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Thread: Tight mouths in wooden double iron planes.

  1. #166
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    Quote Originally Posted by Mike Holbrook View Post
    ....

    I am still a little cloudy on why thicker BU plane irons often come with 25 degree bevels and why Derek suggests 25 for BU planes vs what seems to have become the standard 30 degree bevels for thinner BD planes. Maybe the thicker blades are able to support a 25 degree bevel better and maybe the smaller angle is easier to make a micro bevel on? It also occurs to me that Warren’s experiments with optimal clearance angles might mean the smaller bevel angle works better with the smaller frog bed angle (25-12 is closer to 11)? Could a micro bevel on a BU plane serve a similar function to a chip breaker on a thinner BD plane? It would seem easier to grind 30 vs 25 bevels though and there would not seem to be a great difference in adding micro bevels to a 30 degree bevel.


    The other factor that has me a little confused is how hollow ground plane blades function vs straight or convex blade bevels. I use hollow grinding because I find the resulting bevel to be much easier to maintain. The hollowed edge does have a little different angle that might be a significant enough difference to effect chip clearance? I am wondering if the micro bevel created by sharpening a hollow ground blade along the two edges the hollow makes could essentially function as a micro bevel/chip breaker on BU blades?
    Hi Mike

    The answer to the first question comes in two parts:

    The 25 degree primary bevel for BU plane blades was something I evolved a goodly number of years ago now. It arose out of the challenge to more easily camber BU plane blades, especially those with high cutting angles, such as 38- and, particularly, 50 degrees. At that time, almost all users of LV bevel up planes would either turn to one of the 38- or 50 degree blades they sold. Achieving a camber on these, and especially the more extreme cambers used for a jack plane (such as a 8-9" radius), was a great deal of work. Cambers on BU planes need to be a little greater than on BD planes.

    The idea was to only use a 25 degree primary bevel, and add the desired bevel angle via a micro secondary bevel (using a honing guide - needed as bevel angles on BU plane blades determine the cutting angle, and accuracy is more relevant now). What this did was to minimise the amount of steel needed to be removed to create a camber. It makes adding camber very easy to do. (Note that this does not invalidate the high angle blades sold by Lee Valley - they are appropriate for use is you prefer to use a straight blade. Some argue that they can achieve the same result by clipping the corners of the blades. I have never found this an effective method).

    http://www.inthewoodshop.com/Woodwor...aneBlades.html

    The second part of the question is whether there is a difference between a BU primary bevel at 25 degrees, and a BD primary bevel at 30 degrees. The answer to this is that (a) unless you are shooting end grain, where the bevel is 25 degrees, the rest of the time you will add a secondary bevel and the final angle will in fact be higher than 30 degrees for BU plane blades. And (b), the low vector of a BU plane blade creates less stress on the blade edge than that created on the higher BD blade edge. Tests I did on shooting boards, BU vs BD, revealed that the BU plane (with a 12 degree bed) far outlasted a BD plane (with a 45 degree bed).

    http://www.inthewoodshop.com/ToolRev...tingPlane.html

    To answer your second question: If you are using a honing guide, it does not matter whether you start with a hollow or flat grind. All that counts is the angle of the secondary bevel. In terms of strength of the edge, over the course of several years, I never experienced any chipping on a 25 degree hollow grind on a LV LA Jack used to shoot hard wood end grain.

    Regards from Perth

    Derek

  2. #167
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    Quote Originally Posted by Derek Cohen View Post
    The second part of the question is whether there is a difference between a BU primary bevel at 25 degrees, and a BD primary bevel at 30 degrees. The answer to this is that (a) unless you are shooting end grain, where the bevel is 25 degrees, the rest of the time you will add a secondary bevel and the final angle will in fact be higher than 30 degrees for BU plane blades.
    I think this may understate the usefulness of 25-deg bevels on BU planes. They're certainly excellent for end grain (more on that below) but they also leave an ultra-glassy surface for other cuts IF (big if) the grain is cooperative.

    Quote Originally Posted by Derek Cohen View Post
    And (b), the low vector of a BU plane blade creates less stress on the blade edge than that created on the higher BD blade edge. Tests I did on shooting boards, BU vs BD, revealed that the BU plane (with a 12 degree bed) far outlasted a BD plane (with a 45 degree bed).

    http://www.inthewoodshop.com/ToolRev...tingPlane.html
    I read that article, and in fact it was the one that convinced me to buy the Veritas Shooting Plane. Thank you for the excellent review.

    I think however that the results of your experiment are consistent with more than one explanation. The big uncontrolled variable was that the cutting angles weren't the same. You used a 45-deg cutting angle in the L-N 51, and a 37-deg cutting angle (12+25) in the Veritas. You therefore can't distinguish between the following possibilities:

    1. The blade on the Veritas wore less because the lower cutting angle produces lower cutting stresses and therefore less blade wear

    2. The blade on the Veritas wore less because of the "in-line force vector"

    As an engineer my money is on (1). As much as I would love to geek out on force vectors as I did on a grinding thread a while back, I don't think that's what's happening here. Admittedly it's a bit of an academic point because there's no such thing as a 37-deg BD shooting plane, so if you want that long blade life the BU plane is the only way to get it, regardless of "why". That's why your experiment was convincing to me - the bottom-line answer was the same regardless of the interpretation.

