Spade Bits into Chamber Bits

[sunriseboy]

When a spade bit is converted into a chamber bit, are the two cutting edges to be maintained when the rounded edge is completed. Or is the entire edge to be made sharpened as in a knife blade?

 

[ebklodt]

The ones I use from Vermont Freehand are ground on two sides both with an edge.
I have not had to sharpen mine as I do most my drilling with modified S&D bits or freehand drill with spoon bits.

 

[sasquatch]

Think of a spade bit as a rotating chisel. When you round one off to a pipe chamber sort of shape, you want the leading edge to be cutting and the trailing edge to be probably not touching at all, so there's an opposing bevel on either side. You can shape the thing to be less wide "up top", sort of tear-drop shaped, so that the sides of the bit aren't really doing anything after it reaches whatever maximum width you have on the fat part of the tear-drop too.
Having them cut well, evenly, and fairly sharp is far more important than the actual shape.

 

[sunriseboy]

Thanks for that. That's just what I wanted to hear.