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  1. #1
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    Default Baileys 1867 patent on the Cap Iron

    Within Baileys 1867 patent on the Cap Iron, the claim was made that the cap iron, a thin piece of metal with a curved edge that's fastened to the cutter to keep it stiff. Leonard Bailey | Lemelson-MIT Program

    Lets test that theory by removing the Cap Iron from a Stanley #4, and using the Lever Cap only to apply downward pressure over the Cutting Iron to it metal bed. For the sake of test purposes, the original Cutting Irons thickness was measured at 2.3mm (0.085 "). A much thinner gauge cutting iron when compared to most high end double iron metal bench planes being sold on the market now.




    Its more than likely that prior to 1867, Bailey was fully aware of previous work on Wooden Bodied Bench Planes, that had proven that a closely set Cap Iron could successfully reduce the potential of tear-out on reverse grain. As was the case with single iron Bench Planes, bedded a higher than common pitch angle. Bearing those factors in mind, I will only be testing this modified Stanley # 4 with the grain on 2 types of timber. The 1st being a medium density Asian Hardwood, and the 2nd a high density Australian Hardwood.

    Before I forward the test results, would anyone care to forecast the likelihood that vibration (chatter) will be experienced at the cutting edge.

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  3. #2
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    Default

    Single iron planes have no problems in straight grained timbers, so my guess is no chatter on the first piece. My guess is that it depends on the gnarliness of the second piece of wood, combined with the depth of cut and sharpness of the blade.

  4. #3
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    The results are in;

    working both fine and medium thickness shavings, no signs of any vibration or chatter was experienced from the cutting edge.









    The reader is left to draw their own conclusions from the above results.

  5. #4
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    Default

    The reader is left to draw their own conclusions from the above results.
    Stewie, just how did you hold the blade in the plane - rubber washers? What was the depth of cut? Did you vary the depth of cut? Was there a difference when the blade was dull vs sharp? Is there a difference when the chipbreaker is positioned at different points on the blade?

    What is the purpose of your experiment, and what do you infer from your results?

    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 derekcohen View Post
    Stewie, just how did you hold the blade in the plane - rubber washers? What was the depth of cut? Did you vary the depth of cut? Was there a difference when the blade was dull vs sharp? Is there a difference when the chipbreaker is positioned at different points on the blade?

    What is the purpose of your experiment, and what do you infer from your results?

    Regards from Perth

    Derek
    just how did you hold the blade in the plane - rubber washers? Fiber washers.

    What was the depth of cut? Did you vary the depth of cut? Yes, both fine and medium depth of shaving.

    Was there a difference when the blade was dull vs sharp? I dont work with dull blades.

    Is there a difference when the chipbreaker is positioned at different points on the blade? No Cap Iron was used.

    What is the purpose of your experiment; To seek answers to Baileys claim.

    and what do you infer from your results? That is being left to the reader to make their own judgment.






  7. #6
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    Hi Stewie

    Chatter is potentially an interesting topic. Can you say more about it? What causes it? My questions were meant as a springboard for you to do so.

    Regards from Perth

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

  8. #7
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    Either LB was seeking a solution to problems that your test didn't cover (dull blades?) Or he was using this patent as an industrial intellectual property rights strategic move (patent something, anything then build on it).
    Occasional musings on my blog:
    bridgerberdel.wordpress.com

  9. #8
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    My own personal view which in part focuses on Baileys use of an 0.085" thin Plane Iron, is that the Cap Iron served 3 important purposes, the 1st as a connection point for the adjuster yoke, 2nd as a tensioner to reduced chatter and vibration felt through the cutting edge, 3rd, as a methodology to reduce tear-out on reverse grain.

    Moving on to the current trend by manufacturers in supplying a much thicker Plane Iron. imo,this redirects the Cap Irons role further away from that of a tensioner to the Plane Iron, and more towards a role to inhibit tear-out. Bearing this in mind, what's unclear to me, is why the need to also increase the Cap Irons thickness.

    I would like to also include my own thoughts on the use of the Cap Iron within traditional Wedge Abutment Bench Planes. 2 important considerations. 1st, the general shape of these thicker tapered irons used in both single and double iron format are near identical if you discount the slot that's used as mating point for the Cap Iron. 2nd, a wooden bed is better able absorb vibration emanating from the cutting edge, compared to that of a metal bed. Bearing both those factors in mind, imo, the role of the Cap Iron was less directed to that of providing additional tension to the Plane Iron, and more directed towards supplying a different type of approach to that being supplied by a high angle bed, in reducing the potential of tear-out on reverse grain.

    As a final wrap up, note the additional tension supplied within the shaping of the Cap Iron used on a Bailey/Stanley Plane, to that of a Cap Iron used in conjunction with a tapered iron on a Wooden Bench Plane.

    http://www.woodcentral.com/articles/images/935d.jpg



    Stewie;

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