    Care to make a friendly wager and repeat the experiment with 33-deg bevels on both planes? (such that both have 45 deg cutting angle and 12 deg of relief, and any wear difference will be cleanly attributable to the blade orientation).
    Last edited by Patrick Chase; 03-27-2016 at 8:52 PM.

  3. #168
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    The new stock for the 7 inch smoother plane body has been dimensioned to size. I also completed some tests on the hydraulic press using some hardwood end grain to determine a low pressure setting and achieve a clear impression of the makers stamp. That worked out to be 1 tonne. Unfortunately the attached photo doesn't clearly show the makers stamp on the planes front end grain. Thanks to George for suggesting this stamping take place much sooner within the plane build.



    The next lot of photo's I post will be of the completed plane.

    Stewie;
    Last edited by Stewie Simpson; 03-28-2016 at 12:36 AM.

  4. #169
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    It seems to me that the size of a planes mouth, the "clearance" angle, the bed angle, whether we use a chip breaker or not, whether the plane is bevel up (BU) or bevel down (BD), primary, secondary and in the case of BU planes combined bevel angles, whether we hollow grind, flat grind or use a secondary bevel....are all so interrelated it is hard to talk about one factor out of context.

    It occurs to me that Patrick and I may be missing the point of research like Derek has done. Derek does research related to his own specific interests and specific tools he has reason to want to compare. By trying to apply that information to our own interests and tools we may find ourselves too far from the original context for meaningful comparisons. Patrick finds help in Dereke's research when he applies it to an exact tool, say a Veritas shooting plane, which Derek actually tested. I may find help in figuring out what frog I might want to order on a Veritas Custom #4 plane, which was also the subject of testing. When we start trying to extrapolate how this research may apply to BU planes other than those used in Derek's testing maybe we become to hypothetical to draw solid conclusions, and maybe we do a disservice to the research.

    Thanks for the response Derek, I did find some of the answers I have been searching for. Now that I at least understand the pieces of the plane puzzle that were started in this thread I will start a new thread.

    Sorry to have moved so far afield of your post Stewie. I got lost somewhere trying to figure out specifically what the discussion was about and where it applied. I have two 7- 7.5 inch (different bed angles) planes and a long Jointer/Try plane, from the same Purple Heart as the Jack I posted about earlier. I have not finished them up yet. I am stuck trying to decide whether or not to modify the original designs to work with blades with chip breakers. There has certainly been a great deal of interest in wood planes with double irons in the last couple years. So I am interested in what you are doing and how it may apply to my planes. I am starting a little research on 2" (all my Purple Heart planes use 2" irons) blades with chip breakers. Yours look very interesting. I have a 2" Veritas PM-V11 double iron blade which I use in metal Stanley planes at the moment. I am thinking about ordering a 2 1/4" Hock blade for a Stanley 5 1/2 to see if I like them as much as I like the PM-V11 blades. Veritas does not offer their double irons in 2 1/4. If I am going to modify any of my wood planes for chip breakers I guess I need to decide which ones to use first.
    Last edited by Mike Holbrook; 03-28-2016 at 3:05 PM.

  5. Quote Originally Posted by Mike Holbrook View Post
    [snip]

    If I am going to modify any of my wood planes for chip breakers I guess I need to decide which ones to use first.
    I'd wonder if it might not be a LOT easier to make new planes than to convert existing ones. Am I missing something?
    Fair winds and following seas,
    Jim Waldron

  6. #171
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    I ask that question in a previous thread. I believe all I need is a recess for the nut that tightens the two irons, not so hard to add. That and a little work on the wedge. Not excited about making four new planes and having four planes I probably would not use.
    Last edited by Mike Holbrook; 03-28-2016 at 10:44 PM.

  7. #172
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    Quote Originally Posted by Warren Mickley View Post
    Stewie, you may not have seen discussions of this topic on another forum over the last ten years. In 1976 I experimented with clearance angles and found that roughly 8-11 degrees of clearance was needed between the bevel and the sole of the plane. (On a bevel down plane the clearance equals the cutting angle minus the honing angle.) Since I hone my plane Irons at 30 degrees, full flat bevel, this puts a lower limit cutting angle at around 40 degrees for me. I have suggested that the 45 or 47.5 standard angles are made to give a cushion for those whose honing angles exceed 30 degrees. This cushion helps keep them out of clearance trouble. I have seen videos of well known bloggers etc who obviously hone closer to 40 than 30.

    I bought my fifth of five total bench planes in 1983. The cutting angles of the five are 45, 45, 43, 43, 42. I can see the difference between the 45 and the 42 degree planes. The 42 degrees is very slightly cleaner cutting, but I am not sure it is enough to make a fuss about.

    Warren. The replacement 7 inch smoother I am currently working on has the double iron bedded at 40 degrees.

    Looking forward to seeing it in action when its nearer to completion.

    regards Stewie;
    Last edited by Stewie Simpson; 03-29-2016 at 3:20 AM.

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