Plow plane irons won't sharpen, edge fractures
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- This topic has 10 replies, 7 voices, and was last updated 6 years ago by markh.
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9 April 2018 at 2:05 pm #520828
Hi! I’m having an issue with the record 044 blades that I got on ebay. the metal never seems to be able to get an edge it fractures before getting a burr so I can get never get it really sharp, the smaller cutters will work anyway with a fractured edge but the wider ones won’t
My opinion is that someone tried to harden them somehow? I tested with a file and towards the back of the blade it grabs but at the front edge it skids
is there something I can do about this? would you put it in an oven to soften or is that a bad idea?
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You must be logged in to view attached files.Is the back properly flattened and free of pits? If the back isn’t dead flat, then sharpening the front will just reveal the flaws in the back.
Putting it in an oven to soften it won’t change that, and it will eliminate the blade’s ability to hold an edge for any reasonable length of time.
9 April 2018 at 7:29 pm #521001This was discussed with Narex chisels in another thread.
Sometimes the Harding process alters the top layer, making it brittle.
This is fairly normal. The solution is to sharpen off this Layer exposing more normal steel.you have to take the surface layer off BOTH sides of the iron to remove the brittle layer.
9 April 2018 at 8:19 pm #521023@Edmund: yes I flattened the back on my diamond stones.
@lorenzojose: I’ll try that thanks!- This reply was modified 6 years ago by berlios kani.
- This reply was modified 6 years ago by berlios kani.
10 April 2018 at 10:29 am #521320oh boy 1/8th that’s a ton, the cutter is super hard so it’s already hard to even polish on the diamond stones and the file just skids
I think these are the original record 044 cutters they have the markings and came with the plane so the steel should be good right? unless the previous owner tried to harden the blades? I have heard of some people doing this with plow plane cutters
Hi Berlios,
Your cutters need to be tempered back a little in an oven. You have not got decarburisation – that would have made the surface of the cutter softer and your file would have grabbed that.Paul has shown a method of tempering in the kitchen oven in one of his videos. This is a little (i.e. a lot!) more controllable than other methods since the electric oven temperature is relatively controlled – the only variable is the “time at temperature”. If you have a gas oven at home then you might need to rethink this.
I will try to find a reasonable tempering temperature and time for an O1 steel for you. I know that Record use what they called Tungsten Steel on their cutters – modern O1 steels have about 0.50% Tungsten so this is probably the closest to what you have from Record. Remember that your iron has already partially been tempered. Thus, I would try your preheated oven set at approx 150 Degrees Celsius with the cutter in for about an hour. Wrap the cutter tightly in a layer of Aluminium foil (kitchen foil) to keep any oxygen out during the heat treatment. Then cool the cutter and try to sharpen again. If you can get a burr easily the cutter is ready – if not, you might have to put the iron back in the oven for another hour OR try 170 degrees for an hour. A process of iteration – if you leave it for far too long then the cutter will lose some of its hardness – but this happens gradually. If you want to look up this process on the internet try searching O1 tool steel – tempering. I am recommending the lowest tempering temperature because I don’t know the current hardness of your cutter and this offers much more control of time (and least potential for disaster!).
The cutter was probably like that from the factory. Cutters were hardened in batches of hundreds. The first cutters out of the austenitising furnace and into the quench got the best quench and were likely much harder than the last cutters out of the furnace. Likewise there would have been some cutters in the tempering furnace for much longer than others. Cutters in the tempering furnace for longest would have been relatively softer than those which were in there for the shortest time. You will get a spectrum of hardness readings – your cutter is likely to be from the harder end.
Tempering a bit more will get you back to a more reasonable hardness.
I hope that this helps
Cheers
Mark H13 April 2018 at 9:06 pm #524746Thanks for this detailed reply!
A question that might sound silly… would it be a problem if I open the oven while I am in the middle of the process? someone wants to bake a chicken while I’m using the oven to be saving. just wondering if a change in temperature might be bad.Well that got me thinking! I had to run off to the wife’s cookbooks and find the temperature for roasting chooks. It indicated 160 degrees Celsius for a fan forced oven and 180degrees Celsius for a non fan oven. Thus, you can cook the chook and the cutter together!! Just find out what temperature the “someone” wants to use for the chicken. Your cutter will not do anything to harm the flavour of the chicken!! Assure them of that first! Remember to take the cutter out after an hour or so though. And save yourself the energy cost of performing the task separately.
Changing the temperature does change the dynamics of the tempering process but not by much at those lower temperatures. At much higher temperatures (250-350 degrees C) the carbides in the tool steel will coarsen at an increasing rate – everything happens at a much faster rate with increasing temperature. You risk overtempering if you go for a much higher temperature – the cutter could be softer and thus would have to be sharpened more often. But if that happens anyway, all is not lost – you just have to re-harden the steel. But on a plough cutter it wouldn’t be too much of an issue.
Stick with the lower temperatures of under 200 degrees C. Just be prepared to put the cutter in for another hour.
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