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

[Kees Heiden]

Mechanics of chipbreakers and high cutting angles in woodworking planes.

Kees van der Heiden, The Netherlands, 2014.

Abstract.

When using handplanes, tearout is a typical problem. Two methods to prevent tearout are high cutting angles and chipbreakers set very close to the cutting edge. In previous work it was found that a cutting angle of 60° is equivalent to a chipbreaker setting of 0.1 mm behind the edge when the chipbreaker edge is beveled at 45°. Likewise an angle of 55° is equal to a 0.2 mm setting of the chipbreaker. To compare the two methods a planing machine is used with force transducers to measure the cutting force Fc and the force perpendicular to the wood surface, the normal force Fn. Fc proved to be 30% higher for the plane setups with a high cutting angle, compared to the equivalent chipbreaker settings. Fn is normally negative, pulling the edge into the wood in a standard 45° plane without the chipbreaker. When setting the chipbreaker close to the edge this negative force is slightly reduced, but in high angle planes this is reduced much more and tends towards 0 around a 60° cutting angle, under the circumstances of this experiment. A second experiment has been conducted to measure the forces after a planing distance of 100 meters. The rate of change of Fc is about equal for both methods. The rate of change of Fn is twice as fast for the high cutting angles. The conclusion is that the plane with a chipbreaker is technically more advanced then the plane with a high cutting angle. A hypothesis about how the two methods prevent tearout is proposed in this article too.

The complete article will be published on Steve Elliott's website http://planetuning.infillplane.com/, hopefully this weekend. As soon as I have a link I will post it here.

[Mel Fulks]

I think SCIENTIFIC AMERICAN might be a better fit! But I'm sure it will be found helpful.

[Warren Mickley]

Kees, I have long disputed that high angle planes and double iron planes are equivalent. My experiments in 1976 showed better surface quality from the double iron plane. And I have not seen anything since then to suggest otherwise. Of course a cap iron placed too close to the edge will also have a detrimental effect on surface quality.

[Kees Heiden]

Equivalent in reducing tearout. Not much equivalent in other aspects.

[Steve Voigt]

Kees, I'm eagerly looking forward to this article. Will it change the way I work? Probably not (since I'm already a double iron fan), but so what? It is fascinating for its own sake, and I really appreciate the amount of effort you've put into this. Thanks!

[Kees Heiden]

Here is the link to the article. Steve did a great job. Many thanks also to Bill Tindall, the "professor" of the project and Wiley Horne for the support, critisism and feedback. Thanks also to the Popular Woodworking staff, because the revenue of the chipbreaker article in februari allowed me to invest some money into this project.

http://planetuning.infillplane.com/h...pbreakers.html

[Winton Applegate]

The vertical axis displays the measured forces Fc and Fn. The unit is kgf/6mm. This is the force in kg measured on a wood sample width of 6 mm.

I was wondering what it meant when I first read it on the side of the graph.
kg/6 mm
?
So the sample planed was only 6mm wide ?
Or the sample planed was wider and the UNIT only is 1 6mm unit ?
Kind of leaves out the effect of the bending force of a significant / realistically wide cut with the blade.
Doesn’t it ?

I left the above thought in but now that I have seen the close up in the video and now I see the hewn stock was wider than 6 mm I see the 6mm is just one unit.

If a person took a cut on a plank the curl would be well over an inch wide perhaps even two inches wide. Oops, sorry I forget you use metric to.
well over 25 mm perhaps even 50 mm wide.

While taking a realistically wider cut like that, as compared to the narrow work being planed in the machine, the difference is bound to be significant especially when we include the issue of edge support at the throat or lack of it (see the illustration of the crossection of the plane's frog set forward to close up the throat) (wow I never reallized the support stared so far up the blade) and the difference between a 30° sharpening angle blade tilted up to SIMULATE a 60° BU and a true BU bedded at 12° supported much closer to the edge and sharpened to 48°

Again I would have liked to have seen a wider sample; wide enough to accommodate the full width that the blade could have taken normally in a normal planing operation on a face not an edge. That after all is what we are striving for, a chip out free face surface.
Face planing puts significantly more total force across the face of that blade per unit of time and so could, could mind you lead to the blade flex / oscillations I was talking about.

The cutting speed doesn’t have much effect, certainly not at hand planing speed.

