Thread: Hardening of sawplates

Historical hardness survey of Disston saws 112116b_Page_04.jpg

Historical hardness survey of Disston saws 112616a_Page_09.jpg

73 saws now.

Green diamonds are data points for run of the mill saws. Red diamonds are the upper and lower bounds of the 95% confidence interval.

Blue diamonds are Acme 120 saws.

Gold diamonds are Golden Era, 1897-1917, saws.

Hot pink diamonds are No. 12 saws.

Purple diamonds are taper ground steel backed saws with double houndstooth apple handles, saws I suspect may be precursors to the No. 77 line.

The blue line is a quadratic fit to the data points. The black lines are quadratic fits to the upper and lower bounds of the 95% confidence interval.

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Historical hardness survey of Disston saws 112816a_Page_09.jpg

The numbers are settling and as you can see the differences in hardness variability between the production periods have, by and large, become significant. The lower variability of the Golden Era saws considered in the light of what we know of the company history suggests that in preceding periods the processes of saw blade manufacturing were being perfected. After the methods were perfected modernistic business thinking took over and quality declined in the post Golden Era production periods.

A few more saws need to be added and then another rigorous statistical analysis.

For the hardness however none of the periods is significantly different.

Historical hardness survey of Disston saws 112816a_Page_10.jpg

I wonder if Disston started out like this. https://www.theguardian.com/environm...es-in-pictures

I got one.

First No. 77 backsaw December 2016 003.jpgFirst No. 77 backsaw December 2016 002.jpg

Interesting saw. Made in the 1897-1918 time period this saw has an 8" toothline, is 15 PPI, and lacks evidence of differential / progressive toothing. The plate tapers from 0.025" at the toothline to 0.015" just below the back at the toe. It's filed crosscut and appears to have been sharpened with a standard fleam angle, not the 45^o angle discussed recently on other threads here, and the saw is not set. Even more surprising is the hardness, HRC 49.

The statistician advises that my numbers are correct. Deeper analysis is contemplated.
I won't bore you by repeating all of the above figures, suffice it to say that the trends continue.

The two most important slides are these.

First are the comparisons of the standard deviations in hardness of saw blades between each production period.

Historical hardness survey of Disston saws 120916a_Page_09.jpg

This table gives the results of the Kruskall Wallis H testing of the various comparisons in variability in standard deviation of hardness between production periods. Use of the H test was driven by the characteristics of the data.

Values < 0.05 are considered statistically significant. Loosely translated, a value of 0.05 indicates that there's a 1 in 20 chance that the observed difference between the groups has arisen due to chance. Likewise, an H value of 0.01 implies that there is a 1 in 100 probability that the observed difference is due to chance and H of 0.001 is a 1 in 1000 chance and so on. It's important to bear in mind that these results are estimates. Nonetheless the overall trends evident in the data appear to be solid and I'm quite confident of them.

As you can see, the Golden Era saws show significantly (statistically) lower standard deviation as a group than all other listed production periods other than the 1860-1869 group. At this point there are only data for five saws in my test set for the 1860's. I'm waiting on another batch of rough saws that I think has a few relevant subjects in it.

Finally, comparison of the Golden Era to all saws made from 1850-1896 gives an H value of 0.00023 and comparison of the Golden Era to all saws made after 1917 gives H of 0.00061. These correspond to 1 in 5305 and 1 in 1639 chances that the observed difference is due to chance respectively.

This table shows the relative magnitudes of the standard deviations of each period of saws.



Historical hardness survey of Disston saws 120916a_Page_08.jpg

The Golden Era saws have a 55% lower variability in hardness than the most variable period (1850-1859). The next best period in terms of variability is the period immediately preceding the Golden Era, i.e. the 1880-1896 production range.

Thus, the Golden Era saws really are better. They have the best and strongest screws (Glover patent type), the prettiest handles and the most consistent blades, significantly better than any other production period.

Rob

This is your statement that sums up the halcyon days: Not a single thing, but the combination of all attributes resulting in appeal.

"Thus, the Golden Era saws really are better. They have the best and strongest screws (Glover patent type), the prettiest handles and the most consistent blades, significantly better than any other production period."

Regards
Paul

Paul,

I'm planning to add data in the 1860-69 period to see if the difference there will become significant. I also want to add data for more saws from other manufacturers, The next phase of the Disston study will be metallographic analysis of Golden Era saw blades to see if there is any evidence that they were processed differently from other periods.

Regards,
Rob

Data for 82 saws. All comparisons of Golden Era saws to other medallion periods have now achieved statistical significance.

