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Thread: Frog seating

  1. #1

    Frog seating

    I received a question about the frog needing to be in place when flattening a plane.

    And my answer is there are lots of fairy tails out there. If someone wants to sound knowledgeable, they throw in the frog needs to be attached. My question is do you really think you can move a cast iron plane body into registration with 2 (12-24 ) screws and a screw driver?


    In industry, the piece to be machined is set up so that the largest surface can be machined In its free state. This establishes the parts datum surface. And a datum is a plain, line, surface, or feature assumed to be perfect.The rest of the diffination deals with tolerancing. Dimensions comes from a datum but in itself a datum has no tolerance.The last part paraphrased


    Once the largest surface is machined ( bottom of the plane body) then one has control of all plains of motion, of which there are twelve, and the sides and then the frog seats can be machined by locating on the bottom. Not the other way around.


    If there is a problem with the bottom not being flat then is is because of the person who took the milling marks out when finishing the job, Which would not effect the relation of the planes bottom and the planes seats. Or casting stress being relieved over a 100 years. And the seating area being the thickest eare would be least effected.


    The idea probably came from a person who wanted to sound knowledgeable and to embellish an article to sell a book or magazine. And it continues to get parretted.


    The world is not flat even though every one knew that it was at one time so my questions remains. Do you really think you can move a cast iron plane body into registration with 2 (12-24 ) screws and a screw driver?
    Tom

  2. #2
    Thanks for the lesson Tom, and for sharing your years of experience as a tool and die man. I hadn't thought about it your way before, but it makes sense to me.

    Best regards,
    Fred
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  3. #3
    I'd bet that the origin of this myth comes from confusion between wooden and metal planes. When flattening the sole of a wooden plane, the wedge and iron absolutely need to be installed because the body of the plane does flex when the wedge is set. Probably the good advice that your (wooden) plane needs to be fully assembled when flattening was accidentally transferred to metal planes, where it's not necessary at all.

  4. #4
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    This is an interesting topic.

    Another question might be, is there a problem caused by having the frog installed when lapping the sole?

    This may be the case with a milling machine set up. For hand lapping the biggest problem might be the need to disassemble and clean after lapping.

    For me when hand lapping a plane's sole, it is just as easy to do with the frog in place. If this doesn't cause a problem, it will likely be continued.

    With Stanley/Bailey planes before type 9 the frog was seated on a single platform. Type 9 and later made contact not only in the area where the screws were securing it but also behind the mouth. Could a slight variation in the machining of the frog or the sole cause extra pressure at the back of the mouth?

    More than one of my block planes have had varying degrees of a concave sole. The weight from my hand would cause the plane to cut. At the end of the cut as the weight from my hand diminished, the blade would lift out of the cut. This was corrected with some careful use of abrasive paper on a flat surface.

    A block plane has the blade resting on an area behind the mouth and a pedestal closer to the back of the blade. This is all held securely in place by a screw in the middle. There have been a few in the past who have said over tightening of this screw may cause damage to a block plane.

    By my best estimation the distortion from the weight of my hand is likely not any more than what of a couple of #12 screws are able to bring to bear.

    As always, YMMV!!!.png

    jtk
    Last edited by Jim Koepke; 11-26-2019 at 3:13 PM. Reason: Changed wording about block planes concave soles
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  5. #5
    No, having the frog in place when hand lapping doesn't cause a problem. The problem with hand lapping is 100 year old cast iron doesn't lap very well. And the closey one get to flat the more of the entire surface one need to take off. So one can spend months and still not get it flat.I have fixed enough planes others have tried to hand lap to know it is not worth the effort. One can do as much good by taking a random orbital sander with 180 paper and shining the bottom and then waxing it.

    Having to flatten planes is like having to rebuild a car engine every time one trades vehicles

    Yes, every one knows how to flatten a plane but then everyone also knew if you sailed to far you would fall off the world. And every one also said if man was supposed to fly then God would have given him wings. Flatten planes,, falling off the world and God giving man wings is all a myth. Just because one believes something is true doesn't make it so
    Tom

  6. #6
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    12 planes of motion? Care to elaborate? I understand X, Y, Z. What are the other 9? Thanks

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    Tom, we can agree that lapping the sole of a plane is not a simple operation.

