Mobile Sharpeners: Can Their Sharpening Equipment Get Out Of Calibration Because They Are Mobile?
February 02, 2014
Yes it can, the calibration does get off when doing mobile sharpening. I did mobile sharpening in 5 states down here in the south before I went strictly mail-in for 15 years. Even though your equipment is solid in your van or trailer, going over bumps, hitting pot holes, and going over railroad tracks does vibrate the calibration off. I would check my calibration weekly on my automated blade machine, and the arm position on my scissor sharpening machines. Most times they were still dead on, sometimes they were off just a couple thousands, but that little variation can cause a scissor to fold at the tips, and blades to fail the rub test (explained later on).
In my sharpening shop, the scissor machines never move, but when I roll my two automated blade machines around to clean or when I change the sharpening plate, I check the calibration of the automated arms. Once in a while I have to adjust, but its nothing like when I was on the road bouncing around all the time. Bad calibration can really shorten the life of the cutting surface of the blade because the hollow ground of the blade isn't centered correctly.
I've taught several sharpeners who purchased the same equipment I use the importance of getting the blade centered on the hollow grind of the plate, and not assume the factory marks on the automated arms were correct. And also to check the calibration weekly of their automated machine. Bumpy roads can be certain death to an automated blade machine, but taking the time to check calibration will prevent alot of very angry customers when the blades start to have issues.
Whats “Hollow Ground” on a blade?
Blades dont have flat surfaces like it seems when you look at them. The cutting surfaces are "Pitched" a few thousands so the tips of the cutter teeth, and the very rear of cutter touch the blade underneath it. This enables the blade teeth to cut like a tiny pair of scissors as the teeth go back and forth across each other. If they were flat, they would snag in the first inch of hair you tried to cut with them. Sharpening plates aren't flat either, they are pitched as well to grind this "hollow ground" as we call it to make the blade work. When the blade is put on the plate to be sharpened, the very center of the blade must be in the center of this pitch. If its past the center, or short of the center, cutting life is shortened.This is where calibration is so important.
Hollow ground is checked by rubbing a freshly sharpened cutter blade on a flat steel plate (test plate), sharpeners call this "rubbing the blade out". After you rub it on the plate and turn it over you can see a small shinny area across the very tips of all the teeth, and areas on both sides of the back rail, this shows pretty good hollow ground. If the entire tooth is shinny , its out of calibration too far. If the teeth are shinny on each side but not in the middle of the blade, the calibration is too short. Sharpeners who use a manual sharpening machine (one without automated arms), have no calibration to check. Creating a good hollow ground depends on holding the blade in their hand with a magnet, and going back and forth across the plate trying to keep the blade as straight as they can. With a manual machine, every blade is sharpened differently, and the variation can be enormous.
Here is a question to ask the sharpener your currently using : "When was the last time you checked the calibration of your equipment"? or "Do you rub blades out to check the hollow ground"? If you get a "NO" for either of these questions, that sharpener has no idea what kind of work they are putting out. The blades may cut good now, but for how long? Another reason to rub blades out is to check if the machine is indeed grinding a hollow ground blade. Sharpening too many blades on a sharpening plate will decrease the hollow ground capability of it, and the blades will be sharpened flat and will not work long if they work at all. If a sharpener rubs out blades religiously, and sees the shinny area on the tips of the cutter teeth start to come down the tooth, its a signal to change that sharpening plate.
I know this was kinda long, but Im hoping to have some sharpeners as part of my audience, as well as interested groomers. It may actually let a few sharpeners re-evaluate what they are doing to insure they are putting out good work for their customers. Those that are doing this already know what Im talking about and will agree "Its better for YOU to catch a potential problem, and not let your customer catch it for you". Calibration is an important part of the sharpening process, and the customer perspective of our work is something we never want to get tarnished.
Now everyone knows more than me about all this, and its good to know as a groomer what it takes to ensure your blades are sharpened correctly. Knowledge is power!
Have a great day grooming, and read those labels.
Jeff, just letting you know I am a sharpener in Eustace Texas, (Hoss's Clipper House) and have enjoyed your blog. I've learned a few thing from you in the short time I have been reading them. Like you, I try to educate my clients about proper care and handling of their blades and scissors. Thank you for sharing.
Posted by: John Haverly | August 22, 2016 at 07:51 AM