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Thread: saw sharpening critique/input

  1. #16
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    Thanks! Now I will know if it's day or night, today or tomorrow when I read a message from our Australian friends.

    You are 15 hours ahead of Houston. Dickinson is in the Houston Metropolitan area.
    Last edited by lowell holmes; 09-25-2016 at 2:02 PM.

  2. #17
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    Quote Originally Posted by Stewie Simpson View Post
    More critical as you work your way through 10 tpi/ppi spacing's and above, the rounded gullet formed between 2 teeth will have an effect on those tooths end height. The provided example is not of my work.

    Why would a rounded gullet impact tooth height if the tooth are all uniformly spaced and properly jointed? I'm not arguing that they should be rounded, but I don't see the connection to this specific problem?

    The teeth are clearly not ideal in the picture you posted, but it looks to me as though they're simply unevenly spaced. For example the 5th tooth from the left is shifted to the right, leading to a deep gullet between 4-5 and a shallow one between 5-6. Ditto for the 3rd from the right. Both of those could have been avoided by taking more care to keep the spacing uniform during cutting. There are other, similar examples.

    Similarly, the "land" on the second tooth to the right of the file is larger than any of the others, and the gullet between it and the 3rd is a touch small. That one is easier to fix than the others, since you can address both issues at the same time by filing the back of that tooth.

    Note that the fact that the picture is taken from above and to the side makes the teeth that are set in the direction of the camera look at bit smaller than they really are. You have to look directly from the side to accurately judge tooth shape, though you can accurately judge tooth-to-tooth spacings. In this case the errors are big enough that I don't need to see the side-on shot to know that this saw has problems. I remember seeing that picture on Paul's blog and being... surprised. I wouldn't show something like that in public :-).
    Last edited by Patrick Chase; 09-25-2016 at 3:54 PM.

  3. #18
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    Patrick,

    It's just geometry.

    Please review the attached training aid, and if it's not clear, please say so and we can delve into it further.

    Regards,

    Pete

    tooth height.jpg
    Last edited by Pete Taran; 09-25-2016 at 7:13 PM.

  4. #19
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    Quote Originally Posted by Pete Taran View Post
    Patrick,

    It's just geometry.

    Please review the attached training aid, and if it's not clear, please say so and we can delve into it further.

    Regards,

    Pete

    tooth height.jpg
    Why would you use a rounded file for some of the filing and a sharp file for the others?

  5. #20
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    Hi Pat, I don't think that that is a conscience decision. It's just what files you happen to own and use. The Bahco files, from what has been said here and from my experience, have a more "rounded" edge. Pete is saying the Nicholson files he's getting have a sharper edge, and would be prefered as the illustration shows.

  6. #21
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    Quote Originally Posted by Pete Taran View Post
    Patrick,

    It's just geometry.

    Please review the attached training aid, and if it's not clear, please say so and we can delve into it further.

    Regards,

    Pete

    tooth height.jpg
    Ah, I think I misunderstood Stewie's post. I thought he was saying that the rounding of the file somehow caused the tooth spacing/height variation that's evident in that picture of Paul Sellars' toothline, and was struggling to understand how those were connected.

    Upon reading again I now think that he was making the same point you did, i.e. simply that rounding the gullet reduces the height. I agree (as you say it's 9th-grade geometry), and I already acknowledged as much in #3 when I remarked that the gullet volume would be reduced.

    Never look for complexity where a simple interpretation will do... :-)

  7. #22
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    Yes indeed. I think it is called Occam's Razor.

    As a side note, I used the Rounded Corner syndrome as an early indicator of declining quality. Grobet used to make most files perfect, but the 6" Extra Slim size had about 30% that didn't have filled out corners. I used to cull them out and ship them back. At some point I realized that they were just reboxing them and sending them right back. That was shortly before they had a falling out with Vallorbe.

    Back when Simonds used to make their files in the US, they had the sharpest corners ever. They were a first class file. The Bachos were always square in the corner in the smaller sizes. Nicholsons aren't perfect, but I think they are the best out there at the moment.

    Happy Sawing,

    Pete

  8. #23
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    The NOS Nicholson USA Taper Files are still in high demand from ebay buyers for a good reason. For 12 tpi and above I prefer to use the 180mm Vallorbe 3 Square Needle Files. (The higher the no. the finer the cut.) http://jewellerssupplies.com.au/need...0mm-p-635.html

    I am not alone in recognising the benefits of the Vallorbe Needle Files for high tpi backsaws. There are a number of well known boutique backsaw makers who also use the same product.

    What's driven Vallorbe to maintain the highest quality specs within their merchandise has been the strong demand from the jewellery trade.
    Last edited by Stewie Simpson; 09-25-2016 at 9:54 PM.

  9. #24
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    Since it didn't happen without pictures, here are 4 new-in-box 6" 2XS files. I've focussed on the start of the toothing near the tang, since that allows you to see how sharp the blank's edges are. From top to bottom: Bahco, Grobet, Nicholson, Simonds.

    IQ8I0849.jpg
    Note the squared-off edge in Bahco's blank, and also the weird waviness thing in the edge toothing. It's hard to see, but the (Indian-made) Simonds also has a pretty blunt edge. The Bahco 5" 2XS isn't any better. I posted images of 6" files because I have a wider selection of those for comparison. FWIW that was taken handheld using ceiling-bounced flash with a 90 mm macro lens at 1:1.5 magnification or so, so my apologies for the hinky focus. I was too lazy to break out the tripod and macro rail.

