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  1. #1
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    Default How does a high angle plane reduce tearout?

    I understand how the chipbreaker and mouth effect tear-out, but can't comprehend the principles of how a high angle blade (be it a high angle frog, or bevel up plane with a high angle ground into it) works.

    There are plenty of online resources telling me to use a high cutting angle, but nothing that explains why.

    Can anybody explain what's actually going on?

    Lance

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  3. #2
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    The blade is working more like a scraper.

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    I think the high angle on a bevel up plane basically mimics what a chipbreaker on a bevel down does. I saw a fantastic old video on YouTube ages ago that demonstrated exactly how it all works, can't find it for the life of me...

  5. #4
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    I will add more later when I get a chance. The first bit here is from Steve Elliott's website article on shaving formations. Type lll is the high angle, which does not have a picture ..

    Tuning & Testing Infill Planes

    Chip Classification by Type
    Type 0: When a very sharp blade at a low angle to the workpiece is cutting with the grain, a shaving can be taken in which the fibers of the wood have not been bent significantly. (Think of a paring chisel with a bevel angle of 20º being used to cut softwood.) Unlike the other types of shaving, Type 0 has fibers that have not been broken as in Type I or been forced to slide relative to each other (sheared) as in Type II. When planing softwood with the grain, a Type 0 chip will be likely to produce a surface on the wood that has maximum clarity and an appearance of depth.


    Type I: When a thick shaving is taken by a blade with a greater angle to the workpiece, the wood tends to split ahead of the blade. When planing with the grain, the split wood is removed and becomes part of the shaving. When planing against the grain, the splitting causes chunks of wood to be removed below the cutting line, leaving defects in the surface that are known as tear-out. Type I chip formation is a cyclical process in which the splitting increases until the shaving breaks, and then begins again. The shaving produced is segmented due to its broken nature.


    Type II: When a thin shaving is taken or the angle of the blade is increased relative to the workpiece, a different mechanism of chip formation can occur in which the wood is cut right at the sharp edge of the blade and is then forced to bend sharply. This forces the fibers in the wood to slide against each other inducing a “shearing” effect that causes the shaving to lose much of its stiffness and reduces the chance that the wood will split ahead of the blade edge. A Type II shaving is curly but not segmented. In the images made by Dr. Franz, the line where this shearing starts is clearly visible.

    Type III: If the angle of the blade relative to the workpiece is increased further, a different mechanism for chip formation can occur. This is a scraping action, in which the wood is sheared off right at the cutting edge of the blade. Because of the high angle of the blade, significant forces are created that can deform the wood below the cutting line. Type III cutting is more effective on hard woods than soft ones because of the damage done to soft wood by this deformation.
    From my experience in trying to produce Types I and II, I believe the overwhelming majority of shavings taken by smoothing planes are of Type II. For an account of my attempt to produce a Type I shaving, click here.

    The second article is a link to David Weaver's discussion about setting a chipbreaker: Setting a Cap Iron

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  6. #5
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    Quote Originally Posted by elanjacobs View Post
    I think the high angle on a bevel up plane basically mimics what a chipbreaker on a bevel down does. I saw a fantastic old video on YouTube ages ago that demonstrated exactly how it all works, can't find it for the life of me...
    Ta Elan, I don't know if this is the one you are talking about. It's what finally made it all click when I started using hand planes a while ago. Though it's specifically in regards to the effect of a chip-breaker.



    Quote Originally Posted by derekcohen View Post
    Type III: If the angle of the blade relative to the workpiece is increased further, a different mechanism for chip formation can occur. This is a scraping action, in which the wood is sheared off right at the cutting edge of the blade. Because of the high angle of the blade, significant forces are created that can deform the wood below the cutting line. Type III cutting is more effective on hard woods than soft ones because of the damage done to soft wood by this deformation.
    Thanks Derek. I'll have a read around the links you provided a little more and see if I can visualise what he's talking about. At this stage though, I just can't conceptualise what's actually going on. Can you provide a sketch? (If your artistic skills aren't up to snuff, with three kids, I am well versed in evaluating and interpreting artistic intention )

    Ta,
    Lance

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    Yep, that's the one. I thought it covered angles as well as the chipbreaker, seems I was mistaken.

    There's pages and pages covering the science of chip formation in metals, but not so much for wood.

