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Thread: Are my eyes deceiving me?

  1. #1
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    Nov 2012
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    Are my eyes deceiving me?

    I have had a LV #4 jointer for a fewyears and tried a new method to sharpen the iron. After totallymessing up the edge, I went back to my Mkll honing guide which I haveused many times before. Using 1000 grit to straighten the edge, Ikept getting a variation of more than 1/32 from the left side to theright side. I thought that I was using equal pressure on the iron. I was checking straightness using a 4” Starrett squareand also a precision square. Then I decided to check my brand newPM-Vll which I just received and one that I have not touched. It wasoff the same amount which had me scratching my head. Could both mysquares be off? I thought that one was known to be as accurate asone can expect. Could the new iron be off square?

  2. #2
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    A quick and dirty check of this would be to do the 'draw a line, flip, draw a line' test with the blade. Place your iron's reference edge (same one you used the square on) against the bottom of a piece of paper and draw a line along the blade edge (carefully!). Then flip the iron and draw a line just adjacent to the first line. If they aren't parallel, the iron is off square.


    daniel
    Not all chemicals are bad. Without hydrogen or oxygen, for example, there would be no way to make water, a vital ingredient in beer.

  3. #3
    put a mic on the plane irons sides near the fron and then near the rear. I say the iron's sides are not parallel(?).
    “If liberty means anything at all, it means the right to tell people what they do not want to hear.” -- George Orwell


  4. #4
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    Glenn

    As I wrote in several posts to the cambered plane blade thread yesterday, it is not uncommon for supposedly precision tools to be way out of wack.

    Sadly, Starrett has gone Hollywood and many of its "shop grade" tools are not what they once were. But there are still good tools out there, just not at Home Depot or on the woodworking tool retailer's shelves.

    I don't know the best brands nowadays, but Fowler, SPI and B&S used to be very good.

    Combination squares are not accurate tools, in any case. Only a tiny strip of metal supports the blade and sliding the blade quickly erodes any accuracy the tool may have had wne new.

    I recommend to any woodworker with ears to hear that they go to a machinists supply house and buy a precision, hardened, diemaker's square, a straightedge, a set of feeler gauges, and a dial caliper, and perhaps a micrometer. These must be professional machinists tools, with certificates of accuracy, and money back guarantees. They must not be made in India or China. They will be very expensive, but with proper care, they will last a lifetime. While these can be bought online, you really should check them for accuracy in the store before you buy. How do you check? Ask for the store's best tool to use as a reference. A well stocked and knowledgeable machinists supply store will have tools specifically intended to check the accuracy of other tools. Any machine shop of any significance will have a set of such tools for periodically checking the precision of their own everyday tools as a part of standard quality control, and they buy those tools from machinists supply houses. There are lots of little tricks that will work too, but this method works best. If the store is offended or refuses to let you check the tool in the store, do what professional machinists do and go elsewhere.

    Like a machine shop, you use these new tools to periodically check your everyday working tools for accuracy. For instance, the square you use to check your plane iron or to layout joints or to guide your marking knife is subject to wear and damage, but it still needs to be accurate. The same thing applies to varying degrees most of your layout, marking tools, and measuring tools. When you buy a new everyday square, take your machinists square (bigger is better, and the tiny ones, while cheap, are not useful for checking a 12" square) to the store and examine the tool before you buy it. If you purchase mail order, check the tool fresh out of the box before you use it.

    Feeler gauges are used to check the accuracy of your workaday dial caliper, and to measure the gap between the straightedge or square and a supposedly flat or square surface.

    When you have checked your workaday tools, put your machinists tools back in their boxes and store them safely away.

    These tools can also be used to for daily work, and to check the state of workpieces, but too much of that can get expensive.

    Stan

  5. #5
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    Glenn,

    Your profile does not show your location. If you are anywhere near me, it would be my pleasure to help you sort this out. If you live in another part of the country or world, someone else may be willing to help.

    The first thing to do would be the line and flip test mentioned by Daniel above. If the squares look good, then check to make sure the blade is in the honing guide square.

    Since as Glenn B. says the edges of blades are not always parallel, it is my habit to check a blade's edge from both sides.

    One other question, is there anyone around your shop that likes to play pranks?