I think you will admit that planing at more than the rate shown, on the order of a dive down a plank by an adrenaline charged neander could have some effect on the data.
Cutting faster could increase the oscillations per second and amplitude of the oscillations. There is probably a surface feet per minute number where the friction/heat and the general resistance starts to multiply disproportionally. I don’t think it is at machine cutter speed but down in the hand planing speed.

Cutting is with the grain I believe in the charts. That kind of alternated in the text.
and yet we/you are talking about tear out, which happens against the grain . . . also when planing against the grain mightn't the Fn be different since the edge is being pulled down into the grain ?

OK I was with you up to that point preparing to submit to an over whelming onslaught over the walls of my fortress of peace and contemplative contentment.
I was starting to consider which TEAM of stones to use to do my final sharpening on my hari-kari knife . . . then . . . thennnnnnn
I saw it.

Following the link to David Weaver’s photo of the rowed grain mahogany before and after . . . I must say, I can see what appears to be chatter marks before and after in the tear out areas and they are still there in the tear out free photo.

so not AS good as a BU then ? Rather confirming my flexing blade observations in the past. I am just calling it as I am seeing it.

I CAN see where some one with a BD would then reach for a scraper or (whispering now as if introducing the topic of nipple piercing in a nunnery) sand paper.
I never, until now, really understood the attraction of scrapers. I have a lot of them (as a result of searching for some that are not ruined in the act of shearing or punching them out or what ever, and even found some that are good enough quality to be able to sharpen and use (just so I knew how) but never needed one really.
I noticed in the links the topic / goal of eliminated tear out and chatter was then modified with the words “Nearly” and “Reduce ”.

Kees I read your enlightening article and appreciate all your work. It is fantastic there are great articles still being published in the magazines, well in one magazine anyway.

In the next link to the next vid it looks like the lever on the lever cap was really closed with a lot of force. That could bend the blade further down and add clearance and so make up for some of the rounding from hand sharpening. That was a tip. I had shied away from setting the screw to put that much force/resistance on the lever. That has never felt right to me. Live and learn. I like the bench with the square dogs.

Once again a narrow strip of wood was used in the vid. Keeps the high forces off the less rigid blade configuration. Fairly soft wood. I would be more convinced by a wider face of more challenging wood/hardness and for a longer planing duration than a few strokes. Part of the proof is durability and performance over at least a few board feet of work face.
I know what the charts said. Lets see it on the wood.

It probably sounds like I am just being an idiot that will never allow himself to change but . . . at it’s worst 30% more effort and some reduction in durability (that means a lower percentage for many/ most some what less difficult applications) I might be willing to still go that rout for the trade off of the over all planing experience of the BU (I won’t hammer all that out again in text) .
Time for me to spend time in the shop experimenting with what I have learned and to see what I can do if I practice, practice, practice. I thought I had got past all that but . . .

Well it has been a freewheeling, fun filled, fantastic trip together guys.

I just have one question, I was a little unclear in the second link when you mentioned something called . . . a . . . sander ? ? ?
Kees what issssss that ?

TTFN
(ta ta for now)

[David Weaver]

Winton, that's not my photo. That's ellis wallentine's photo (the editor of the article). I requested initially that he work (he had just begun experimenting with a cap iron) to eliminate the tearout as I wouldn't consider it acceptable, and ellis felt that showing a reduction in tearout was as good as showing an elimination. I didn't agree, but didn't figure it to be a good time to be an inflexible jerk given that ellis was volunteering his time.

None of the pictures, in fact, are mine.

Your grasping at straws at this point asserting that there may be a materially nonlinear effect without any real reason to suspect such a thing occurs, especially when you can literally go to your bench and feel that it doesn't, is a waste of discussion with no possible payoff.

"only a 30 reduction" in something that is a very physical effort.

[Steve Voigt]

While taking a realistically wider cut like that, as compared to the narrow work being planed in the machine, the difference is bound to be significant especially when we include the issue of edge support at the throat or lack of it (see the illustration of the crossection of the plane's frog set forward to close up the throat) (wow I never reallized the support stared so far up the blade) and the difference between a 30° sharpening angle blade tilted up to SIMULATE a 60° BU and a true BU bedded at 12° supported much closer to the edge and sharpened to 48°

I can't speak for Kees, but my impression is he was trying to compare standard angle BDs with chipbreakers to high angle BDs without. Comparing BUs would be a whole other thing.

