Mechanics of chipbreakers and high cutting angles in woodworking planes. Abstract.

[David Weaver]

It might be helpful for a beginner in order to find the sweet spot.

I figured it might be something marketable because the bulk of the money is probably spent by beginners. I reset a cap iron before a plane needed to be sharpened again last night. It's the second time I did that this year. I wouldn't be in the target market for their plane, but gadgets do seem to sell (set screws near in plane mouths, etc).

I can't imagine it would be very cheap to make a matching iron and cap iron with a device like that, though, especially one that beginners (who pick up a bunch of planes and expect things like smooth adjusters without breaking in a plane or getting used to it) would find tolerable.

[Winton Applegate]

Use the lever cap winton!! You know you want to. (I wonder if it fits. I does on stanley planes).

Hey, you brought back a memory. I seem to remember doing that in High School shop class. Or I knew that from some where. Probably high school.

Yes it fits, see photo, but I would NEVER even consider doing that to the bronze CI. Nails on a chalk board for me. I couldn’t stand the dings it would put in the CI. Call me a candy a$$.

Thanks for reminding me though.

What does the iron at the top of that plane say? Does it say "Lie Nielsen", or is it blank? If it's blank, it's probably W1 steel.

Hey . . . . ! I went and looked for the LN stamping on the blades. The 35° that I used in the “Learning Episode” has the stamp
but
the 30° does not. Hmmmmmm

and finally . . . at the time of my previous post I forgot to check sharpness preservation of the double iron in this LE (Learning Episode) so I checked that tonight also.

See the photo of the edge with the white stuff on it. The way I test the blade for sharp at the bench is I lay the flat back of the blade on my finger nail and use it as if testing on end grain for sharpness. If it BITES with the blade flat it is fully sharp (or I didn’t get all the wire edge off Ha, Ha, Ha,). If I have to tilt the blade up a degree to get it to bite I am still good. If it is scraping / shaving curls off at that point it is getting dull. If it is sliding and not doing any thing it is past done and needs a full sharpening.

Where you see white stuff along the edge it was scraping / shaving curls off with the blade tilted up a degree (roughly). Where there is no white stuff it was biting and so much sharper there toward the corners of the blade.

So it took a good hit in the sharp department. I need to go back and get the tearout again and then do the BU thing and see how all that goes just for comparison.

And so ends another episode of “ As The Winton Turns”.

[Winton Applegate]

parameter (or even less)

A few more operations than required to keep my mouth tight!

See now that is what I always tell these guys . . . it is all in how you hold your mouth while working. The rest just falls into place from there.

Simple stuff. If it's sharp it will yield great results. Period. Tricky wood? Alternating figure? No big deal. You've got a sharp plane and now you have to learn how to use it on an organic substrate that plays by its own rules. Never met a piece of wood that I could not tame with a sharp plane and an intelligent touch.

W E L L L L L . . . .
I think we rather proved the opposite here. I mean the blade sharpness was seriously deadly but because the chip breaker was back to ~ 1mm it was tearing out big time.

Throat / mouth no I think I have put that one to bed. With a sharp blade on BU with the right geometry the throat opening makes no difference.

And throat opening on Bevel Down planes ? . . . yah . . . like . . . who still uses those ?
Oops I fell into my old shtick there

sorry, sorry

I stand on the shoulders of giants.

You totally said it there. I agree. I think that every time I walk into my shop and look at the photos on the wall of my teachers (through magazines, books and videos).

But none of them told me about this sweet spot CB thing.

Hey David I got to get a photo of you for the teacher wall.

(PS: I guess I need photos of more than just D. W. on this CB thing) (I got to get a bigger wall)

[David Weaver]

Winton, you said it pretty straight up about the sharpness. With the cap iron set right (or with a high angle plane), if the geometry is there, the chip will be fine and there will be no tearout. Sharpness after that is about surface brightness.

One of the reasons that I've been using only a washita is because the double iron allows it. A settled in washita that gets stropped on bare leather still shaves hair, but it definitely does not have the initial whiz bang that the shapton 15k pro does. It's more even keel from start to lack of clearance.

