[Herb Stoops]

The only time I used a spiral bit was making sink cut-out in vanities,and I don't remember which it was up or down. All my bits are straight and I am happy with them.
Herb

 

[Herb Stoops]

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.

That was my thinking too ,but it does not make them more inefficient than before. They run from 1/8"-$22., to 1/2"-$93 new, so it wouldn't pay to resharpen the smaller ones, when shipping is included, IMO.
Herb