NOTE: I did NOT use any de-oxidizing agent on the file after electrolysis. I only lightly scrubbed the file with a tooth brush in line with the cutting edge reliefs. The only residue it did not remove was some copper galling. Cheers Rob
Very interesting Rob. I reckon the two processes compliment each other. The electrolysis is quite a violent action and probably loosens deposits in the file teeth. This allows the vinegar to get underneath and really do a good job. I wonder if an ultrasonic cleaner would be as effective as electrolysis? I really liked the microscope shots, lets you see the before and after really clearly. Cheers, Alan.
I think you are right Alan. That file was real bad, and the electrolysis removed over 50% in a relatively short time. Normally I would run it for 24 hours. So it did good. The vinegar just webt on with the job and it turned out as good as one could hope for. You should do a video on it with your US cleaner. The microscope did well. Made it all much more believable and evident as to what was actually happening. It's only a VGA one but quite handy. Cheers Alan
A very interesting and educational video Rob. A file is something I just can't scrap infact, I bag every one I see regardless and have a hoard of the recoverable type, old ones. It's hard to tell if a file is any good or not when they are in a clogged dull shape, usually because they havn't been looked after properly in the first place I may add. I now know a way to recover those files with very little effort
Hi Ian. I don't think I've ever thrown out a file either. I was all set to make something out of it and then a "miracle " happened. Just goes to show. Cheers Rob
I’ve tried resharpening some of my worn out but expensive jewellery files with acid (strong solution of granular PH down swimming pool acid). It sort of worked, the edges of the teeth got sharper but under magnification you could see that they were actually quite ragged, not really smooth anymore. They worked ok for a bit but they got blunt again after a while, they just didn’t have the strength to bear up. I’d class it as a way of squeezing a bit more life out of an old tool rather than a means of getting it good as new again.
Yes, nothing simple is going to restore knife edge angular facets onto any blunt /damaged file i've seen. Adelaide Saw Works used to throw them out at the slightest sign of dullness. That's where my old man got all his from, still perfectly servicable for home use. Cheers Rob
I'm guessing that if it was used for jewellery it would be clogged with precious metals? The ragged edge sounds like that. I would drop them in an ultrasonic overnight and check again if it is still the same try using aqua regia . It is 50/50 hydrochloric and nitric acid at same dilution if I remember correctly. That will remove the precious metals from clogging up the files. This is only my opinion based upon vague memorys and shouldn't be taken as gospel BTW.
I have swam in this pool far too many times already Rob. I still "sharpen" my worn files in acid. My choice is sulfuric and there are just as many opinions on that as there are people willing to try the process. I think there is a discrepancy in the way we use the word sharpen. As you have shown, cleaning makes a big difference in how easily the file removes material. With a nice layer of "schmoo" built up in the grooves acting as a depth stop the file stops cutting and appears "dull". Clean out the schmoo and the file cuts better. All the file cards in the world support that concept. I clean my files before etching them with acid. Any material on the surface protects the metal underneath from the effect of the etch. Dirt, rust, or grease of any kind will cause the effect on the surface to be inconsistent. So I think we agree on the cleaning idea. Once we are working on a clean surface the etch will do its thing on any exposed surface of the file. My theory is since the cutting edge has 3 surfaces, the leading, trailing, and the very narrow cutting edge, the etch is removing material from all of them at once. Remove an atom from the leading edge and the tooth profile is thinner. Remove an atom from the trailing edge and the tooth profile is thinner. Remove an atom from the cutting edge and the tooth gets shorter. Rince and repeat. Proceed until the cutting edge has been reduced to the minimum one atom wide and the file requires less effort to bite in the material to be cut. Now into the weeds. Files are essentially a cutting edge raised with a chisel as a chip from the base metal. They aren't a honed bevel created on the edge of a profile like a knife, tap, or drill. The profile is saw toothed and jagged. The etch will not improve the surface beyond making the tooth narrower at the cutting edge and shorter. Not an uncompromised position. The more consistent the profile is before use causes degredation, the longer it will cut. Once degraded, after sharpening, the edge degrades quicker because the tooth profile is smaller. Fine