Greetings,
Lee's "Sharpening" has a jig for setting blade projection for the Eclipse
honing guide. I'm making one. The objective is to easily set the guide for
bevel angles other than the standard 25 and 30 degrees. In order to place
the pegs, I had to do the trig. Turns out that although the imprinted
instructions are in millimeters, the device (mine, anyway) was
manufactured in inches. Having been through the trig, and discovering that
one doesn't have to account for the changing tangent of the surface to the
roller (sigh of relief), I asked my spreadsheet to make a list of
projections for various bevel angles. I post it here for y'all to file and
forget. Someday, someone will google for the info, and here it'll be. Note
that the values in the imprinted instructions differ from my analytical
values. The table is free; so what if no one will need some of the extreme
angles!
Bevel, degrees
Chisel Projection, mm
Iron projection, mm
15 83.8 104.6
16 77.0 96.4
17 71.0 89.2
18 65.7 82.8
19 60.8 77.0
20 56.5 71.8
21 52.5 67.0
22 48.9 62.7
23 45.6 58.7
24 42.6 55.0
25 39.7 51.6
26 37.1 48.5
27 34.7 45.6
28 32.4 42.9
29 30.3 40.3
30 28.3 37.9
31 26.4 35.6
32 24.6 33.5
33 22.9 31.5
34 21.3 29.6
35 19.8 27.8
36 18.4 26.0
37 17.0 24.4
38 15.7 22.8
39 14.5 21.3
40 13.3 19.9
41 12.1 18.5
42 11.0 17.2
43 9.9 15.9
44 8.9 14.7
45 7.9 13.5
--
"e to the x du dx, e to the x dx,
cosine, secant, tangent, sine;
3 point 1 4 1 5 9,
Go Tech!"
On Thu, 16 Sep 2004 10:40:34 -0500, Australopithecus scobis
<[email protected]> wrote:
>On Thu, 16 Sep 2004 15:55:52 +0100, bugbear wrote:
>
>> There's a fundemtal glitch. If ya' wanna be dead nuts
>> accurate you have to allow for the thickness of the blade.
>
>Exactly. It matters for the plane iron. The table I provided is
>for stock 3/32 irons. Your point suggests I should supersede my post to
>make that clear. Thanks for the reminder.
The taper on the body of a chisel makes it very difficult to come up
with a chart as you need to know the thickness of the body of the
chisel along a line passing from the center of the roller and normal
to the top (not upper) surface of the chisel.
My chisels are tapered anywhere from 1.5 to 6 degrees.
If you start out with a blade that's been ground at too sharp an
angle, then you could measure the projection of the heel of the
original bevel. You could then sharpen until the new heel meets up
with the original heel, and the thickness of the blade would not be a
factor.
Australopithecus scobis wrote:
> Greetings,
> Lee's "Sharpening" has a jig for setting blade projection for the Eclipse
> honing guide. I'm making one. The objective is to easily set the guide for
> bevel angles other than the standard 25 and 30 degrees. In order to place
> the pegs, I had to do the trig.
There's a fundemtal glitch. If ya' wanna be dead nuts
accurate you have to allow for the thickness of the blade.
Fortunately the actual angle is NOT critical, but
repeatablility between successive sharpenings
is very useful.
BugBear
On Wed, 15 Sep 2004 23:27:25 -0500, Australopithecus scobis
<[email protected]> wrote:
> Lee's "Sharpening" has a jig for setting blade projection for the Eclipse
>honing guide.
Just as an aside, don't use one of those Eclipse-style "unicycle"
guides on a waterstone. Soft stones will develop tramlines faster than
the iron gets sharpened.
--
Smert' spamionam
On Thu, 16 Sep 2004 15:55:52 +0100, bugbear wrote:
> There's a fundemtal glitch. If ya' wanna be dead nuts
> accurate you have to allow for the thickness of the blade.
Exactly. It matters for the plane iron. The table I provided is
for stock 3/32 irons. Your point suggests I should supersede my post to
make that clear. Thanks for the reminder.
--
"Keep your ass behind you"
On Fri, 24 Sep 2004 13:43:09 -0500, Ed Bailen wrote:
> The taper on the body of a chisel makes it very difficult to come up
> with a chart as you need to know the thickness of the body of the chisel
> along a line passing from the center of the roller and normal to the top
> (not upper) surface of the chisel.
>
> My chisels are tapered anywhere from 1.5 to 6 degrees.
>
> If you start out with a blade that's been ground at too sharp an angle,
> then you could measure the projection of the heel of the original bevel.
> You could then sharpen until the new heel meets up with the original
> heel, and the thickness of the blade would not be a factor.
Always measure the projection from the cutting edge to the front face of
the jig. We don't care about the back of the bevel; it could be hollow
ground Kirby-style.
For plane irons, thickness matters. For chisels, it does not matter. The
back of the chisel is held in a fixed, known position. The geometry does
not change with chisel thickness. The Eclipse doesn't care how thick or
tapered the chisel is; the projections work. True, it is a PITA to clamp
tapered chisels in the Eclipse. I find that narrow and tapered chisels
wobble from side to side, so I do them freehand while dreaming of a
Veritas jig.
--
"Keep your ass behind you"