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Thread: Saw File Hardness Measurements
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19th April 2015, 05:34 AM #1
Saw File Hardness Measurements
All,
After weeks of delays I'm happy to announce that the packets of files have been forwarded to the three other testers, they should arrive early to mid next week.
I've also begun measuring the hardness of the test files on my Rockwell C scale tester. The data for the four new files is tabulated and after I double check it I'll be forwarding it to Brett to avoid biasing the perceptions of the other testers. The raw data for the larger group of files tested previously should be tabulated by the end of the day. After that I'll begin the N45 testing. More later.
Cheers,
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, 09:30 AM #2
Okay, here's the first presentation of calibration data.
File hardness instrument calibration data 041915a_Page_1.jpg
File hardness instrument calibration data 041915a_Page_2.jpgFile hardness instrument calibration data 041915a_Page_3.jpg
Overall pretty good. The instrument is slightly non-linear but repeatability is good when compared to historical data and the drift over the course of the measurements was less than 1.5%.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, 09:38 AM #3
Here's the raw and corrected data for the measurements on the files. The first four test article names are blacked out to preserve the objectivity of the three independent use testers. The other files listed are those that were subjectively tested in the last file testing exercise.
File hardness data raw and corrected 041815a_Page_1.jpg
File hardness data raw and corrected 041815a_Page_2.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, 10:59 AM #4
Good work Rob! Thanks very much for the testing.
Could you PM me the names of the first four files please?
Would it be possible to list the previous set of files in the order shown below? That would make comparisons much easier, as they are largely listed in numeric order in the original report. The order is in ascending class of the ppi range for testing.
There were 6 pairs of files that were identical except the one of them had a hot (~70° and cooling) Citric Acid bath for 30 minutes.
The files were as follows (and this is in report order), with the overall comment:
23 Bahco Oberg 140mm Needle Cut 4 BEWARE
1 F.Dick 4" DEST (Citric acid induced failure) FAIL
2 F.Dick 4" DEST FAIL
3 Grobet USA 4" DEST FAIL
4 Japanese 6" DEST (but actually no taper) FAIL
4A Japanese 6" DEST (but actually no taper) (Citric acid) FAIL
5 Pferd 5" DEST BUY IT
6 Pferd 5" DEST (Citric acid induced failure) FAIL
7 F.Dick 5" DEST BEWARE
7A Bahco 5" DEST FAIL
26 Liogier 180mm Needle BUY IT
8 F.Dick 6" DEST (Citric acid induced failure) FAIL
9 F.Dick 6" DEST BUY IT
10 Grobet Swiss 5" EST BEWARE
11 Pferd 6" EST (Citric acid induced failure) FAIL
12 Pferd 6" EST FAIL
13 Liogier 6" EST PASSABLE
14 Grobet Swiss 6" EST PASSABLE
15 Bahco 6" EST BUY IT
16 Liogier 4" ST PASSABLE
17 Liogier 4" ST (Citric acid) BEWARE
18 Bahco 6" ST THE SHOW CHAMPION - BUY IT
20 Liogier 6" RT PASSABLE
Here are the notes from the original report regarding Citric Acid Testing:
Citric Acid sharpening was performed on 6 files, and a duplicate untreated file was also included. The testers were asked to pay particular attention to the
differences between each file in the various pairs. One of these pairs was the Japanese file, another was a French made Liogier, and the other four pairs were of
Indian origin.
In three of the Indian pairs, the acid treated file was a poorer performer, and in one of them it was marginally better, but both files in this pair performed extremely
poorly. The acid treated files broke more teeth than the other file almost universally.
In the Japanese pair the acid treated file scored better, but this would appear to be due to better corners on this file, rather than any improvement made by the acid
bath.
In the French pair the untreated file scored marginally better than the treated file. Tester C scored the acid file better, but that was because it had a better shaped
corner(the specific corner that he used), rather than any improvement made by the acid.