files cut slower. We just made the teeth finer in the etch. There is no free lunch. Not only does the etch make the profile shorter the physics of the process means the cutting edge spacing between teeth, the pitch, remains the same. An equivalent tooth profile on a file meant to have that size of tool profile from the beginning will have the pitch finer and the cutting edges closer together. Up until now we have been talking about degraded tooth profiles. In my estimation there are as many variations on how badly degraded the files are that live long enough tto be considered worth etching with acid. The etching method you have used is very similar to most. The file is dipped in the acid, sits for a time, and is removed. Etching a flat surface will not create cutting edges. Etching a file with broken, chipped, or missing cutting edges will not replace the missing material. A grindstone doesn't add material when sharpening an edge it removes it. The only difference is the grindstone only works on one surface at a time. Consider a tool with a similar action to the file. A broach has a series of teeth formed on the surface. They are ground to a sharp point by removing material from the leading edge and the trailing edge or relief angle. Over time the teeth wear and can be sharpened by again removing metal from the leading and trailing edge. Eventually the tooth is worn to the point it is too far gone and the broach is scrapped. Files are difficult to sharpen with a mechanical abrasive process. I don't want to have to control the profile of the grinding wheel small enough to grind the edge on a 10" mill bastard file. My eyes are too old to fiddle with such tiny tools. The only reasons I considered using an etch to sharpen a files tooth profile is the file was scrap before I started. Nothing to lose but a little time and I waste so much as it is another hour isn't noticeable. I can putter with other things while the etch is happening. A small gain with minimal investment in time and materials has convinced me the process is worthwhile. Etched files will never be sharp as new. If done correctly, a file with worn cutting edges can be made to bite better than before the etch. Okay. Walk away Dave. I have little expectaion of changing minds with this long winded explanation. Strangely I do feel better having spent the time chewing this cabbage again. Having swam in the murky water of file mythology I have to go and wash off the schmoo. Goodnight. 😁😎
Hi Dave, I have seen that this is a favourite subject of yours and am pleased you took the time to comment. It's an interesting subject. I think there are a range of issues to consider here and while cleaning is the main recovery process, the subject of acid dipping is a secondary topic with quite a few twists to it. As a viewer commented earlier, etching does not work in a uniform fashion/rate on differently shaped surfaces/angles. So immediately we have a major complication and of course it would be unrealistic to expect damage recovery to occur for missing and bruised edges. Ultimately etching will destroy the base object, but there may be short term gain initially in reprofiling some edge deformities. I have gone as far as intended looking into this concept and I hope viewers have got a better understanding of what is actually going on, from the videos and informed comments. I think the word "sharpening" is a misnomer for what is basically rejuvination. Cheers Rob
@@Xynudu I started the practice in about 2000 after a friend suggested it. The first trial was a success. About 3 batches I forgot and left the files in the sufuric bath over night.There were holes completely through the files. 😁 Over the years I improved the process. If you want to get attention this will do it. 😁😎 Let the crazies rant. Pull up a chair and watch. It will be interesting. 😁
As a Technical teacher I have cleaned many files using only vinegar. An overnight soak then a piece of copper pipe rubbed along the rows of teeth caused them to be sharper. I suspect this method etches the blunt area allowing it to be sharper. Just a thought.
I'm doing a soak and measure test of a high carbon steel roller at the moment, to see how much metal the etch removes in 24 hours (if it's even measurable with a 3 decimal mike). Stay tuned. Cheers Rob
I think about it like this, imagine you drop a piece of round bar in your etch solution. If the etch takes a consistent amount of material off the surface of the bar, you'll have decreased the radius of that bar. Now if instead of a round bar you're etching some geometry with a corner that has some radius (say a dulled file tooth) the etching process will leave a corner with a smaller radius, which is therefore sharper. I can't say I've actually tested this empirically myself, but I think that's the principle
Electrolysis does do a good job of cleaning files, but I use battery acid to sharpen them. Vinegar is too weak an acid to do the job. Some file are beyond this treatment.