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    The others have covered it pretty thoroughly, but here's a couple of my own observations, fwiw.

    The first is that to get super-close cap-irons to work well, you have to be meticulous about the fit between cap-iron & the top of the blade. I and many others have struggled with that aspect. If you are starting out with old planes, be aware that many have had a hard life & very little attention to details such as the fit of the cap-iron. And even when the fit is good, some of our hard, recalcitrant woods seem to be able to work their way between C.I. & blade, which stops any sweet function very quickly! I think some of my early trouble was caused by cap-irons being mis-matched to the lever-cap. One plane in particular had the wrong cap, which I eventually figured out because the adjuster was always right at the end of it's travel just getting the blade to engage. Not only does the distance from edge to adjuster slot vary between makes & models, but he curve at the bottom can vary in diameter to the extent that the lever cap may not be bearing down at the right spot. If the pressure point is too far back, it tends to lift the front of the C.I., unless you put a goodly relief bevel on it to ensure the front remains in contact with the blade.

    The other is that I did some experimenting with different blade angles with & without cap irons, last year. The results apply to the planes I used (several different infills) and the woods I was planing, so I'm not claiming they would apply in all situations, but for the record, I could discern no beneficial effect from a cap iron at blade angles over 55 degrees. My 60 deg. plane with a single-iron blade worked as well as my best 45 degree with close-set cap iron on the nasty pieces I was using for my test beds. This surprised me somewhat, because if you look at the geometry, a single-iron cutter at 60 degrees should not be turning the chip anywhere near as much as a cap-iron honed to the recommended angle. There is close to a 30 degree difference at the contact point of the cap-iron, though this diminishes rapidly as the chip slides up.

    I think there is more to this business than we currently understand - certainly more than I understand!

    Cheers,
    IW

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    The others have covered it pretty thoroughly, but here's a couple of my own observations, fwiw.

    The first is that to get super-close cap-irons to work well, you have to be meticulous about the fit between cap-iron & the top of the blade. I and many others have struggled with that aspect. If you are starting out with old planes, be aware that many have had a hard life & very little attention to details such as the fit of the cap-iron. And even when the fit is good, some of our hard, recalcitrant woods seem to be able to work their way between C.I. & blade, which stops any sweet function very quickly! I think some of my early trouble was caused by cap-irons being mis-matched to the lever-cap. One plane in particular had the wrong cap, which I eventually figured out because the adjuster was always right at the end of its travel just getting the blade to engage. That in turn led to the discovery that not only does the distance from edge to adjuster slot vary between makes & models, but the curve at the bottom can vary in diameter to the extent that the lever cap may not be bearing down at the right spot. If the pressure point is too far behind the top point of the curve, it tends to lift the front of the C.I., unless you put a goodly relief bevel on it to ensure the front remains in contact with the blade.

    The other is that I did some experimenting with different blade angles with & without cap irons, last year. The results apply to the planes I used (several different infills) and the woods I was planing, so I'm not claiming they would apply in all situations, but for the record, I could discern no beneficial effect from a cap iron at blade angles over 55 degrees. My 60 deg. plane with a single-iron blade worked as well as my best 45 degree with close-set cap iron on the nasty pieces I was using for my test beds. This surprised me somewhat, because if you look at the geometry, a single-iron cutter at 60 degrees should not be turning the chip anywhere near as much as a cap-iron honed to the recommended angle. There is close to a 30 degree difference at the contact point of the cap-iron, though this diminishes rapidly as the chip slides up.

    I think there is more to this business than we currently understand - certainly more than I understand!

    Cheers,
    IW

  10. #9
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    Quote Originally Posted by Xfigio View Post
    I understand how the chipbreaker and mouth effect tear-out, but can't comprehend the principles of how a high angle blade (be it a high angle frog, or bevel up plane with a high angle ground into it) works.

    There are plenty of online resources telling me to use a high cutting angle, but nothing that explains why.

    Can anybody explain what's actually going on?

