Article 25176 of rec.woodworking:
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From: leach@bedford.progress.COM (Patrick Leach)
Newsgroups: rec.woodworking
Subject: Planes plainly explained, I hope.
Date: 13 Oct 1993 10:39:19 GMT
Organization: Progress Software Corp.
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  Here's a re-post of my plane theory scribblings, which I first
entered when I was doing my bad trip at Stratus. If anyone feels this
and part II are worth puting in the handtoold FAQ, be my guest.


  To understand fully the function of a plane, an examination of the
action that occurs at the cutting edge is necessary. For purpose of
example, a simple chisel will suffice since a plane is nothing but a
box, which holds captive a chisel, commonly at a 45 degree angle, or
pitch, to the wood's surface, and thrusts the chisel forward. The 
various tasks in which a plane finds common use can all be done by the 
chisel alone, the simplest of the single edge cutting tools. But, the 
sheer effort and skill required to keep a chisel on its course, along 
with preventing it from digging in, are all solved by the control the 
plane affords. Regardless, whether a plane or a chisel is in use, there 
is a common action that occurs at the cutting edge.

  Before the action of the chisel as a 'plane' can commence, the action
of the chisel proper must be understood. But to understand the action
of a chisel, it must first be recognized that the chisel is nothing but
a wedge, albeit the perfect wedge. The wedge proper, when driven into the
wood, forms a line of cleavage that follows the grain of the wood nearly
along its point of entry. There is nothing controlling the path of the
wedge, save for the parallel layers of the grain, which results in a
very uneven surface. The wedge doesn't cut the grain, it only separates
it with the force at the end of the wedge where it is struck, not at its
bevelled point.

  The chisel solves the eratic nature of the wedge by offering some
degree of contol over its action. This is accomplished by bevelling one
one side of the `wedge' only; the opposite side being kept flat. This 
flat side follows the path of its bevel since it is in the same plane
as its bevel. The bevel bites the wood, throwing the waste up its bevel
side, as the wedge does. Thus, the wood can be cut, instead of cleaved,
and a truer surface be made.

  The chisel's bevel influences the movement of the chisel as it is 
forced into the wood during its cutting action. The chisel moves in a 
line coincidental to its bevel, following from the back, or heel, of the 
bevel toward the cutting edge. It does this no matter the chisel's orien-
tation. A shallower bevel offers less resistance to the wood's surface,
and will yield a cleaner cut. A steeper bevel, obviously, offers more 
resistance, and often splits the surface, acting, in this case, like the 
wedge.

  A chisel held perpendicular to the wood's surface, aligned with a
scribed line, and then forced directly downward into the wood, will 
not only bite into the wood, but will also move backward away from the
bevel, jumping across the scribed line. This fact rears its ugly head
when a mortice is first started at its end lines, resulting in undercut
mortices.

  If the chisel is then tilted 45 degrees so that the bevel is now
facing up from the wood's surface, and the same force on the chisel as
before is applied, with the addition of a slight forward thrust, one 
of two things will occur; 1) the chisel will skip across the surface 
of the wood, if the tenacity of the wood is greater than the thrust
applied to the chisel - the chisel chatters; 2) if the downward force is
greater than the tenacity of the wood, the cutting edge will dive into 
the wood and either bind until it stops, or split if greater thrust is
applied, owing to the fact that the bevel is nearly perpendicular to 
the wood's surface and resists any forward movement of the chisel. In 
this latter situation, the bevel, with its tendancy to draw the chisel 
deeper and deeper into the wood, in essence, is attempting to separate 
the wood, like a wedge, instead of cutting it.