Historical hardness survey of Disston saws 121016a_Page_12.jpg

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Golden Era saws show a degree of variability in hardness that is less than half as large as that seen in the saws from the 1850's. The high variability of the 1850's saws can be understood in light of the fact that Disston began producing his own steel around 1855 and he had no instrumentation available to test his product. The next best era relative to the Golden Era is the 1880-1896 range.

I interpret the progressively smaller standard deviations from the earliest saws through to the Golden Era as evidence of the gradual improvement of manufacturing processes, a kind of non-quantitative QC enabled long experience as there were no hardness testing instruments commercially available until Brinell in 1899/1900.

The 1918-1928 saws that succeeded the Golden Era are only about as good as are the saws of the 1870's. The WW2 and Post WW2 saws are a little worse than the 1870's. The lower consistency of the saws from these periods is likely due to economic pressure in the form of competitors, the Great Depression of 1929, and profit taking. WW1 (1917-1918 for the US) and WW2 also certainly played a role. In addition to the competition from other saw makers the introduction of portable electrically driven saws, evidenced by Porter Cable's first circular saw patent in the early 1930's, was likely also drawing away customers and putting pressure on the company to reduce costs.

Originally Posted by rob streeper

In addition to the competition from other saw makers the introduction of portable electrically driven saws, evidenced by Porter Cables first circular saw patent in the early 1930's, was likely also drawing away customers and putting pressure on the company to reduce costs.

Rob

My information is that portable circular saws were available even before then. You may have seen this sticker before that was pasted on the inside cover of a 1926 copy of Simonds' Carpenter's Guide.

Simonds Carpenters guide 1926 001.jpg

It was a sort of reason for Simonds cessation of handsaw production.

Regards
Paul

Paul,

Thanks very much for the information. In my review of the patent literature related to saw blade manufacturing technology I found that patents for electrically operated machinery with integral electric motors began appearing right around 1900. The 19th century sawing machines all appeared to be line-shaft driven.

The earliest electrically driven saw patent that I've found is this:

US1165298 Portable drag-saw machine._Page_1.jpg

US1165298 Portable drag-saw machine._Page_2.jpgUS1165298 Portable drag-saw machine._Page_3.jpgUS1165298 Portable drag-saw machine._Page_4.jpg
Not really what comes to mind when one thinks of 'portable electric handsaw'.

The first patent for what we'd consider a truly portable electric circular handsaw is this:

US1568328 Electric handsaw and grooving machine_Page_1.jpg

US1568328 Electric handsaw and grooving machine_Page_2.jpgUS1568328 Electric handsaw and grooving machine_Page_3.jpg
Still very different from what we use today but it has the important elements of an arbor mounted blade, a skid plate and a handgrip incorporating a power switch. The issue date also corresponds with your Simonds catalog. Could you post some pictures of the pages of the catalog that show electrical saws?

The patent I referred to in my above post is this:

US1854510 Portable power driven saw_Page_1.jpg

US1854510 Portable power driven saw_Page_2.jpgUS1854510 Portable power driven saw_Page_3.jpgUS1854510 Portable power driven saw_Page_5.jpg

Not Porter Cable but Dewalt, a continuation of an application first filed in 1927, just after Simonds pulled the plug on handsaw manufacture. A very similar saw is now sold as the Skil No. 77 or Model 77.

The number of patent designs really took off in the early 30's.

Another patent showing a recognizably modern design that followed the above application by just a few months is this:

US1806528 Portable power-driven saw_Page_1.jpg

US1806528 Portable power-driven saw_Page_4.jpgUS1806528 Portable power-driven saw_Page_3.jpgUS1806528 Portable power-driven saw_Page_6.jpgUS1806528 Portable power-driven saw_Page_7.jpg

It's interesting that with the above few patents appearing over a very short interval the portable electric circular saw attained the form that is retained down to this day. Subsequent patents are refinements and enhancements of the above two basic designs. Attached below are a few more applications from the 30's.

I'm sure that all of the handsaw manufacturers saw the writing on the wall and that the electric saws severely dented sales.


Regards,
Rob

Rob

I don't have any pictures of the Simonds circular saws. The last Simonds catalogue I have is from 1923. I have not sought out anything after 1926. Homesey has posted some links to Mark Stanbury's website where there are some later publications. There may be something there.

https://archive.org/details/@mark_stansbury?&and[]=creator%3A%22simonds%20manufacturing%20co.%22&and[]=creator%3A%22simonds%20saw%20and%20steel%20co.%22

Regards
Paul

Paul,

Sorry, I thought the '26 catalog was yours. I had a look at your link, no dice, only the '23 Guide For Carpenters.

Regards,
Rob

Rob

The 1926 Carpenter's Guide is mine, but it's not a catalogue: Just a guide with formulae and tips on carpentry. It has pictures of some of the Simonds handsaw range, but not circular saws.

Regards
Paul