The thicker the chip, the more important the geometry issue is.

Sean Hughto had my school picture in another thread, I think it may have gotten removed. If he didn't, you can post it on your wall. I'm certainly no "teacher"! That sounds like a responsibility!

[David Weaver]

Hey, you brought back a memory. I seem to remember doing that in High School shop class. Or I knew that from some where. Probably high school.

Yes it fits, see photo, but I would NEVER even consider doing that to the bronze CI. Nails on a chalk board for me. I couldn’t stand the dings it would put in the CI. Call me a candy a$$.

Thanks for reminding me though.



Hey . . . . ! I went and looked for the LN stamping on the blades. The 35° that I used in the “Learning Episode” has the stamp
but
the 30° does not. Hmmmmmm

and finally . . . at the time of my previous post I forgot to check sharpness preservation of the double iron in this LE (Learning Episode) so I checked that tonight also.

See the photo of the edge with the white stuff on it. The way I test the blade for sharp at the bench is I lay the flat back of the blade on my finger nail and use it as if testing on end grain for sharpness. If it BITES with the blade flat it is fully sharp (or I didn’t get all the wire edge off Ha, Ha, Ha,). If I have to tilt the blade up a degree to get it to bite I am still good. If it is scraping / shaving curls off at that point it is getting dull. If it is sliding and not doing any thing it is past done and needs a full sharpening.

Where you see white stuff along the edge it was scraping / shaving curls off with the blade tilted up a degree (roughly). Where there is no white stuff it was biting and so much sharper there toward the corners of the blade.

So it took a good hit in the sharp department. I need to go back and get the tearout again and then do the BU thing and see how all that goes just for comparison.

And so ends another episode of “ As The Winton Turns”.

Couple of bullet point thoughts..
* the flat side of the iron wears faster with a cap iron in a good position (I guess this should be no surprise, the chip is being held against the iron and abrades it more). The bevel side, I don't know that there's any difference, I can't remember from the kawai paper. Guess what I'm saying is that your test is bound to show up the cap iron used iron because it's testing the face that now wears faster, though in use I haven't seen any real consequence to that wear, limited clearance is still what sends me back to the stones.
*W1 irons from LN wore about twice as fast as their A2. The steel is less wear resistant, and they were probably softer, too. IIRC, they had a bear of a time heat treating them
(I hope nobody ever breaks out the end of their lever cap on my suggestion to use it as a screwdriver. I wouldn't do it the first time I took the cap iron off of a flea market plane, but every time after that I do.

[Sean Hughto]

Sean Hughto had my school picture in another thread, I think it may have gotten removed. If he didn't, you can post it on your wall. I'm certainly no "teacher"! That sounds like a responsibility!

Yeah, it got removed, but I don't think it was cause a yer puss, so here it is again:

[Don McConnell]

While I generally try to stay out of threads in which it would seem I have a vested interest in the outcome, I'm finally feeling compelled to comment at least briefly on Kees' research. Frankly, I've been hoping someone else would point this out and I could stay out of it. But that doesn't seem to be happening, so, here goes.

There are a handful of difficulties/issues which are inherent in this kind of research, and I'm not completely sanguine that those have been successfully addressed in this research. And I'm not entirely sure how I would address them. But I'll forego that discussion in order to get to the basic flaw I see in the design of this research. As I read the article, Kees, your basic preparation of the iron was to grind at 25º and hone at 30º, resulting in an included angle of 30º for the iron when used at common pitch and with a cap iron. It then seems that you simulated the higher angles of attack by adding a back bevel of 5º, 10º and 15º, which would leave included angles of 35º, 40º and 45º. If this is the case, it is not analogous to an iron prepared with a 30º included angle and bedded at 50º, 55º and 60º, respectively, as would have been done with the 18th century single iron planes with higher bed angles. In other words, you've introduced a variable (actually two, with the subsequent difference in relief, or clearance, angles), which you have not controlled for at all. I believe this brings into question all of the comparative data you've generated, at least as it relates to your primary thesis.