We can assume quite safely that the steel used in the Indian files is inferior to the Japanese and French steel (that’s the only reason they are being produced in India
– too get a cheap file). It would appear that acid treatment of lesser quality steel has a greater detrimental impact on it than on better steel. The Japanese acid file
scored better than its counterpart (but because of the corner, not the treatment) and the French acid file only scored marginally lower than its mate. In other words,
in files of quality steel, the acid didn’t cause it to be a disaster, but equally, it did not aid performance.
In short, the Citric Acid treatment contributed nothing positive whatsoever, and seems to have a very bad effect on lesser quality steel. After I had treated
the files I noticed that they felt much “grabbier” (sharper) to the skin, and under a loupe of 8x magnification the treated files looked MUCH sharper and cleaner.
Encouraged as I was by this I kept the caveat that this must translate to improved performance, and it did not – quite the opposite.
This leads me to wonder about those who claim that their old files are much improved after an acid bath – are they just being fooled by the grabbiness on their skin
(and it is a very significant difference in feel). I wonder if they have ever done any empirical comparisons, because the evidence from this test would appear to be
incontrovertible, although the sample was fairly small to make a bold statement, I suppose. Six-nil is pretty convincing though. Perhaps the effect is less noticeable
with Engineer’s files where there is not so much concentrated stress on the corners.
Whatever it is, there seems to be no point in putting saw files into an acid bath – it won’t improve the performance of a new file, quite the opposite in fact. For an old
file – well, they are worn down and there is no substitute for missing steel! There may be some short term temporary benefit with an old file made from good
steel, but that was not the object of this testing. One thing is absolute – the height of the teeth is reduced as the file wears down, and acid treatment can only make
them shorter still, certainly not longer.
THE ORIGINAL REPORT IS ATTACHED TO SAVE PEOPLE LOOKING FOR IT.
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19th April 2015, 11:26 AM #5Innovations 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, 11:29 AM #6
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19th April 2015, 11:40 AM #7Innovations 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, 11:52 AM #8.
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I don't understand what is mean by the Tang and the Tip?
Would it be possible to post a picture of where on the files the measurements are being made.
Even a picture of a file with some coloured dots on it will do.
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19th April 2015, 12:04 PM #9Innovations 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, 12:12 PM #10
Hi Bob,
Here's a couple of pictures but I've got to sign off soon, I'm about to go do some drinking. By tip I mean the region of the file lacking serrations at the end opposite where the handle goes. Here:
tip shot.jpg
By tang I mean the section of the triangular body of the file just below the bottom edge of the serrations. Here:
tang shot.jpg
There are of course lot's of important issues such as perpendicularity of the indenter to the indented surface, surface roughness, bend in the test articles etc. etc to be considered.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, 12:21 PM #11
Ah, that explains why there are no tip results for the needle files - no blank area at the tip.
I would expect that the shoulder area would be in the vicinity of the tip hardness, as the toothing begins just below it. One could expect that the tang itself would be quite soft by comparison, as it should be to prevent snapping off).
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19th April 2015, 01:01 PM #12Innovations 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, 01:11 PM #13
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19th April 2015, 02:09 PM #14.
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19th April 2015, 03:07 PM #15SENIOR MEMBER
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Interesting results, thanks for doing all the hard work Rob. I suspect that hardness is optimal for a certain range, say 58-63. Outside that range there are problems of too brittle and fracturing teeth, or too soft with rapid wear. Interesting that some files with a rating of 6+ were way below 58 (I assume the Japanese file test score is an error). And 7A at 18.51, surely would not cut at all? Should any file below 48 cut tempered 1095 spring steel? I am sure Rob will resolve these testing matters.
The other quality factors – steel quality; smoothness of grinding/honing; teeth cutting; file shape – need to be factored in to the analysis to assess relative quality, to say nothing of consistency of contents of a box. A multi-factor comparison of single and double cut might be interesting as well as a comparison of Saw files with 3-Square files. As I have not carried out multi-factor analysis since 1966, I will leave this to others.
Cheers
Peter
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