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Thread: Flattening back of plane blade

  1. #1
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    Flattening back of plane blade

    I just picked up an stanley no3. I am trying to flatter the back of the blade and it is going slow.
    Here you can see the high spot in the middle if that was a hollow it would of been a easy job.
    20190908_164642.jpg

    how should I go about getting this thing flat? Is there a short cut or is ti just going to be a long time at the diamond stone.
    I have a coarse diamond stone, 1000 and 8000 shapton stones.

  2. #2
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    Search David Charlesworth, "ruler trick".

  3. #3
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    Use 80-100 grit sandpaper on a flat surface. That will be a lot quicker than using diamond stones. Once it is flat than use the diamond stones.

  4. #4
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    Quote Originally Posted by Jim Matthews View Post
    Search David Charlesworth, "ruler trick".
    Whether or not you employ the ruler trick, the hump may cause a bigger problem with the chip breaker.

    If the blade is properly hard, a file will likely not cut much.

    David Weaver once posted about a set up he made to hold a blade while working the back. It was a piece of wood he could attach to the blade so he could apply preasure to the area being worked.

    What one wants to avoid is rocking the blade side to side while trying to flatten the back. Some suggest only working the back by going back and forth along the long axis of the blade across the sharpening media.

    You may want to preserve your stones and use a coarse sandpaper on a flat surface for the rough part of this job.

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

  5. #5
    For me it seems like the belly in the middle rolls and perpetuates itself, Iíve had good results hollowing very lightly between lapping on the coarse diamond plate. If you have a way to hollow the iron just enough, staying away from the leading edge, it might save you days of agony.

  6. #6
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    Justin, I would hang in there until it is done. You only have to do it once.

    Unfortunately, the high area means that the more you do, the more you need to do. And then, finally, it is over. This is the situation where one would use the side of a Tormek or CBN wheel. Assuming that you do not own these, work with 120 grit (80 grit leaves deep scratches). I have a 1m long glass-on-MDF plate for such purposes. The long strokes are less fatiguing.

    Depending on the length of the blade and whether it was laminated, you could turn it over and bevel the other side.

    Regards from Perth

    Derek

  7. #7
    Quote Originally Posted by Derek Cohen View Post
    Justin, I would hang in there until it is done. You only have to do it once.

    Unfortunately, the high area means that the more you do, the more you need to do. And then, finally, it is over. This is the situation where one would use the side of a Tormek or CBN wheel. Assuming that you do not own these, work with 120 grit (80 grit leaves deep scratches). I have a 1m long glass-on-MDF plate for such purposes. The long strokes are less fatiguing.

    Depending on the length of the blade and whether it was laminated, you could turn it over and bevel the other side.

    Regards from Perth

    Derek
    For some reason, using the side of the tormek gives me a lapped back that I canít swipe the wire edge off on my diamond plates or oilstones. After honing, I go to swipe the burr off the back and the flat area from the tormek doesnít reach the front edge of the iron when lapping on the stone. I think it must be due to the geometry of the high spots and hollows on the back, but the best idea I could come up with was to lap on the surface Iíll be lapping on when I sharpen.

  8. #8
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    A bad "hump" like that? I lay the iron on my bench, with the high spot facing up, and marked.....then a few whacks with a large ball pean hammer, checking as I go, until the worst is flattened.

    Beltsander, clamped in the bench vise, with the top handle in the vise. Have a cup of water handy. Stand to the side of the sander, lay the back of the iron on the spinning belt....count to 3, dunk the iron, check the back.....100 grit belt, and it helps if it is worn a bit. Repeat as needed, until the back is flat....then just polish it up.

    Use your fingertips to hold the iron to the belt....when the fingers say they are too hot, dunk the iron.

    Also, check the chipbreaker. Lay it on a flat surface ( BEFORE you do anything else to it) and see if it rocks. Either the curved section has a hump in the middle, or it is the inside of the hump.
    same as the iron, lay it with the high spot up, a few taps, and check for any rocking....sometimes, the ends are lower than the middle, to where the corners only will contact the iron. Goal is to bring the high spot down, so the edge is a straight line across. Also, sight down the length of both the iron and the chipbreaker....sometimes they have sat wat too long, clamped down too tight...and soon have a bow along the length. Both can be hammered out...BTDT. Do NOT clamp an iron in a vise, and try to straighten it by hand.....cuts from when it snaps take a while to heal.

    get both flat and straight, first.....then you can sharpen however you please ( Millers Falls called for a single bevel, @ 25 degrees) just remember...even a butter knife can be polished like a mirror, and still not cut cold butter....
    Craftsman rehab, shavings.JPG
    Craftsman #3 ( Sargent # 408)....single bevel, angle is 25 degrees. Had to fltten the iron and the chipbreaker, first. There are no gaps between the iron and chipbreaker.

