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

  1. #1
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    Default 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.)
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    Proud machining permanoob since September 2010

  2. #2
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    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.

  3. #3
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    Quote 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.
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    Proud machining permanoob since September 2010

  4. #4
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    Quote 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.

  5. #5

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    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...

  6. #6
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    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!

  7. #7
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    Quote 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
    .

  8. #8
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    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........

  9. #9
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    Quote 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.

  10. #10
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    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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