  This detrimental affect can be lessened by lowering the pitch of the
chisel so that the bevel is now somewhat aligned in the direction of
the thrust applied on the chisel. The bevel now meets the wood's sur-
face at an angle more acute than before, and lends assistance, instead
of resistance, while the chisel is thrust forward. The chisel can be 
assisted further by grinding a shallower bevel, making the angle of the
bevel still more acute. However, the chisel will still tend to chatter, 
or bind as the case may be, but these tendancies diminish sharply as 
the pitch of the chisel is further lowered. Once the chisel is laid flat
to the wood's surface, the finest control over it can be had; the chisel
excels as a paring tool in this orientation.

  If the chisel is oriented as before, at 45 degrees, but with the 
bevel side down, it should be apparent that the bevel side of the chisel
is now very acute to the wood's surface, and, thus, very much in
alignment with the forward thrust applied to the chisel. However, this
alignment is not totally in harmony with the thrust, for if it were,
the chisel fails to cut. The bevel still makes contact with the wood's 
surface at an angle that draws the chisel inward in unison with the 
forward thrust. If the chisel is drawn into the wood too deeply, the
chisel may be rocked back to lower its pitch, which then lowers the bevel 
angle's contact with the wood's surface further, causing the chisel to 
bite less than before, producing a thinner shaving. This rocking action 
is how a drawknife can be made to cut effectively. For the purpose of the 
common bench plane, the chisel, or iron, is commonly held at a pitch of 
45 degrees to the wood.

  If the chisel, in the same orientation as just mentioned, is rocked
back too far, the heel of the bevel will make contact with the wood's
surface and will overcome any chance of the cutting edge making a cut.
This can be solved by reducing the bevel angle in relation to the
pitch of the chisel; the shallower the chisel's pitch, the smaller the
honing angle. It makes sense theoretically, but in practice it fails.
The smaller honing angle reduces the amount of steel directly behind
the cutting edge, which then offers the cutting edge very little support.
The cutting edge will be very keen, but will chip and break whenever it
meets a knot, or a harder wood. The benefits of lowering the chisel's
pitch here, soon become impractical, so the chisel can be flipped over
where another benefit, explained later, is gained.

  Now it's proper to examine the action of the wood itself as it is
removed from the surface as a consequence of the chisel. As the chisel
is pushed at its handle, an appliaction of forward thrust propells the
chisel across the wood's surface, which then cuts the wood. The cut wood 
must be moved aside in order for the chisel to continue along its way. 
This cut wood, known as a shaving, moves up along the blade, in an arched 
shape as the cut progresses. The shaving gains leverage the farther up 
the blade it travels, a detrimental fact examined later.

  An additional downward force, perpendicular to the wood's surface, may 
be applied at the cutting edge to increase the depth of the chisel's cut.
In this case, the force required to bend the shaving, as it travels up the 
blade, is often greater than that force required to cut or separate the 
wood fibers. This results in a split in front of the cutting edge, which 
runs with the grain and usually deepens, stopping the chisel in its tracks.
In short, a very thick shaving results, with the chisel digging deeper
and deeper into the wood until the wood's tenacity halts the forward
motion of the chisel.

  Conversely, if the downward pressure is lessened, a thinner shaving
results, which can then bend easily without splitting the wood. The
shaving offers very little resistance at the chisel's cutting edge, but
the resistance is there nonetheless.

  With respect to the wood's grain, some beneficial and harmful actions
can be noted, especially when the shaving removed is thick. The risk of
splitting the wood is minimized by thrusting the chisel with the grain.
In this case, the shaving tends to break apart as it travels up the
chisel's blade, owing to the fact that as the shaving travels up the 
blade, the shaving's points of contact with the iron have their grain
oriented so that the grain points downhill from the pitch of the iron, 
toward the wood's surface. It is impossible for any sizeable amount of 
leverage to develop since the shaving will split along its grain farthest 
from the chisel's cutting edge, toward the top of the shaving where it's 
met with only the resistance of the shaving itself. Thus, planing with the 
grain will often defeat any leverage the shaving may gain during its 
formation, resulting in shavings that tend to curl back upon themselves
tightly. But, this is not always the case; woods with a tenacious grain
can present a problem here because the fibers adhere to one another
stronger.

