The Harbor Freight 96687 Circular Saw Blade Sharpener.

I bought this in April, 2010, at my local HF store. Normally $70, they were
on sale for $60. And in the advance sale flyer they handed out, there's a
coupon for only $50, valid in a week or two.

I also bought a package of 2 spare wheels (one diamond, one emery) for $10.

I searched the web to see what other people had to say about it. Mostly I
just found postings asking for owner's opinions. I did find one page on a
welding site describing using one for sharpening metal-cutting cold saws.
He said it worked out quite well. The next step up that I've seen in
circular blade sharpeners suitable for a home shop is on ebay from a couple
of sellers in China and costs about $400 ($270 + $130 for shipping). It
looks like a substantially nicer machine from what I can see in the small
pictures. I'd sure like to try one. (Donations to the fund will be
gratefully accepted!)

First of all, I'd say the sharpener is easily worth its price. It takes a
lot of experimentation and learning and practice, and quite a bit of setup
time converting from one tooth angle to another. And its tooth alignment
registration stop pawl is tricky to adjust for the right grinding wheel cut
on the tooth. It badly needs a fine adjustment mechanism of some sort. The
knob that holds the blade-holder arm in position is hard to get tight
enough. The pivoting arm that the blade tooth registration stop slides on
needed to be smoothed with a file, and moving the stop is still a bit
jerky. Changing the grinding wheel is made a bit inconvenient by the 3
small screws that hold the wheel guard side onto the rest of the guard. So
far I've been leaving it off while I'm experimenting.

The instruction manual is minimal. The parts are not well identified and
there is no picture or drawing of the machine set up and ready for use.
There is no information on actually sharpening a blade. You have to already
know how to use the grinder before you get it, or else teach yourself to
use it. It might be nice to have an old scrap blade or two to learn on.
It's not really too bad, though, because it doesn't take off much metal at
one time, so you're not too likely to totally ruin a blade. It does take a
lot of fiddling to get the angles set right for the bevel angles and to get
the cutting edge of the tooth parallel to the wheel.

But the machine is a lot handier than trying to keep consistent angles with
a file as I go around a circular blade in a vise. And it does carbide. I
know - I can use diamond hones on carbide tips, but that's really slow. And
it's hard to keep the tooth surface flat.

So far I've had the grinder for about a week and I've used it on three
steel blades and a carbide one. I can't sharpen the sloping top of saw
teeth. The grinding wheels just work on their edges. Well, the diamond one
for sure, because it's a very thin steel plate. The emery one might be
usable on its rim but it's very narrow. The wheel tapers to a thin edge on
the outside or right hand side. In the instruction manual is a diagram
showing grinding the top of a blade tooth with the edge of the wheel, but
the wheel shape in the diagram is not the same as the wheel with the
machine. The rim of the wheel would need to be a bit wider and beveled
instead of thin and rounded.

If you're not already quite familiar with sharpening principles like
clearance angles and judging surface flatness by the bright spots left by
filing or grinding, don't buy the machine. If you can't teach yourself or
you don't want to experiment, learn and practice then don't buy the
machine. If you're in a big hurry to get your sharpening done, don't buy
the machine.

But if you are patient and like learning new skills, then it's a fun and
rewarding purchase.

I recommend it.