On Thursday, July 7, 2016 at 6:32:45 AM UTC-10, Brooklyn1 wrote:
> On Thu, 7 Jul 2016 01:41:50 -0700 (PDT), dsi1 <dsi10ahoo.com>
> wrote:
>
> >On Wednesday, July 6, 2016 at 7:58:00 PM UTC-10, John Kuthe wrote:
> >> On Wednesday, July 6, 2016 at 5:56:05 PM UTC-5, dsi1 wrote:
> >> > On Wednesday, July 6, 2016 at 4:55:26 AM UTC-10, Janet B wrote:
> >> > > My food processor and Ninja blades are getting dull. Is there a way
> >> > > to sharpen them or must I buy new blades?
> >> > > Janet US
> >> >
> >> > I'd just try sharpening the blades with a Dremel motor tool. How hard could it be?
> >>
> >> What Sheldon said about removing too much material!
> >>
> >> John Kuthe...
> >
> >I'd use a silicon carbide rubber point - that would probably work dandy.
>
> Actually that's about the worst way to dress a blade, you'll only make
> it worse, you'd end up with a blade all wavey and gauged... if too
> cheap to buy a file use the fine side of an emery board, even the
> small nail file on a nail clipper would work and use it as draw
> filing, not cross filing, and cut into the edge, not away from the
> edge or you'll create a burr that will fold over making the edge
> duller than when you began. Remember, files cut in one direction
> only, lift the file on the back stroke or it's all for nought and
> you'll destroy the file... same with a saw blade. Unless you're a
> very skilled/accomplished craftsman do not use any power equipment on
> cutting edges. The highest skilled metal fabricators would always
> choose the method(s) of least risk to accomplish the goal. There
> would never be any reason to use a power tool for dressing one or two
> edges, power tools are reserved for mass production whereas one can
> afford to risk losing a small percentage of parts for achieving the
> benefit of achieving greater production. In this instance one or two
> parts are involved, so I would strongly recommend using only hand
> tools. I happen to be highly qualified in the use of all machine
> tools yet with my own personal applications wherever possible I always
> choose hand tools with cutting edges. I own a professional bench
> grinder but still I hand file my lawn mower blades, and I hand dress
> them often rather than allowing them to become so dull as to require
> machine grinding... it's actually easier and much quicker than
> removing the blades for grinding and than to necessitate removing
> large amounts of metal thereby greatly reducing the life of the
> blades. In case anyone doesn't know rotary mower blades are only
> flame hardened for a small depth of their cutting edge, perhaps no
> more than 3/8", then it's soft parent metal... this to reduce
> shattering from metal fatigue. So anyone who uses a rotary mower it
> behoves to replace blades after about 100 hours of use, before one has
> a terrible accident, the mower user probably won't be struck when a
> blade shatters but someone nearby coucd be seriously hurt or killed as
> though struck with a large caliber bullet... shattered mower blades
> have gone through walls. Rotary mower blades typically shatter at
> their weakest point, where the center bolt goes through.

I've used the Dremel since the late 80's so it's not going to be a problem. I wouldn't use it for sharpening a lawnmower blade - or would I?