is just guesswork. Test cutting does not reveal tooth contact.

1. A known-accurate disc surface
2. Accurate transfer of disc surface profile to blade

1. Use of a validated disc surface
2. Use of an accurate test/rubbing block to check tooth contact

Sharpened clipper blade is rubbed on test plate with equal and light pressure (about 1 lb.) in a figure eight pattern or back and forth motion.

The usual lapping disc honing area is 5" to 6" wide and lathe cut to a semi-precision plane. Varying surface finishes exist. The risk with this semi precision plane is that you do not know how good or bad it is. The showing of high or low spots (uneven wear of the surface) after some use indicates the original inaccuracy (a true surface always wears to an even curve with no high or low spots). This variance of accuracy has been a contributing factor to the inconsistency in sharpening clipper blades.

Three years ago The Shop, Inc. introduced a precision machine scraped disc surface that is verified, by the scraping process, a true plane, eliminating this risk. All other systems on the market use an unverified disc surface. We sell only verified disc surfaces. We season each disc, sharpen blades on it and then check the tooth contact pattern to be absolutely sure that the disc you receive is accurate and will make good blades immediately. No other manufacturers test their disc surfaces before shipping. We do not expect the customer to do our quality control for us.

A 5" to 6" honing band also makes it more challenging to produce the optimum straight tooth contact pattern. You must follow as straight as possible the hollow grinding ridge for a greater distance than on The Shop's 3 1/4" honing band. Fatigue has a definite effect on the quality of result when sharpening manually and the shorter stroking distance is a definite plus to lessen errors due to tiredness. A straighter, far less crescent pattern can be more easily achieved. The more even and equal the tooth contact, the better. The scraped 3 1/4" band also has a more efficient grinding rate than a 5" to 6" band on the same diameter disc due to a higher average surface speed and more grit grinding by sitting on a more accurate and solid surface.

"Tooth contact pattern" refers to the "footprint" of the blade. How the teeth will contact the teeth of the opposing blade determines how well and for how long a blade will cut. The optimum contact pattern is an equal amount of surface contact on all the teeth. This distributes the spring pressure and cutting load equally and will allow for even wear. Each tooth will cut the same as the others, lessening the tendency of one or more of the teeth to fail prematurely. By rubbing a freshly ground blade on an accurately ground test block, the high points will be burnished and can then be seen visually. This reveals the "tooth contact pattern". On a hollow ground blade, the contact should be primarily the tips of the teeth and at the back of the rear rail. The amount of hollow grind and how much pressure is used in the rub test will determine how much contact area is burnished and how far down the teeth it shows. On a flat ground blade virtually the whole surface should show contact. This test procedure checks both the integrity of the disc surface and the grinding technique used. Test cutting does not reveal tooth contact.

We believe hand sharpening can be done skillfully most of the time, but all of the time is what is required. Precise control of the blade as far as placement on the disc and maintaining even pressure as the blade is being ground is imperative for an accurately sharpened clipper blade. We manufacture our automated mechanism to eliminate the inconsistency of doing blades manually. By traveling back and forth on the disc parallel to the center line of the disc with constant and equal pressure on the blade, the true profile of the hollow grind ridge is accurately ground into each and every blade. The result is superior cutting and maximum blade life.

Disc diameter does not determine the hollow grind or blade life. There is a misconception by many people that disc diameter and grinding speed play the determining factors in the hollow grind and sharpness of blades. We have proven results that show that better than factory results can be achieved on discs of any diameter clear down to 6" if the proper angle is machined into the plate and then the surface scraped for accuracy. Any amount of hollow grind can be achieved no matter the disc diameter. It is the angle that it is machined to that determines the amount of "hollow" it will grind into a blade. Keep in mind that the disc profile is somewhat irrelevant unless it is accurately transferred to the blade by using proper sharpening techniques.