I am in hopes that you will use this machine awhile and then post a fine review. Not only am I very curious about these machines maybe it will shed some light into the murky replies I get from my dealer and perhaps others on this site. My dealer has one and will sharpen only those blades that are pretty straight and simple. For example he will sharpen most blades on lawntractors and ZTRs but not most push mower blades. He claims that his machine will not do those blades like mulching blades for example. I have always wondered if he is just to lazy to reset his machine, does not want to bother, has a problem with liability, or if a person needs a different machine for different blades.
Possum , Allow me to comment on the murkiness and dealer knowledge. He probably knows he cannot grind "rotary" or "twist" blades , but not why. A straight blade will lie obediently on a straight flat grinder bed and allow constant angle cutting edges. A blade with twist cannot be sharpened accurately on the same machine. A twist blade must be ground on a "finger" which supports the cutting edge as it spirals accross the grinding wheel surface. Although I have never seen or used a rotary lawnmower grinder the process described is how tool room grinding is done. The machines are expensive and use "air bearing spindles." If you have not choked on this explanation , read on.
I looked at you tube demo of a flat blade lawnmower grinder (make unknown) . I can see the appeal of such a machine but they look expensive and IMO (based on you tube) they are wasteful of blade material and of the pink wheel used ($$$). Further , although they could perform a secondary blade "clearance" grind behind the cutting edge , this was not shown. (to narrow the blade taper).
If enthusiasts do not have ?$600? ?$1000? to invest in such a machine I suggest "freehand" grinding tutuorial in this forum which accomplishes as much or more as the machines. Your $mil hands and senses can follow the twist blades when the flat grinder cannot. The cheap grey grinding wheel will work well at 1/4 the price of pink or white. :smile:
PS A rotary lawn mower blade has much in commom with a metal cutter. It demands (I'm pretty sure) quite accurate and constant blade dimensions as it cuts by passing a scissors-like edge accross a fixed cutting strip ( don't know what they call it). Since the blade set is a cylinder locked into position if each blade is not identical only some blades will cut. On the other hand the scythe config of (at least my) Craftsman blade only demands a good edge which need not be perfectly straight. Another reason the latter can be hand ground. Hope this helps.