  Pushing the chisel against the grain is another matter altogether. The
shaving here gains leverage the farther up the blade it travels, since the
shaving's grain is oriented just the opposite as described for a shaving
with the grain. As the shaving grows, and travels up the blade, the grain
is oriented so that the fibers compress against themselves toward the
chisel's cutting edge. As this compression grows in strength, it acts as
a lever where it exerts more and more force at the chisel's cutting edge, 
and ahead of it. This leverage builds continually until it can overcome
the wood fiber's adherance, which results in the wood being torn from the 
surface before the chisel can cut it. This is known as tear out.

  Naturally, this problem of tear out is something that can be avoided
in the perfect world where all grain behaves nicely; the rule of thumb
that states "plane with the grain" works in this fantasy land. Such is
not the case for those based in reality, where the grain dives, knots
live, and tenacious woods abound. This problem was solved by some unknown 
18th century `genius'. He (it may have been a she for all we know) dis-
covered that by immediately breaking the shaving, as soon as possible 
after it is cut, and thus compromising any inherent strength the grain
may have, tear out can be reduced considerably. The shaving's ability to 
build up leverage is greatly minimized, even when going against the grain. 
This invention finds its use on plane irons, as the cap iron, and will be
explained in greater detail later.

  The transition from a cutting action to a splitting action occurs
later if the pitch of the chisel is lowered. The leverage gained as the
shaving moves up the blade takes longer to build up and, therefore, be-
come detrimental. However, a chisel employed with a lower pitch to the
wood's surface requires a smaller honing angle, otherwise the chisel
will fail to bite the wood well in the case of the chisel bevel side up,
or will contact the heel in the case of bevel side down. But there is a 
drawback in this situation - the smaller honing angle will have less steel 
behind the cutting edge to lend it support when the bevel side is down.
This results in an edge that can chatter, due to the flexing of the steel 
at the cutting edge, or, more likely, frequent chipping of the cutting 
edge. To be used effectively, the chisel is then flipped so that the bevel
edge is up and the low pitch can be taken advantage of to reduce tear out.
Turning to the actual plane, a smaller honing angle, and grinding angle, 
can be taken advantage of here, as the plane offers support all along the
flat side of its chisel, its iron.

  There is yet another way to minimize the risk of tear out through the
use of a chisel alone. The wood is 'fooled' into believing that the pitch
of the chisel is lower than what it actually is. This is accomplished by 
holding the chisel at an angle skewed to the forward thrust applied across 
the wood's surface. Visualize a single wood fiber cut with a chisel moved 
in a motion that is perpendicular to it. The fiber must climb the chisel 
at the full amount of pitch in which the chisel is held. If the chisel is
skewed to this forward motion, the fiber does not climb straight up the 
blade, but, instead, climbs the blade diagonally. The path of travel is 
farther, but it is less steep, a fact that climbers surely recognize.
-- 
--------------------------------------------------------------------------
Patrick Leach
Just say Plane theory 101.
etc.
--------------------------------------------------------------------------


Article 25180 of rec.woodworking:
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From: leach@bedford.progress.COM (Patrick Leach)
Newsgroups: rec.woodworking
Subject: Planes plainly explained, I hope.
Date: 13 Oct 1993 10:40:21 GMT
Organization: Progress Software Corp.
Lines: 171
Sender: leach@tubuai (Patrick Leach)
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  Now that the mechanics of the simple chisel are recognized,
various contrivances can be added to the chisel to regulate
its pitch, its depth of cut, its support, its thickness, all 
in an attempt to eliminate tear out.

  The first object to add is an iron fixed onto the chisel, 
on the opposite side of the bevel. As explained earlier, this
iron, the cap iron, breaks the shaving as it is lifted from 
the wood's surface thus reducing tear out by eliminating any
leverage gained by the shaving.

