You might want to think about some bigger gears - mod 2 or 2.5, ideally the biggest you can fit in within reason. 1.5 isn't terribly strong when you're considering that you'll be violently stalling the system, possibly reversing direction while moving the axe at high speed if you mess up a bit with the timing, that kind of thing. You might end up breaking a tooth.

On an 8mm shaft, you may get away with grubscrews and red (the strongest) loctite, but you'd be better off with a keyway in the shaft and gear (might be a bit small for that) and a machine key, shaft and gear with a flat side to the hole / hex shaft and hub / whatever, or another method of torque transfer. Grubscrews shouldn't be used to transfer significant torque, that's not their job.