Don McConnell
Eureka Springs, AR

[David Weaver]

It does appear to do more to simulate a bevel up type orientation of an iron, where the steeper angle does imply a greater included angle.

It would be interesting to see test numbers with the iron as don is suggesting.

(in my experience with single and double iron wooden and infill planes, I don't think the conclusion will be much different, but it would be interesting - some of the numbers might be closer together.)

[Kees Heiden]

While I generally try to stay out of threads in which it would seem I have a vested interest in the outcome, I'm finally feeling compelled to comment at least briefly on Kees' research. Frankly, I've been hoping someone else would point this out and I could stay out of it. But that doesn't seem to be happening, so, here goes.

There are a handful of difficulties/issues which are inherent in this kind of research, and I'm not completely sanguine that those have been successfully addressed in this research. And I'm not entirely sure how I would address them. But I'll forego that discussion in order to get to the basic flaw I see in the design of this research. As I read the article, Kees, your basic preparation of the iron was to grind at 25º and hone at 30º, resulting in an included angle of 30º for the iron when used at common pitch and with a cap iron. It then seems that you simulated the higher angles of attack by adding a back bevel of 5º, 10º and 15º, which would leave included angles of 35º, 40º and 45º. If this is the case, it is not analogous to an iron prepared with a 30º included angle and bedded at 50º, 55º and 60º, respectively, as would have been done with the 18th century single iron planes with higher bed angles. In other words, you've introduced a variable (actually two, with the subsequent difference in relief, or clearance, angles), which you have not controlled for at all. I believe this brings into question all of the comparative data you've generated, at least as it relates to your primary thesis.

Don McConnell
Eureka Springs, AR

There are two parts. In the first part I have measured the forces with a sharp blade. In this part I have sharpened the blade at 30 degrees and put a tiny backbevel on the face side, to be absolutely sure that I removed all of the wear plus the wire edge on the face. That backbevel is about 0.5 degree. To be able to measure the several cutting angles I made the mesuring jig adjustable. The blade holding thingy can be rotated. So your concern doesn't apply to the first part.

The second part of my article contains the wear data over a 100 meter planing distance. Here I had to use a different approach, because I was doing all the planing with the pictured wooden plane, and only use the test jig to measure the forces. In this case I had to use that 45 degree plane, so I used a backbevel of 15 degrees to simulate the 60 degree plane. This now had a clearance angle of 15 degrees, much like one of the modern bevel down planes.

When you look at the 0 meter point of that second test, you will see that the values are not too different from the values in the first part. I don't want to compare these absolute values of the two tests too much, because I made several structural changes in the apparatus in the mean time, But the relative difference between the high angle data and the capiron data at 0 m is also comparable to the values from the first test. This was confirmed in a test I did in the first version of the apparatus, but did not publish. The amount of clearance doesn't really make much differrence to the forces involved.

So yes you have a point there, regarding the wear data and the 18th century plane. We could argue about that. 15 degree clearance angle is still a lot, and at least I tested all three configurations with the same clearance angle, so the different forces from the high cutting angle surely do something to the wearbevel that isn't done in both of the 45 degree configurations. But I didn't test it with 30 degree clearance,that's right. Seems like I've got work to do, give me a couple of weeks though, I first must make a 60 degree plane.

[Gary Muto]

....I think chatter is a function of both Fc and Fn. During my first research, comparing the tearout abilities of high angle planes and chipbreakers, I struggled on one piece of wallnut with my Stanley with a 15 degree back bevel. It chattered like crazy and I had to reduce the width of the testpiece. No such problems with the chipbreaker set close to the edge. That test really tested the limits of the Stanley plane. Te negative force Fn actually helps against chatter. It keeps the blade in the cut, while at the high angle the wood tries to expell the blade. The latter combined with the higher Fc leads to chatter......

Kees,

Nice work and an incredible amount of effort. I'm not able to take the time to get through this whole thread, at least yet but it is very interesting.