  Naturally this cap iron can't be fixed permanently to the
chisel, henceforth called the cutting iron or iron, due to the
fact the cutting iron wears from use. The cap iron must be free 
to move when the workman either needs to hone the cutting iron,
or when he wants to back the cap iron off of the cutting edge
a bit. 

  The distance at which the cap iron sits back from the cutting
edge greatly determines the kind of shaving the cutting iron
produces. With the cap iron practically on the cutting edge,
very tight, crisp curls result, with the likelihood of tear out
diminished due to the shaving's leverage being compromised
nearly as soon as the shaving is cut. For the finest smoothing,
this setting of the cap iron is prefered.

  Should the cap iron be set back noticeably from the cutting
edge, a coarser shaving may be had, but at the risk of tearing 
out the wood. This will all be explained in greater detail later.

  Next, a suitable method of securing the cutting iron is mand-
atory so that its pitch may be held constant during use, some-
thing that is very difficult to do freehand. This is commonly
done by a support that attaches to a base. This support, if
adjustable to the base, is called a frog; if non-adjustable, is
called a bed.

  The troublesome problem of chatter, a fact briefly touched 
upon during the chisel description, is something that presents
itself in other situations - those being a cutting blade that
is too thin in cross-section, a frog, and a plane of insufficient
weight.

  There are two general classes of cutting irons, the tapered
iron, and the parallel iron. The tapered iron thins in cross-
section along its length away from its cutting edge. These can
be, and often are, very thick at their cutting edge, making them
very useful while new, but problematic as the iron is re-ground
throughout its life. Parallel irons, on the otherhand, don't
taper in cross-section. They are the same thickness along the
entire length of useable cutting steel.

  Adjustable frogs can contribute to chatter when the cutting
iron is thin in cross section, as is the case for common Stanley
irons. The reason for this is due to the frog's necessity to
be adjustable; as the frog is moved forward, in relation to the
base, there becomes a small unsuported portion of the cutting
iron along with the never supported bevel. Though this problem
is usually insignificant in most applications, there are woods,
because of their tenacious grain, that present a problem for the
cutting iron to cut cleanly. The thrust of the iron cannot over-
come the wood's tenacity, and the cutting iron flexes backward
a bit building up tension on the wood's surface. As the thrust
continues forward, the tension between the cutting edge and the
wood either is overcome, causing the cutting iron to release its
tension making the iron jump forward, or the the iron embeds
itself in the wood and the force of thrust is overcome causing 
the plane to bind. This same action is noticeable if the iron 
attempts to take too deep a cut.

  A thicker iron is less apt to flex due to its mass, and can be
used on plane's equiped with frogs, though these planes rarely
admit thicker irons without some modification. 

  A plane that uses a bed to support its iron fully, like a common
wooden plane, nearly eliminates chatter, for the iron is fully 
supported, except at its cutting edge. Chatter can be a problem for 
these style planes if the iron is deeply set, usually because the
plane's mass, or the downward force exerted on it, is insufficient
in relation to the set. The workman will need to exert more down-
ward pressure, thus increasing the amount of forward pressure to
thrust the plane forward, in order for the plane to cut evenly with 
a deep set.
 
  Parallel irons are commonly used in planes of this design for the 
fact that no matter how many times the iron is ground, the iron's 
cutting edge will always remain constant within the as yet discussed
mouth. Unless the cutting iron is secured to a frog, tapered irons
will increase the effective mouth opening as they are ground. The
addition of an adjustable mouth can overcome this deficiency.

  Finally, tear out can be reduced with the addition of a bearing 
surface ahead of the iron. In the simplest of terms, the nearer the 
bearing surface to the cutting action of the iron, the finer the 
planed surface produced. The distance this bearing surface is situ-
ated from the cutting edge is known as the mouth. A plane can func-
tion without a mouth, or more properly, a mouth infinitely wide. 
These are, however, special purpose planes used only over small areas,
like in a stopped rabbet where a normal plane can't reach, and are of
little value for smoothing or putting a finish surface on the wood. 
These planes, called edge or chisel planes always have their bevel 
up, their irons seated at a very low pitch, and a very fine setting
all in their effort to overcome tear out.

