Hi,

I have posted some thoughts and calculations about different ways to
sharpen a plane blade in a bevel down plane and the affect on cutting
edge support. I'm interested to know what people think. I am planning
on analysing bevel up planes and back bevels in bevel down and bevel up
planes. Any bright ideas could be incorporated easier now than after.

http://members.shaw.ca/petermichaux/...nGeometry.html

There is an excel spreadsheet at the bottom you can download and play
with too.

Thanks,
Peter

On 1 Apr 2005 23:07:28 -0800, wrote:

Hi,

I have posted some thoughts and calculations about different ways to
sharpen a plane blade in a bevel down plane and the affect on cutting
edge support. I'm interested to know what people think. I am planning
on analysing bevel up planes and back bevels in bevel down and bevel up
planes. Any bright ideas could be incorporated easier now than after.


man that some serious brain work (G) wonder how much it matters in real life?
you forgot laminated blades though (G)
hollow grinding though is slower then flat grinding. even if I went to this
method it is not practical to use a grinder they are slow and heat up the steel
too much. I do all my grinding on my belt sanders. the speed is so much faster
it's not even worth thinking of grinding wheels anymore.
I like the back bevel idea myself I have not played around too much with it
yet. I recommend it to people who can't afford more then one plane. it's cheaper
to get two irons for the different angles.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

Wow! That's pretty complicated. I do hollow grind & then finish them
off on a flat stone - no microbevel, usually. I'll keep touching them
for quite a while & eventually they get to a point where I put them on
the grinder again, maybe a year or two. (I'm a hobbyist, so I don't
use them for hours a day).

I will put a microbevel on one occasionally. Seems to work better on
some woods some times, usually wild grain. Not sure I always do it as
well as I should, though. I tend to resharpen for the single bevel
soon after.

I'm not an expert, though. I've been using hand planes for quite a few
years & have always gotten a lot of satisfaction out of them. There's
something about a long, thin curl & a glass smooth finish that is very
satisfying.

Jim

Peter,

Here are some random thoughts. Sorry if they seem a bit blunt or sharp...
My sole intention is to improve your analysis.

It seems to me that your analysis needs some more analysis. You state:

"I wanted to investigate how different practical sharpening methods affected
the edge and blade support in bevel down planes. The cutting edge is
supported by both the blade metal behind the cutting edge (edge support) and
where the blade contacts the plane bed (blade support). I don't know which
means of support is more important. I suspect the closer to the edge the
greater the importance."

Since you do not know which means of support is more important and can not
show why it would be important, it is impossible to make any sort of
conclusion.

A simple free body diagram would show the blade subject to a force at the
cutting edge which is downward and backward (from the point of view of the
person planing). If we analyze the forces around the point where the blade
contacts the frog it is true that the closer to the bottom of the frog we
get the moment around that point would be less. This moment is counteracted
by whatever force is applied by the cap iron or wedge or whatever is holding
the blade down. So if the "problem" with plane blades was that they tend to
rotate too much about this point, then hollow grinding might be a solution.
However, if you look at the geometry of the situation, simply making the
blade thinner has a much greater reduction.

It would seem to me that other factors will play a larger part in plane
performance than the shape of the back side of the blade. I have no real
analysis to back this up, and I've got neither the time or desire to do so,
but it seems to me that it is possible to conduct this sort of analysis -
though it requires more than just geometry to do so. Geometry is necessary
for the analysis, but it is not enough to really understand the situation.
In my opinion contouring the bevel side of the blade is most useful in
reducing the time necessary to put a new edge on the blade (as there is less
material to remove) than it is useful in increasing the structural integrity
of the plane iron. Remember that the blade is most flexible where it is
thinnest (at the cutting edge) and is thousands (if not millions) of times
less flexible by the time you get to the point where it contacts the frog.
Stiffness is proportional to the cube of the thickness.

So, how about the case where you have a flat ground bevel, but the clearance
angle is minimized? What would you define as the minimum clearance angle?
Why?


