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  1. #16
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    Quote Originally Posted by rob streeper View Post
    Added data for more manufacturers today. Fixed a math error present in the first post above too.

    The Lie Nielsen bench chisel data shows a surprisingly high standard deviation because one of the chisels is softer toward the cutting edge, apparently it has been overheated at some point.

    N.B. Group Std. Dev. = Standard deviation of all of the measurements taken on the chisels of a particular manufacturer, Avg. Std. Dev. = Average of the standard deviations of each chisel for a given manufacturer.
    a question and a suggestion.

    Question
    Is it valid to compute averages and standard deviations across multiple chisels?
    My expectation is that each chisel is hardened independently of other chisels -- what you are testing may come from different hardening batches. (The 1/2" chisels may have been hardened separately to the 3/4 ones.)
    This leads me to wonder if, by only taking one measurement per chisel, what you are actually measuring is the consistency of hardness across batches, rather than the actual hardness of individual items within a batch.
    Comment?

    Suggestion
    Perhaps rather than report average hardness across batches and the confidence interval, perhaps it might be more useful to plot the range of hardness you have measured? see attached chart
    Chisel Hardness Study, the first step.-chisel-example-jpg
    Attached Images Attached Images
    regards from Alberta, Canada

    ian

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  3. #17
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    Thanks Ian, I appreciate your help and suggestions.

    You raise an important question, one unfortunately that can't be answered easily. My motivation for posting the two separate graphics showing the standard deviations was meant to illustrate to the degree the data permit what you're asking. Since the plots are now on page 1 of two I'll repost them here for discussion.

    In the plot below I posted what I'm calling the 'group standard deviations'. This is the standard deviation of all 15 measurements taken for each manufacturer.

    In the plot below I've plotted the average of the standard deviations of each of the three chisels for each manufacturer.



    Comparing the results for the Blue Spruce Butt chisels it is apparent that the Group SD and the Average SD are similar in magnitude. I interpret these results as telling us that these chisels have low inter and intra chisel variability. Considering now the results for the Marples bench chisels it's apparent that the Average SD is considerably lower than the Group SD. I interpret these results as telling us that the Marples chisels have low intra tool variability and higher inter tool variability. Finally, considering the LN bench chisel results it's apparent that they have high intra and inter tool variability, i.e. each individual chisel isn't very consistent in hardness and that the hardness varies from one tool to the next suggesting that, as you mentioned, batches vary. The Sorby's are the most consistent, but also the softest.

    As with my work on the hardness of saws, the tool to tool variability is a surrogate for quality/process control from batch to batch or otherwise over time. The variability in each chisel is a composite measure of the processes used on each tool. The softer regions of the LN bench chisels were close to the ground bevel of the primary cutting edge suggesting the possibility that at some point in grinding the tool was insufficiently cooled causing it to become softer. All of the LN chisels were bought second hand however they all looked like they had factory grinds on receipt. The Blue Spruce paring and Pfiel chisels are the only tools bought new from the manufacturers or distributors. The Marples chisels were the only set that were obviously user-sharpened. The others were all sold to me as 'new'. None of the tools showed any signs of abuse such as discoloration due overheating.

    The Disston Golden Era saws have the lowest variability and are the most esteemed among collectors and users. The Sorby, Blue Spruce and LN mortise chisels are the most consistent but I know nothing of their general reputations in woodworking circles.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  4. #18
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    Default Phase 2

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

  5. #19
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    Rob

    Thank you so much for all the time and effort you are putting into this study.

    I already take a few points from the investigation. The first, and although it may seem negative I don't intend it this way, is that the study sample is still small. I fully appreciate the difficulties and cost ( to an individual) of gaining a significant sample size. It's just not really "on" in practical terms.

    The second point is how easily reputations can grow or in this case be debunked. I liken it to buying wine, where my knowledge is sadly lacking. I tend to buy on the label, the price and to a lesser extent any reputation I think I might know. So it is with the chisels. In the case of chisels, appearance and reputation are paramount.

    The last comment is that nothing is ever quite equal. You have done exceptionally well to compare these chisels: All are bevel edged and all are the 1" size. The only small variable is the sharpening bevel. In other circumstances I could see where the lesser angle would result in initial sharpness and lesser force quickly going to excessive force and bluntness. Conversely a higher angle resulting in higher initial force but longer edge retention at the same level. Your tests, looking at the Marples and Lie Nielsen for example, completely contradict this supposition.

