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Thread: Lapping

  1. #1
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    Default Lapping

    Given my penchant for for acquiring old tools and restoring them to useable condition, I feel like there is a strong possibility I am going to spend a lot (more) of my time lapping tools. Sometimes something like an old chisel can take half an hour of rubbing the back in circles before I'm ever even ready to consider attacking the bevel. While very rewarding, this isn't particularly fun, and if I could find a better way to do it then I'd be all over that.

    So how do you guys lap metal tools - new or old? I hear that plate glass works and so does granite. There are also some commercial lapping plates out there. Anyone have any experience with these?

    For people who use granite or glass, where do you get it (preferably for free)?

    Also, what do you do when you come across an old #7 or #8 plane? Something long which is in genuine need of flattening. Given that these are longer than a sheet of sandpaper, I find it tricky to get them flat. I restored a #7 a while back and it has become obvious to me that it needs to be ground flat again.

    Open to any kind of suggestions, feedback, or anecdotes about lapping and how to do it quickly and effectively.

    Thanks a lot in advance,
    Luke

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  3. #2
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    I went down to the local stone mason. He had pallets of cutouts from stove tops, sinks etc. that he let me chose from.

    "Cost ?" I asked ... "Take as many as you want" he said ... "I have to pay to get rid of it".

    Two pieces ... 1 about 300mm to 450mm square that I now have permanently on my bench for sharpening and lapping plane irons and chisels. The other, a bit longer than my #8.

    Spray on contact adhesive with sand paper purchased in rolls works for me.

    Word of advice though ... Take a large bottle of water, straight edge and feeler gauges along. They can be a little dipped in their length, so try to choose the flattest one you can while you are there.

    That water is to wash off all the accumulated gunk.



    The
    Glenn Visca

  4. #3
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    I use a piece of glass shelf with 80 grit psa (mirka gold) roll stuck to it. I ordered it from a glass shop, it was $20 and they rounded the corners off for me when I told them what I was doing for it. It depends on a flat bench surface beneath it since it can flex (but I have that - the flat bench). The reason I use the shelf piece, aside from cost, is that it's long enough - 8x42, to take a good stroke, and thick enough that I can put it between dogs without a plane nailing a dog while getting lapped (big deal for wooden planes).

    For large planes, I use the glass surface as a reference and put marking fluid on it, and instead of lapping the large planes, use the reference surface to mark the sole with fluid, then sand off the high spots with a piece of wood backing 60 grit or so paper. The block of wood is about 2x3 inches. It can really dig and remove material fast, something you can't much do with an 8 if you're lapping. Once I no longer have a high spot, I clean off the glass, adhere paper to it and do what I'd call a "check lap" to clean up the bottom. ON a bad 8, it never takes more than an hour. When I first started, I lapped an 8 for 5 hours because I didn't know that I had too many abrasive points of contact to the point that they really couldn't do any work. Spot sanding heavily to knock off the high spots, or if the plane is convex, remove a lot of material, without the bias of a lap works really well.

    I have done *a lot* of this over the last 10 years until I got picking up used planes out of my system. Probably 50 planes. Not many of them required that much time on the lap.

    If a 7 is far out (twist, etc), I will do what I described above for the #8. At my weight (just under 200 pounds), I can get enough weight on a 6 to lap it without doing that, but 7s are questionable and 8s, 200 pounds isn't enough.

    The product of proper lapping will be a plane sole that has the mouth slightly lower than both ends. For a skilled user, that's what you want - it is preferable to perfectly flat. If that doesn't make sense, it will over time. I'd call that a bias in favor of the user.

    I have made two videos about this, they are long (that's life). I have strong opinions, but they are based on experience:

    https://www.youtube.com/watch?v=khP74IuFljY (see toward the middle where I lap this plane - I was making a point in this video that it doesn't take long to have a bulletproof smoother of a *non-desirable* later stanley type in a very short period of time)

    And a thorough discussion of lapping, etc:

    https://www.youtube.com/watch?v=RVy789Oxq98

    I don't expect everyone to agree with me. I expect people that use their planes from soup to nuts and who have refurbished a lot will have no difference in opinion from me, though. I will leave plane shaped jewelry to others.

  5. #4
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    Quote Originally Posted by Luke Maddux View Post
    ...... Sometimes something like an old chisel can take half an hour of rubbing the back in circles before I'm ever even ready to consider attacking the bevel. While very rewarding, this isn't particularly fun, and if I could find a better way to do it then I'd be all over that.