    We can also likely agree that it involves more than just pushing a plane back and forth on an abrasive surface.

    We likely agree using a flat surface with abrasive sheets isn't going to produce a surface flat to some precise measurement. My contention, from experience, is it is possible to use care and make a plane's sole flat enough to do its job quite well.

    If one wants the sole to be flat to a couple thousands over the full length and width it will require a machine shop or buying from LN or LV.

    My position on lapping the sole of a plane is to not do it unless there is a problem that can be demonstrated as being caused by the sole being out of flat. Then my first suggestion would be for a person to find a machinist such as yourself to do the job. Failing that, they should find someone with some experience. Finally if that is not available in their locality they should approach lapping very carefully and have a plan to accomplish their goal.

    Of all my planes, only a very few had problems that were fixed by lapping with abrasive sheets on a flat surface.

    One thing many do not realize is without much effort it is very easy to make the sole of a plane much worse than it was with a few minutes of running a plane back and forth on abrasive paper.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  8. #8
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    Back to the frog seats:

    About the only thing I usually do when rehabbing a plane....a wire cup brush is run on the seats....mainly to remove all that thick paint....I take the seat down to bare metal ( along with the underside of the frog) then try the frog on the cleaned up seats....IF anything needs corrected ( RARE...) then a flat file that spans the entire seat area, is used a couple times, until the base and the frog sit nicely. Same with the face of the frog...more to remove all that paint...and sometimes a bit of rust. I usually just go for clean, bare metal on the face. A quick check with a straightedge...all the way down and out the mouth.

  9. #9
    Quote Originally Posted by Tom Bussey View Post
    I received a question about the frog needing to be in place when flattening a plane.

    And my answer is there are lots of fairy tails out there. If someone wants to sound knowledgeable, they throw in the frog needs to be attached. My question is do you really think you can move a cast iron plane body into registration with 2 (12-24 ) screws and a screw driver?


    In industry, the piece to be machined is set up so that the largest surface can be machined In its free state.
    And there lies a potential flaw in the logic, as it applies to hand planes. Because their "flatness" (whatever that means) is only of value when the plane is actually _used_, in its working configuration. Perhaps this is what is throwing people off.

    Think about it.

    (And no, I've never had to lap a plane sole.)

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    (And no, I've never had to lap a plane sole.)
    My suspicion on some of the planes that came through my shop needing work on their sole is they were previously "lapped" by someone with no idea of what they were doing.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  11. #11
    Quote Originally Posted by Jim Koepke View Post
    My suspicion on some of the planes that came through my shop needing work on their sole is they were previously "lapped" by someone with no idea of what they were doing.
    You can talk about your suspicion all you want, and I will counter that with my conviction that you are probably right.

  12. #12
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    LOL!

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  13. #13
    Quote Originally Posted by Doug Dawson View Post
    And there lies a potential flaw in the logic, as it applies to hand planes. Because their "flatness" (whatever that means) is only of value when the plane is actually _used_, in its working configuration. Perhaps this is what is throwing people off.

    Think about it.

    (And no, I've never had to lap a plane sole.)
    Im thinking about it, and the wording of your statement. I very much want to understand, having a personal interest in the subject. When you say used in its working configuration, do you mean under the tension of the lever cap? Something has been throwing me off with my jointer plane and Im very interested to understand your point of view.

  14. #14
    Quote Originally Posted by Mike Cornwall View Post
    Im thinking about it, and the wording of your statement. I very much want to understand, having a personal interest in the subject. When you say used in its working configuration, do you mean under the tension of the lever cap? Something has been throwing me off with my jointer plane and Im very interested to understand your point of view.
    What I mean is, in full trim as used to plane a surface, or to joint an edge (over some non-trivial length.) It doesn't need to be more complex than that.

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