Straightening a Saw Plate
#11
This is one of those controversial topics, but the forum seems fairly civil these days and I'd like to toss this out on the workbench, so to speak. (sorry, some American cheese for 'ya for free!) I will try to explain this so that in case you don't understand some of these concepts you may after reading this, but if I mis-state something please some of you other more knowledgeable, please let me know.

This relates to what is known as tensioning the saw plate by hitting it with a ball peen hammer on an anvil, as well as how many refer to the folded back on handsaws has some magical property that will keep the proper tension to the plate.

All of this is supposed to keep the saw plate flat. On a perfect saw you would have a perfectly flat plate, with equally distanced teeth to create just enough width so the blade didn't bind, and the plate would be slippery smooth as you cut through any type of sappy or dried out wood (which also contain saps). But as many of you know, we don't live in a perfect world and I realize that even when I sharpen my handsaw I will not get it perfect, but it will average out between all the teeth to get a clean cut through the wood. This is something that I learned from watching Tom Law's old video on saw sharpening. What a classic, it was before Jennie Alexander realized she wasn't John, if that makes sense? I hope the haters don't come after me on that piece of American Cheese!

Next I would like to talk about "upsetting", a common term used by blacksmith when they forge steel, often some type of iron. This is taking a hammer, often a peen or a rounding hammer is what I use, to basically distort and move the metal around...to spread it out, widen it, but to change the physical shape of the metal as once it cools it's pretty much like that for good. It will not change but slightly due to temperature, but it will change back to the place it was at prior to this extreme condition. For this reason machinists will often heat/freeze components to fit them together, such as bearings, but it's only like .001"-.002" is most cases, metal doesn't move like wood does due to the properties.

Now let's talking about the way a tree hold tension in it, this is what I really refer to as tension. This tension will give you a bad hair day quick even cutting with even a pit saw, the grain can be so strong this tension will cause the tree to basically unravel and expand as you cut away fibers that are holding it from unraveling. Metal doesn't do this, metal just shrinks a small amount in only extreme temp conditions.

I have also used the peening method in the past with the intent that I know I'm upsetting the saw plate, but I'm using it in a way to flatten the plate, and it probably just gets down to the terminology I have a difference with. However, the way it is used makes people subconsciously think about this "tension" as correlating to stress. This difference of view has gotten me into heated discussions with people, but I have always just wanted to have a rational conversation about it. I think I may have a better way, but it is not yet proven.

My idea is that we can use heat also to change the shape of metal. Often when welding we need to keep the heat towards the thick piece of metal if both are not the same thickness/size, as the heat can be a problem. This is also true when upsetting metal, you can upset too much and distort it in the opposite direction than desired.

What I would like to hear any of your thoughts on is do you think using heat could be a better way to get a saw plate flattened to as close to flat as we can? Rather than using a peen to beat it into submission? I think using a torch with heat could allow you to place the heat into a specific area, but using a tig torch could issolate the amount of heat to such a small area, the danger of destroying a saw plate would be to burn through the material entirely, or what is known as blowout in the welding world. If the material gets hot enough that it starts to melt, it will continue to melt faster that you can move in some cases, and can cause bigger issues in itself. Better in this situation to stop immediately and let it cool. But we can control heat much better than we can a peen, so there are advantages, IMO.

I'm just curious if anyone else thinks heat might do less damage to the metal in the end, than you would do by peening it with a ball peen or similar non-flat hammer.

But here's an idea I have been pondering.

DISCLAIMER: I'm similar to Underhill, I use humor, or what I find to be humor is the way I look at things. This seems to have been done through the history of America. I'm sure we were spouting this type of humor at the Brits the entire time they tries to take our possessions or violate our rights to privacy of what we own. I know many people don't like me here, but I'm ok with that. I don't want to be any adversary type people. It's easy to move along, but even if you opposed my view in the opposite direction, I will still off you the courtesy to your view.
Alan
Geometry was the most critical/useful mathematics class I had, and it didn't even teach me mathematics.
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#12
Another thought I want to toss out on the workbench as well...