More generally, I think you're missing the point. This isn't a blind experiment with a neutral observer. He's trying to (broadly) quantify results that anyone who has learned the double iron has experienced in a very visceral way. You can nitpick about shaving width or planing speed, and yes, those things might shift the numbers around a little, but I don't think you can seriously claim that they would alter the basic shape of the graph. And I say that because I've experienced the results in my shop, as have countless others. Before I learned to set the chipbreaker, I got tearout; now I don't. My 45° and 50° double irons stop tearout better than than the 55° planes I've used, and they are easier to push. In fact, that is one way you know you've set the cap iron a little too close; if it feels like a 55° or higher plane, back it off just a hair. If you get tearout, you backed it off too much. The sweet spot is somewhere in between.

You're right, the pictures in the WC article leave something to be desired. As Dave explained, those aren't his. A bunch of people have posted good pics of the chipbreaker effect on other forums; for example, google the thread "chipbreaker success" on Woodnet and look at the last couple pages.

Here's a pretty unexciting pic, but it does make the point. Where the grain swirls, by the pinhole knots, the wood is changing color, and everything is nasty, an ideal recipe for tearout. But there is no tearout. You can zoom in as close as you want.


photo-207.jpg

it probably sounds like I am just being an idiot that will never allow himself to change but . . . at it’s worst 30% more effort and some reduction in durability (that means a lower percentage for many/ most some what less difficult applications) I might be willing to still go that rout for the trade off of the over all planing experience of the BU.

You're right, it does sound that way! But I don't think anyone is trying to convince you to sell your BU planes. The chipbreaker works; whether you want to use it is up to you. If you prefer BU planes, right on. No one cares. But at some point you have to decide if you are arguing, in the face of all the evidence, because you think you're right, or if you're arguing just because you like to argue.

I'd suggest you take the route Derek took, and actually spend some time trying to use the double iron properly. If you decide, as he did, that you still prefer your BU planes, then cool. But at least you'll be able to argue from experience.

[Kees Heiden]

Two videos. The first is European maple (not as hard as rock maple). The second is jatoba. (I can only link one video and will post the second in the next post) Both are planed absolutely smooth, no chatter marks.



My testing rig on the lathe can't handle large forces. The sensors run out of their range and the carriers are suspended on leaf springs which start to act weird when the force is too large. I tested 5 and 10 mm wide samples and the results from the second were more or less exactly twice as large. I also compared a very slow speed (using the normal lead screw) and the speed used for all tests (using the thread cutting lead screw). Results were about the same. Kivimaa in 1950 wrote that the cutting speed has no effect on the force Fc. Walker and Goodchild did see some change, the force becomes less when cutting speed increases. I have no reason to believe this will be different for high angles versus capirons. My speed was 3 meter/min. That is 5 cm / sec. That's slow for a handplane. A handplane will be moved 5 to 10 times faster.

The downwards force Fn was measured at 0.5 kgf/6mm (I got that notation from Kato). A full width blade would be 8 times as wide (usually a bit narrower due to camber). That's 4 kg down wards force. Kato measured forces with different grain angles and found somewhat more downwards force when planing against the grain, but not magnitudes of difference. 4 kg is not much! And we're talking about a Hock blade which is thick, and a solid bedding on beech. People have used planes like that for ages and made some truly remarkable stuff, dimensioning all the wood by hand. A Stanley blade is thin and likes to flex. That's not ideal and can cause chatter and sound a bit like a tin toy at times. A wooden plane is not at all like that. If it chatters it is a defect, poor bedding or poor fit of the wedge. It sounds different too. I wonder how the new LV planes are like.

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.

My artice describes two tests. In the second part I used a 45 degree bedding angle with a 15 degree back bevel to simulate the 60 degree cutting angle. That is an edge configuration close to what you find on a BU plane with a high cutting angle. You will see at 0 meters (sharp blade) that the difference with the first test is not much. The Fn is now (slightly) positive, Fc is a little higher, but within the accuracy limits of the measuring jig. I had also changed the setup, made things more rigid. Of course, I should have repeated the first part of the experiment, but hey, I am only human and I had to paint the house and replace the windows from the garden shed.

BTW, the 30% increase in Fc is the minimum. I skewed everything in favor of the high angle plane. The equavalency tests were done with a Stanley plane with a 44 degree bevel on the chipbreaker, here I compare them with a 50 degree bevel which generates higher forces. In that equivalency test I concluded that a 60 degree plane is equevalent to a chipbreaker at 0.1 to 0.2 mm from the edge (depending on the wood). In the new test I compare with 0.1 mm only. So depending on the type of wood I expect the difference to be more rather then less.

