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  1. #46
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    Rob

    That Ames tester looks like a beauty and I can envisage a whole number of myths being destroyed.

    It was very disappointing to find a specialist saw maker using inferior grade product. When I first spied the chart with just maker numbers I knew what was coming.: One didn't measure up! It would be interesting to approach them for their comments. Maybe they would be interested in redeeming their reputation.

    The hardness of saws has always been limited by two things: the ability to file them sharp and the ability to set the saw. Even back in the day Disston acknowledged this limitation. In fact the setting was even more problematical. Disston allegedly used a harder steel (well same steel, but tempered harder) in their "no-set" 120 ACME saws, which points to the setting more of an issue than filing at that time. Today, as DSEL points out, the files are inferior. I bought one from the local hardware store recently (Nicholson, I think) and it wouldn't touch my Simonds from the word go. I hadn't expected a gem, but that left me disgusted !

    Disston maintained that their premium saws used better steel, but there is some conjecture over this and if nothing else Disston were extremely adept at marketing. It would be interesting to compare a No7, a No.8 and a No.12 from the same era.

    I feel sure your testing has not finished and it would be interesting to see more results. Thank you for the information already supplied.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

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  3. #47
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    Hi Paul,

    Like everything saw plates involve compromises. I want to see if there's a better way. That's why I'm looking into cryogenic treatment - it both hardens the steel and increases it's resistance to abrasion. After hardening the steel can be drawn by heating back to Rc 52 or thereabouts but the scratch resistance is retained.
    Saw files are a paradox. Given the resurgence in popularity of handsaws I'm somewhat surprised that one of the major file makers hasn't stepped up with a superior product. By searching I've been able to lay in a pretty good stock of older Nicholson three-squares but prices are going up and they're getting harder to find. The new Nicholsons such as are found in the home stores are totally unsuited for saw filing - rough, crooked and the teeth come off easily. They're fine for general use but are only useful for deburring in saw work.

    Cheers,
    Rob

  4. #48
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    Default Disston saw plate hardness values

    Today I pulled out my Disston hand saws, disassembled them so that I could measure the hardness under the handle where the test dimples would be hidden and tabulated the results. I did not make any special effort to polish the test points but the steel was clean and free of visible contaminants.
    Disston saw plate hardness measurements 011015a.jpg
    From these values I can see that Disston saw plates are pretty hard, harder than the 1095 that we use these days in the custom saw production.
    The steel was nothing special according to the Disstonian Institute (http://www.disstonianinstitute.com/steel.html), similar in carbon content to our modern 1080 steel. In fact 1080 is likely superior in some ways due to it's slightly higher manganese content which confers better hardenability characteristics.

  5. #49
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    Good stuff Rob,

    The stock standard 1095 spring temper is usually around 45-50 Rc, I've found that with 1095 coil product, the temper can be inconsistent across the sheet, and often the edges are harder. In any event, if the hardness is up around 60 it's going to be brittle, and should be avoided... also when it gets that hard it becomes very tough on files.

    I'd think even 55 is starting to get too hard for saw plate.

    How are you correcting for the material thickness with your testing?

    Ray

  6. #50
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    Hi Ray,

    These were all tested at 30 kg loading on the N scale. Referring to http://www.continentalht.com/userfil...sion-chart.pdf for the appropriate scale to use. I re-tested on 45 kg loading where permissible. The 0.015" stock produced consistent and repeatable readings, suggesting that, although it is not recommended, the 15 kg loading N scale is good enough. After all we're not talking about nuclear reactor pipes or turbine blades here, no issues of life and death.

    Interesting that Disston used steel that was pretty consistently above the Rc52 hardness that everybody thinks is the benchmark. Perhaps a red herring?

    Thanks,
    Rob

  7. #51
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    Default Analysis of results

    I did some analysis of the results including t testing to get an idea of the statistical significance of my measurements. Students t test is a way of calculating the significance of the difference between two sets of measurements. The smaller the t statistic the more significant the difference.

    The conclusions I draw are:

    1) 1095 steel is a consistent product. Despite the fact that the test materials were purchased from different sources over a period of several years the hardness values for the products were all very similar with a remarkably low standard deviation of 0.34 Rc points. Plus these tight results show you that both my technique and my hardness tester are working well.

    2) Of the custom makers, only one is using 1095 steel. The other two makers represented in my collection are using softer material. Maker 3 is using very soft metal, 40% softer than 1095, - likely because it's cheaper and/or easier to work with. Maker 2 is using something that is about 7% softer. The highly significant t values (t < 0.05) for these measurements indicate a high degree of confidence that the measurements are not due to chance.
    Maker 2's saws work just fine for me, but I'm not using them for production work. Maker 3's saw is a dog. Makers 2 and 3 are names that everybody in this area knows well so I won't reveal them. Let's see if either of them are willing to come clean.

