Some cats are easily overstimulated - particularly male cats. When that happens, they often bite. The trick is NOT to overstimulate him, or to read his physical cues so that you'll know when he's becoming overstimulated and stop petting him before he reaches the biting point. If his cues are too subtle for you to read easily, then simply don't pet him when he cuddles up next to you. Just enjoy the closeness without any actual petting.

If you can't resist petting him, and you can't read his cues before he bites, then you'll need to address the biting when it happens. In that case, blow HARD directly into his face at the exact moment when he bites. Cats aren't stupid. If you time the blow correctly, he'll easily make the connection between his bite and your blow.

Laurie

Here is some information from a veterinary journal:

Petting-induced aggression

Some cats that are not fearful, in pain, or exhibiting any of the other emotional states described in this article bite while being petted. This problem can be disconcerting for the family. Such cats often seek attention, crawl into laps, or rub against legs and seem to enjoy the initial physical contact. But after a certain amount of petting occurs, the cats suddenly bite and run off. It seems that these cats have a threshold for how much physical interaction they can tolerate and cannot communicate that they have had enough in an acceptable manner. However, an observant owner knows when a cat is about to bite since the cat usually shows signs, including fidgeting, tail twitching, tenseness, leaning away, flattened ears, horizontal retraction of the lips, and hissing.

Treatment. Instruct the family to never absentmindedly pet the cat. Desensitization and counterconditioning should be attempted only when the cat voluntarily approaches. The threshold for the bite behavior must be determined, and petting should stop well before the threshold is reached. For example, if a cat always tolerates five seconds of petting but may bite after that time, then petting sessions should initially be three or four seconds. If the cat shows no sign of anxiety or aggression, it should be offered a tasty food treat. The owner should consistently say "good kitty" or some similar phrase every time the cat takes the treat. To encourage the cat's participation in the petting sessions, the sessions should be held just before feeding time and food treats should be withheld except during training. If the sessions take place on an owner's lap, the cat should not be restrained and should be allowed or encouraged to jump down (a treat can be tossed to the floor if necessary) as soon as each session is complete.

Sessions with the cat in someone's lap or next to someone on the sofa should be frequent, and, gradually, the length of the petting sessions should be increased. With time, the cat will learn to tolerate longer and longer petting sessions in anticipation of a food reward. Eventually, the treats can be phased out, and the cue words good kitty can be used without food to promote a relaxed state.

Physical punishment has a high chance of backfiring, isn't conducive to trusting relationships, doesn't address the root issue (only the symptoms of it) and isn't even necessary. There are kinder ways to deal with behavior modification.

The goal is to find out why he's biting. Cyalexa and Camlam both gave very good advice. It sounds like he either becomes fearful or becomes over stimulated. Reading his body language should determine which and you can work on addressing the problem. If he's fearful, work on counter conditioning and building trust and confidence. If he's over stimulated, try to drain some extra energy before engaging in petting him and promote calm behaviors and short sessions.

Another thing you can do is keep a toy handy. When he becomes nippy, redirect him to the toy. Either a soft one for biting or a lure toy. He can learn bite inhibition this way. Rough play or stress is directed to the toy as an outlet, not to you.

I think this all makes sense about him being overstimulated and me having to stop just before he starts biting. I've already observed his behaviour a little after reading these posts and I agree that this is what is going on. It's tough because I'd want to cuddle 24/7 with my pets if it were up to me!

My cat likes to bite or swat, but she gets a certain look in her eyes when she's reached that point. I try to limit the petting when she is in a playful mood or when she's on high alert from watching birds and squirrels through the window. It's best to pet her when she's relaxed and sleepy, or first thing in the morning.

phish my cat does the same, one minute she's enjoying the petting and then it just gets to a point where she'll start biting, although I can usually tell before it gets to that stage. If she starts biting, I just slowly pull my hand away and stop petting her. It's like a fine line sometimes with cats between pleasure and annoyance, and as laurie said, if you sense that the biting is about to start, then you need to just stop with the touching and just let them be near you. I wouldn't scold her for it, just back off with the affection and let her just be there at that point.