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

  6. #6
    Though it seems unlikely in your case, if the face and the back planes are not parallel ( that is, the front to back thickness varies from one side of the chisel to the other ) you can expect those very results when using a honing guide. If I remember correctly, LV uses a lapping machine for plane irons. And I would imagine they are surface ground first. The lapping machine looks to me like it's rife for non-parallel faces on the plane blank, but I always assumed every iron would be checked or there was some magic process that would keep that from happening.
    I had an elderly German chisel last year that was driving me nuts until I found this very problem. But I've never seen it in a surface ground plane iron.
    let us know how it goes...
    russ

  7. #7
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    For measuring thickness, I have a digital caliper. What is the difference between it and a micrometer? Would a micrometer be much more accurate? Also, is a diemaker's square the most accurate square on the market?
    Last edited by Glenn Samuels; 02-05-2013 at 10:50 PM.

  8. #8
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    Quote Originally Posted by Glenn Samuels View Post
    For measuring thickness, I have a digital caliper. What is the difference between it and a micrometer? Would a micrometer be much more accurate? Also, is a diemaker's square the most accurate square on the market?
    Digital calipers tend to read thousandths of an inch, though some may go to four places. Micrometers tend to read to ten thousandths of an inch though some only to thousandths of an inch.

    Someone else will have to comment on the die maker's square. So far for my work a square that passes the parallel line drawing test is good enough.

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

  9. #9
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    Dial calipers are easier to use and have more functions than a micrometer, but they are not as rigid and not as accurate. A micrometer is a tool that the woodworker uses very little. I have used mine for measuring tool parts such as plane blades, and checking hardware tolerances. You can get by without one.

    Diemaker's squares are made from a single piece of steel. They are thicker, more rigid and typically better made than the typical 2 piece machinist's square. They are also hardened. The edges of the long tongue are beveled to an edge and blued black to help you see light passing between the tongue and the workpiece. Much easier to use. They also take up less space since they are flat.
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  10. Quote Originally Posted by Glenn Samuels View Post
    For measuring thickness, I have a digital caliper. What is the difference between it and a micrometer? Would a micrometer be much more accurate? Also, is a diemaker's square the most accurate square on the market?
    You do not need a micrometer to work wood.

    You don't need a diemaker's square to work wood.
    Last edited by Charlie Stanford; 02-06-2013 at 7:26 AM.

  11. #11
    Not to be thick, but how does the plane cut with the iron sharpened as it is?

    If you're getting an even shaving across the width of the plane, does this make a difference?

  12. #12
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    Quote Originally Posted by Charlie Stanford View Post
    You do not need a micrometer to work wood.

    You don't need a diemaker's square to work wood.
    I would be inclined to agree here, considering some woods can move up to what. . .1/8" due to seasonal changes?

    Check your "square" board on Monday. Check it again on Tuesday. I can almost guarantee my paycheck that it won't be "square" anymore unless you seal it in a sequestered room with controlled temperature and controlled humidity, and even then, it might still move.

    Just my humble opinion, here.
    The Barefoot Woodworker.

    Fueled by leather, chrome, and thunder.

  13. Quote Originally Posted by Adam Cruea View Post
    I would be inclined to agree here, considering some woods can move up to what. . .1/8" due to seasonal changes?

    Check your "square" board on Monday. Check it again on Tuesday. I can almost guarantee my paycheck that it won't be "square" anymore unless you seal it in a sequestered room with controlled temperature and controlled humidity, and even then, it might still move.

    Just my humble opinion, here.
    The poplar board on which the Mona Lisa is painted is moving and there is no piece of wood in the entire world situated in such a stable, ultra-controlled environment.

    That said, even if wood did not move one doesn't need machinist's tools to work it. Mr. Stradivari didn't need them nor did a whole raft of famous instrument makers, designer/makers, craftsmen, etc. through the centuries.

    Tight tolerances for moving metal parts are achieved in a tool room with highly precise machinery and highly precise measuring tools.

    Precision is achieved in a woodshop by using the workpieces themselves as measuring implements (using a shelf to mark a dado for instance) or by taking off measurements with simple tools - like gauging a chisel's width with a mortise gauge - very, very precise but does not involve a nominal measurement at all. If you find yourself in a woodshop thinking you need a digital caliper you've missed the boat completely or gone off on some odd and totally unnecessary tangent that has more to do with a personality quirk than it does woodworking accuracy.
    Last edited by Charlie Stanford; 02-06-2013 at 9:27 AM.

  14. #14
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    That's definitely my experience, Charles. The more precise the issue, the less likely I am to use a measuring device. Tapes and rules and calipers are only for rough sizing in my shop.

  15. Quote Originally Posted by Sean Hughto View Post
    That's definitely my experience, Charles. The more precise the issue, the less likely I am to use a measuring device. Tapes and rules and calipers are only for rough sizing in my shop.
    No doubt about it....

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