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Thread: Tight mouths in wooden double iron planes.

  1. #16
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    I made a quick sketch of the mouth (scale 1:10), as suggested by Steve. Wear angle 85, bedding 45, capiron leading edge at 45 for 1mm height. Mouth = 0.4 mm (1/64"). There is still a bit of a constriction, but that is inevitable when the wear is at 85 degrees and the cap + bedding is 90 degrees. But there is room enough for the shaving and it is very conceivable that the curl touches the wear before it curls downwards, thus the shaving is directed upwards.

    Something to try on my next smoother.

    foto (3).JPG

  2. #17
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    In your setup the chipbreaker face is pitched at 92.5-97.5 deg (bed angle + chipbreaker face angle). With a wear angle of 75 deg the mouth actually *narrows* quite substantially between the cutting edge and the chipbreaker. I suspect that what's actually happening is that there's enough room for a curl to form just above the edge, but not enough room to pass that curl through the "choke point" just above. I think this is what you were trying to describe in different words?

    The obvious fix is to increase the wear angle as you did, though obviously that may cause other problems down the line.

    The other potential fix (and one that I've personally had good luck with) is to make the highly-angled face of the cap iron as short as possible. If you look at the Kato-Kawai video closely you can see that the shaving is always hitting the cap iron's face within the first 0.1-0.2 mm. In my experience you can get good tearout mitigation with a face as short as 0.25 mm, though others (Derek) think that's way too small, so YMMV. I currently use <=0.5 mm faces on my own planes and they work well. Doing this mitigates the problem by reducing the amount of narrowing due to the wear angle.

    More broadly, the conventional wisdom is that close-set cap irons and tight mouths don't mix, though there have been times where I've used both to great effect on difficult wood. IMO the keys to getting it to work are to keep the cap iron face short as described above, and keep the total cap iron face angle (bed + cap iron face) no larger or at least not much larger than the wear angle. That's why I say things like "total face angle of 90-95 deg" when people ask for advice instead of directly calling out the face angle itself - it depends on the bed angle and the plane's throat geometry.
    Last edited by Patrick Chase; 03-01-2016 at 10:57 AM.

  3. #18
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    Quote Originally Posted by Kees Heiden View Post
    I made a quick sketch of the mouth (scale 1:10), as suggested by Steve. Wear angle 85, bedding 45, capiron leading edge at 45 for 1mm height. Mouth = 0.4 mm (1/64"). There is still a bit of a constriction, but that is inevitable when the wear is at 85 degrees and the cap + bedding is 90 degrees. But there is room enough for the shaving and it is very conceivable that the curl touches the wear before it curls downwards, thus the shaving is directed upwards.

    Something to try on my next smoother.

    foto (3).JPG
    The steepest part of the cap iron face looks way higher/taller than it needs to be here. I would reduce that to 0.5 mm or perhaps even less.

  4. #19
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    Exactly...

    Of course one shouldn't forget, this is easy to draw on paper but actually pretty hard to execute in real life.
    Last edited by Kees Heiden; 03-01-2016 at 11:07 AM.

  5. #20
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    Quote Originally Posted by Steve Voigt View Post
    It's very possible to make the mouth pretty small, about 1/64", and still have a very close-set CB. Two things help. First, make the wear angle between 80°-90°. Second, make sure the shape of the cap iron is right. The curve of the cap starts about 1/2" from the edge and reaches a max of around 45°-50°. But the acceleration of this angle matters a lot. If it accelerates quickly and stays near 45° for most of the curve, clogging will be more likely. If the curve stays shallower at the beginning and then rapidly increases when it gets close to the edge,clogging is less likely.
    What Steve says here is exactly what I was trying to describe in #17 - the steepest part of the cap iron doesn't need to be very tall to work, and making it
    higher is a recipe for clogging. 0.5 mm is more than adequate, and 0.25 works.

  6. #21
    Quote Originally Posted by Kees Heiden View Post
    Just curious Steve, do you make them with a 1/64 mouth (0.4 mm)?

    I have measured several of my old planes, all Dutch from late19th century. The wear is indeed more like 75 degrees.
    I've made them with a mouth of 1/64," and that works fine, but they usually end up between .020-.030 (for non-roughing planes, of course). I try not to be too hung up on it.
    "For me, chairs and chairmaking are a means to an end. My real goal is to spend my days in a quiet, dustless shop doing hand work on an object that is beautiful, useful and fun to make." --Peter Galbert

  7. #22
    Quote Originally Posted by Kees Heiden View Post
    I made a quick sketch of the mouth (scale 1:10), as suggested by Steve. Wear angle 85, bedding 45, capiron leading edge at 45 for 1mm height. Mouth = 0.4 mm (1/64"). There is still a bit of a constriction, but that is inevitable when the wear is at 85 degrees and the cap + bedding is 90 degrees. But there is room enough for the shaving and it is very conceivable that the curl touches the wear before it curls downwards, thus the shaving is directed upwards.