If we consider heat as a possible method for flattening a saw plate, what about using 2 pieces of heated material to press the plate back into being flat again? Kinda how a dry cleaner's press worked in the old days. Press the textile and use steam to clean and get the wrinkles out...my family was long into cleaners, then they branched out into liquor. This is how I think of these wacked out ideas, just wanted you to know in this case.
Smirk

You could even have two plates that press but leave the set teeth alone, just press the flat plate. You could also have tapered plates for tapered saw plates, so they would press at the correct angle, if that is even possible. I think they saw plates are uniform enough, but honestly not sure. There are a lot of factors and it could be that peening is just more convenient or more practical in the end. Just seems to me there's a better solution than the peen, even though used in the past...even by me.
Alan
Geometry was the most critical/useful mathematics class I had, and it didn't even teach me mathematics.
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#13
(04-16-2022, 06:31 PM)TraditionalToolworks Wrote: Another thought I want to toss out on the workbench as well...

If we consider heat as a possible method for flattening a saw plate, what about using 2 pieces of heated material to press the plate back into being flat again? Kinda how a dry cleaner's press worked in the old days. Press the textile and use steam to clean and get the wrinkles out...my family was long into cleaners, then they branched out into liquor. This is how I think of these wacked out ideas, just wanted you to know in this case.
Smirk

You could even have two plates that press but leave the set teeth alone, just press the flat plate. You could also have tapered plates for tapered saw plates, so they would press at the correct angle, if that is even possible. I think they saw plates are uniform enough, but honestly not sure. There are a lot of factors and it could be that peening is just more convenient or more practical in the end. Just seems to me there's a better solution than the peen, even though used in the past...even by me.

I'm not much of a metallurgist to be able to comment on the use of heat to flatten plates; all I can say is when I do hammer handsaw plates (leaving backsaws aside for the moment) I don't peen them with the rounded end of a hammer.  I only use the flat side, and with judicious strikes so as not to deform the plate's surface with dimples.  A few strokes, then sight the plate, a few more, etc. until I see how the metal is reacting and then adjust the blows accordingly.  Smalzer once did an article at Wood Central on this topic, and is the only one I've seen and I saved it to a pdf, attached.

The late Stephen Shepherd (R.I.P. 2018) in Full Chisel Blog also weighed in on this topic, I saved it as well, attached.  Glad I did.

Both are worth reading and digesting.


Attached Files
.pdf   Smalzer on Straightening Handsaws.pdf (Size: 241.59 KB / Downloads: 42)
.pdf   Beating a Saw with a Hammer « Full Chisel Blog.pdf (Size: 889.89 KB / Downloads: 46)
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#14
Thank you Admiral, those are two to keep for the long term.

I have no input on the heat vs beat topic, other that I have ruined a couple of saw plates by uneducated beating on them with the rounded end of a ball peen hammer.
It's all wood.
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#15
If you use heat, you should be prepared to reharden the saw.....
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#16
I can’t comment on the relative merits of impact vs heat for the longevity of the saw plate, but I suspect that heat won’t get a lot of traction in woodworking shops simply because I suspect that most woodworkers aren’t equipped for and/or comfortable with specific applications of heat to metal. And as Pedder indicated, the potential re-treatment of the saw plate for overall hardness/temper.
Dave Arbuckle was kind enough to create a Sketchup model of my WorkMate benchtop: http://www.arbolloco.com/sketchup/MauleSkinnerBenchtop.skp
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#17
I wouldn't depend on heat to properly tension a saw plate. For one, the heat is a temporary thing. While it may seem straight when you've applied the heat, as soon as the plate cools, you're back to the original configuration. It's possible heat can relieve tension, which would be a bad thing. Some of the more expensive saws back in the day (Pre-WWII) were both tapered and tensioned. It takes a skilled craftsman to properly tension a saw using a hammer. If you don't know what you're doing with a hammer, you can easily distort the saw.