  A plane with a mouth opening too small to admit the passage of
shavings is useless. So a plane must be designed with a suitably
sized mouth in order for it to be the general purpose tool and 
offer practical use for the workman. These common planes handle the 
vast majority of applications, with some tweaking of the frog, the 
depth of cut, and the position of the cap iron in relation to the 
cutting iron. However, these common planes were found to be in-
adequate in design for stubborn woods.

  Turning back to the cap iron, recall that the distance it is set
back from the cutting edge of the iron will determine the resulting
shaving's characteristics. The farther back the cap iron is set from
the cutting edge, the coarser the shaving will be as it is lifted
from the wood's surface. Here too, the iron's set, or the amount the
iron projects from the sole, will effect the shaving.

  Consider a cap iron secured so a fine shaving results; the cap iron
is but a hair's thickness back from the cutting edge. If the iron is
set fine, that is it projects from the sole the smallest amount 
possible to lift a shaving, the expected thin shaving will result.
But, if the iron is set deeper, the same shaving will also result, con-
trary to what might be expected. A thin shaving results here because
the cap iron prevents the cutting edge to penetrate the wood's surface.
In both cases of the iron's set, once the shaving is lifted from the
wood's surface, it is immediately turned back upon itself by the cap
iron. Very thin and wavy shavings, usually 3 to 6 inches long (they'd
be longer, but the weight of the shaving breaks itself due to its
thinness), are produced with this combination of cap iron position and 
set, and is the optimal setting for final smoothing of a surface.

  If the cap iron is set back a distance, say 1/8"-1/4", from the
cutting edge, the plane will produce long, continous shavings. When
planing with the grain, these shavings will be very tightly curled -
the shaving's grain, as it rides up the cap iron, assists the cap iron
as it turns or breaks the shaving back upon itself. If planed against
the grain, the shavings will have a slight arc to their length - the
grain's orientation, as it passes over the cap iron, works against and
resists the cap iron's attempt to break the shaving. Naturally, the 
plane's mouth must be a sufficient width to admit the shaving, or the
plane will choke. Regardless of the direction the plane is pushed in 
relation to the grain, the resulting surface of the wood, with the cap 
iron set back from the edge, will be of a lesser quality than that pro-
duced with the cap iron nearer the cutting edge.

  There is another combination of cap iron distance and iron set that
must be recognized - the cap iron is close to the cutting edge, and the
iron is set deeply. This combination is undesirable, since it causes 
the plane to choke. The shaving is immediately turned back on itself by
the cap iron, but is then interrupted by the bearing surface of the
sole ahead of it, the front of the mouth. The shaving can't curl, but 
instead collides with itself. As more and more shaving is lifted, the 
shaving's progress is further impinged, causing the shaving to pack
tightly upon itself. The plane's mouth becomes choked, and the plane
stops cutting.

  One other point about choking bears mentioning - a cap iron that
doesn't fit tightly against the cutting iron, along its full width,
will cause the plane to choke. Any opening between the two will permit
a shaving to lodge between them, and the same action as described
before will occur. Make sure the cap iron is ground straight and flat.
-- 
--------------------------------------------------------------------------
Patrick Leach
Just say Plane Theory 101.
etc.
--------------------------------------------------------------------------