-j

wrote in message
oups.com...
Hi,

I have posted some thoughts and calculations about different ways to
sharpen a plane blade in a bevel down plane and the affect on cutting
edge support. I'm interested to know what people think. I am planning
on analysing bevel up planes and back bevels in bevel down and bevel up
planes. Any bright ideas could be incorporated easier now than after.

http://members.shaw.ca/petermichaux/...nGeometry.html

There is an excel spreadsheet at the bottom you can download and play
with too.

Thanks,
Peter

Steve,

wonder how much it matters in real life?

Maybe it doesn't matter much. I did want to debunk the idea that
hollows are theoretically inferiour to other methods in all cases. In
this case it would be the best with the proper equipment. Also it
points out that using a 25 degree primary bevel and a 30 degree
microbevel is probably a bit wasteful in terms of edge support. I was
just curious what would be the best geometry for a given blade
thickeness and then I thought some other people might be interested in
what I was thinking about but not able to do the calculations.

hollow grinding though is slower then flat grinding. even if I went to
this method it is not practical to use a grinder they are slow and heat
up the steel too much. I do all my grinding on my belt sanders. the
speed is so much faster it's not even worth thinking of grinding wheels
anymore.

This is great feedback! I had an idea about this last night. A way to
hollow grind with a belt sander is to use the curved part. Maybe make a
belt sander with 6" diameter wheels to rotate the belt and then set a
tool rest in front of one of those. If you use the middle of this
curved surface I do not think that "dubbing the tip" would be a problem
because the belt is tensioned from both sides as it continues to move
past the blade and along the wheel. You could even go up to the finest
abrasives that come in belt form. I don't know if that is fine enough.
Also the wheel diameter would never shink like grinding wheels do.

Thanks Steve.

Peter

Hi J,

You have brought up some interesting points. Yes a deeper analysis
could be done. But I'm sure that my analysis has debunked the myth that
hollow shapes are necessarily worse. Also I'm satisfied that primary
angles should be close to the microbevel angle (the 25/30 degree double
bevel combo is probably wasteful in terms of support.)

It's true that my conclusions are not based on an analysis of the
stresses in the metal and resulting flex. This is only a concern when
comparing the double bevel to the hollow grind/flat hone. And this
ended up being the important comparison. For really thin blades
(0.080") the two geometries are within thousandths of an inch and I
don't think there would be a substantial performance difference. But a
properly sized grinding wheel could match any primary bevel angle. For
thicker blades you can use a larger wheel to make the hollow and so
that method wins again. So over all the hollow grind/flat hone method
can always win in a geometry comparison against the double bevel. But
the "other factors" affected my conclusions. I think I'll reword my
conclusion.

My idea was to look at which way to sharpen a blade of given thickness.
Thicker blades seem to give better performance and manufactures of high
quality planes use thicker blades than the 0.080" Stanley blades. So I
presume that the increased contact height of a thicker blade is not a
serious penalty to pay for the increased stiffness of the thicker
blade. The thickness of the blade is so important that Steve Knight's
1/4" blades apparently give incredible performance even without a cap
iron to pretension the blade and with a larger contact height as he
uses single or double bevels. When comparing different blade
thicknesses it is not the flex of the bevel that counts, it is the flex
along the length of the blade.

This stuff is complicated. In fact modeling it will always be
insufficient. Experimental evidence would be the only way to ensure all
things are accounted for.

In theory the minimum clearance angle is the bed angle. That is like
using a chisle to chop a mortise. But if you did this then after the
first few shavings are made and the blade edge crumbles and dulls then
the cutting edge will be above the bevel surface and you will not
produce another shaving because you will not be able to push down the
wide bevel to compress the wood enough to get the cutting edge into the
wood.

Because the plane blade extends below the sole, it is slowly worn down
just like in honing but here the wood is the abrasive. Brent Beach
suspects that when this worn area gets large enough the blade feels
dull as you drag it across the wood with great pressure. So a large
clearance angle would reduce the frequency of sharpening. I guess it is
a trade off between edge toughness due to included angle, supportive
geometry, sharpening frequency and desired wood surface finish. For a
particular wood and task (face or eng grain) there will be an optimum
clearance angle for your assessment of the correct balance of the
tradeoffs. There probably isn't one optimal clearance angle for all
woods/tasks. I think I will add something about this to my page.
Thanks. I did the analysis at 15 degrees clearance because that seems
to be about what people like to use.