As Pedder mentioned, if you apply enough heat to move the metal, then you've also ruined the heat treat on the saw. Reheating, quenching, and tempering will more than likely make things go from bad to worse. Ever watch Forged In Fire? Those guys are heating and quenching fairly thick steels and ending up with cracks and warps fairly often. Thin saw plates are ripe for warping. When saw makers taper a saw plate, they do it after the plate is heat treated.

P.S.. I have a B.Sc. in Metallurgical Engineering.
Still Learning,

Allan Hill
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#18
(04-18-2022, 06:43 AM)AHill Wrote: I wouldn't depend on heat to properly tension a saw plate.  For one, the heat is a temporary thing.  While it may seem straight when you've applied the heat, as soon as the plate cools, you're back to the original configuration.  It's possible heat can relieve tension, which would be a bad thing.  Some of the more expensive saws back in the day (Pre-WWII) were both tapered and tensioned.  It takes a skilled craftsman to properly tension a saw using a hammer.  If you don't know what you're doing with a hammer, you can easily distort the saw.

As Pedder mentioned, if you apply enough heat to move the metal, then you've also ruined the heat treat on the saw.  Reheating, quenching, and tempering will more than likely make things go from bad to worse.  Ever watch Forged In Fire?  Those guys are heating and quenching fairly thick steels and ending up with cracks and warps fairly often.  Thin saw plates are ripe for warping.  When saw makers taper a saw plate, they do it after the plate is heat treated.

P.S..  I have a B.Sc. in Metallurgical Engineering.
...
I'm with Allan..Any heating within the capability of the woodworker will destroy the saw. And most likely, any attempt at straightening and tensioning will as well, altho you may "luck out" if the bend isn't too severe and near the toe. The ruined plate does lend itself to making scrapers and small knives, so all is not lost if you do ruin it. It is good high carbon steel and can be hardened well beyond 60Rc...As Allan says, watch Forged in Fire and you can see how that is done.

Here's a link to saw tensioning and straightening that explains the procedure better than any other I have found, by a person that made his living working on saws...

https://www.youtube.com/watch?v=N_KikzIarLg
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#19
(04-18-2022, 09:23 AM)Timberwolf Wrote: ...
I'm with Allan..Any heating within the capability of the woodworker will destroy the saw. And most likely, any attempt at straightening and tensioning will as well, altho you may "luck out" if the bend isn't too severe and near the toe. The ruined plate does lend itself to making scrapers and small knives, so all is not lost if you do ruin it. It is good high carbon steel and can be hardened well beyond 60Rc...As Allan says, watch Forged in Fire and you can see how that is done.

Here's a link to saw tensioning and straightening that explains the procedure better than any other I have found, by a person that made his living working on saws...

https://www.youtube.com/watch?v=N_KikzIarLg

I would caution that Forged In Fire rarely shows the part where the bladesmiths are doing thermal cycling, annealing, or tempering.  They almost always show the quenching part because it makes for nice TV.  They often use some more exotic steels on Forged In Fire, which optimally require more complex heat treating compared to plain high carbon steel.  For example, 5160 steel used in leaf springs may require a schedule of:  Forging --> Normalization --> Annealing --> Austentizing -->  Quench --> Double Tempering.  Doing it right takes about 4 hours. So, if they are forging 5160, they are probably leaving some steps out.  True, you can get a functional knife from just quenching and tempering, but you're not going to get the optimal grain structure, which translates to the best mechanical properties.
Still Learning,

Allan Hill
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#20
This is one of those topics that will usually include somebody who'll chime in with a "you don't have a hair on your a$$ if you haven't beaten a saw straight then proceeded to use it to make a perfect reproduction of a Goddard-Townsend secretary in recovered sinker mahogany."
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