Civic EG

My Honda's drain plug threads on its old oil pan stripped so I bought an oil pan from You Pull and Pay. I attempted to install this oil pan this last week with the help of my brother. While he was torquing the oil pan screws down one of them snapped. I was able to get the the screw out using a small screw driver and loosening the screw (putting the flat head on a jagged part of the remaining screw). I then spent precious study time after school to work on it (later that week). Again, an oil pan screw snapped (in a different place this time). This was even with a new screw we bought from a local hardware store. Slightly more frustrating this time but I was still able to get out the rest of the broken screw with a flat head. The two screws both seemed to have broken off with just over half of the screw being inside the threads on the block. The screws are being torqued down to the amount which our Heynes manual orders (I believe it's around 10 ft/lbs). So I'm confused on why the screws keep breaking. Could it be a bad torque wrench? Have we coincidentally just used two defective screws? Thanks in advance for the comments.

Are the threads clean? debris in the threads can cause the screw to not go in all the way. As for the torque amount, 10 ft lb is hardly anything. That's like tightening with just using your thumb and index finger to hold the wrench. If you're cranking down much harder than that, I might suspect a defective torque wrench.

Also that 10 lb/ft is for a 10.9 grade screw which is what the OEM Honda hardware should be. The stuff you are buying at the hardware store is probably 8.8 or worse which you can't apply that same amount of torque to.