Primary bevels with a diamond stone?
Dave G
interest your postings. I just received a Veritas Bevel-Up Jointer
Plane for Christmas so this got me to look again. I have a couple of
comments.
It is also my experience that new plane blades are not sharp enough to
use. Both of my A2 blades (25 and 38 degrees [really 23 and 33
degrees]) from Lee Valley were nicely sharpened with primary and
secondary bevels but looking at them with an 8X loop showed large
scratches all the way to the edge. These would give a person a nasty
cut but wouldn't do much to a piece of oak... I was happy that the
backs were very flat and easily polished.
My standard method is to set the primary bevel with a coarse / very
coarse DMT diamond stone and then move on to the 40/15/5/.3 sandpapers
that you described. My grinder is of poor quality and I restrict its
use to lawn mower blades and such. I don't trust it with a chisel or a
plane blade. Have you ever tried a coarse diamond stone to set your
primary bevel? The very coarse side is a lot finer than the 60-grit and
it does take a few minutes to get them set. By mounting this in a sheet
of MDF I can use the my standard jig and then move right on to the
glass-mounted sandpaper.
Last fall I attended a workshop given by Garrett Hack about planes and
I was amazed how well he could use them. I have always been frustrated
with my planes and realized there were at least two factors for my
problems. First my planes weren't really sharp enough and second, I
needed to practice. I came back and flattened all the backs of my
irons, and used my version of your jig (mine is made out of brass and
has tapped threads for the screws) to sharpen them. I have been
experimenting and am not (yet) convinced about the need for all the
back bevels.
I took a number of these irons into work and used a microscope to image
the bevels. These pictures pretty much matched your images. If I were
to do more of this I would need to work on the positioning of the blade
and the light source. The problem with the steel is that it is too
reflective and is tough to focus on.
In your recent article regarding the 60-grit sandpaper, you had one
image where there were several different colors. If the grit had
different thicknesses and had opposite sides that were parallel then
you can get internal reflections and interferences that can generate
very significant colors. For tabular silver halide crystals with
reflected light the grains can appear almost any color from white to
yellow, to dark blue. It will happen with other materials too.
I also built an Excel spreadsheet that automatically does my
calculations for each blade and holding jig. I'm not sure if I can
attach it here but am willing to send it to anyone who requests it.
Keep up the good work and thanks for the useful information.
Dave G
Brent Beach
> My standard method is to set the primary bevel with a coarse / very
> coarse DMT diamond stone and then move on to the 40/15/5/.3
> sandpapers that you described. My grinder is of poor quality and I
> restrict its use to lawn mower blades and such. I don't trust it with
> a chisel or a plane blade. Have you ever tried a coarse diamond stone
> to set your primary bevel? The very coarse side is a lot finer than
> the 60-grit and it does take a few minutes to get them set. By
> mounting this in a sheet of MDF I can use the my standard jig and
> then move right on to the glass-mounted sandpaper.
Diamonds are a mystery to me. I have heard conflicting stories about
using diamonds on tool steel. Some say it works well, others that the
diamonds wear out in no time. DMT makes a 10 1/2" very coarse/coarse
stone that I may try out some day.
> Last fall I attended a workshop given by Garrett Hack about planes
> and I was amazed how well he could use them. I have always been
> frustrated with my planes and realized there were at least two
> factors for my problems. First my planes weren't really sharp enough
> and second, I needed to practice. I came back and flattened all the
> backs of my irons, and used my version of your jig (mine is made out
> of brass and has tapped threads for the screws) to sharpen them. I
> have been experimenting and am not (yet) convinced about the need for
> all the back bevels.
Can you send me a picture of your jig?
For me, because I use a jig that lets me do back bevels, there is no
question that they are worth the effort. The upper surface wears - you
can ignore it, or you can fix it every time you sharpen.
> I took a number of these irons into work and used a microscope to
> image the bevels. These pictures pretty much matched your images. If
> I were to do more of this I would need to work on the positioning of
> the blade and the light source. The problem with the steel is that it
> is too reflective and is tough to focus on.
I have a new microscope - a binocular type scope that produces 45X
images. The image is far better than the QX3 - when I look through it I
see far more detail. I suspect that a lot of the QX3 final image is
digital magnification.
However, getting that image to the screen is a problem. The new images
on the Norton 3X page are taken with this microscope and a digital
camera. Not completely happy with this solution yet.
> In your recent article regarding the 60-grit sandpaper, you had one
> image where there were several different colors. If the grit had
> different thicknesses and had opposite sides that were parallel then
> you can get internal reflections and interferences that can generate
> very significant colors. For tabular silver halide crystals with
> reflected light the grains can appear almost any color from white to
> yellow, to dark blue. It will happen with other materials too.
>
> I also built an Excel spreadsheet that automatically does my
> calculations for each blade and holding jig. I'm not sure if I can
> attach it here but am willing to send it to anyone who requests it.
Thanks for the offer.
If you can think of a way to do the same thing in a web page, let me
know. I looked into it a few weeks ago - generating the numbers into the
clipboard so someone could save them to a file, or print them, but did
not find anything easy.
> Keep up the good work and thanks for the useful information.
>
> Dave G
Brent
--
Victoria, B.C., Canada