    Something to try on my next smoother.

    foto (3).JPG
    As Patrick indicated, the shape of your CB is almost the opposite of want you want. It is a subtle thing (visually), but small changes can make a big difference, because all the action is happening in a very small space.

    (Btw, it was Dave Weaver who helped me figure that out in a way that was quantifiable and explainable. That happened quite recently. I was doing the right thing, but more or less on instinct. Being able to explain it makes it easier to repeat on a consistent basis.)
    "For me, chairs and chairmaking are a means to an end. My real goal is to spend my days in a quiet, dustless shop doing hand work on an object that is beautiful, useful and fun to make." --Peter Galbert

  8. #23
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    Yeah, that was a quick sketch. I don't really make them with a straight section, they end up much more rounded. But to be honest I didn't really pay too much attention to the exact shape of the capiron. So I thought, what the heck, lets try a picture. Here is my iron plus capiron flat on the bench. For reference put my 45 bevel square next to it. Then taking a picture though the magnifying glass.

    So, in a 45 degree bedded plane with 90 degree wear, it would look like this. To me this doesn't look like a shaving trap causing capiron.

    foto (6).jpg

  9. #24
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    Quote Originally Posted by Kees Heiden View Post
    Yeah, that was a quick sketch. I don't really make them with a straight section, they end up much more rounded. But to be honest I didn't really pay too much attention to the exact shape of the capiron. So I thought, what the heck, lets try a picture. Here is my iron plus capiron flat on the bench. For reference put my 45 bevel square next to it. Then taking a picture though the magnifying glass.

    So, in a 45 degree bedded plane with 90 degree wear, it would look like this. To me this doesn't look like a shaving trap causing capiron.

    foto (6).jpg
    Nope, that's not a bad profile at all for your current configuration (85 deg wear angle and 45+45 = 90 deg cap iron face angle). If you thinned it out a bit more immediately behind the first ~0.5 mm of the face (i.e. reduce the radius of curvature of the part of the cap iron immediately behind the face) then that might allow you to either increase the bed angle (you started at 47.5 right?) or decrease the wear angle while still avoiding clogging.

    There's a very delicate tradeoff here between continuity and clearance. Your current cap iron profile has very good continuity, and that's probably optimal for your current setup with relatively favorable angles (wear angle is only 5 deg less than cap iron face angle). In a setup with less favorable angles you might want to push the tradeoff more in the direction of "clearance".

    My $0.02 FWIW...
    Last edited by Patrick Chase; 03-01-2016 at 4:12 PM.

  10. #25
    Kees, that looks right to me.
    "For me, chairs and chairmaking are a means to an end. My real goal is to spend my days in a quiet, dustless shop doing hand work on an object that is beautiful, useful and fun to make." --Peter Galbert

  11. #26
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    Still this one caused me grieve with a 75 degree wear angle. Raising the wear angle to 79 cured the sick plane, but I am at 1 mm mouth now (0.04").

    Never mind, it works now and the next one I'll start with a steeper wear angle.

  12. #27
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    Quote Originally Posted by Kees Heiden View Post
    Still this one caused me grieve with a 75 degree wear angle. Raising the wear angle to 79 cured the sick plane, but I am at 1 mm mouth now (0.04").

    Never mind, it works now and the next one I'll start with a steeper wear angle.
    Or you can inlay a piece of harder wood to tighten the mouth back up and claim you meant to do that all along...

  13. #28
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    If I may be so bold to offer some feedback. Your mouth is quite far to the front at 0.25 from the length. English practice was to put it at 0.3 from the front. And your abutment line is indeed clashing with the top of the wear. It would look better if tge wear were higher. And with a bedding angle of 50 degrees it gets tight eith a wear angle of 85. Unless you make the capiron very flat.

    I don't really design. I look at a lot of old planes and the rest follows naturally. So you understand where I'm comming from.

  14. #29
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    I wonder what advantage there is with a smoother having a bed angle above 45 degrees if it uses a double iron? A lower cutting angle should produce a clearer finish. Bearing in mind that the lower the bed, and the more interlocked the grain, the greater commitment there must be to use the chipbreaker to control tearout.

    Two views of a 50 degree bed: for one building a plane for others, it offers a range of choices (i.e. to use chipbreaker, or not). On the other hand, if the plane is for oneself, the choice of the 50 degree bed angle is wishy-washy (sitting on the fence, so to speak). When I chose the frogs to keep in my Veritas Custom planes, they were 40 degrees (#7) and 42 degrees (#4). This was a commitment to using the chipbreaker.

    Regards from Perth

    Derek

  15. #30
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    Derek. You may need to raise your personal concerns on higher angle frogs with Rob Lee.

    regards Stewie;
    Last edited by Stewie Simpson; 03-02-2016 at 2:25 AM.

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