    So how do you guys lap metal tools - new or old? I hear that plate glass works and so does granite. There are also some commercial lapping plates out there. Anyone have any experience with these?
    Yep, one of the chores I most detest is lapping the back of an ill-treated chisel! As far as I can see, there is no really easy solution, and all solutions can add their own problems. Lapping isn't the best way to truly flatten anything - there is always going to be a certain amount of rounding of the leading edges, due to cutting grits building up in front of the metal. Using a circular rather than back & forth motion just ensures the rounding is on all edges. However, it's the least worst method available to me, so I do it, but with diamond plates. I can get the main area flat fairly quickly, with my selection of coarse to medium diamond grits, but getting it flat right to the very edge takes forever! As another Forumite pointed out, it's a 90/10 business; you spend 90% of your time & effort getting the last 10% flat. What I tend to do on a severely un-flat chisel or plane blade is work on the back first, using a fore & aft stroke, which inevitably rounds the leading edge a bit. I then grind the bevel, and as often as not, it needs a good deal of metal to come off for straightening, & getting rid of rounded corners caused by the previous owner using horribly dished stones, so most of the rounding due to the lapping disappears, and a small amount of extra time on the finer grits returns a decently flat back.

    Quote Originally Posted by Luke Maddux View Post
    ....Also, what do you do when you come across an old #7 or #8 plane? Something long which is in genuine need of flattening......
    Avoid it like the plague!...

    But if you insist on torturing yourself, I think D.W.'s approach makes sense....

    Cheers,
    IW

  6. #5
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    Thanks for that, fellas.

    I spoke with a guy a while back who owns a grinding business. Like that's all he does... grinding.

    I told him about my wonky #7 and he said he could do it for "Less than $50". Not sure what that means, but if it saves me hours of lapping plus the associated consumables, it sounds worth it. Plus he was local and seemed nice enough.

    Anyone ever had a plane professionally ground?

    Cheers,
    Luke

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    Quote Originally Posted by Luke Maddux View Post
    Anyone ever had a plane professionally ground?
    I had an old No.4 done a few years ago. The bloke knew what he was doing, he is a planemaker.

    You need to make sure it's assembled (frog in situ and tight - as it would be in use) while it's being ground. Also need to make sure the bloke grinding knows he needs to be careful clamping the plane, so as not to snap off a cheek or two

    Cheers, Vann.
    Gatherer of rusty planes tools...
    Proud member of the Wadkin Blockhead Club .

  8. #7
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    Quote Originally Posted by Vann View Post
    I had an old No.4 done a few years ago. The bloke knew what he was doing, he is a planemaker.

    You need to make sure it's assembled (frog in situ and tight - as it would be in use) while it's being ground. Also need to make sure the bloke grinding knows he needs to be careful clamping the plane, so as not to snap off a cheek or two

    Cheers, Vann.

    Cheers, Vann. Those are things I wouldn't have thought of.

    Luke

  9. #8
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    Quote Originally Posted by Luke Maddux View Post
    Thanks for that, fellas.

    I spoke with a guy a while back who owns a grinding business. Like that's all he does... grinding.

    I told him about my wonky #7 and he said he could do it for "Less than $50". Not sure what that means, but if it saves me hours of lapping plus the associated consumables, it sounds worth it. Plus he was local and seemed nice enough.

    Anyone ever had a plane professionally ground?

    Cheers,
    Luke
    I'd ask him if he's done it successfully with a plane body before, and then ask what his philosophy about it is. If he takes off a whole bunch of metal, he's going to reduce the weight of the plane which is going to change the feel and not in a good way. He may also have warpage issues with heat.

    If he says he's just taking a tiny bit off to get everything square, flat and cleaned up and that he's doing what he can to avoid warpage, it might be worthwhile if you don't want to lap it.

    There's a guy in the US who does it (who isn't an option for you because of shipping) who says it's charity work more or less that he uses to keep himself busy and make not much money for his time. He also describes it as being an odd bird project for a machinist to do correctly.

    I'd personally rather work on the skill of flattening it myself IF you have a flat reference surface to use to be able to check progress. If planes needed additional machine work, it would've been common when the world was full of old school machinists and users of the planes. I've never seen an old plane with evidence of it, aside from jewelry planes that a machinist scraped by hand, presumably as a display of skill.

  10. #9
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    Quote Originally Posted by D.W. View Post
    There's a guy in the US who does it (who isn't an option for you because of shipping)...
    I believe Jim Davey does it in Oz.

    Cheers, Vann.
    Gatherer of rusty planes tools...
    Proud member of the Wadkin Blockhead Club .