    At various times in the past I have regurgitated the content of an article I read many years ago. It compared three chisels and was nowhere as scientific as your study. It compared a modern chisel (this was back in the eighties), a Japanese chisel and what the author described as a "pre-nuclear chisel." In this he meant produced before WW2 and his contention was that the steel included less re-cycled material, which may have come to the fore during that war when raw material was at a premium.

    The test was to pare off end grain ( of some pine I think) until a noticeable light reflected off the edge indicating the sharp edge had been lost. The modern chisel went for about 6mm, the Japanese chisel achieved 17mm and the "pre-nuclear" chisel achieved over 30mm. Unfortunately my memory lets me down here, but you probably get the drift. I have long since lost the article.

    I continue to watch your thread with interest.

    Thanks.

    Regards
    Paul
    Bushmiller;

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

  6. #20
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    Paul,

    No offense taken of course. The limitation on the study due to sample size is obvious but given my plans not too important. I'm looking here for the influence, if any, of hardness and bevel angle. I don't see a pattern. The Pfiel, which is at about 20o, does surprisingly well where the Sorby and Marples are very poor even though their included angles are larger. There's not much to be said about hardness here either. The Marples and Blue Spruce paring chisels are both close in included angle and the Marples is harder but it's performance is much worse.

    Both the Blue Spruce and Lie Nielsen are alloy A2. I suspect that the differences I've observed are due to decarburization of the steel. If the performance of the BS chisels was due to some problem with overheating in post hardening machining I suspect that the softened zone would go deeper than the depth that was removed by my re-sharpening of the paring chisel. Oxygen mediated decarburization tends to be shallower than the annealing seen in overheating.
    I have no idea what alloys are used in the other chisels.

    Given these observations my plan includes making my own batch of test chisels from A2, O1 and perhaps D2. I'll evaluate these chisels the same way as above and vary grind angle holding hardness constant and then look at the effect of hardness holding grind angle constant across the various alloys. It's starting to get cool here so a good time to do some heat treating.

    Here's some additional analysis of the sharpening data I posted on the other thread.


    No significant gains in sharpness going from 5000 to 8000, from 8000 to 10000 or from 10000 to 12000 but if you look at the 5000 compared to the 12000 there is a statistically significant gain in sharpness, even though the net gain is only around 8%. The primary gain is in consistency of the edges, again something that I need to spend more time investigating. This level of super-sharpness however is quickly lost from all of the chisels except the Lie Nielsen and the Craftsman, which appear to be magically self-sharpening. I'll have to get to the bottom of that observation too.

    Regards,
    Rob

    P.S. Thanks for expressing your appreciation. My motivation is to understand how chisels work. There's so much non-quantitative talk on the net and in woodworking books that I find myself not being able to tell which end is up with these tools. The morass of anecdote, experience, ego, propaganda, more or less baseless opinion and disinformation floating around is a source of great frustration for me, thus I design and execute these experiments to satisfy my curiosity in as objective a way as is practical.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  7. #21
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    These will become my test chisels.

    chisel steel bars.JPG

    All are 1/4" X 1". The plan is to evaluate the effects of included angle and hardness on edge retention.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  8. #22
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    The Complete Guide to Sharpening (by Leonard Lee) tries to be all things to all people. . . . . and it isn't.
    I picked up a few things:
    a) there has to be enough steel behind the edge to support the edge in service.
    That means that the total included bevel angle must change.
    Are you shaving soft, wet protein whiskers or are you chopping pork ribs for Sweet & Sour?
    b) hardness (Rockwell) has a number and it can be measured.
    c) the scanning electron microscope images ( pages 32 & 33) made mockery of my sharpening technique.
    They suggested simplification which was and is better.
    d) the bonding agent and quantity in an artificial stone will have an influence.

    Your 4 identical test chisels, identical sharpenings and in one species of wood should be very revealing.

  9. #23
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    Hi RV,

    I still have some more makers that I want to test as shown above but in my experiments with the chisels I make I'm planning to do work on soft (pine, my baseline above), medium (hard maple?) and hard (live oak? Verawood? haven't decided yet) species.

    I'm thinking of single bevels (at first) ranging from 20o to 35o in 2.5o steps as this range seems to cover the breadth of commonly used included angles. Secondary bevels maybe later.

    I'm also going to look at HRC between max as quenched (probably in the mid 60's) down to about 45 or 50 HRC in ~5 unit steps.

    +/- cryo treatment of the HRC (s), included angle(s) and alloy(s) that perform best. Should keep me busy for a while.

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

  10. #24
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    Rob

    I am not sure if you will be making four chisels, one from each sample of steel, and gradually change the bevels testing as you go or whether you will be making more than one chisel from each type of steel in a range of bevel angles. I appreciate that in either event you can always return to the chisels to introduce a secondary bevel at a later stage if you wish.

