I recently purchased a used SAM Pro-Master from a guy on these boards. According to him (and according to the pull counter), the machine only had about 30 racquets strung on it. It seems practically like new. Anyway... In stringing three racquets thus far on it (and I am a newbie), I've had trouble with the string popping out of the clamps when doing the first few mains. (The clamps are five-tooth diamond dusted.) To alleviate this problem, I tightened the clamps, but I am very afraid they are now too tight and could damage string. I managed to successfully complete three racquets, and all seems fine with those sticks. Today, I was attempting (I gave up to write this post) to string my first gut job. (Wow - what coil memory!). I loosened the clamps slightly to avoid damaging the gut, but now the string is still popping out of a completely locked clamp when I pull tension. I tightened them slightly but am still having the problem. When the string pops out, I can see a tiny white cloud of dust where some of the diamond dust is coming off. The clamps are tight enough to make little white teeth marks on the gut but not tight enough to hold the string. Very frustrating. Any tips/advice would be greatly appreciated. Do the clamps need cleaned better? Do they sound like faulty clamps? Could it be operator error? I have un-used three-teeth clamps for badminton racquets. Should I try using those instead? Thanks.