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Bench grinder jig with a horizontal 'slide' for sharpening.

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  • Bench grinder jig with a horizontal 'slide' for sharpening.

    So I've recently picked up the beginnings of the woodworking habit and the #4 plane I bought is duller than a butter knife.

    It strikes me that the right thing to do is to have something I can use to sharpen it back and forth across a bench grinder that will keep it square with the wheel.

    As the primary purpose is truing and truly flattening wood surfaces I have to imagine that the precision requirements of the blade being "flat" are pretty fine.

    I'm thinking some kind of jig with a cross-slide would do the trick. But I'm having a hard time visualizing what the supporting structure would look like.

    Any thoughts on this? My bench grinder is still sitting in a box (only just got it as a gift.)
    ----
    Proud machining permanoob since September 2010

  • #2
    First figure out if your bench grinder works without running off the table. I suggest finding a 200lb+ table to clamp it to...

    then realise that the tool rests on the typical bench grinder are as flabby as wet noodles. So whatever you make, expect to clamp it to the 200lb table as well.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      Originally posted by Black_Moons
      First figure out if your bench grinder works without running off the table. I suggest finding a 200lb+ table to clamp it to...

      then realise that the tool rests on the typical bench grinder are as flabby as wet noodles. So whatever you make, expect to clamp it to the 200lb table as well.
      yep. I've got just the thing. It's about 150 pounds of slab with legs made out of 4x4s. The stock tool rests are indeed craptastic.

      All so far part of the plan.
      ----
      Proud machining permanoob since September 2010

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      • #4
        Originally posted by madwilliamflint
        yep. I've got just the thing. It's about 150 pounds of slab with legs made out of 4x4s. The stock tool rests are indeed craptastic.

        All so far part of the plan.
        50lbs of 4x4 I hope! I said 200lbs not 150!!

        But seriously, Hope those legs are rigid.. Bolting it down is best, but clamping the bench grinder to be bench can do in a pinch.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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        • #5
          If the edge is simply dull from use, then hone it on stones. Sharpening under power is great if you know how to do it but will sure ruin a blade if not done properly. Besides, you should learn to sharpen by hand if you haven't already done so - one trouble with relying on a power tool are those times when it's not immediately available or down for service...

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          • #6
            A bench grinder is only useful for rough shaping of the blade. Ie "straight",
            degree of hollow ground, chamber if its for a roughing plane, etc .. but you
            said its a #4.

            Use as coarse a grit as you can find as that will help prevent overheating.

            To answer your question, you can clamp a small block of (whatever) to your
            iron and use that as a stop against the grinder rest. the length between
            that stop and where the iron touches the wheel will determine your angle.
            (45 degrees? bevel-down plane?)

            After that I suggest a good series of stones, or sandpaper to get your
            cutting edge.

            have fun!

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            • #7
              Originally posted by madwilliamflint
              As the primary purpose is truing and truly flattening wood surfaces I have to imagine that the precision requirements of the blade being "flat" are pretty fine.
              random thoughts on sharping planes

              A woodworking tool only sees the grinder if its been badly damaged; a big chunk out of it for example requiring removing a lot of material. Planes and chisels are high carbon steel not hss so a grinder will draw the temper - heat the surface up enough that loses some hardness. Even with extreme care, where the molecule of steel meets molecule of abrasive the temp will be too high for the steel. Unless you are extremely careful this drawing of temper will go too far into the steel. After grinding (can't remember when i've ever needed to) you coarse stone, fine stone etc.

              The two surfaces comprising wood working edge should each be like a mirror. You get there with progressively finer stones, I have up to 8000 grit, and the blades never touch a grinder. The coarsest stones remove material fast enough to take care of minor nicks etc. Water stones are my preference, they cut quickly

              Those little roller rigs that hold the plane blade/chisel at the correct angle are very handy ...not too expensive irrc but they'd also make a good shop project
              .

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              • #8
                I was an avid woodworker for many years before I got bit by this metal bug. I never recall seeing anything saying to use a grinder on plane blades, and can only imagine problems. With a few good stones (like Arkansas stones) a blade can quickly be brought back properly.
                If everything seems to be going well, you have obviously overlooked something........

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                • #9
                  Originally posted by madwilliamflint
                  So I've recently picked up the beginnings of the woodworking habit and the #4 plane I bought is duller than a butter knife.

                  It strikes me that the right thing to do is to have something I can use to sharpen it back and forth across a bench grinder that will keep it square with the wheel.

                  As the primary purpose is truing and truly flattening wood surfaces I have to imagine that the precision requirements of the blade being "flat" are pretty fine.