    This is going to be a very interesting test.

    Regards
    Paul
    Bushmiller;

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

  11. #25
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    May I suggest that you use the very same piece of wood of each species for all tests?
    In the conifers, the ring count per inch is a great indicator of carving quality, tool edges being equal.

    For example, When I'm shopping at a mill for western red cedar, I use a ruler.
    I'm looking for logs, posts and blocks which show 20-40 rings per inch.
    15 or less is soft crap that I won't touch. 50/inch is boney but carvable.

    Do ring counts on spruce and cedar guitar tops in a music store. Educational.
    I cannot see that pine would be any different.

    I have a diversity of wood carving tools with different total included bevels. I have measured them.
    Wood carving knives are 12* , no more that 15*. This includes revised farrier's hoof knives.
    All gouges (mostly Pfeil), stop chisels and carving skews (Narex) are 20*
    Elbow adze, D-adze and Stubai carving adze & draw knife are 25*
    Samona spoke shaves are 28*
    Stanley Bailey #5 is 30*

    Narex skews arrived at 25*, CrV steel and lovely to sharpen. But, 25 is a fat angle to push wood open by hand (not with a mallet)
    So I scrubbed them down to 20* like the Pfeil. Excellent and felt no need now for years to mess with them again.
    Pfeil is considered the gold standard for wood carving tools. All gouges are 20* and there's no worries in either soft or hard woods like birch and maple.

    I would so like to carve with those when you get them made.

  12. #26
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    Paul,

    I'm planning four chisels. I'll start them at 20o and max HRC, test in species 1 and re-sharpen and change to species 2 and so on. Then I'll re-grind and sharpen to the next higher included angle and go through the species again. When I've tested all four alloys at 20o to 35o inclusive in each species I'll temper the chisels to the next softer HRC and repeat. What I hope to find is the optimum combination of alloy, hardness and included angle for working with the broadest possible range of species. Once accomplished I'll compare the chisels before and after cryogenic tempering to determine the effect. I think it likely that there will be different optimum combinations of chisel characteristics for working on different woods of differing hardness, we'll see.

    Regards,
    Rob


    RV,

    Yes on the same bit of wood all the way through, preferably clear pieces. I'm looking to use species that are relatively inexpensive, widely available and commonly used to increase the relevance of my results to the broader woodworking community and in addition to allow others to replicate or expand my results if they wish.

    If you'd like to have the test chisels after I'm done you're welcome to them, if there's anything left.

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

  13. #27
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    Sensible wood choices. Addresses the issue of availability.

    It's been a wood carver's argument for decades = do you need different bevels for hard woods and soft woods?

    I say no. 20* is good for everything except the hardest like maybe teak and ebony.
    Others claim that you MUST use 25* for hard woods with secondary bevels and nano-bevels.

    When I discover that 20 begins to crumple badly, I'll try 25. That day has not come.
    I've got blocks of mahogany that I've yet to get to (never?) and that may shift my thinking.

    In the meantime, western red cedar is the carving wood of choice in the Pacific Northwest community
    and I can stick with that.
    = = =

    I want to pay attention to your initial steps in the shaping of these chisels.
    Lots of PacNW native carvers make their own adze blades from salvage leaf spring stock.
    It's on my bucket list.

  14. #28
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    Rob

    That's a lot of work. Thank you in advance.

    Regards
    Paul
    Bushmiller;

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

  15. #29
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    Default Sharpening Jigs

    During the above experiments it became apparent that the sharpening jig used, i.e. the Somax/Eclipse, was influencing the results. Thus I embarked on another study of jigs. Here they are.

    Sharpness testing results 121217a_Page_29.jpg

    From the upper left are the Somax/Eclipse, the Kell #1, Kell #2 with big wheels, antique hinged, General Tools #810, Pinnacle and Veritas Mk II with the PM-V11 chisel stuck up it. Not pictured is the BCTW HG-1.

    Again using the Blue Spruce 1" paring chisel as a test donkey I sharpened across 400, 1,000, 3,000, 5,000, 8,000, 10,000, 12,000, 16,000 and 30,000 grit stones with the following results.


    The maximum sharpness attained with each jig, without regard to the stone on which it was attained.






    A number of things are readily apparent. First, most sharpening jigs can't make effective use of stones > 8,000 grit or so. The longer jigs however allow exploitation of the very fine grit stones > 12,000. Price of the jig is no guide.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  16. #30
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    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

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