BTW 2. You think a negative Fn is bad, I think it is good. In a 45 degree plane the wood is cut and the shaving is pushed out. In a 60 degree plane there is no upwards lifting of the shaving, the wood is pushed forward and fails in compression. That is the first step towards scraping and could explain the less prestine surface in some woods reported by Warren and David.

BTW 3. You're the first with real critique. Thanks for that. Critique is good and helpfull. I don't claim that my investigation is complete. There is so much more to test and only so little time. These tests are time consuming and I should have given up on my day job. Anyone wants to sponsor me?

[Kees Heiden]

[Adam Cruea]

I can't speak for Kees, but my impression is he was trying to compare standard angle BDs with chipbreakers to high angle BDs without. Comparing BUs would be a whole other thing.

More generally, I think you're missing the point. This isn't a blind experiment with a neutral observer. He's trying to (broadly) quantify results that anyone who has learned the double iron has experienced in a very visceral way. You can nitpick about shaving width or planing speed, and yes, those things might shift the numbers around a little, but I don't think you can seriously claim that they would alter the basic shape of the graph. And I say that because I've experienced the results in my shop, as have countless others. Before I learned to set the chipbreaker, I got tearout; now I don't. My 45° and 50° double irons stop tearout better than than the 55° planes I've used, and they are easier to push. In fact, that is one way you know you've set the cap iron a little too close; if it feels like a 55° or higher plane, back it off just a hair. If you get tearout, you backed it off too much. The sweet spot is somewhere in between.

I tried and tried and tried to stop tearout with my 45* frogs and couldn't, no matter how close I set the breaker. With a 50*, I notice that it's gone, as long as the blade is nice and sharp (it also leaves a super-smooth surface).

I have no idea how anyone can do it with the old-style Stanley breakers. Every time I try, I get wood shavings shoved up under it. I'm not saying it can't be done, just that I don't have the skillz necessary to mate old-style breakers with blades that well.

[Kees Heiden]

Adam, I think also that mating the two is the most difficult bit of using the capiron. There are several possible problems in your plane. When you peek between the two with a back light, do you see any gaps?

Or maybe the very edge of your chipbreaker doesn't come down like a real edge, the very last bit of the edge of the chipbreaker should touch the blade, not a part a little way up. You prepare the chipbreaker on a hard flat stone or fine sandpaper on glas, but the top end of the chipbreaker should drop down a bit during that operation, like in this picture.
DSC04496_zpsf801205d.jpg

Or maybe the capiron lost its spring over the years? You can bend it in a vice to get some spring back. Also turning the levercap screw a quarter of a turn tighter can increase the pressure to prevent shavings from entering under the chipbreaker.

[Steve Voigt]

I tried and tried and tried to stop tearout with my 45* frogs and couldn't, no matter how close I set the breaker. With a 50*, I notice that it's gone, as long as the blade is nice and sharp (it also leaves a super-smooth surface).

I have no idea how anyone can do it with the old-style Stanley breakers. Every time I try, I get wood shavings shoved up under it. I'm not saying it can't be done, just that I don't have the skillz necessary to mate old-style breakers with blades that well.

Kees' advice in the previous post is good. FWIW, I prefer the aftermarket blades/breakers, like Hock. I know some people really like the originals, but I like the thicker blade. And the Hock CBs work well if you put a slight secondary bevel on them.

[Adam Cruea]

Adam, I think also that mating the two is the most difficult bit of using the capiron. There are several possible problems in your plane. When you peek between the two with a back light, do you see any gaps?

Or maybe the very edge of your chipbreaker doesn't come down like a real edge, the very last bit of the edge of the chipbreaker should touch the blade, not a part a little way up. You prepare the chipbreaker on a hard flat stone or fine sandpaper on glas, but the top end of the chipbreaker should drop down a bit during that operation, like in this picture.
DSC04496_zpsf801205d.jpg

Or maybe the capiron lost its spring over the years? You can bend it in a vice to get some spring back. Also turning the levercap screw a quarter of a turn tighter can increase the pressure to prevent shavings from entering under the chipbreaker.

I'd be guessing it is just that the cap iron has lost the spring as when I generally mate old breaker with old iron, I find they're flat together (as in, the screw only holds the cap iron in place. . .it doesn't "squish" anything). I don't have any issues with the newer caps/irons (LV/LN), so I'm pretty sure it's just the old breakers are unsprung.

Of course, I could just tell my wife that the old blade/breakers need replaced in my #2 and 603.