    Lance
    Hi again Lance

    Here are the four methods of setting up a plane for planing:


    The shape of the shavings is generally a way of determining what is happening at the edge of the bevel. There are essentially two kinds of shavings we want to pay attention to:

    Type I shavings break ahead of the blade. Imagine that you shoved a chisel into the end of a board and levered it up. The wedge action would cause it to split. That is what is happening in a Type I shaving. The further out from the blade the shaving (chip) forms, the greater the possibility of tearout. The only timbers that are immune are those with straight grain. You can see this in the extreme left (BD, no chipbreaker, common angle - like a Stanley plane). The shavings are curly, and bunch into circles.

    Type II shavings break close to the blade. This does not give them a chance to create a wedge as they are forced upward, and Newtons Law (equal and opposite reaction) means that force is pressed down as well at the edge of the blade. This is achieved in two ways: either the closed up chipbreaker (about 0.4mm from the edge of the blade) bends the shaving upward, or a high cutting angle (on either a BD or BU plane) does something very similar. Type 2 shavings are straight (or fairly straight).

    A BU and BD plane can offer the same high cutting angle. On a BD plane, one can do this via a high bed (say 60 degrees, as on a HNT Gordon plane) or a high bed (such as a 55 degree frog on a LN #4) or a backbevel on a common angle plane (a 15 degree backbevel on a 45 degree bed creates a 60 degree cutting angle).

    The BU planes have low beds (12 degrees), however the cutting angle is the bevel angle plus the bed angle (so, 50 degree bevel + 12 degree bed = 62 degree cutting angle).

    The higher the cutting angle, the closer it moves to a scraping cut.

    In theory, a low cutting angle should create a cleaner surface than a high cutting angle (e.g. think of the relatively rougher surface left behind by a scraper). Therefore, a common angle smoother with a closed chipbreaker should out perform a smoother with a high cutting angle. In practice, this may be so, but is difficult to see, and after a finish it is no evident.

    A smoother with a closed chipbreaker is ultimately better at controlling tearout than a high cutting angle. It depends on the timber, however. I have smoothed panels made of book-matched panels (i.e. where the grain runs against/opposite one another), and only the closed chipbreaker plane will do this successfully. On less demanding situations, a high cutting angle can work as well.

    For many, learning to set the chipbreaker close up is too difficult ... or so they believe, and give up. It is not hard, but it takes practice. I'd say at least a year to get consistent. For this reason, a BU plane with a high cutting angle is preferred. It is so easy to set up and use. So why not?

    I have an article here (this is actually part 3 of four) on the differences: http://www.inthewoodshop.com/ToolRev...omPlanes4.html

    The first part is here. I think it is worth reading: http://www.inthewoodshop.com/ToolRev...omPlanes1.html

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  11. #10
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    Quote Originally Posted by IanW View Post
    The first is that to get super-close cap-irons to work well, you have to be meticulous about the fit between cap-iron & the top of the blade.
    Augh, been there, suffered from that. The first plane I bought was an old #4 that needed a bit of work. Despite everything I could do, I just couldn't get it to work well and it ended up sitting on the shelf for about six months. At one point work got particularly stressful, so in an effort to blow off some steam I left the office early and decided that that was the day to get that stinking #4 to work well. It turned out that despite thinking I had got the chip breaker seated well, there was still a sliver of light showing between it and the blade. After more work on the back of the blade and the chipbreaker, they seated perfectly, and the plane is now a joy to use.


    Quote Originally Posted by IanW View Post
    I could discern no beneficial effect from a cap iron at blade angles over 55 degrees. My 60 deg. plane with a single-iron blade worked as well as my best 45 degree with close-set cap iron on the nasty pieces I was using for my test beds. This surprised me somewhat, because if you look at the geometry, a single-iron cutter at 60 degrees should not be turning the chip anywhere near as much as a cap-iron honed to the recommended angle. There is close to a 30 degree difference at the contact point of the cap-iron, though this diminishes rapidly as the chip slides up.

    Good observations. See my thoughts related to this in response to Derek's post below.

    Quote Originally Posted by derekcohen View Post
    I have an article here (this is actually part 3 of four) on the differences: http://www.inthewoodshop.com/ToolRev...omPlanes4.html
    The first part is here. I think it is worth reading: http://www.inthewoodshop.com/ToolRev...omPlanes1.html
    Hmmm, there went my morning! I thought I'd read most of what you'd written about planing troublesome grain, but as this was within in a tool review, I missed it.