  11. #10
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    I've been giving this more thought and I have a couple of questions:

    First, why is it not considered acceptable to lap on the cast iron wings of a table saw? I admit, this is exactly how I've done it in the past. I've had good results with planes up to a #5, but I didn't have good results with a #7. I just lay the sandpaper flat and pour mineral spirits over it until it sticks to the table enough to use for lapping.

    Second, what is the deal with granite and glass? Why are these two media considered the best readily available thing on which to lap planes? Glass is basically a super viscous liquid, meaning it's subject to change over time just like metal. Granite, on the other hand, is just stone which has been cut with a saw and then ground and polished. So how are these two better than cast iron?

    Interested to hear what folks have to say.

    Cheers,
    Luke

  12. #11
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    Quote Originally Posted by Luke Maddux View Post
    I've been giving this more thought and I have a couple of questions:

    First, why is it not considered acceptable to lap on the cast iron wings of a table saw? I admit, this is exactly how I've done it in the past. I've had good results with planes up to a #5, but I didn't have good results with a #7. I just lay the sandpaper flat and pour mineral spirits over it until it sticks to the table enough to use for lapping.

    Second, what is the deal with granite and glass? Why are these two media considered the best readily available thing on which to lap planes? Glass is basically a super viscous liquid, meaning it's subject to change over time just like metal. Granite, on the other hand, is just stone which has been cut with a saw and then ground and polished. So how are these two better than cast iron?

    Interested to hear what folks have to say.

    Cheers,
    Luke
    Luke not glass, but "Float Glass". This is supposed to be dead flat. This is because of the way it is made. "Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin". Full explanation here. I can't speak to Granite but it's supposed to be flat. My neighbor is a glazier and was able to get me some offcuts. They did the job. There's lots of opinion on these forums on how flat you have to be to get a good result. Some people say that you just need to be flat on the toe, heel & the mouth, and others spend huge amounts of time fattening on emery paper to get their planes flat. I get good results with my planes now but I wonder if it is because my technique has improved. I like your idea of using the table saw bed as a base and don't see why it wouldn't work.

    TT
    Learning to make big bits of wood smaller......

  13. #12
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    Quote Originally Posted by Luke Maddux View Post
    I've been giving this more thought and I have a couple of questions:

    First, why is it not considered acceptable to lap on the cast iron wings of a table saw? I admit, this is exactly how I've done it in the past. I've had good results with planes up to a #5, but I didn't have good results with a #7. I just lay the sandpaper flat and pour mineral spirits over it until it sticks to the table enough to use for lapping.

    Second, what is the deal with granite and glass? Why are these two media considered the best readily available thing on which to lap planes? Glass is basically a super viscous liquid, meaning it's subject to change over time just like metal. Granite, on the other hand, is just stone which has been cut with a saw and then ground and polished. So how are these two better than cast iron?

    Interested to hear what folks have to say.

    Cheers,
    Luke
    A table saw wing is fine as long as it's confirmed flat. When I got a table saw years ago, which I no longer have, it was hollow a full hundredth along its 27 inch length front to back. It was a delta hybrid and spec from the manufacturer was .012, so I had no remedy for it, and in reality, it made no difference for me using it as a table saw, but lapping by hand already introduces a bit of convexity (mouth below ends) and I wouldn't want that much more bias.

    If your wings are flat, you're good to go. I choose glass on a bench because I can control the flatness of the bench by planing it flat, then the glass doesn't need to be that thick (glass flexes). dead flat pieces of granite are rarely long enough to be handy. My run of glass is 42 inches long, I use it to finish lap wooden planes now, but metal ones now and then, too. It's only 3/8" thick, and something like 8" wide, with nowhere that a 1.5 thou feeler fits between the glass and a starrett edge.

    As far as glass goes, I asked the glass supplier when I got my lap about 7 years ago if it was float glass, and he said all glass of that type is float glass now. I don't know if manufacture in australia is the same, but I'd imagine if you get a glass shelf (which is technically what my piece is, a replacement shelf for a cabinet - that makes it cheap as opposed to custom glass), it will be float glass. If there are irregularities in the surface, you'll be able to see them looking across it.

  14. #13
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    D.W.,

    Yeah, I watched your video. I'm going to head in the direction of something like yours.

    My #7 is corrugated, so I'm hoping I can get some good results with fewer strokes.

    Cheers,
    Luke

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    Quote Originally Posted by Luke Maddux View Post
    My #7 is corrugated...
    Hmmm. It could take a long time to get all the hollows out of that one .

    Cheers, Vann .
    Gatherer of rusty planes tools...
    Proud member of the Wadkin Blockhead Club .

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    Manufactured wood products like MDF are pretty flat, so mounting a piece of float glass on MDF is an effective way of having a flat, flex free surface.

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