I also do not have much to add to the discussion other than some bacic mechanics. this might be a little dry:

I think the chatter is induced by vibration or more specifically resonance. Resonance is vibration at the natural frequency. Everyting deflects under load and has a natural or resonant frequency. The natural frequency is not a result of input but of the properties of the object in vibration. In this case it is hte blade and chip breaker that is below the fixed point (lever cap). It's natural frequency is purely a function of the stiffness and mass of the two components of the system. The exact equation is
f = SQRT(K/M) F is frequency, K is stiffness or spring rate, M is Mass.

I don't think the forces would change the chatter any more than plucking a guitar string harder or softer would change the note (frequency). The properties of the wood being cut may have an effect but I doubt it. The wood properties might change the forces and perhaps the amplitude of the chatter.... I think.

[ian maybury]

I guess Kees that technically there's actually two variables involved in that situation - first the included angle of the cutting edge, and then the clearance angle. I've seen the view expressed that increasing the included angle can make quite a difference, but have no idea if that stands up. The view also gets expressed at times that reducing the clearance angle as on a BU increases the rate of wear of the edge, but ditto.

It's sometimes informative to watch actions when trying to figure out how somebody is thinking. The new custom planes by Lee Valley (presuming they peform as might be expected) are interesting in that regard. Their bodies retain many of the features of BU planes. The iron which is still quite thick seems quite a bit thinner than on a BU (couldn't find a number), and is mounted BD, and on a frog which delivers bed angles of 40 deg and above - which should ease sharpening and especially cambering. It delivers marginally reduced clearance honed at 30 deg at the mainstream 40 deg frog angle (10 deg vs 12 deg on a BU) - which might suggest that it's not seen as a significant issue.

The addition of a cap iron with a close setting (1/64in) recommended for use on tear out prone woods tends to suggest that the company sees benefit in this. Against that they seem (unless i'm misreading the instructions) to suggest running with no cap iron for other work - possibly because it makes heavier cuts hard work? This feature could make for a very free cutting plane on heavy cuts judging by the way a scrub performs - and gives the option to run high pitch angles as well/as an alternative.

This tends to validate the close set cap iron line of thought, but for situation specific use as the guys here have been saying. The jury is perhaps still out as to whether this set up is regarded as delivering any improvement over an appropriately sharpened BU - in that the design changes could be targeting ease of cambering and sharpening as much as anything. In that the current thick BU blades do need quite a lot of metal removed in certain sharpening situations - e.g. regrinding the primary bevel, putting on larger amounts of camber etc

Another benefit is a conveniently set mouth opening compared to a bedrock.

Either way it look like they have done quite a job of eliminating most of the perceived disadvantages of the BU design in the eyes of BD afficionados, while retaining many of its benefits and perhaps more to the point enhancing their uniqueness...

[Kees Heiden]

Kees,

Nice work and an incredible amount of effort. I'm not able to take the time to get through this whole thread, at least yet but it is very interesting.

I also do not have much to add to the discussion other than some bacic mechanics. this might be a little dry:

I think the chatter is induced by vibration or more specifically resonance. Resonance is vibration at the natural frequency. Everyting deflects under load and has a natural or resonant frequency. The natural frequency is not a result of input but of the properties of the object in vibration. In this case it is hte blade and chip breaker that is below the fixed point (lever cap). It's natural frequency is purely a function of the stiffness and mass of the two components of the system. The exact equation is
f = SQRT(K/M) F is frequency, K is stiffness or spring rate, M is Mass.

I don't think the forces would change the chatter any more than plucking a guitar string harder or softer would change the note (frequency). The properties of the wood being cut may have an effect but I doubt it. The wood properties might change the forces and perhaps the amplitude of the chatter.... I think.

Hi Gary,

Thanks for your comment. Chatter has the habbit of being triggered somehow. It appears suddenly somewhere in the middle of a board. The Stanley plane isn't known as the most chatter resistant design ever made. Especially with the thin original blades you can have some trouble now and then.

In the situation I wrote about, I tested the Stanley plane on a piece of curly wallnut. 45 degree to 55 degree gave no chatter problems, and resulted in a smooth results. Likewise with the capiron settings of 0.3 to 0.1 mm from the edge, no problem at all, smooth surface. But the 60 degree cutting angle suddenly produced a remarkable amount of chatter. Because you write about resonance, would it be some kind of harmonic resonance where the cutting action excites a frequency which happens to be the same as the natural frequency of the plane blade? But why didn't the chatter happen at 55 degrees, which is the same blade, bedded the same way, only with a slightly different backbevel?

