Everything I've read on preparing for an edge glued joint with hand planes
shows the board clamped with the edge facing up. Assuming the board is
short enough to fit on your bench, why isn't shooting with your plane
sideways on the bench the preferred way? It seems easy to place another
board under the one to be joined so you end up with an open space on the
bottom. Plane one face up and the other face down and you should cancel out
any slight variance from 90 degrees. I know I read about this somewhere but
it certainly doesn't seem to be common practice. What am I missing? The
only thing I can think of is that maybe the majority of planes aren't
machined at exactly 90 degrees from sole to side. You would also abuse a
single section of your iron I suppose, making sharpening necessary earlier.
Since we don't know the setup used to do either, a milled surface is more
likely to be square simply do to the nature of the setup required. A great
deal of "ground" surfaces on consumer products are produced on a belt sander
with no reference to a particular angle other than the original surface. It
is likely though, that the usual way of producing plane bodies would be to
mill them to clean up the casting then belt sand them for finish. Due to the
handwork, this would introduce errors but would be so slight as to be
insignificant for the intended use. Top of the line planes, such as the
Lie-Nielson, are surface ground.
It seems that most production metal planes are cast. When I was on the shop
floor, and admittedly that was some time ago the next part of the procedure
to true the casting up would be to mill the necessary critical surfaces for
precision performance . As production milling operations generally produce a
true but relatively rough surface the final operation would be to grind the
milled surfaces to a fine and even more accurate level. The setup for the
grinding operation probably amounts to simply placing the casting on the
grinders magnetic bed.
If you are going to belt sand the item then why not just take the basic
casting and sand that rather than destroy any accuracy imparted by the
Examination of many of the mass produced items by the likes of record
,stanley et al shows the final grind is on a relatively coarse stone and
the steel seems to have a somewhat coarse grain structure . The grain
structure on the more expensive planes appear to be finer the same being
true of the grind and in addition the castings appear heavier and might have
been green sand castings .Given the difference in prices this is
understandable. Of course basically the same results can be obtained with
either, it all ends up depending on the skill of the operator, and a little
Cast iron should have at least .015 to clean up to ensure full clean up
(more is better and is the norm). You can easily mill to a 63 microinch
finish. To clean up the milled finish, you would only have to remove a few
.0001s. To clean up the rough casting, you would have to sand off .015 or
more. Removing a few tenths by hand is not going to effect accuracy to any
meaningful degree for this purpose. Sanding from rough cast, there is
little chance of any kind of accuracy. In addition, sand castings are not
very accurate as to form and they are intentionally cast with a draft angle
to enable the form to be extracted from the mold. The difference in finish
you see between high end planes and production line one is the difference
between surface grinding and belt sanding. The stones used for surface
grinding cast iron are very course to avoid loading. A fine surface finish
is easily achieved with a course wheel in machine grinding where the machine
controls depth of cut. In freehand grinding, you would need a much finer
grit to achieve the same finish. Someone good with the belt sander could do
five planes in the time it would take to surface grind one.
A very good example of this process is a shop I worked in about a year ago.
We turned out thousands of "ground" parts. They were all milled to size and
belt sanded for finish. We had people that did nothing but sand all day.
They were very good at it. They had a horizontal belt sander that took about
a twenty foot belt. Three people at a time used this machine.
Tell that to the group that grind their plane irons to a one micron
tolerance at times and 5 microns all the time . Personally in my view the
only reason to beltsand a milled surface is for the very reason you
mentioned you can do 5 in the time it takes to grind one . Thus what appears
to be a fine accurate ground surface is actually is a hand beltsanded one
with no where near the accuracy
of it's ground counterpart and quite liklly less accurate than the milled
blank that was started with.
I am probably wrong here but I thought one of the virtues of cast iron was
it did not load up
If you start with a 63 microinch surface finish and you sand just far enough
to remove the milling marks, you will achieve an accuracy level as good as
most do when lapping. If you think about it, it is nothing more than
lapping. Only difference is instead of you pushing the plane across the
abrasive paper, the paper is moving and you are holding the plane to it.
