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  • My #6 isn't flat...

    It never really occurred to me to check the flatness of the sole of my #6... but I did so last night, and... it's quite a fair bit convex (high spot in the middle).

    It's been a reasonably good performer for me, but not perfect. I've been considering replacing the blade for a lee valley one, but now that I see that it's not flat, I'm also considering trying to flatten the sole.

    I've never done this before, and the orientation (convex vs concave) seems like it would be more difficult to flatten.

    Any thoughts on whether I should really try it? If so, any tips on how to go about it? (Mostly I'm looking to ensure I'm taking material off the convex part, so I need to ensure I'm not rocking back and forth and actually making it worse!).

    I don't really care about keeping the sides exactly 90 degrees to the sole... I'll never use a #6 as a shooter.

    Cheers,
    --Jeff
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  • #2

    Re: My #6 isn't flat...

    The best way that I have found to lap something flat is to coat the sole with machinist's ink then lap away (permanent black marker will work just as well; any residue can be removed with alcohol when the lapping is done). The high spots will reveal themselves quickly and you will be able to see if you are maintaining symmetry as you lap. Convex is no more or less difficult to lap out than concave using this technique. One technique point worth mentioning is to retract the iron but do not disassemble the plane while lapping such that you have any assembly strains accounted for as you go. It isn't too difficult to ensure that the sides are maintained at 90 degrees to the sole either, assuming that the plane body is reasonably square in the first place of course.

    I use carborundum paper on heavy plate glass to get started; 180 or 220 until the thing is flat, 320 and 400 to remove the scratches and I usually polish with 600 as the final bit. Cast iron sands away pretty quickly so check often as you lap.

    There are probably many other ways to do this but the forgoing works well for me and requires a minimal investment of elbow grease!

    Ken
    nnieman likes this.

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    • #3

      Re: My #6 isn't flat...

      A few ways; the best (easiest and fastest): scraping the metal off. You can use engineer's blue and a flat reference to see where the high spots are, or just do it with a straightedge. Carbide scrapers work best, but HSS ones work well with cast iron too.
      If you're confident enough in your skills you can start with a belt sander or even a ROS and hog off metal from the middle (high spots), and then final flattening on glass with sandpaper or whatever you have or already use.
      Or, alternately, use your flat surface but only put a piece of sandpaper about 6" long in the middle. Glue regular paper (not abrasive) or very fine sandpaper at the ends, so you're only taking off metal in the middle as you move the plane back and forth.
      Frank
      SPCHT

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      • #4

        Re: My #6 isn't flat...

        Ken has good advice,but I find cast iron so easy to read I don't bother with bluing,and if you don't have a serface plate or heavy glass, chances awing of your table saw or bed of a jointer will do,just keep the slurry away from the cutting tool or blade and clean up well after.i also like to completely cover the sand paper with carpet tape and stick it down,and use a light oil

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        • #5

          Re: My #6 isn't flat...

          I hate to show my ignorance, but what's a #6?

          Noel
          "Being so impressed with the beauty of nature, I never cease to be amazed at how the
          'touch of the human hand' can transform it into another kind of beauty that is so uniquely human.
          "
          John Snow, Outdoorsman and Retired Teacher

          Comment


          • #6

            Re: My #6 isn't flat...

            Carbon based: Why do you think that it needs to be flat?

            Noel; A # 6 larger than a # 5 and smaller than a # 7 it is the numbering method that was given to represent plane sizes.

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            www.solidwoodmachinery.com

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            • #7

              Re: My #6 isn't flat...

              Originally posted by beachburl View Post
              I hate to show my ignorance, but what's a #6?

              Noel
              He's talking about a hand plane. They are numbered from 1 to 8, shortest to longest.

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              • #8

                Re: My #6 isn't flat...

                I just now re-read my post (#2 above) and I forgot to mention that I lap cast iron dry, no lubricant of any sort so no slurry to clean up. I machine cast iron dry too FWIW! The dry process is very easy to clean, a few seconds with shop vac equipped with dusting brush. While I am correcting omissions, I will mention that I just attach the sandpaper to the glass or granite with a couple of strips of masking tape along the long edge of the paper.

                I agree with Al that cast iron is easy enough to read when lapping but I presumed, perhaps inappropriately, that the OP was not very comfortable doing this type of work and a felt tip marker is pretty inexpensive insurance.

                Ken

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                • #9

                  Re: My #6 isn't flat...

                  Originally posted by carbonBased View Post
                  It never really occurred to me to check the flatness of the sole of my #6... but I did so last night, and... it's quite a fair bit convex (high spot in the middle).