Article 25579 of rec.woodworking:
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From: leach@bedford.progress.COM (Patrick Leach)
Newsgroups: rec.woodworking
Subject: Re: metal plane questions
Date: 22 Oct 1993 09:55:01 GMT
Organization: Progress Software Corp.
Lines: 86
Sender: leach@tubuai (Patrick Leach)
Distribution: world
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In article <20931018005302/0004839378NA3EM@mcimail.com>, Joshua Proschan <0004839378@MCIMAIL.COM> writes:
|> I find, with a variety of Bailey-style bench planes, that if I follow
|> the standard advice for very fine shavings on difficult wood, and set
|> the cap iron as close to the edge as possible (about 1/32") and the
|> throat as close as possible, the cap iron collides with the top of the
|> mouth before the edge can protrude.  This seems to leave four
|> possibilities:
|> 
|> 1.  Set the cap iron close, and open the throat as needed.
|> 2.  Set the throat close, and move the cap iron back as needed.
|> 3.  Compromise; use moderate settings on both.
|> 4.  Forget about the throat, and align the frog with the base to
|>     minimize chatter.
|> 
|> Which approach should be used, for which types of wood?  Any general
|> rules?

  Welcome to the reality of a general purpose Stanley plane. You've
found its physical limitations, and perhaps now can understand why the 
Norris style planes were made. Norris style planes were made for one
use only - to remove the finest shavings for final smoothing. Stanley
planes were made for a range of uses - from the roughest work, where
they can tackle any wood, to final smoothing, where most woods are
managable. It's the difficult woods where they fail miserably, without
any modification of them.

  A general rule for a common bench plane is that the frog's position,
cap iron position, and set are all related. Put simply, if the frog is
set all the way back, then the cap iron is backed off from the edge,
and the iron set a bit deeper, all of which help to make a coarser cut
when you want to remove a lot of wood. When you want a fine cut, reverse
everything - frog forward, cap iron close to the edge, and iron set
shallow. But, as you've found, there is a limit to how fine this latter
setting can be made. That's why Hock irons and books devoted to plane
tuning are out there for your consumption - to make a general purpose
plane something into which it wasn't designed, a finely tuned machine
capable of tackling any wood.

|> 
|> 4.  Grind away enough of the top of the throat so that the cap iron
|>     clears.
|> 
|> This clearly won't work; but raises another question.  The planes I have
|> all have the edge at a slight angle to the vertical, tilting forward
|> (away from the blade).  Wooden planes normally have the throat undercut.
|> What is the correct geometry for the front edge of the throat in a metal
|> plane, in relation to the iron, chip breaker, and lever cap?

  There is no correct geometry. Various manufacturers made this to what-
ever was was easiest to allow a relatively fine set of the iron. All that
matters is there to be sufficient material ahead of the iron, to form the
mouth, and enough clearance for the cap iron. Since cap irons have differ-
ing curvatures across the many manufacturers, there is really no standard
way of finishing the throat.

|> 
|> A final question:  I have a cheap Stanley #4 (hardware store variety,
|> marked "12-204 Made in England") that I have tuned, and that works quite
|> nicely.  There are two annoyances remaining.  One is the plastic tote.
|> I started making a wooden tote, and realized that the only advantage my
|> wooden-toted planes have is appearance; none of them are particularly
|> comfortable.  It seems that a tote which swells to the sides in the
|> middle, and widens in profile toward the bottom, would be an
|> improvement.  On the other hand, I've never seen such a tote described
|> anywhere.  What are your opinions on the best shapes for plane totes?

  This is kinda like asking what the best beer is. Whatever tote fits your 
hand is the best. For you. Ohio Tool, Sandusky, and Disston made totes
shaped for right handed dudes, which are supposedly more comfortable to
hold. They have a flattened left side, and are shaped on their right to
a form for the closed right fist. I've tried them, but can't comment on
their comfort since I'm a leftie and anything in my right hand feels
odd (except scissors or a beer).

|> 
|> The other annoyance is the plastic adjustment nut.  I tried the metal
|> nuts from my other planes, and they seem to have a different thread
|> pitch.  Any suggestions on sources for a replacement?


-- 
--------------------------------------------------------------------------
Patrick Leach
Just say Guinness is best, with Pete's, Bass, and Newcastle a close 2nd.
etc.
--------------------------------------------------------------------------


