Diagram showing clearance angle for an ice auger.  Information taken from http://acwc.sdp.sirsi.net/client/en_US/default/index.assetbox.assetactionicon_0.view/1024624?rm=ARCTIC+CONSTRU0%7C%7C%7C1%7C%7C%7C0%7C%7C%7Ctrue and based on a diagram there.
Own work
Mike Christie