                  It's been a reasonably good performer for me, but not perfect. I've been considering replacing the blade for a lee valley one, but now that I see that it's not flat, I'm also considering trying to flatten the sole.

                  I've never done this before, and the orientation (convex vs concave) seems like it would be more difficult to flatten.

                  Any thoughts on whether I should really try it? If so, any tips on how to go about it? (Mostly I'm looking to ensure I'm taking material off the convex part, so I need to ensure I'm not rocking back and forth and actually making it worse!).

                  I don't really care about keeping the sides exactly 90 degrees to the sole... I'll never use a #6 as a shooter.

                  Cheers,
                  --Jeff
                  I guess the first question is "how far out is it"?

                  If it's not terribly out of flat (1/8" would be really bad), I'd suggest investing in a granite surface plate from Lee Valley. A bit of machinists blue dye paste on the granite plate and then move the sole of the plane over the plate will transfer blue dye to the high spots on the sole of the plane. A simple machinist scraper can be used to remove the blue dye and a bit of the cast iron. Once all the blue high spots are removed, you go back to that granite plate and gently rub the sole of the plane on it. Again you will see blue spots indicating the high spots on the sole and can remove them with your scraper. This takes some time and may be overkill in your case.

                  Plan B: I'd just get the glass surface lapping glass plate, loose silicone carbide grit and possibly the plastic sheets that Lee Valley sells and just lap the sole flat. It's quite quick and easy to do (make figure 8s, with no pressure) and the sole should respond promptly. A bit of layout dye or even just a felt marker will coat the sole and after a couple of figure 8s, you'll know how flat you have gotten the sole.

                  Personally, I'm not super happy with the wet/dry paper on a flat surface, but then, I'm a fuddy duddy machinist..... and sometimes I lean towards the overkill side.

                  As for "should you try or not", you already know it's out of flat, and you know it's not good enough for your purposes, so it's really of no value to you until it's fixed!

                  For the record, I have a Lee Valley plane that ended up with a bit of rust on it due to my neglecting it.... a few seconds on the lapping plate and I knew it was never flat in the first place. It didn't take long to fix it... but it just shows that you can never *trust* someone else... just check it out and if need be, make it right.

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                  • #10

                    Re: My #6 isn't flat...

                    To further show my ignorance, I didn't know there could be a problem like this.
                    I guess that's what 'lifelong learning' is.

                    Noel
                    "Being so impressed with the beauty of nature, I never cease to be amazed at how the
                    'touch of the human hand' can transform it into another kind of beauty that is so uniquely human.
                    "
                    John Snow, Outdoorsman and Retired Teacher

                    Comment


                    • #11

                      Re: My #6 isn't flat...

                      Noel, the big secret is "If you don't notice anything when you use the tool... it's not a problem".

                      If, on the other hand, if it always seems slightly off to you, it may be a problem. We all work to a tolerance we are comfortable with. For some, that tolerance is 1/32", for others it's closer to 0.001" and there will be those who say that wood cannot be reliably worked to 0.001" as it moves too much with changes in humidity.

                      I talked to a Delta rep many years ago and he complained about "machinists" who were demanding more accuracy out of their woodworking machines than the rep felt was possible when working wood. The problem, as far as the machinist saw it.... the Delta machine was made out of metal, not wood! :-)

                      At the other end of the spectrum we have people who buy a $20 set of digital callipers and think they actually are accurate to 0.001" because the digital display says so, not realizing the difference between resolution and accuracy. When a machinist wants to measure to 0.001", he breaks out the big dollar and calibrated micrometer, makes sure the shop temperature is within specifications for the micrometer and then places the micrometer in a stand to avoid transferring heat from his hand to the micrometer which would throw the reading off, clean the measuring surfaces to make sure there is no dust or grime anywhere and then proceeds to check the measurement.

                      As for why a plane might be out of spec.... I once visited a foundry where they made cylinders for ocean vessels. Once a cylinder was cast and cooled, it was placed in an outdoor yard to weather and age for 10 years before machining it to size. They felt it took 10 years to reduce the warping tendencies due to stresses in the metal. Smaller items of low cost are frequently cast and machined in a matter of days to keep costs down, thus the possibility of warping is much more likely. To a carpenter, it probably does not matter... to someone who works with super tight and fancy joints... it may be intolerable. This brings us back to "It's not a problem if it doesn't cause you any problems".

                      Sorry... I do tend to get long winded.

                      Regards

                      Christian



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