I bought this to use with my XtremepowerUS jackhammer. Shaft and key fit without problems. I've used it to break up tightly packed clay full of shallow surface roots. My original plan was to loosen the trench and then dig it with a shovel. The router is unlikely to scratch the surface. After breaking 2 shear pins I gave up the tiller. I was able to easily break up a hard pack with this shovel. Then go back to the original plan to plow and dig it up. This is the widest shovel or chisel I could find. 8", 10" and 12" wide versions would be nice.