What's the secret? I have a Whall clipper to do the Schnauzers and the blades are about $20 new so, I figured I could surface grind them. I jigged them up and took about .010" off top mating surfaces and I thought I did a good job but they don't cut at all and I can't see why not. The look like they should! Am I missing something? Are they magic?
My wife was doing the dog grooming thing for a while. Visits from the sharpening guy were at least a monthly occurance sometimes more often.
The sharpener that he used was pretty much the same to look at as the Glendo sharpeners that you see advertised in Home Shop Machinist, with a slow moving abrasive disc. The sharpening guy went on at length how the lap had a special radius on it to sharpen the blades better than one could do by other means, but it sounded of tripe, and I would not stake too much money on a bet that there was any or a lot of curvature to it.
You are carving off about half the available material at .010" . Think in terms of knocking them down in steps of .0001" to .0002" at a time if you wish to not be buying new blades frequently.
They are lapped on a plate that is very slightly cone shaped to produce a slight hollow grind. Most sharpeners charge around 5 bucks or so a set to do. It's work I don't pursue because of the airheads in the haircut industry. The lapping machine might remind you of a record player.
Blades for cutting hair need a little 'tooth' to keep the hairs from sliding away from the blades as they close. So a polished edge, like you'd use for a woodworking plane, isn't worth a damn for cutting hair. You might consider grinding the edges with a coarser grinder wheel than you'd otherwise use. People who sharpen scissors for a living use a special file to give the edge the tooth; I can't think of the name of it offhand but it's something like 'veining file', or something like that.
It depends on the clippers. Some clippers are sharpened flat and others are supposed to have a slight curve in them. The sharpening is done on a lap which basically a slow turning plate laid flat and charged with abrasive.
Out in farm country, shearing cutters are sharpened on a dry lap, have seen improvisied ones made from a flywheel using clover or diamond grit. There's also a fixture to hold the cutters and combs. You can improvise with a piece of plate glass and valve grinding compound figure 8'ing the cutters, or a sheet of 180 w/d on a flat plate.
I've gotten by on a 12" disc sander using a homemade holder-- light touch-n-go--- course grit on larger blades fine for smaller.
Scissors don't cut... They shear... They need not only to be sharp but the blades need to touch... Loose scissors don't cut... Also the sharp part of the scissors is the part that needs to touch... Some blades need sharpened on the mating surface also...
The magic is a 15" disk with a 0.5 or 1.5° taper (I can't recall which). Glue on grit is 60 to 220. 800 rpm. Blade or comb is placed close to outer edge with abrasive advancing against the point of the teeth.
This slightly concave surface insures the cutting pair contact at the teeth points and the heel. Last time I checked, retail for the disk was $510.
Can someone quickly tell me what the surface radius would be at 15"?
Tom, Re-read Bam's reply to your question about sharpening clipper blades. What he said is correct!
I have a sharpening business, and although I don't do clipper blades myself, I do know how they are done, using horizontal flat honing/sharpening machines.
They are sharpenened on a horizontal spinning, flat-appearing plate, which has an abrasive mixture of grit and lard oil applied to the plate. The blade(s) are held such that the teeth are oriented radially.
The sharpening plate is ever-so-slightly domed, meaning that it is slightly higher in the center, compared to out at the periphery. The difference in height between the center and the peripehery varies, depending on who manufactured the plate, and what type blades are to be sharpened on that particular plate.
So, if you lay a straightedge radially on the plate, you should see that the plate is flat, but the straightedge isn't quite horizontal. It's higher near the center of the plate. Hence the dome shape of the plate. It helps if you visualize a dome-shaped plate, but one which is tall rather than flat, and you imagine applying a flat blade to the dome, you'll see how the blade ends up with a hollow grind.
The reason for the dome shape is to produce a hollow grind on the blade surface being sharpened. Most clipper blades are sharpened with this hollow grind. And you might be interested to know that all scissors also have a hollow grind. If you open up any scissors and examine the inside of the blades (the surfaces facing each other when the scissors is closed), you'll see this hollow grind. This hollow allows the two blades to cut together, and also maked the edges a bit thinner/sharper.
What I have described is how blade manufacturers sharpen new blades, as well as any knowledgeable sharpener. And each time a blade is sharpened, you only remove perhaps a few thousands. So, if you removed the hollow when you sharpened the blades, they probably won't cut.
I would also add that often even perfectly sharpened blades won't cut, due to problems with the clipper malfunctioning, or being improperly set up or misadjusted.