Then I ripped the board in half so it was 2cm wide, and the chatter went away. The same plane setup, the same wood, no chatter. Reducing the cutting width reduces the forces on the edge. These things sure get complicated!

BTW, the chatter had no influence on the tearout.

[ian maybury]

Pardon my coming in again Kees, but one guess is that chatter could be down to the onset of failure/a different failure mode in the shaving at high pitch angles.

The horizontal/driving force causes a slicing action due to the blade sharpness. A 'diving' force results due to the blade's pitch angle. The reaction to this diving force lifts up the shaving - which also causes splitting ahead of the cutting edge if the wood is so inclined/the pitch is low enough. The blade face/pitch angle and the chip breaker geometry combine to bend and roll it upwards. Luckily (not really) this rolling action generates a reaction force - especially when the shaving collides with the chipbreaker, but there's presumably also friction between the shaving and the various surfaces. Which controls splitting by pushing the shaving back down into the surface.

Progressive blade wear/blunting messes with this balance by generating increased backwards and upwards acting forces - the precise direction these forces act in may depend heavily on what's happening at the cutting edge. (where the wear bevel forms, and possibly also dependent on how and where the wood is cleaving)

It's as you guys say likely that maintaining the right balance of these forces is necessary to retain enough Fn and a low enough driving force for comfortable handling, and at the same time to deliver a smoothly cut surface - with sharpening restoring the balance.

The bending of the shaving must entail compression to shorten the top surface and/or stretch stretch its bottom surface - don't know if bent wood ultimately fails in compression or tension. (concrete for example has minimal tensile strength, but lots of compressive strength, while steel is typically treated as being able to handle the same ultimate load/stress in both directions)

One possible mechanism for chatter is that at high angles of attack it might be that the shaving starts to peel off in good order, but that shortly afterwards it impacts the chipbreaker hard enough/is then bent tightly enough to fail. (could be an abrupt collapse in compression, or in tension) With the result that the blade (which was deflected back under the various forces) gets to spring forward. Only to start cutting normally again and for the cycle to repeat. The situation could be worsened if it happens that the natural frequency of the blade is matched by the frequency of this cycle - but resonance might not be necessary. A thicker/stiffer blade might sidestep at least some of the issue by being strong enough not to significantly deflect - or by having a natural frequency well away from that at which the failure cycle occurs. This would also see the downwards force applied by the chipbreaker alternately applied and released too - which would cause cyclical changes in how the wood cuts (it might cycle between splitting and not splitting), and would also feed back into a shuddering/cyclical speed changes in the movement forward of the plane. Which in turn...

Reduced pitch angles and/or thinner shavings would likely restore a steady state cutting action - because the forces and stresses (it's possible to bend a thin piece of material much more tightly than a thick one before reaching a stress level that will cause failure) resulting from the various bending and compressing actions might not get high enough to cause failure of the wood/shaving.

PS It'd be dead interesting to do some testing with chip breaker and non chipbreaker equipped blades of varying thickness/flexibility at varying pitch angles and cutting speeds - with a high speed camera. Could be that chatter is a lot about a change from a steady state cutting action to a dynamic one involving chip failure...

Just indulging by speculating….

[george wilson]

I would not encourage using the cap iron for a screw driver. It is cast iron,and can chip. The plating can get damaged too. Certainly not recommended for a nice bronze cap iron.

I have an original special screwdriver for loosening the chip breaker. It has a wide,squat handle,and the blade is as wide as the chip breaker screw,but only about 3/4" long.

[David Weaver]

For the poor, HD had (probably doesn't any longer) a large handle screwdriver with a wide blade, but it was literally only the screwdriver blade sticking out of the handle.

I don't know if they have it any more.

I do like to use the lever cap, though, I fit into the category of folks like david charlesworth was talking about who get jammed up using the ruler trick because I have to find the steel ruler that I'd use.