Thread: Hardening of sawplates

I just caught a calibration error and fixed it in these tables. Measured and corrected hardness measurements went up by about a half point, the relative differences are the same as above. The interpretation of course remains the same too.

Custom saw plate hardness measurements 012015a_Page_1.jpg

Custom saw plate hardness measurements 012015a_Page_2.jpg

Custom saw plate hardness measurements 012015a_Page_3.jpg

Plates are in the mail, rob. I would assume you'll get them saturday or so. I think the label said your zone is a two-day ship priority from me, and I dropped them off at staples last night (PO was closed). I figure they'll get picked up by the real PO from staples today.

We'll see. As long as you don't send them back to me, I don't care what you do with them.

Originally Posted by D.W.

Plates are in the mail, rob. I would assume you'll get them saturday or so. I think the label said your zone is a two-day ship priority from me, and I dropped them off at staples last night (PO was closed). I figure they'll get picked up by the real PO from staples today.

We'll see. As long as you don't send them back to me, I don't care what you do with them.

Hi David,

Thanks for letting me know, I'll keep an eye out.
I did some experiments yesterday to examine the effects of hammering on the springiness of the blade. I now know what is meant by 'fast and loose'.

Cheers,
Rob

The saw plates from DW arrived. Here they are. The larger of the two looks something like a D12 and the smaller looks like a D8. Both have a slight bend to them but nothing that should interfere with the testing.

saw blade pictures for testing_Page_1.jpgsaw blade pictures for testing_Page_2.jpgsaw blade pictures for testing_Page_3.jpg

I laid out grids on the blades starting 1/2" back from the toe at the tooth line. I ran perpendiculars every inch to the heel of the plates. I then struck lines parallel to the tooth line beginning about 1/2" above the tooth edge at 1/2" intervals. Testing will be done at the intersection of each grid line. Results will be reported like this: X coordinate, Y coordinate, Rc/HRC hardness.

smaller blade with grid.jpglarger blade with grid.jpg

Hopefully the values up an inch from the tooth line will be instructive.

I noticed that on at least one of the two (can't remember now) that even after I filed off the teeth, there was still some distortion at the edge of the plate from them being set previously (probably by a machine or a tool that didn't provide much support to the back of the plates).

The larger of the two sawplates is a disston #7 that is circa 1900 or so. The smaller is a D8 of about the same age. I believe as stock, they were both crosscut, the #7 with 8 or 9 points, and the D-8 with 10 (I think the mark is still there on the plate at the back of the D8).

Originally Posted by D.W.

Hopefully the values up an inch from the tooth line will be instructive.

I noticed that on at least one of the two (can't remember now) that even after I filed off the teeth, there was still some distortion at the edge of the plate from them being set previously (probably by a machine or a tool that didn't provide much support to the back of the plates).

The larger of the two sawplates is a disston #7 that is circa 1900 or so. The smaller is a D8 of about the same age. I believe as stock, they were both crosscut, the #7 with 8 or 9 points, and the D-8 with 10 (I think the mark is still there on the plate at the back of the D8).

I also noticed that the #7 plate has what looks like a roughly linear pattern of round impressions parallel to the tooth line. The D8 also has stripes but the hammer marks, if that's what they are, are less distinct.

I've made an interesting observation relating to silicon. On the Disstonian site (http://www.disstonianinstitute.com/steel.html) the silicon content of the steel is discussed as a byproduct of manufacturing, which it often is. However, here (http://www.collectionscanada.gc.ca/o...01/MQ45601.pdf) the author writes that the Bauschinger effect is facilitated by the presence of silicon. Is it possible that the silicon content of Disston saw blades is intentional? Bauschinger published his work on the effect in 1881, just after Henry Disston's death. I'd bet a nickel that somebody at Disston saw Bauschingers paper and worked it into their manufacturing processes. I know that hammer hardening was practiced before 1881 but Bauschinger provided understanding for what was common knowledge allowing the properties of the blades to be better controlled.