Leonard Lee writes "Anything between 30 and 35 degrees is quite
acceptable. If you go much lower than 30 degrees you encourage blade
chatter; if you go much higher than 35 degrees any wear dulls the blade
much faster, but, more significantly, you reduce the relief angle
unacceptably, particularly on planes with a 45 degree bed. Bevel-down
planes as a group represent an exception to the rule that blades should
be sharpened at the lowest angle consistent with edge retention,
because the bevel angle has no bearing on the cutting angle. A sturdy
edge is wanted, and a basic grind angle between 30 to 35 degrees will
give you good blade stability and the least chatter."

It is too bad Lee doesn't say what he thinks the relief angle is for.
He has implied it is involved with more than how quickly the blade
dulls as Beach has suggested.

Thanks for your thoughts!

Peter

This is great feedback! I had an idea about this last night. A way to
hollow grind with a belt sander is to use the curved part. Maybe make a
belt sander with 6" diameter wheels to rotate the belt and then set a
tool rest in front of one of those. If you use the middle of this
curved surface I do not think that "dubbing the tip" would be a problem
because the belt is tensioned from both sides as it continues to move
past the blade and along the wheel. You could even go up to the finest
abrasives that come in belt form. I don't know if that is fine enough.
Also the wheel diameter would never shink like grinding wheels do.

Knife makers do that. but I don't think you can get enough accuracy to go all
the way with belts.
myself when I make irons I grind the bevel at 30 degrees before heat treat.
then I use the makita freehand with the zirconia paper at 120 grit to flatten
the back and get the bevel accurate. then I free hand on my shapton stones. from
the makita to sharpened takes me at most two minutes and usually less.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

So you are using a single bevel?

On 2 Apr 2005 11:46:21 -0800, wrote:

So you are using a single bevel?

yes since I can make planes at any angle. but if someone can only afford one I
recommend a back bevel since I grind to 30 degrees a double bevel would be too
much. plus it's easier to free hand sharpen when you do the whole bevel.
if you use good fast sharpening tools like shapton stones the speed is not
really a issue.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

wrote

Steve,

wonder how much it matters in real life?

Maybe it doesn't matter much. I did want to debunk the idea that
hollows are theoretically inferiour to other methods in all cases.

Although not specifically related to planing, there is a discussion of the
properties of hollow ground blades on my web site. Please look at
'Sharpening Notes' - 'Hollow Grinding, Good or Bad'.

.................................................. ........In
this case it would be the best with the proper equipment. Also it
points out that using a 25 degree primary bevel and a 30 degree
microbevel

Perhaps Peter means 'secondary bevel'? A microbevel is a third, very narrow,
highly-polished bevel.
--
Jeff Gorman, West Yorkshire, UK
email : Username is amgron
ISP is clara.co.uk
www.amgron.clara.net

wrote

Hi J,

........................... But I'm sure that my analysis has debunked the
myth that
hollow shapes are necessarily worse.

If we take J's very valid point about blades being most flexible near the
cutting edge, it could be argued that in view of the hollow-ground geometry,
hollow-ground blades caan be theoretically inferior. For notes about the
strength of hollow ground blades, please see my web site - Sharpening
Notes - Hollow Ground, Good or Bad?

.......................................... Also I'm satisfied that primary
angles should be close to the microbevel angle (the 25/30 degree double
bevel combo is probably wasteful in terms of support.)

It may be of interest to note that the tapered, often laminated older irons
fitted to traditional bench planes were given a primary bevel ground at
about 12-1/2deg, taking the point of support even further higher up the
frog.

Thicker blades seem to give better performance and manufactures of high
quality planes use thicker blades than the 0.080" Stanley blades.

A very common belier, but in what regard is this true? Much is made in
woodworking literature of chatter whereas the most common problem with a
properly set-up plane is skitter. Please check with my web site - Planing
Notes - Skitter and Chatter.

