Do you actually have one?

In fact there are a broad range of accessories including a whole
variety of abrasives. One has to shop around to find the best
prices, which are not at all expensive.

If you are using a Rotothingy to do anything other than very crude
hacking of holes, then you deserve the results that you have
experienced with cutting pipe.

I find that I use my Multimaster very regularly. In fact it hardly
goes back in the box.