[ger21]

Also, an upcut spiral will chip a lot when cutting dadoes and rabbets in plywood. Downcut will give a much better edge.

 

[ger21]

Yes, they are sharpened on the same machines that make them.

I'd be surprised if Whiteside sharpened spirals for free. We usually pay about $20-$25 to have 1/2" spiral bits sharpened. Sharpening a spiral bit is not a fast process, and the grinders can cost $500,000.

And when they get sharpened, they get considerably smaller, depending on how worn they are. The bits we get sharpened usually end up about .015-.02" smaller with each sharpening.