Metal Hardness
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- This topic has 9 replies, 5 voices, and was last updated 8 years, 3 months ago by markh.
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4 January 2016 at 6:09 pm #133629
Hello All,
I’ve got an issue with a Record 044 Plough Plane I bought a few months ago. Something is up with some of the irons, as when I go to sharpen them, it leaves a very jagged, fractured edge. I watched Paul’s video on heat treating steel, and since they seemed brittle, put it in the oven at 325 degrees for an hour, and it seemed to have little affect. Was this the right approach, should I try it again for a longer period, or should I try something else?
Attached is a video of me filing the back edge of the blade, which works fine and takes off steel, and then filing the cutting edge, which is much higher in pitch, and takes no metal off.
Thank you,
JamesAttachments:
You must be logged in to view attached files.This is very interesting James,
It’s important to know what sharpening media you are using?
You’ve done what I would suggest by tempering it in the oven for a good hour – time isnt particularly important with tempering I’ve found, on most of the O1 tool steel its quoted to be tempered at an hour per inch of thickness.
The file sounds correct to me for proper hardening of the steel, you can use tools pre-temper they are just incredibly hard (65HRC and up) so I dont think the jagged edge is down to heat treating entirely.. although I don’t have the qualifications to say this for certain..
I think what’s most important is finding out how you sharpen your irons, a jagged edge is typically a sign of a coarse stone – which will still cut well and a lot of knife people like a jagged edge in certain exotic steels.
hope this helps! I’ve done a lot of dabbling in knife and tool making but am not a pro,
Thanks!
4 January 2016 at 7:21 pm #133633I’ve used everything from sandpaper, waterstones, and even went out and bought a diamond stone, and still get the same results. The photo I took is right after I used it on a hand cranked grinding wheel (so it didn’t get hot) in hopes of taking more metal off to get rid of the edge that split off, hence the shavings still stuck to it. But every method still leaves me with that jagged edge. When I sharpen one or two other irons that came with the plane, they come out razor sharp and no issues of ragged edges, so it’s this particular iron, and a couple of the others in the set.
Thanks you,
James4 January 2016 at 7:33 pm #133634I just tested the iron that I have successfully sharpened and it sounds just like this bad one. So I really have no idea what to do next. I’ve spent hours sharpening just this one blade…
The tip of the iron could’ve been overheated by a past owner, the only thing I thikn you could try would be grinding a good chunk of the steel away – say a good 5-10mm then regrind your bevel. Or you could just chuck it! depends how valuable it is to you.. If it’s the 1/4″ size its very common so can be picked up again.
4 January 2016 at 9:43 pm #133639See how you get on with your remedials Jay Doubleya but if you’re interested Toolnut do a set of 8 new ones for £37.50 or if not Toolbazaar have a set of 7 decent looking secondhand ones for £23.
5 January 2016 at 4:55 am #133643James, it sounds to me like that one iron has been hardened – possibly by accidental heat build up, such as when it is ground and not cooled (as someone else mentioned). If tempering the iron didn’t work, you could try a complete reboot of the iron. To do that, you need to soften the iron first, by heat treating to red hot and non-magnetic and allowing to cool very slowly. I’ve not don’t this yet, as I don’t have a good method to perform the slow cooling. I’ve read you can do it in a fireplace or fire pit, allowing the heat-treated iron to sit among the coals until they are cool. Once it is softened, verify it is soft by seeing if a file cuts. Then grind the appropriate bevel and re-harden the iron using a torch. I’ve done this using a propane torch, heating until the iron is red hot and no longer magnetic (approx. 1400-1500°F), then quenching in canola oil. This is followed by tempering for an hour in the kitchen oven at 350°F and then a final sharpening.
Good luck and let us know how this works out.
5 January 2016 at 11:43 pm #133683Thanks for the advice everyone. I think I’ll try the blowtorch method, as I had already been contemplating that in the back of my mind. If that fails, I’ll try ordering a new set of irons.
I’ll update you all when I figure out the solution.
Thanks,
JamesHi Matt,
The anneal (slow cool) you mention will serve no purpose in this case – unless you want to drastically reshape the blade. The re-austenitization (reheat to dull red) as part of the hardening process will effectively give the “reset” that the blade may need. I must admit I’ve not seen a blade as ragged as that one – post sharpening. Remember that thousands of those blades were manufactured and in large heat treatment batches. It wouldn’t surprise me if some of them didn’t quite turn out as the manufacturer would have hoped (with the right hardness at the cutting edge) and escaped the quality control net. The blade shown in James’ video is certainly making the right sounds to indicate a hardness differential. If the other blades in the set are sharpening up okay then I’d just forget about that blade – or re-heat treat (harden and temper) it if its an uncommon width.
Cheers
MarkH -
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