MIDI sync issues

[mnoxious]

Ok I'm new to the whole syncing midi devices up to each other etc i've always avoided it. Anyway here's the situation... the other day we laid down some vocal and keyboard tracks down using the singers drum machine to establish the BPM. Then we tried tracking using a different drum machine set at the same BPM as the singers drum machine. Well they didn't sync even though the new drum machine triggered the recording. So do drum machines have the same clock from day to day? That is could I slave the new drum machine to the original drum machine and just use the singers drum machine as the master clock? Would it matter that we are doing this days later? Any input or references to material I could read on this subject would be great. Also would there be any advantage of me purchasing a clock source like MOTU Digital Timepiece to be able to slave them both on separate days? Would they be exactly in sync? Any help is appreciated.

Thanks,
Mark