    I don't know when the penny dropped, but a combination your drawing, re-watching the entire Kawai and Kato video (I'd not seen the version with subtitles) and reading your review (including additional links) seems to have answered a whole slew of questions. It's that beautiful moment when a whole range of disparate bits of information I've gleaned join together to form a comprehensive picture, and dare I say it, understanding.

    So at the end of the day, what appears to matter is the total angle at which the tool (blade or blade + chipbreaker) is presented to the wood, regardless of the mechanism that achieves it. I was particularly interested in the results of the planing test in your article, where the top four were different tool configurations, but achieved a similar result.

    Now, onto the chipbreaker. I have been trying to ensure I set the chipbreaker as close to the blade edge as possible. I find it problematic though, because I have to factor in the movement of the chipbreaker as it flexes when being cinched down. There is nothing to dampen the joy of a freshly honed plane blade quite like overshooting the blade edge with the chipbreaker. Bah!

    Thanks everyone for your responses. The biggest question that remains is with this new knowledge, can I keep myself in the office today, or will I find myself in the workshop putting some of these insights into practice? It probably doesn't help that my office is directly above the workshop.

    Lance

  12. #11
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    I have struck this problem in another sphere totally unrelated to hand planes. You can measure the chip breaker set back by using feeler gauges to set it. Assemble the CB and blade, place a feeler gauge you think is close to the clearance you want on a flat surface and carefully place the vertical blade assembly with the chipbreaker on the feeler gauge. The blade will then be pushed down and the CB will be sitting on the feeler gauge creating the set back. Try that setting and if the CB has not got enough clearance use a thicker feeler gauge, rinse and repeat as necessary. I have seen some criticism of this method which I can't understand as it does work.

    d044eb56f00df6563ff6ca74b1a4aebd--woodworking-shop-woodworking-projects.jpg
    CHRIS

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    Quote Originally Posted by Xfigio View Post
    ..... I have been trying to ensure I set the chipbreaker as close to the blade edge as possible. I find it problematic though, because I have to factor in the movement of the chipbreaker as it flexes when being cinched down. There is nothing to dampen the joy of a freshly honed plane blade quite like overshooting the blade edge with the chipbreaker. Bah!....
    Lance, you are not alone. I have (or had, see next para.) a couple of blade/cap-iron combos that drove me crazy every time I had to sharpen - it got to the point I would avoid sharpening those beasts for as long as possible because I knew it would be a struggle. I would get everything sitting perfectly, tighten the screw to almost there, re-check, tap the CI a little if it was off, then cinch it down. The result was almost always the the CI slewed and went over the edge of the blade...

    Not so long ago I decided enough was enough & took a good hard look at what was going on. I noted two things, one was the roughly-worn surface on the screw where it mates with the blade, the other was small score-marks on the blade caused by the rough bits of the screw catching on it. I cleaned up the blade surface with fine W&D on a block (most blades are pretty soft from the beginning of the slot up), and with a fine file, I carefully knocked off the dags from the screw as best I could. I would have liked to put the screw in the lathe & re-face it, but trying to set that short screw up square in the lathe chuck looked like more trouble that it was worth, so I thought I'd just try the file first. Anyway, my first-aid had a remarkably beneficial effect (smearing the bits with a little light oil probably helped, too) and I am able to put those blades & CIs together virtually hassle-free, now.

    By coincidence, I actually made a new CI screw yesterday to replace one whose thread stripped. The freshly-machined screw tightened like a charm, absolutely no unwanted movement at all. Bliss! Some rainy day I might make a couple more...

    Not sure if your cap-iron setting woes stem from the same source, but it might be worth checking the state of the mating surfaces & doing some judicial cleaning up if it looks necessary (& using a little lubricant between screw-head & blade)...

    Cheers,
    IW

  14. #13
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    Quote Originally Posted by Xfigio View Post
    ..... I have been trying to ensure I set the chipbreaker as close to the blade edge as possible. I find it problematic though, because I have to factor in the movement of the chipbreaker as it flexes when being cinched down. There is nothing to dampen the joy of a freshly honed plane blade quite like overshooting the blade edge with the chipbreaker. Bah!....
    Lance, you are not alone. I have (or had, see next para.) a couple of blade/cap-iron combos that drove me crazy every time I had to sharpen - it got to the point I would avoid sharpening those beasts for as long as possible because I knew it would be a struggle. I would get everything sitting perfectly, tighten the screw to almost there, re-check, tap the CI a little if it was off, then cinch it down. The result was almost always the the CI slewed and went over the edge of the blade...