    3) Disston's products varied in hardness over the years. The Disston saws in my collection were manufactured in the period spanning post WW1 to post WW2. The variability is not too surprising because the concepts of industrial quality control were in their infancy in the early 20th century. Disston also used steel that is harder by just under 4%, or 2 Rc points, than is 1095 but the difference is on the edge of statistical significance (t = 0.04).

    As far as saw files go, sharpening old Disston saws is going to be harder on your files than is sharpening modern saws. If you're really worried about the longevity of your files get some saws from Maker 3 and your files will last a long time but you may not get much wood cut.

    Further, modern custom saws made with raw 1095 steel are not as hard as are older Disston saws. If the plate hardness is important and if Disston optimized his products we've actually taken a step backward in our unquestioning use of 1095.

    I'm gonna go lick my wounds now.

  8. #52
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    Off topic, but I was a bit fascinated looking at the median rather than the mean over your measurements.

    It's not important I know, but a non-parametric test in these circumstances might be the most appropriate choice.

    Thanks for the info and the testing.
    Lovely how 'facts' (physical observations) speak 'indisputedly' without emotion/opinion.

    Cheers,
    Paul

  9. #53
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    Quote Originally Posted by pmcgee View Post
    Off topic, but I was a bit fascinated looking at the median rather than the mean over your measurements.

    It's not important I know, but a non-parametric test in these circumstances might be the most appropriate choice.

    Thanks for the info and the testing.
    Lovely how 'facts' (physical observations) speak 'indisputedly' without emotion/opinion.

    Cheers,
    Paul
    Hi Paul,

    I agree, I don't have an appreciation of the shape of the distribution. Probably a bit much for this forum. Nonetheless the data is what it is.
    I was looking at the Disstonian website here http://www.disstonianinstitute.com/steel.html and noted this: "The saws with multiple values for hardness were hardest in the area under the handle, and softest in the area close to the teeth.". Hardness testing is sensitive to the surface finish, that's the reason why testing blocks are so nicely finished. The area under a saws handle, if it's not pitted or covered with goop is going to be the least scratched surface on the plate while the area near the teeth will have the roughest finish. Thus one would expect that Rockwell testing near the teeth would return anomalously low values because of the relatively rough surface. In other words, test the area under the handle and make sure the steel is clean or your readings are meaningless.

    Cheers,
    Rob

  10. #54
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    Here's the data with medians calculated. They're not much different from the means so the analysis is reasonable.



  11. #55
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    Oh yes. It was the agreement that I was thinking over.

  12. #56
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    Quote Originally Posted by pmcgee View Post
    Oh yes. It was the agreement that I was thinking over.
    I was hoping for normal distributions and it looks like they're pretty close.

  13. #57
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    I realized during dinner that I have saws from another custom maker, here Custom Maker 4. Custom maker 4 makes very hard saw blades, Rc 61.4. I also added measurements from the Atkins #26 pattern makers saw I have posted on this site in the past. It too has a very hard blade, Rc 57.4. I have a few more Disstons that I'll test later on when I have a chance.

    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  14. #58
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    (Disston 240 median s/b 52)

  15. #59
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    Hi Rob. What does concern me greatly is that by not naming Maker 3 your unfairly clouding the reputation of other Boutique Saw Makers (including myself).

    Whats relevant is that you also making backsaws for sale. Now I personally believe its far from the case, but there may be other saw makers asking if your primary motive is more geared towards raising your own saw making profile.



    On the Sawmill Creek Forum where you also posted this data, you stated;

    Hi David,

    People are getting sued by companies here for writing negative comments on the Internet. See: http://www.forbes.com/sites/investop...eview-on-yelp/

    Speech is still free in America as long as nobody objects to what you have to say - that's why I have to be careful.

    As to Maker 3 and the results I got, who knows. Maybe it's a one-off problem. Maybe one lot of steel was unevenly hardened. As to Maker 3 and the results I got, who knows. Maybe it's a one-off problem. Maybe one lot of steel was unevenly hardened.

    While on this forum you are heading in a totally different direction by insinuating Maker 3 was aware his saw plate was below spec.

    My suggestion Rob would be to email a copy of your data to Maker 3 and note your concerns. My bet is Maker 3 will be in contact with his saw plate supplier asap.

    Nothing personal Rob.

    regards; Stewie.

  16. #60
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    Interesting findings. Are you going to share the results with the saw makers?
    I think you should give the problem saw maker the feedback.

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