Originally Posted by rob streeper

I also noticed that the #7 plate has what looks like a roughly linear pattern of round impressions parallel to the tooth line. The D8 also has stripes but the hammer marks, if that's what they are, are less distinct.

I've made an interesting observation relating to silicon. On the Disstonian site (http://www.disstonianinstitute.com/steel.html) the silicon content of the steel is discussed as a byproduct of manufacturing, which it often is. However, here (http://www.collectionscanada.gc.ca/o...01/MQ45601.pdf) the author writes that the Bauschinger effect is facilitated by the presence of silicon. Is it possible that the silicon content of Disston saw blades is intentional? Bauschinger published his work on the effect in 1881, just after Henry Disston's death. I'd bet a nickel that somebody at Disston saw Bauschingers paper and worked it into their manufacturing processes. I know that hammer hardening was practiced before 1881 but Bauschinger provided understanding for what was common knowledge allowing the properties of the blades to be better controlled.

No clue if the spring in disston saws was sprung/compressed enough (like a car spring would be) to need that treatment. I do know that the saws that are 115 years old are still awfully nice to use. As many saws as I have with bright plates, those two just weren't worth fiddling with to refurbish further and then put them in my till and not use them.

Okay, here's the data. These are first draft - I have not hand checked all of the input values. The corrections applied are as before, the first stage corrects for the offset of the instrument. The second stage adds about 2% to the values to compensate for roughness. These saws appear to be on the softer side, roughly Rc/HRC of 48-49 at the tooth line. Softer toward the spine. No real difference in hardness under the handle. More tomorrow.

Custom saw plate hardness measurements 012715a_Page_1.jpg

Custom saw plate hardness measurements 012715a_Page_2.jpg

Still watching
Keep the great reading(work) coming Rob
Sorry it's all way over my head for commenting on

Just a side comment, I do remember filing those saws (the #7 was the first saw I ever filed), and would say they are in the same range as the rest of my saws save a few. The straw tempered saw that I mentioned that couldn't be filed (which was obviously defective or given to someone as a ruse and never intended for general circulation) was miles harder, and I have some that are subjectively harder and softer, but I'd rate those middle of the road in hardness given what I've filed.

You may have some exceptionally hard saws. Maybe a couple of more will be donated (I don't have any more good plates that I just want to throw away).

Not that it's particularly important, but the 7 plate is a #7 and not a D7. I doubt it would make any difference which it was, though.

Both have medallions from the 1896-1917 period, which I consider to be my favorites along with those one medallion prior (my favorites because they are relatively consistent in hardness and don't drop teeth when being set). I would go so far as to call them ideal hardness. They hold their teeth well enough and don't have surprise spots that ruin files.

Here's the calibration data. I'm having to move the instrument to use it so I recalibrate before each use.
012715 HRC calibration data and curve 012815a_Page_1.jpg

012715 HRC calibration data and curve 012815a_Page_2.jpg

Here are some more corrections. I've changed the designation D7 to #7 per David's information. I also bolded those values taken in the areas under the handles and done some formatting. I still need to double check all values against my notes.

Custom saw plate hardness measurements 012815a_Page_1.jpg

Custom saw plate hardness measurements 012815a_Page_2.jpg

Custom saw plate hardness measurements 012815a_Page_3.jpg

Originally Posted by D.W.

Both have medallions from the 1896-1917 period, which I consider to be my favorites along with those one medallion prior (my favorites because they are relatively consistent in hardness and don't drop teeth when being set). I would go so far as to call them ideal hardness. They hold their teeth well enough and don't have surprise spots that ruin files.

Interesting information because Rockwell testing wasn't available until around the beginning of WWI. (http://www.qualitymag.com/articles/8...rdness-testing)

Thus Disston's '52' could not have been applied in marketing materials before 1914 because the instruments and the associated Rockwell scales were unavailable before that year. Does anybody have any Disston advertisements that say anything about Rockwell testing from that time period?

Another interesting bit of information. http://www.vintagesaws.com/noway/noway.html