you would likely know if you had a diamond cutting wheel or not... they're quite silver and shiny

also they cost much more than normal cutting wheels - I couldnt say whether you had one included in your pack when you bought it, altho I would lean towards the fact that you're using standard cutting wheels and not diamonds. diamond wheels cost ~$6 apiece if i remember correctly, but you will go through one in the same time you might go through 6 normal ones, or more.
I agree with mel, if you could c-clamp the blade to a table and then cut the handle off that way, you'd be much safer. and even then depending on how close to the handle you clamped down, if you still have vibrations you just need to steady the handle with one hand which should cut out a lot of unnecessary A)danger and B)wasted blade movement which likely is resulting in much less effective cutting