Hardened "No-sharpen" saws
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Does anyone know if I can use a propane torch to remove the temper from just the teeth of a no-sharpen handsaw and file it? Will it be too soft to use if I do this, or will it even work? Thanks
I thought that only made it harder (isn’t that how you temper it to begin with)?
Did you watch Paul’s video on sharpening the frame saw on the start page? He shows you how . If it wil soften you can sharpen .
If you like to know more about steel, hardening, tempering, annealing and normalising, check here: https://www.youtube.com/watch?v=hw4Rl0uG7ok
It answers more than just your question, but I think, it is very helpful to understand the types of steel used in our tools.
A second video will show, how it is actually done.Dieter
Thanks to everyone who replied. I did heat the teeth and they now take sharpening. When I’ve used the saw enough I’ll let you know how durable the teeth are and how often I have to re-sharpen.
Thanks again.Hello i have a question for those in the know.
Does Anyone know what the plates on disposable saws are made from? is it carbon steel
with the teeth pulse hardened. (whatever that is)
If its only the teeth are hardened the rest of the plate could be used for all manner of things.
It seems an awful waste when you think of what must be the hundreds of thousands of these saws that are dumped every year.I don’t know, what type of steel is used in today’s saw blades and if the body is hardened too. It probably differs from manufacturer to manufacturer or even from type to type. If you consider recylcling a blade, try it with a file. If the file bites, you can work the metal easily. People who are preparing for a zombie apocalypse are even turning files into knives, and they have developed crude methods to soften the steel. so, even if the back of a saw is hardened, you can still recycle it.
I have a nice card scraper from an old saw blade, that is still quite hard (blueish). It can be sharpened, but I cannot drill holes (tried that for another purpose). Compared to another card scraper, removing the old bur and flattening the edge takes more time though.
Dieter
I found it quite difficult to temper (soften) only the teeth with a torch. You don’t want to anneal the steel completly, only temper back to appropriate hardness to match rest of the blade.
For me putting the blade in an electric kitchen oven worked fine close to the high end of power setting. No problems with fitting a 500mm saw diagonally, longer ones would have to be somehow hanged from top front corner to lower back corner. Thermostats in home ovens are not very accurate so pay attention during the process. Also depending on where the heating elements are located temperature might not be as even in the whole volume as needed – heating in the “fan mode” seems to equalize temperature better. Wider part of the saw (the heel) could also heat at a slower rate – so just observe the colour change and react accordingly. I believe dark to light blue is what you want to achieve for a handsaw.
Remember that some saw blades are coated to protect them against rust – the coating is not that easy to remove but wears out with use – hopefully you’re not putting a brand new saw in the oven! Same goes for the painted markings. The change of colour with temperature occurs due to thin iron oxide layer being formed – for that to happen you need to have fresh steel exposed.
Afterwards let it cool, joint the teeth and sharpen away! You can also recut teeth with a hacksaw, shorten it or even surface grind with a belt sander – this is something I have not tried but Paul mentioned for restoration of heavily rusted saws with potential.
I think I read somewhere you can just break off the hardened teeth and start from scratch filing new teeth.
David
from Germany
I once attempted to grind down the teeth with an angle grinder, going slowly not to overheat the steel etc. The plate below the teeth was still quite hard and my file was getting worn really quickly.
Krzysztof.
Small update – heating to get blue temper would likely work for premium quality spring steel like 1095. I doubt that disposable saws are made out of this grade – one I have tempered to blue gets dull quite quickly.
Another one I have tempered only to ~220 Centigrade is much better, and this is consistent with the info on hardness vs temperature of spring steels: http://www.anvilfire.com/FAQs/temper_colors_hardness.htm
All very interesting must have a try when i get some time.
After a disposable saw has wore out you can turn it into card scrapers and also if you don’t need those it can always be recycled.
My current saws are the disposable Japanese kind and I love them but when they dull I have plans to buy a permanent set of saws (probably still Japanese as that’s what I’m used to now)
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