Positive (ad nauseum) musings about negative rakes
 

Scraping hard end grain with a negative rake scraper is 'in' these days
and a commercial tool, like night follows day, has predictably appeared
in our catalogs.

What is this all about, anyway? What is negative rake? Which is raked
negative, the long or short bevel? Which bevel is positioned up when
negative rake scraping? Is the arris on the front of my Viking hook
tool that prevents dig-ins a negative rake scraper? I guess you can't
have a scraper's edge without two surfaces (bevels) meeting somewhere.
Does their included angle determine rake? If I tilt the flat top
surface that completes my standard scraper's bevelled edge downward with
the handle upward and the edge kept above center inside and below center
outside do I have in effect a negative rake scraper? With a lantern
type tool holder I can change top rake on my metal lathe without
grinding the bit.

I'm probably just changing semantics instead of rakes; positive,
negative, neutral, relief, clearance, whatever. I'd sound even more
like I know what I'm saying if I could work in "proprioception",
"chatoyance" and "chiaroscuro" in an off-handed manner. I don't and I
can't. :)

I sure would appreciate it if some of you would waste some information
(empirical or scientific) on me and maybe a few others about scraping
with negative rake.


Turn to Safety, Arch
Fortiter



http://community.webtv.net/almcc/MacsMusings

Positive (ad nauseum) musings about negative rakes
 

Hi Arch

Maybe empirical but certainly not scientific, we do know the dollar
value of "NEW" or "IMPROVED" tools, and all your troubles will be over
if you use the "NEW" tool !!!
I would put the negative and the positive and improved, the
oval-----....---- skew/scraper/etc. tools all in the same category,
they must work for someone at sometime in some way I think, then again
???? WHAT was wrong with the old one ?? , have to learn to use them ???

Always blame the tool, right ??

Have fun and take care
Leo Van Der Loo

Positive (ad nauseum) musings about negative rakes
 

Arch,
I didn't think it'd be you who would immediately bring up another scientific
versus reality topic?!!
I agree with all you said and Cindy Drozda agrees, too. Only she swears it
makes the difference between white knuckle work and pleasurable turning; and
can't tell you why but it works!
Cindy did a demo around here about a month ago and boxes are her specialty -
end grain work. I'd have to go back to my notes to see what her bevel angle
was but the "negative rake" angle I recall was about 5 degrees off the flat
of the scraper.
I just did a box today and used a scraper lifted off the rest so as to get
it to work. Hell, maybe I created that "perfect" angle and the difference is
that they get to keep it flat on the rest and parrallel to the ways at
center point.

I'll tell you one thing I tried today that worked SWEET. Bill Grumbine in
his video and Ellsworth, too, have this thing of bringing the wings of your
gouge up about 45 degrees to the rest and the wood, then barely cutting into
the oncoming wood. Put your sandpaper away. First do the Ellsworth thing of
scraping with the lower gouge wing to get those fine sweeping, rutless,
curves and then get that great finish shearing at 45 degrees to remove that
last little end grain tearout. DON'T be aggressive or you'll get hurt.

I guess you can't
have a scraper's edge without two surfaces (bevels) meeting somewhere.
Does their included angle determine rake? If I tilt the flat top
surface that completes my standard scraper's bevelled edge downward with
the handle upward and the edge kept above center inside and below center
outside do I have in effect a negative rake scraper? With a lantern
type tool holder I can change top rake on my metal lathe without
grinding the bit.

Positive (ad nauseum) musings about negative rakes
 

Arch, negative rake scraping isn't new but it has been newly
discovered. When I first tried a negative rake scraper it didn't
impress me so I put it back on the tool rack and forgot about it. After
watching Stuart Batty demonstrate one I decided to try it again. My
tool is 1 x 3/8 inch. I reground it to a steeper 45 degrees on both
sides. I was turning a nice piece of quilted maple. It's difficult to
get a good surface on good tight quilt because the grain is constantly
changing, resulting in small tear-outs. I couldn't get a good enough
burr on the tool with my 60 grit wheel, so I went to a zircon 60 grit
belt on my 1-inch belt sander. This worked very well. I used the tool
level, and renewed the burr every 10 or 15 seconds. When the burr was
gone it didn't work at all. The quilted wood smoothed up very nicely.
I'm impressed. I think that it won't work well with very soft wood, in
fact the harder the wood the better it works. Because of the negative
rake, the tool isn't apt to dig in as it will when the tool is ground
in the conventional way. It's not to remove wood, just to smooth it up.
Use a very light touch. If you want to give it a try, just put a good
burr on a skew and have at it.