Thread: Taper Grinding Saw Blades
28th May 2019, 01:26 PM #31
These are some of the data I got from measuring a Golden Era No. 12. The x axes of the following three plots are in centimeters up from the toothline. The measurement denoted 1 is the measurement 1 cm above the tooth points. The trendlines are cubic polynomial fits done in Excel.
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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28th May 2019, 09:39 PM #32
Thanks for those measurements Rob.
I think to some extent we are talking about the same thing. If I can return to Gavin's post (#22) where he pointed to a patent on taper rollers. My contention was that Disston did not use the patent to any great extent and that was because the saw plates showed a taper pattern that I felt did not fit with "rolling." Taper grinding usually works in two directions: From the toothline to the back and from Handle to toe along the back of the saw. To my mind it would produce a taper similar to the Simonds pattern I showed in post #24.
The measurements I took would seem to bear that out: BUT my 1" micrometer will not reach into the middle of the saw plate so I cannot check what is happening there. This is from a Disston publication:
Disston Taper Saw Grinding..PNG
These next pix are from a "Disston publication Disston Handbook on saws," which was published over a number of years. I have seen four editions 1902, 1907, 1914 and 1917."
Disston taper ground in gauge measurements.PNG
Above is the tapering in gauge thickness of 19 at the toothline and the handle down to 22 at the toe. Below are the grinding machines they used.
Disston grinding of blades.jpg
Some of the grinding wheels were large. Not all would have been used on handsaws. Some of the larger wheels might have been for the crosscut logging saws. I recently saw a picture of a crosscut saw that was 20' long: A special order I think . Stock saws up to 8' long were listed in catalogues.
Disston grinding stones.PNG
The point I was making was that Disston did not appear to have adopted the use of rolls for tapering their saw plates despite owning the patent. Apart from the patent there is nothing in their literature that suggest they used any other method than grinding wheels.
"Power tends to corrupt. Absolute power corrupts, absolutely!"
28th May 2019, 10:57 PM #33
Yes, I think so too about the rolling patents.
Rolling would be easiest before hardening. It would be quite difficult and time consuming to roll an already hardened blade and not crack or bend it. A blade rolled soft would likely deflect on quenching requiring a lot of hammer work to get it straight again.
Rolling a hardened blade differentially to taper it would add a gradient of unbalanced internal stresses, more at the thinner back and less toward the teeth. I would imagine that rolling the blades would make them quite difficult to straighten.
Grinding was (and still is ) done on blades after they were hardened. In fact, hardened blades can be straightened by grinding or by hammer tensioning or both.
RobInnovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.
29th May 2019, 10:27 AM #34
Here's some data from an Acme 120.
As you can see, they were hollow ground, but only just. Reality is markedly different from Disston advertising.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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