The principal value of thick blades lies in their inherent rigidy, necessary
when bedded with wedge systems that are less effective than the lever
systems employed by Bailey, Norris and similar designers.

It can be argued that the thinner Stanley blade is, because of its
flexibility, more efficiently bedded by the lever cap system pressing it
against a machined metal frog (that ,incidentally, is more stable than a
wooden plane's frog).

.....................The thickness of the blade is so important that Steve
Knight's
1/4" blades apparently give incredible performance even without a cap
iron to pretension the blade

However much as we might enjoy theorising, I reckon that the principal
purpose of the cap iron is to deflect shavings. Please recall that many
older bench planes did not use cap irons, and moulding planes still lack
this feature. I supect that Mr Knight's and Krenov's planes have escapement
geometries that allow easy passage of the shavings and hence do not need cap
irons to serve as deflectors.
--
Jeff Gorman, West Yorkshire, UK
email : Username is amgron
ISP is clara.co.uk
www.amgron.clara.net

Jeff,

Thanks for your thougths.

I read the article on your site a while ago and also about hollow
grinding in Leonard Lee's book. Both are about chisle sharpening and
have created the myth that hollow shapes are less supportive in all
cases. The conclusions cannot be easily translated to bevel down
planes.

Two methods that require work on the entire bevel to sharpen are a
single bevel and hollow _honing_ which is like the Tormek system. For a
given included angle the hollow honed shape wins hands down. It has a
lower contact height on the frog.

Two methods that require work on less metal when re sharpening are the
double bevel (primary/microbevel) and hollow grinding followed by flat
honing (as described by Krenov). They have the same geometry at the
tip. They can both have the same support angle because you can choose
the primary bevel angle or the grinding wheel diameter. But the hollow
ground/flat honed method leaves more metal behind the blade and has a
lower contact height. So the hollow shape wins this comparison too!

But both comparisons are based on geometry and after that available
equipment and the time necessary to make a quality cutting edge must be
factored in.

How well does a blade with 12 1/2 degree primary perform in difficult
woods?

I wasn't concerned with skitter in my statement but your article is
interesting and I'll have to think more about the chatter issue. If the
chatter is occuring in the very tip then it doesn't matter how thick
the blade is. If the chatter is due to the length of the blade flexing
and your plane is holding the blade the best it can then it does matter
how thick the blade is. You measured the frequency of the resulting
sound which is interesting. What we really need to know is the
wavelength in the blade to determine where the chatter occurs. We could
ask for some experience...

Has anyone ever remedied chatter by buying a thicker blade? But the two
blades were probably different metals with different rigidities.

Thanks again. Your comments will help me word my thoughts more
carefully.

Peter

Steve,

Which shapton stones do you use? Professional series? What grit do you
start on after the 120x belt? How far do you go? 8000x, 15000x, 30000x?

Thanks,
Peter

I do mean a secondary bevel. In general the vocabulary here seems to be
a bit mixed up. My secondary bevel is very narrow and highly polished.
So it is a microbevel. I'm not using a third bevel.

On 3 Apr 2005 12:40:16 -0700, wrote:

Steve,

Which shapton stones do you use? Professional series? What grit do you
start on after the 120x belt? How far do you go? 8000x, 15000x, 30000x?


I use 120 grit zirconia on the makita then 1000 5000 and 12000. I have the hippo
stones and they are the normal shapton's not the pro's. even with my use I show
very little wear on them. I can go pretty far between flattening's with those
big stones.
but I would prefer the 8000 over the 12000 but they don't make that grit in a
shapton hippo stone.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

Steve,

I've been reading the old posts and it seems like you have tried a lot
of sharpening systems and have sharpened a lot of blades. Sorry to be
picking your brain but probably you are one of the most worthwhile
people to ask about this stuff. If I have it right you use the
following sharpening system

120 grit ziconia PSA disk on a horizontal flat lap Makita 9820-2.
and follow that by 1000x, 5000x, 12000x Shapton Hippo stones.