    Not so long ago I decided enough was enough & took a good hard look at what was going on. I noted two things, one was the roughly-worn surface on the screw where it mates with the blade, the other was small score-marks on the blade caused by the rough bits of the screw catching on it. I cleaned up the blade surface with fine W&D on a block (most blades are pretty soft from the beginning of the slot up), and with a fine file, I carefully knocked off the dags from the screw as best I could. I would have liked to put the screw in the lathe & re-face it, but trying to set that short screw up square in the lathe chuck looked like more trouble that it was worth, so I thought I'd just try the file first. Anyway, my first-aid had a remarkably beneficial effect (smearing the bits with a little light oil probably helped, too) and I am able to put those blades & CIs together virtually hassle-free, now.

    By coincidence, I actually made a new CI screw yesterday to replace one whose thread stripped. The freshly-machined screw tightened like a charm, absolutely no unwanted movement at all. Bliss! Some rainy day I might make a couple more...

    Not sure if your cap-iron setting woes stem from the same source, but it might be worth checking the state of the mating surfaces & doing some judicial cleaning up if it looks necessary (& using a little lubricant between screw-head & blade)...

    Cheers,
    IW

  15. #14
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    Thanks Ian, I've bookmarked your comprehensive comments to have a look when I get back into the workshop after we're back from travelling over Easter.

    Regarding the machine oil, I cottoned on to that a whole ago when I was having difficulty advancing and retracting the blade. A lite wipe of oil makes a huge difference.

    Lance

  16. #15
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    Lance wrote: Now, onto the chipbreaker. I have been trying to ensure I set the chipbreaker as close to the blade edge as possible. I find it problematic though, because I have to factor in the movement of the chipbreaker as it flexes when being cinched down. There is nothing to dampen the joy of a freshly honed plane blade quite like overshooting the blade edge with the chipbreaker. Bah!
    Chris suggested: You can measure the chip breaker set back by using feeler gauges to set it. Assemble the CB and blade, place a feeler gauge you think is close to the clearance you want on a flat surface and carefully place the vertical blade assembly with the chipbreaker on the feeler gauge. The blade will then be pushed down and the CB will be sitting on the feeler gauge creating the set back.
    Ian wrote: Not so long ago I decided enough was enough & took a good hard look at what was going on. I noted two things, one was the roughly-worn surface on the screw where it mates with the blade, the other was small score-marks on the blade caused by the rough bits of the screw catching on it.
    The problem I have with Stanley chipbreakers is that they are flexible, and may ease over the edge of the blade when tightened down ...




    Solid type chipbreakers, such as the LV/Veritas and LN, do not flex like this, and are easier to position in a reliable manner ...



    Actually, I find the latter two chipbreakers a little too flat, and add a very slight bend in them to create a smidgeon of flex. That make it easier to get a tight fit.

    I wrote about some of these factors when reviewing the LV chipbreaker, and also commented that the LV chipbreaker screw is the best of all as it is easiest to finger tighten. Article here: http://www.inthewoodshop.com/ToolRev...ipbreaker.html

    Setting the distance of the chipbreaker back from the blade is something that you need to learn to do without a jig. The reason is that there is not one distance/number that works for all set ups. The angle at the leading edge should be around 50 degrees, but some have found higher works for them (do this with a honing guide). The thicker the shaving, the further back you can set the chipbreaker. Ditto for the steeper the leading angle, and also conversely: the lower the leading angle of the chipbreaker, the closer it needs to be set.

    The higher the bed/from, the less critical the angle at the leading edge. In this article, where I set up a 50 degree LN #3, the leading edge is 45 degrees: http://www.inthewoodshop.com/Woodwor...ipbreaker.html

    I think that the leading edge for my Veritas Custom #3 is 50 degrees, but keep in mind that the frog is 42 degrees. I am tempted to push it up to 60 degrees and see it this is better.




    A sign that the chipbreaker is positioned correctly is, as I mentioned earlier, the shaving becomes straight (not curly). A sign that it is too far forward (too close to the edge) is that the shaving starts to accordian (crinkle).

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

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