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Thread: Saw File Hardness Measurements
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19th April 2015, 03:08 PM #16
Here's a somewhat better correlation but this one still isn't strong enough to impress a sociologist.
Std dev of hardness vs hardness for saw files 041815a.jpgInnovations 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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19th April 2015 03:08 PM # ADSGoogle Adsense Advertisement
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19th April 2015, 03:39 PM #17
Here's a hardness vs. user rating plot with each file identified.
HRC hardnsss vs. user rating by file type 041815a.jpgInnovations 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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19th April 2015, 04:04 PM #18
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19th April 2015, 10:10 PM #19
I think that in the cases of files 4A, 7, 7A and 12 the annealing of the tang softened the steel quite far up the bodies of the files - this could be considered a measure of manufacturing consistency or lack thereof. Note that the tip measurements for those files are higher. The plates I've prepared thus far are based on the average of all measurements for all files and thus the files with softer tangs will lower apparent hardness. I'll work up the figures with the tip data alone later.
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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19th April 2015, 10:21 PM #20Deceased
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19th April 2015, 10:41 PM #21Innovations 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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19th April 2015, 10:51 PM #22.
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19th April 2015, 10:53 PM #23Deceased
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Hi Rob. Excellent work.
Stewie;
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19th April 2015, 10:56 PM #24
When considering these data some important procedural and technical points must be borne in mind.
Hardness testers such as the one used for these measurements require that the force applied to the indenter diamond be 'normal' or perpendicular to the surface of the object being tested. Given the variability in positioning of the files, their triangular cross sections and the fact that the v-block anvil on this tester is a 90o type it is likely that at least some measurements will have been made with the surface of the file skewed.
The v-block anvil only supported the opposite edge of many of the files during testing. If the opposite edge or the anvil supporting the edge distorted under load the HRC values reported would be lower than the actual hardnesses of the files.
Surface roughness causes negative deviations in HRC measurements, the rougher the surface the lower the measured hardness and the higher the error.
Measurements at the tips of the files are more problematic because of the perpendicularity issue discussed above.
Bends, even imperceptible bends, that arch the body of the test article above the anvil a the test point will cause strong positive deviations in measured hardness values relative to the true hardness.
Thin materials also show negative deviations in measured values due to plastic flow under load. This problem is the reason that the N and T scales were developed.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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19th April 2015, 11:19 PM #25Deceased
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Hi Rob. Considering the front 1/2" of the file edge is rarely touched during the saw sharpening process; its possible to exclude readings within this area as well.
regards Stewie
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19th April 2015, 11:33 PM #26
Hi Stewie,
My plan is to first do HRN45 testing on this batch of files in the same way that the HRC testing was done. Next I'll grind away a two inch long segment of teeth from the middle section of each file on one face and repeat the HRC and HRN testing there. Finally I'll cryo-treat the files and repeat the HRC and HRN45 testing.
Given that cryotreating is known to increase the abrasion resistance of ferrous alloys and further that the process works on both martensitic and non-martensitic alloys I think that an abrasion type tool such as a file may benefit greatly. Plus it's easy for me to do because I have all of the equipment to perform the treatment and measure the results.
RobInnovations 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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19th April 2015, 11:51 PM #27
citric acid treatment of saw files analysis 041815a.jpg
Citric acid decreases both measured hardness (roughness effect) and user ratings but the differences are not statistically significant.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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20th April 2015, 12:15 AM #28
Yes Bob. Not just the same material but the same piece. In the report you can see pics of the plate that they used, and there are three sets of toothing. Furthermore, the three testers were all using the same file - one corner each. Even then there were inconsistencies within the same file - some of the results were wildly divergent within the same file.
It was all blind testing - all identifying marks on the files were ground off, and even ones that didn't have a mark were ground as these would have been known by their lack of mark as Liogiers.
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20th April 2015, 12:21 AM #29
Rob, I guess you're trying to see if you can increase the performance (hardness?) of them? Don't forget that these files are knackered now and performance increase (or not) won't be able to be measured.
EDIT: However, it would be very interesting to treat about 4-5 new files and compare them against untreated.
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20th April 2015, 12:26 AM #30
I was looking for a pattern there but three are up and three are down which doesn't really prove much. Surely the Japanese file (citric) is an aberration - I can't see the graph whilst replying but the drop in hardness is something like 30 Rc - can't see an acid bath doing that.
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