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Post by Tiers1 on Jun 23, 2015 23:19:03 GMT
So I suck at sharpening. I am terrible. I stumbled upon the work-sharp Ken Onion edition...which is a tool that is essentially a mini belt grinder. It arrived today and I went to task on a sword that I own- not particularly expensive but with quite a good temper. Now, I did do my diligence before using this item but it was only after I used it that I saw a bunch of stuff about bench grinders overheating edges. I probably went over the edge about 40-50 times figuring out how to go about things...half of those times with a course belt (sparks flying). No water was used to cool the blade Yes, it is terrible I know. The steel is quite hard and it really does not appear that all that much material was removed. I did eventually get it pretty sharp with a convex edge. The sword is very large and the I never really felt the blade get hot at all, even near the edge...I am assuming the rest of the blade acted as a kind of heat sink...that is about the only thing that keeps me hoping I did not ruin the temper of the edge...but I am ready for the truth...did I?
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Post by brotherbanzai on Jun 23, 2015 23:32:46 GMT
If you never felt the blade get very warm, it's unlikely you did any damage to the temper of the blade. It's certainly possible that you may have damaged the very edge. If it's a fairly meaty blade, just take a file to it and hand file the edges to remove any steel that was overheated. If the file won't easily cut, then the edge is still hard, so no problem that way either.
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Aikidoka
Member
Monstrous monk in training...
Posts: 1,452
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Post by Aikidoka on Jun 23, 2015 23:34:33 GMT
You say you touched the blade in between passes with the belt sander and it didn't feel hot?
If that's the case, then it should be fine. I always check the blade after each pass, both to see the effect on the edge and to feel if the blade is getting warm. If it does get warm, I stop and let it cool down. As others have mentioned on this forum, it can take quite a while for the blade to go from cool to warm, but then only seconds to go from warm to "Holy crap, that's hot!"
If it never got hot to the touch then I would think you didn't do any harm.
EDIT: Ah... just saw brotherbonzai's post.
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Post by brotherbanzai on Jun 23, 2015 23:42:07 GMT
Never hurts to have reassurance from more than one source ;)
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Post by DigsFossils-n-Knives on Jun 24, 2015 0:38:05 GMT
A good sign that the steel was overheated and you lost the right temper is a discoloration of the steel. If the edge didn't discolor then you might be ok. If your edge holds well, then again you're ok.
Keep in mind that the heat would have been generated right where you were making contact with the belt. In your case the edge. The edge could have been heated quite high and you wouldn't have known by holding the "bulk" of the blade.
Last thing. There are steels that require a very high temperature to temper. Those steels are more forgiving to overheating.
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Post by Brendan Olszowy on Jun 26, 2015 5:35:19 GMT
Just a note - when checking the edge for discolouration, you'll need to be looking at the rear of the edge (opposite side to the one which is in contact with the belt). No point looking for discolouration if you've already ground it off. A gold colour is ok, a purple colour is ok. A dark blue colour is ok - but once you get into the range of silvery blue colours, it will be uncertain - then feeling it with a smooth file is a better way to tell. I reckon the safest bet is to only go to a belt grinder if it's a real thick 'stage' edge, and you need to remove some bulk (really the whole bevel needs a regrind if the edge is that thick). Once you're down to a butter knife edge (0.5mm / 1/32" - Windlass edge) it's worth using files and stones. Besides, the belt grinder is going to make a mess of your swords original surface grain (satin texture, which runs length ways).
If you want to try your hand at crafting a good edge geometry with files purchase yourself a 2nd cut and a smooth Mill File and research 'drawfiling'. Thats how I do it. :-)
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Post by DigsFossils-n-Knives on Jun 26, 2015 11:20:29 GMT
Just a note - when checking the edge for discolouration, you'll need to be looking at the rear of the edge (opposite side to the one which is in contact with the belt). No point looking for discolouration if you've already ground it off. A gold colour is ok, a purple colour is ok. A dark blue colour is ok - but once you get into the range of silvery blue colours, it will be uncertain - then feeling it with a smooth file is a better way to tell. I reckon the safest bet is to only go to a belt grinder if it's a real thick 'stage' edge, and you need to remove some bulk (really the whole bevel needs a regrind if the edge is that thick). Once you're down to a butter knife edge (0.5mm / 1/32" - Windlass edge) it's worth using files and stones. Besides, the belt grinder is going to make a mess of your swords original surface grain (satin texture, which runs length ways). If you want to try your hand at crafting a good edge geometry with files purchase yourself a 2nd cut and a smooth Mill File and research 'drawfiling'. Thats how I do it. :-) Good points about the color but keep in mind that that the temper temperature varies from steel to steel. So dark blue might not be ok for some steels. more data on this site: www.hudsontoolsteel.com/technical-data/knifesteelbasics
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Post by Brendan Olszowy on Jun 30, 2015 5:53:31 GMT
In reference to the above charts, Ignoring the low carbon 40 point steel in the middle, 600F is shown above as a fine tempering heat, given the lowest hardness shown for a H.C steel at 600 is 51 - for the 1070. Perfect for a sword (long blades over ~20"). Higher alloy can go even hotter.
So I maintain - dark blue is fine, anything lighter becomes uncertain and will depend what the alloy is and the ectual heat achieved. The colours become a light blue, then a more silvery barely blue, then it can get a hint of pink to the silvery colour - that might be at around 1100F? This is before getting into glowing reds. But regardless. One can be confident that a dark blue won't ruin their temper, but when working with the very fine edge, there's every chance that it will barely visible and be stuffed at the very very edge.
As long as we're getting technical, another factor to remember is it takes time and exposure to oxygen to achieve these heats. As such a split second exposure and quick removal (cooling) may not actually achieve a correct indicative oxide colour to show what really happened. Also notable when using gas sources of heat for tempering - where exposure to oxygen is limited - in which case the heat source need to be removed regularly and a few seconds of exposure to oxygen allowed so as to see the true oxide.
In light of all this I also maintain my belief in using hand tools over power tools for sharpening and honing the edge. And just because one only sees dark blue doesn't mean one didn't stuff their temper. Caution is good. :-)
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Post by DigsFossils-n-Knives on Jun 30, 2015 10:55:28 GMT
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Post by Brendan Olszowy on Jun 30, 2015 12:03:03 GMT
Haha, Yep, I haven't changed my tune despite having crafted many more blades in that time :-)
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Deleted
Deleted Member
Posts: 0
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Post by Deleted on Jun 30, 2015 13:58:37 GMT
Totally agree Brendan, grinders and belts are for shaping bars of steel into blades, sharpening a finished sword is a job for hand tools!!! In my mind it's important to learn to do the final sharpening by hand, where the amount of steel that's removed and how it's removed can be finely controlled, before using machines which have far less control and can stuff an edge more easily.
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Post by pokey on Aug 14, 2015 1:15:49 GMT
i hate hand sharpening! just go easy on the belts and you will have no dramas imo, they are great tools
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