Announcement

Announcement Module
Collapse
No announcement yet.

How to correct plane blade that is slightly convex

Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts

  • How to correct plane blade that is slightly convex

    What is a good way to flatten a blade which the non-bevel side is slightly convex (bevel side is concave).

    On the non-bevel side, I used a coarse Norton oil stone and also a 60/100 grit sand paper but it has no effect on it whatsover. I am trying to keep it flat using a block of wood over the blade while sanding it down.

    The scratch marks look uniform at 60/100 grit but when trying to sand at 220 grit, there are some non-uniform scratch marks at the top left hand tip on the back of the blade (non-bevel side). This is when I realized that the blade not flat.

    Doing some reading I think there is nothing much that can be done to it.

    Any suggestion?

    Regards,

  • #2
    Re: How to correct plane blade that is slightly convex

    Hi Diesel:

    I am not sure I understand your question exactly, but I think so - so here goes.

    I have flattened the back side of many plane blades (chisels too for that matter) The way I do it is as follows:

    Buy several belt sander belts of various grits.

    Cut them open (I ususally do so on the splice) so you can lay them flat on a known flat surface - piece of glass or granite, table saw wing, jointer bed.... I clamp mine down on my TS using a couple of small blocks of wood. I position them roughly 1/2 inch in from the edge.

    Now you have a 4 x 21 or 4 x 24 inch flat suface to work on.

    Put the back of the blade flat onto the flattened belt. I usually hold the blade at roughly 90 degrees to the belt (like a letter T). You really only need to worry about the last 1 inch of the blade or so - maybe 2 inches at the most.

    Rub back and forth - watch the scratch pattern and change grits as required to flatten the back of the blade - but only in the area of the bevel.

    The reason I use my TS table is because it is flat and I can hang the blade over the edge, thereby ensuring that the back is absolutely flat against the sand paper.

    After sanding, I do the same thing on my water stones - one is 1000 grit and the other is 4000, to polish the back side of the blade and to ensure it is really flat.

    Then I sharpen the front (bevel) side normally.

    I hope this makes sense and it is easy to follow. If you have any questions, I will try to answer them, or maybe post a series of photos.
    Last edited by leer13; 03-15-2007, 05:13 PM. Reason: spelling errors
    "Dad, E means empty, NOT broken" - my cousin Doug, to his dad after the tractor ran out of diesel and Ed claimed the gas gauge was broken.

    Comment


    • #3
      Re: How to correct plane blade that is slightly convex

      I am using the Norton 3x 60 grit sheets. It seems like it is taking forever to flatten the blade. I have started over about 3 times. Basically when I get to the 220 grit it is quite noticeable that from the tip of the blade down to about 1/2" the scratch marks are still more coarse then the area below it. I am not changing grit until I see it being consistent. I don't want to start over for a 4th time

      Perhaps my blade needs a lot of work and time or maybe my method is wrong but this is starting to get frustrating.

      I hope this provide further info for you.

      Maybe I'll get a picture out to you based on my progress.

      Comment


      • #4
        Re: How to correct plane blade that is slightly convex

        Hi diesel:

        I find that the whole point is getting the back of the blade flat, against my table saw table. This allow me to put lots of pressure on the blade and to ensure that is absolutely flat. Sometimes it takes a long time, that's true. I have used belts because you get a long stroke when sanding too - sometimes a 60 or 40 grit is needed to really hog off lots of material. It has taken an hour or more at times to flatten some blades.

        Another idea - chuck the blade and order a replacement from Lee Valley. they make very good blades that only need a final hone. They will ikprove the performance of your planes too.

        A friend of mine uses a glass plate and wet-dry paper to do the same thing. He uses various grits, from 60 to 400 to lap his blades.
        "Dad, E means empty, NOT broken" - my cousin Doug, to his dad after the tractor ran out of diesel and Ed claimed the gas gauge was broken.

        Comment


        • #5
          Re: How to correct plane blade that is slightly convex

          I also thought about getting a replacement blade. I will give this a bit more time and see what happens ... it just seems like it is taking forever. Buying a sanding belt seems to be the more economical way than buying sanding sheets.

          Comment


          • #6
            Re: How to correct plane blade that is slightly convex

            Flattening the back of a plane blade is far less important than it is on a chisel. The flat back of a chisel helps guide the cut but that is not the case on a plane blade. If you have a badly convex blade (sounds like you do) you only need the edge of the blade to be flat (1/8" of flat will last you for a good many sharpenings). One other trick that I have used is to lay a steel (thin) ruler on the stone to very slightly lift the top of the blade so that only the edge of the back of the blade is touching the stone. A few rubs like this and you will have a sharp edge, essentially you are creating a 0.5° back bevel.

            The other option is to get a new A2 blade from LV, that was the single largest improvement to the performance of my planes.

            The sanding belt is a great idea but don't cut it. Instead install it in the sander (if it is a belt sander clamp it upside down to your bench) and have at it but remember to cool the blade. Once you have reasonably uniform scratches then switch to the finer grits by hand.

            Comment

            Working...
            X