  9. #9
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    Quote Originally Posted by steven c newman View Post
    A bad "hump" like that? I lay the iron on my bench, with the high spot facing up, and marked.....then a few whacks with a large ball pean hammer, checking as I go, until the worst is flattened.

    Beltsander, clamped in the bench vise, with the top handle in the vise. Have a cup of water handy. Stand to the side of the sander, lay the back of the iron on the spinning belt....count to 3, dunk the iron, check the back.....100 grit belt, and it helps if it is worn a bit. Repeat as needed, until the back is flat....then just polish it up.

    Use your fingertips to hold the iron to the belt....when the fingers say they are too hot, dunk the iron.

    Also, check the chipbreaker. Lay it on a flat surface ( BEFORE you do anything else to it) and see if it rocks. Either the curved section has a hump in the middle, or it is the inside of the hump.
    same as the iron, lay it with the high spot up, a few taps, and check for any rocking....sometimes, the ends are lower than the middle, to where the corners only will contact the iron. Goal is to bring the high spot down, so the edge is a straight line across. Also, sight down the length of both the iron and the chipbreaker....sometimes they have sat wat too long, clamped down too tight...and soon have a bow along the length. Both can be hammered out...BTDT. Do NOT clamp an iron in a vise, and try to straighten it by hand.....cuts from when it snaps take a while to heal.

    get both flat and straight, first.....then you can sharpen however you please ( Millers Falls called for a single bevel, @ 25 degrees) just remember...even a butter knife can be polished like a mirror, and still not cut cold butter....
    Craftsman rehab, shavings.JPG
    Craftsman #3 ( Sargent # 408)....single bevel, angle is 25 degrees. Had to fltten the iron and the chipbreaker, first. There are no gaps between the iron and chipbreaker.
    The ball peen hammer sounds like a good idea I will try that tomorrow if I have time. belt sander I would try on a junk blade first.
    The chip breaker just needed some cleaning and a little time on the stones now I think it my be the best one I have.

    2 side questions
    you sad about the chip breaker being clamped down to tight. On this no3 there is a nice bit of spring (compression) befor it is tightened all the way down. Should I stop befor it bottoms out? I can go all the way down with just finger tightening.

    Is the knob on a no3 the same size as a 4 or 5?

  10. #10
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    #3 #4 #5 are all the same....the only thing that changed was the height of the knobs....they went from a "Low" knob, to a taller knob, and finally a shaped to fit the ring around the base of the tall knob....

    When these older planes sit for too long, and someone had torqued things down tight....then things get a bit "curvy''.....Tighten enough that things do not move on their own...like when you use a plane....just a bit past snug. Tighten the bolt between the iron and the chipbreaker until you can move either....

  11. #11
    I broke a few irons trying to whack a belly out of them. I should have put a piece of wood or something on the belly and whacked that instead.

  12. #12
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    Quote Originally Posted by Jim Koepke View Post
    Whether or not you employ the ruler trick, the hump may cause a bigger problem with the chip breaker.

    David Weaver once posted about a set up he made to hold a blade while working the back. It was a piece of wood he could attach to the blade so he could apply preasure to the area being worked.

    You may want to preserve your stones and use a coarse sandpaper on a flat surface for the rough part of this job.

    jtk
    Here's my adaptation of David Weaver's plane blade back flattening system. It uses 80 grit self adhesive sand paper on a granite surface plate. This jig allows concentrating pressure directly over the plane back and saves your fingers. I've never experienced a hump on a blade as shown by the OP though.
    Attached Images Attached Images
    I wish that I knew what I know now... Ron Stewart from Ooh La La

  13. #13
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    A dozen years ago I posted this photo of flattening the back of a blade ...



    http://www.inthewoodshop.com/Woodwor...%20Blades.html

    Regards from Perth

    Derek

  14. #14
    Do you by any chance have a Worksharp? That and a diamond lap blade would make quick(er) work of this.

    If you do not, I'd probably save my diamond stone for less drastic work, and use a few sheets of coarser grit sandpaper lubricated with a fair amount of patience.

  15. #15
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    If you lay wet or dry sandpaper wet on your table saw table, it makes a good sharpening surface. Afterwards, wipe the surface with a thin coat of Johnson floor wax.

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