From the old posts it is hard to tell how you currently flatten your
stones. It seems like you do not and would not use diamond stones. Do
you flatten the 1000x on something (???) and then the 5000x on the
1000x and then the 12000x on the 5000x? Do you flatten them all on the
same thing? Or do you rub three stones together?

Flattening waterstones is really the only reason I have stayed away
from them even though I have some (low quality ones). I know that the
Shapton's require less maintenance.

It is interesting to see what your system has evolved into.

Thanks,
Peter

On 3 Apr 2005 22:35:24 -0700, wrote:

Steve,

I've been reading the old posts and it seems like you have tried a lot
of sharpening systems and have sharpened a lot of blades. Sorry to be
picking your brain but probably you are one of the most worthwhile
people to ask about this stuff. If I have it right you use the
following sharpening system

yes I have played a lot for sure (G) wore out so many stones it's not funny (G)

Flattening waterstones is really the only reason I have stayed away
from them even though I have some (low quality ones). I know that the
Shapton's require less maintenance.


yes they go if you push it maybe 10 sharpening's between flattening's if you
don't have to rework the edge. I get maybe 20 out of a hippo stone.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

wrote in message
oups.com...
This stuff is complicated. In fact modeling it will always be
insufficient. Experimental evidence would be the only way to ensure all
things are accounted for.

Peter

There are some pretty sophisticated models out there so I wouldn't be so
certain that it is insufficient.
The real question is whether it is worth modeling or analyzing. Either flat
or hollow grind works well enough that I would
not bother with trying to determine which is "better". I'm not about to buy
a grinding machine to put a hollow grind on any of my tools. That said, my
shovel DOES get a hollow grind when I touch it up with the grinder...

-j

J,

You are right, there are some sophisticated models. But you have to
include everything. Like how much slip is there between the cap iron
and the blade as the blade flexes. Maybe there is a little slip there.
Including all the little things would be tough. Probably easier to
build experimental equipment and just test the systems. Probably even
easier just to stop worrying and sharpen up a blade and do some
woodworking. I was just curious.

That said, my shovel DOES get a hollow grind when I touch it up with
the grinder...

haha

Peter

Steve,

Is how you flatten the stones a trade secret?

Peter

Even though the question wasn't to me I'll jump in.

I sharpen mine using their abrasive power. Others with more knowledge can
probably explain what's in it, but its an abrasive power that comes in
different grits. I use a Shapton lapping plate, but another surface could
probably do. The advantage is the lapping plate is it's flatness. I use the
professional stones, but then I don't sharpen near as much steel as Steve,
hahahaha.

The Shaptons are much harder than regular water stones, so flattening is
needed much less. Harelson who imports them in to the US got me in the habit
of using the whole stone for sharpening which also cuts down on the need to
flatten.

Go here to see an explination of how to flatten.
http://www.shaptonstones.com/informa...pingplate.html

Also see here for comments on alternate methods to flatten.
http://www.shaptonstones.com/information/faq.html

Bernie


wrote in message
ups.com...
Steve,

Is how you flatten the stones a trade secret?

Peter

On Sun, 03 Apr 2005 20:23:37 -0700, the inscrutable Steve Knight
spake:

On 3 Apr 2005 12:40:16 -0700, wrote:

Steve,

Which shapton stones do you use? Professional series? What grit do you
start on after the 120x belt? How far do you go? 8000x, 15000x, 30000x?


I use 120 grit zirconia on the makita then 1000 5000 and 12000. I have the hippo

Speaking of zirconia, where can I get 120 grit belts in 1x30" size?
Anyone buying those now?


--
The clear and present danger of top-posting explored at:
http://www.netmeister.org/news/learn2quote2.html
------------------------------------------------------
http://diversify.com Premium Website Development

On 4 Apr 2005 11:49:20 -0700, wrote:

Steve,

Is how you flatten the stones a trade secret?

right now I use the lapping plate but I think I may go back to diamonds.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

Speaking of zirconia, where can I get 120 grit belts in 1x30" size?
Anyone buying those now?

A & H abrasives
18008316066
just order three or more to save 10% size does not matter to cost since they are
sold by the sf.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.