Hi There, This is Ken, and I'll answer your question!
Your choice of tool depends somewhat how large a diameter hole you want. If you are thinking fence post holes or a 3 ft. diameter for a well, then these do not apply. However, the basic difference between roto-hammers and hammer drills and jack hammers is that the first two are used for drilling round holes (normally less than 12 in. deep), where as a jackhammer uses various types of chisel bits, and creates an irregular and much larger hole, and can go much deeper.. Here are two videos for you to watch:
If you have any further questions, please let me know.
I'm looking to create some flat areas (hill side property) and the soil is clay. It is a good size project and if I'm understanding you correct a jackhammer is the tool to use.
What are your thoughts about entry level electrical chinese made jackhammers (Neiko and generic) On a home owner budget which one would be a good buy.
Well, there are Chinese, and then there are Chinese :>) I'm not familiar with the brand you mentioned, although I have made many purchases from Harbor Freight tools (if not available locally, they also sell online) and I have never gotten a bad product, except for one, an impact wrench. The only reason I did not return it is I am currently in Mexico.
If you buy from a place with a written guarantee, why worry?
I know what you mean about clay.I used to live in Sacramento. I destroyed a rototiller there, and wound up using a pick axe.
What you want to look for is amperage. The higher the better. If you have 240V available and can purchase a 240V tool, even better, less line loss on the cord. If you are going electric, be certain to use the shortest cord which is practicable, and as big of a wire size as is possible. As a contractor, for heavy work, I use a 3 wire #12 cord (good for up to 20 amps). It also goes without saying, that you should connect to a ground-fault protected outlet when working outdoors.
Good luck on your project..