    Stewie's posts convinced me a while back to switch to needle files for everything above 14 tpi or so. As he says they tend to be a lot better made. As far as I can tell Nicholson, Glardon-Vallorbe, and Grobet Swiss all come from the same factory in Switzerland (they're all marked "Made in Switzerland" and have identical toothing, knurling, and taper profile. The only thing that's different is the engraving of the brand name). Bahco needle files are also Swiss-made, and have the same taper profile (to within a couple mils) and toothing as the preceding trio but with slightly different knurling and the brand name printed on. "Grobet USA" needle files are made in Italy, appear to be identical to Corradis, and are also decent.
    Last edited by Patrick Chase; 09-26-2016 at 2:03 AM.

  10. #25
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    The following video up to 1.40min will help buyers identify Swiss Made Files.

    https://www.youtube.com/watch?v=gZ2K6OOA53I
    Last edited by Stewie Simpson; 09-26-2016 at 12:18 AM.

  11. #26
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    Quote Originally Posted by Stewie Simpson View Post
    The following video up to 1.40min will help buyers identify Swiss Made Files.

    https://www.youtube.com/watch?v=gZ2K6OOA53I
    Thanks!

    She's explicit in that video that "Grobet Swiss" and "Glardon Vallorbe" files are the same thing. Taking what she says at face value that would indicate that the Swiss-made Bahcos and Nicholsons are indeed from the UMV factory as well.

    For some reason I thought Otto Frei's prices were fairly eye-watering for needle files, but you prompted me to look again and they're extremely competitive. 3-square 200 mm cut-2 files are $7.60 each in box quantity. Isaac at Blackburn wants $15 for that file. Hmm... (digs for credit card)
    Last edited by Patrick Chase; 09-26-2016 at 12:49 AM.

  12. #27
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    Quote Originally Posted by Pete Taran View Post
    Yes indeed. I think it is called Occam's Razor.
    As an engineer I've seen "Occam's Razor" used to justify some mind-blowingly bad interpretations of data, but yeah, in this case the shoe fits .

    I view Rounded Corner Syndrome as an important attribute (which is why I brought it up in #3) but one of several to be weighed. The Bahcos in particular have crisply formed toothing (you can see the difference relative to the others in the full-res version of the image I posted in #24) that's long lasting by current taper-file standards. The rounded corners make them less than ideal for fine-pitch saws, but on balance I think they'e competitive with any other currently available product.

    EDIT: The Bahcos also have noticeably deeper toothing than some others. While I personally don't see that as a determining factor either way, I sometimes wonder if the folks who claim "5X greater life!" with Bahcos simply aren't carding enough...
    Last edited by Patrick Chase; 09-26-2016 at 1:51 PM.

  13. #28
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    The major disadvantage that I can see to a rounded corner file is that it's much easier for the file to rotate and, at one point, the file "float" in the gullet. When I use a crisp edge file, it's almost impossible to get the rake wrong. The file really sit well.

    Normand

  14. #29
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    The thing I like about the Bahco files is they seem to stay sharp considerably longer than Grobet or the newer Nicholsons. I've not tried any of the Indian made Simonds files though.

    In crosscut saws I combat the flat that the Bahco leaves in the bottom of the gullet by adding slope to the gullet. It doesn't get rid of the flat, but it does produce a taller tooth by virtue of changing the tooth geometry a bit, so it lessens the impact of the flat-bottomed gullet.

    On rip saws, I don't slope the gullets because it adds some fleam to the front of the tooth. The workaround here is to use a smaller size file than typical on saws beyond 7ppi where gullet size really matters. I've noticed that if the gullets get too small on fine-toothed joinery saws, for example, the saw will choke and bind in the kerf.

    As someone else mentioned, the corners of the file wear out well before the faces do, so I pretty much always disregard the "rule" of file size should be twice the tooth height.

    I'm of the opinion that there isn't a saw file made today that can compare to a NOS made-in-the-USA Nicholson. Or at least I haven't used one yet, anyway.
    ---Trudging the Road of Happy Destiny---

  15. #30
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    Quote Originally Posted by Normand Leblanc View Post
    The major disadvantage that I can see to a rounded corner file is that it's much easier for the file to rotate and, at one point, the file "float" in the gullet. When I use a crisp edge file, it's almost impossible to get the rake wrong. The file really sit well.

    Normand
    Err, exactly the opposite is true. There are 3 cases to consider:

    • If the file corner is exactly the same radius as the gullet bottom then the file registers on both faces (the front and back of the adjacent teeth) and the gullet bottom. This is good in the sense that there's no play in rake or fleam (i.e. there's only one set of angles in which the file can register).
    • If the file corner is more rounded than the gullet bottom then the file "wedges" against the tooth faces without contacting the bottom. This is also good, again because there's no play in either rake or fleam.
    • If the file corner is sharper than the gullet bottom then the file only registers against the gullet bottom. There is play (what you call "float") in both rake and fleam, and you have to rely on muscle memory or a guide to preserve your angles.

    I found the float/play in the 3rd case to be fairly noticeable when I switched from taper files to needle files for my 14-15 tpi dovetail saws. When I was exclusively using taper files it wasn't a problem, and now that I'm consistently using needle files on those files it hasn't recurred.
    Last edited by Patrick Chase; 09-27-2016 at 12:03 AM.

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