                  I'm thinking some kind of jig with a cross-slide would do the trick. But I'm having a hard time visualizing what the supporting structure would look like.

                  Any thoughts on this? My bench grinder is still sitting in a box (only just got it as a gift.)

                  If you can find one, buy one of the old hand driven wet grindstones for restoring your blade. The (very) slow speed and continuous wetting ensures that the temper of the blade is not compromised. It can be done on a bench grinder, with great care, but if any 'color' appears on the blade, you've tempered it and will now need to grind back beyond the limits of the color.

                  Comment


                  • #10
                    To answer your questions, there are rests sold by woodworking supply houses such as this http://www.leevalley.com/US/wood/pag...=1,43072,45938

                    I have one and it works ok. It would be easy enough to make a more rigid shop made version however.

                    With regards using a grinder, if you work with wood long enough it will be seen that yes it is sometimes necessary to return to the grinder. Unless you work exclusively in plantation grown woods, sooner or later you're going to hit a nail or somehow damage the edge. It happens. You will swear. Possible quite a lot. Nobody in their right mind is going to sit there all day lapping out the ding! VERY carefully grind the edge back, for the reasons cited above, being careful not to overheat the blade. Don't try to get a fine edge, it's pointless and you will simply draw the temper on the edge. Grind at an angle around 5 degrees less than your final intended angle. Grinding is a method to set the bevel angle, NOT to sharpen the tool. White aluminium oxide wheels are available for bench grinders that grind cooler, however great care is still needed. Once the angle is established and you have a clean edge, go to whatever method you prefer to sharpen and finally hone the edge. That is another discussion entirely, however will be around 5 degrees steeper than the angle you ground. This is the reason it's pointless to try to get a fine edge off a grinder, as it will just be removed anyway.

                    With regards the vibration, if your grinder is badly vibrating you're using crap wheels, end of story. It's possible to balance bench grinder wheels, and I've heard good reports from those who have taken the trouble to do so. Most of us don't however. I have a box full of wheels, they're all good quality, and all run reasonably well balanced straight from the box. Properly dressed and mounted a good quality wheel should simply create a slight buzz when running that will require the grinder to be bolted down to prevent it "walking", but nothing more.

                    Enjoy your woodworking.

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                    • #11
                      There exists, or used to exist, a holder with a roller on it that allows you to sharpen a plane iron on a flat stone at a consistent angle. I'll look later and see if I can find mine and get a picture up. If I were re-shaping a really beat-up iron, I'd either use a belt sander or do it freehand on the grinder, with the expectation of honing it later. Once you're used to doing this it's not that hard to get a good straight edge, at least good enough to get right in the honing stage.

                      Remember, too, that the main issue is getting a straight edge on the iron. It's somewhat less important to get it perfectly square, because the plane allows you to fine adjust the tilt.

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                      • #12
                        Ah ok. Thanks everyone.

                        Yeah I would have made an abysmal mess of my plane blade with nary a care in the world.

                        I poked around a bit and "sent away for" what appears to be the right thing.
                        ----
                        Proud machining permanoob since September 2010

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                        • #13
                          There are several plane and chisel sharpening guides on the market still, including one from Stanley. If you Google for the Stanley #200 sharpening guide, you'll see the traditional one they sold for years. Rather clumsy, I think. Here's one I have, which I rarely use, but it does work. The angle is determined by a combination of where you clamp the blade, and the adjustment within the frame of the guide. It doesn't completely remove the need for a little honing skill, but it is very effective at fighting the tendency to rock the blade and produce a rounded edge.

                          Last edited by bruto; 08-10-2011, 08:19 PM.

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                          • #14
                            Don't waste money or time trying to grind planer irons square. They should have some curve across cutting edge so that there is a a little bit of the edge sticking thru the sole with the corners still in the body of the plane. A straight iron will leave nothing but scratches and gouges on surfaces wider than it is. There is much about proper planing that is not exactly obvious. Most planes today have square irons because it was customary ship a new plane with a square iron so the new owner could shape it to his own needs. You will only find a correctly shaped iron in a plane if the plane was owned by someone knew how to plane. Not many of those folks left now.

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                            • #15
                              My best results sharpening chisels and plane irons have been with using a roller jig, such as shown above . Mine is a plastic one, but works well enough. I roll it on an 8 x 12 inch stone surface plate, and use wet or dry sandpaper with some water. 320 to 400 grit suits me , but some people go even finer. The only drawback is trying to get the exact same angle the next time I sharpen the iron.
                              Last edited by Bill736; 08-10-2011, 11:27 PM.

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