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Question to Robin Lee re: Lapping

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  • Question to Robin Lee re: Lapping

    I guess the only way this is ever going to be answered is if we ask the one person who would be totally in the know.


    There has been questions asked about the Lee Valley plane blades being lapped. From your web site, the following tech bulletin is posted.

    Lapping

    We now lap our Veritas A2 and O1 plane blades* on the face (non-bevel side) to a flatness tolerance of 0.0002" or better over the working surface, and with an average roughness surface finish of 5 microinches (0.000005") or better. On our regular and bevel-up plane blades, the working surface is the section of the face that extends from about 1/8" below the bottom of the screw slot to the cutting edge; on shoulder and bullnose plane blades, it is the widest section of the face from the shoulder to the cutting edge. Average roughness (Ra) measures the height variations in the surface over a given area and then provides an average roughness value to represent the surface finish the lower the value, the better the finish. While the blade faces are both smooth and true, they can still benefit from final polishing. You will also still need to hone the intersecting bevel.
    Your surface smoothness is listed as 5 microinches. From my calculations, works out to about .14 microns, or well beyond any water stone or paste that you provide. See your chart here

    Please verify if this is true as there is some confusion as to why then in the last part of your tech bulletin you say that :

    While the blade faces are both smooth and true, they can still benefit from final polishing

    How can you polish something that is already smoother than any finish that I can put on it?


    I know that many woodworkers here in the Canadain Woodworking forum are interested to know as we are all passionate about our craft and want to make sure we are working with the sharpest blades possible.

    Matt Mackinnon
    Matt

    People are like a box of chocolates. It's hard to tell initially which ones are nuts.

  • #2

    Re: Question to Robin Lee re: Lapping

    Re: Question to Robin Lee re: Lapping

    Matt,

    If I'm reading this correctly average roughness (Ra) isn't a measure of 'scratch depth' (as caused by an abrasive). It's an average of the 'out of flatness' of the surface, that is how much of the surface is +/- 0.0002". As an example 5 points: 0.0001, -0.0002, 0.0001, -0.0001, 0.0002; would have a Ra of 0.00006".

    The final scratch depth will be be determined by the abrasive. This is a lapping process, so they'd need a lower grit to get it done in a reasonable amount of time. The description in the Chris Shwarz book says it takes an hour... Which actually seems like a long time.

    Since I'm in a betting mood... I say 4000 - 6000 grit, manmade abrasive. If I win I plan to reward myself with a new Veritas plane. If I don't well then... maybe I'll buy a saw.

    All kidding aside, that's still a very flat and polished back, as I'd define them as a woodworker. I usually take the soothers to 8000 grit... Though I suspect it's really not needed. The tolerances I see people 'requiring' are probably too tight to be meaningful for woodworking.

    I hope Robin gets back to you. I always enjoy reading what he has to say.

    Comment


    • #3

      Re: Question to Robin Lee re: Lapping

      Re: Question to Robin Lee re: Lapping

      I can't say for sure, but I think Buster is on to something. The stylus on the machine that measures the surface irregularities must come to a point, and that point isn't going to be smaller than even a 600 grit particle, so it won't read tiny scratches. I think this might be an apples and oranges thing, though it doesn't seem like it at first.
      Mike in Orangeville, ON
      http://ifonlyyouwood.blogspot.com/

      SPCHT

      Comment


      • #4

        Re: Question to Robin Lee re: Lapping

        Advertising

        He has commented that due to advertising there has to be a safety factor in what you claim. His other comment was it is well above the 1000 Norton water stone and closer to the 4000 grit. I give the 4000 grit about 10 minutes and 5 on the 8000 stone followed by a few minutes on the .5 micron paper. A 30x jewlers loop will show you where you need to spend a few more minutes getting a "deep" scratch out. lol

        Comment


        • #5

          Re: Question to Robin Lee re: Lapping

          Re: Question to Robin Lee re: Lapping

          Hi Matt -

          Geez - you guys actually read and verify what we write??

          Firstly - let me say that you have to take into account the difference between the grit size of a shapening medium, and the scratch pattern it leaves... a five micron abrasive will leave a surface scratch pattern much finer than 5 microns...affected as well by pressure and speed of application.

          Also - the the blade CAN benefit from additional honing/polishing (though not necessarily the lapped surface) as we do not (cannot) lap the bevel itself...and Buster makes a good point - it's the average surface we state the tolerances on; there can be deeper scratches in the pattern...

          In terms of flatness - yes it's true, most people can only make the blade worse by lapping it... but I'd never dare say that you can't make something better by careful sharpening....

          Cheers -

          Rob

          Comment


          • #6

            Re: Question to Robin Lee re: Lapping

            Re: Question to Robin Lee re: Lapping

            Rob,

            Were you throwing Buster2000 a bone when you said he was right so he would buy a new plane?

            Buster2000: I want to see proof! You have no excuses you publicly promised to buy a new plane!

            Merry Christmas!

            Brad

            Comment


            • #7

              Re: Question to Robin Lee re: Lapping

              Re: Question to Robin Lee re: Lapping

              My bet was regarding lapping grit... but since you're twisting my arm...

              Comment


              • #8

                Re: Question to Robin Lee re: Lapping

                Re: Question to Robin Lee re: Lapping

                Atta boy! I knew you just needed a little push!

                Brad

                Comment

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