Oh no! There you were, using your clippers on your dog, and suddenly the clippers started chewing the hair rather than cutting it, your dog yelped and jumped, and you couldn't seem to make the darned things work! What went wrong?
Rule number one: Never clip a dirty dog. The dog needs to be oil free and have no dirt on him whatsoever. Dirt and oil will dull your blades faster than anything else. When a blade begins to drag through the coat and chew the hair it pulls the hair instead of cutting it, which is why your dog yelped.
Was your dog completely dry? Damp hair has a way of clogging the blades on a clipper. This is especially important for dogs with thick coats, like Chow Chows. Thick hair has a unique way of clogging up your blades.
The first thing to do is to use some blade wash. The blade wash should be in a little dish, not too deep, maybe a half-inch or so. Run your clippers with the blades attached in the blade wash for a few seconds, just covering the cutting edge. You should hear a difference in the clipper motor; it should sound like it's running faster. Then take the clippers out of the blade wash and continue running them upside down so the blade wash can drip off. You do not want any of the blade wash to get into the clippers because this will ruin them. Turn off your clippers and use an old lint-free rag to wipe the blades dry. T-shirt material is absorbent and works great, so save a couple of old ones to cut up for clipper rags.
Clipper issues are the top reason people stop grooming their own pets. They get into a hurry, don't bathe or dry the dog first, and they are never instructed how to clean the blades. Of course they no longer work! If you are using very inexpensive clippers that are not meant for clipping animal hair, you can expect clipper issues.
If you look into the blade wash, you'll probably see the hairs that were clogging up your blade — miniscule hairs that bunch together and can stop clippers in their tracks. Ideally, you should use your blade wash every time you groom, and you may need to use it while you are grooming. Blade wash will help clean out your blades, but you also need to keep your blades oiled. Some blade washes, such as H-42® blade cleaner, are dual purpose. They contain a lubricant, so you can wash your blades, wipe them off, and be done with it. You do need to wipe the blades off thoroughly or you'll end up with a greasy dog.