This is not being done by Joe Monkey Weekend Hacker on an $85.00 dollar
Black an Decker. On an 80 grit belt, you would have to work quite hard to
remove .001 over the width or, harder still, length of a plane sole and if
you did, that amount would mean nothing for what a plane does. Yes, cast
iron will load a grinding wheel quickly. I once decided to regrind a cast
iron surface plate We didn't have grinding wheel for cast iron as we did
nothing but steel. I thought I could probably get away with it. The grinder
(surface grinder) left burn marks at each stroke. I tried dressing the
wheel very course(think Tormek). It was better but still left burn marks.
Went next door and barrowed a wheel for cast iron. Quite course with an open
structure. That worked.
A five micron grind (grit size. No one is holding 5 micron tolerances) is
way overkill. While superfinishing is quite effective in some applications,
this is not one of them. There are other points of edge failure that far
override the superfinish. It does give them something to do however so it is
not a complete waste of time. I have read about everything I could find on
the subject of sharpening for over thirty years and there is only one thing
that is universal. No one will ever agree on the best way.
As another poster mentioned, shooting boards used to be fairly commonplace
before the advent of machine jointers. I still have mine, although it's
seldom used now.
Mine is made from a piece of 1" ply about four feet long and 12" wide.
Glued & screwed on top of that is another piece of 1/2" ply, same length and
about 8" wide. They're arranged so that one long edge of the first piece
corresponds to one long edge of the second, giving an stepped board, rather
like an elongated L-shape in cross-section.
A stop - about 3/4" x 1" x 8 " - is dadoed, glued and screwed into the 8"
ply board at rt angles to its length (accuracy is important here) and a
couple of inches from one end or the other (if you lay the board on the
bench transverse to you, with the high bit - ie the 8" board - uppermost
and toward you, the stop will go at the LH end if you're right-handed and
Place the shooting-board on the floor. Lay the board to be shot on the
upper 8" piece, abutting the stop and overhanging the step between the ply
boards by about 1/8" or so. Take the longest plane you have (I use a No 7),
sharpen it like a razor, set the cap iron as close as you can get it to the
edge (1/64 or so), set the depth of cut to as shallow as possible while
still taking a shaving, then lay it on its side on the lower step with the
cutter toward the board to be shot. Helps a lot if you lube the lower step
and the side of the plane with candle-wax or somesuch.
Kneel on the board to be shot to clamp it to the shooting board, then simply
plane away at the middle 2/3 or 3/4 of the board, ignoring the ends, until
the plane no longer cuts. You've now got a mostly square-edged board which
is minutely hollow along its length, so take a couple of shavings all the
way through the board until you're getting a full-width shaving the full
length of the board. Voila.
Bear in mind that it's not the fact of the plane running along the step of
the board that straightens the long edge - it's the truth of the long sole
of the plane. The sole of the plane shouldn't actually run along the step,
which is why you have that 1/8" overhang. (Unless you are squaring the end
of a board, which is a slightly different technique)
As you correctly point out, when you're setting up the plane it does help to
set the cutter parallel to the plane sole, and if the sole is at true right
angles to the side, so much the better. However it's not crucial, since all
you have to do is to shoot one board with its face-side up and it's mating
board with the face side down, and any small variation from a right-angle
will cancel itself out. This is not true however if you are squaring an
end - you need the setup to be accurate for that.
As for blunting one portion of the blade before the rest, I've never found
it to be a problem. Most of the hard work's been done already, probably in
the vice by going down to the line with a No 5 or so. All your jointer
plane is doing is the last final tweak, so it should seldom need sharpening.
It all takes a lot longer to describe that it does to carry out, but it's
pretty easy, extremely accurate and a very satisfying job, if a bit sore on
my old knees!
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