No need for the electrolysis and acid. Degrease then leave vertically in the acid until you are satisfied that it is sharp enough. Any acid will do it but some take longer than others.
Hi Rob, interesting stuff indeed. I have files, and a microscope, guess what I am going to be doing? Just need to get some vinegar at next shopping trip. Cheers, Jon
Hi Jon, Interesting stuff for sure. I would be pleased to see you do a similar video to assess my findings. I used the cheapest vinegar available. They don't even quote the percentage (it's all greatly diluted with water) so I expect it's 2 - 5%. The end result (of cleaning) was very impressive. The re-sharpening (facet repair) seemed to be strangely undetectable ;) Cheers Rob
you can do the same thing to wood saws with hardened teeth. You can't file em sharp because they're hardedned but the acid will eat away the teeth until they're something like sharp.
Read about this years ago. But battery acid was used. My 2 bobs worth is that the very thin cutting edge gets dissolved by the acid leaving a somewhat stiffer but blunter edge which would allow it to cut again.As for putting chalk on files I dont think that is a good idea . In my experience that calcium salt in the chalk causes massive rusting,
Hi Shawn, The nylon tooth brush did a great job. I did use my file card on it as well, but it was already pretty clean, so I can't judge how effective it would be. The toothbrush is good because you can use it in the tub easily. Cheers Rob
Hey Rob. You're missing what's going on. Electrolysis will remove rust, by converting the iron oxide. It will also blow some of the crud off by the formation of bubbles, but with a file that action will be minimal, as the crud is in deep grooves you're not accessing. If you only have surface contact with the crud, electrolysis won't remove it unless it's rust or some other compound that gets removed, dissolved or otherwise affected by either electrolysis or the electrolyte itself. Electrolysis is not removing any base metal. Vinegar, on the other hand, absolutely is removing metal. It will get behind the crud it's not acting on and let it drop out, but as it acts on pretty much all metals it will also be dissolving the crud. With the steel of the file, it's producing iron acetate and hydrogen. As far as I can tell from your microscope shots, the edges are still damaged, but they are significantly finer through the erosion caused by the vinegar - i.e they are sharper. See 2:38 vs 13:56 What's really telling is to take a really totalled file (er a super cheap new one), and leave it in vinegar for a week or so. Don't expect to be filing with it afterwards.
I can't see how weak vinegar is going to remove enough hard high carbon steel to be even noticeable to the naked eye in 12 hours. As I said, the irregularity will still be the same, even if minutely reduced in size. If acid/vinegar really did work people would be tossing chisels, scissors and knives into a tub of the stuff, but I don't see any evidence of that happening. The real issue is the clogged file reliefs, which is pretty obvious. Cheers Rob
@@Xynudu You'd be surprised how active vinegar is. As an example, a bath in vinegar overnight will remove galvanising very effectively, and you don't need much. The hardness of a high carbon steel doesn't come into it, it's a chemical reaction not a mechanical one. The main issue with dull files is that the cutting edge gets rolled over. It's a very thin piece of steel, and vinegar will remove that. I have an idea for an experiment. Take a piece of clean steel, attach a glass tube to it, add a known quantity of vinegar, and heat gently (to speed things up) until it stops reacting. Measure the depth of the resulting etched pit.
@@Xynudu Oh, I intend to, Rob. That was a note for myself, not homework for you. At the moment I'm looking at the exact chemistry involved to see what to expect, and thus get something that is definitely measurable, and I'll probably look at finding some cheap glass tube tomorrow. I already have a remnant of old file that can be used as victim. Like they say, "talk the talk, walk the walk"... Going skiing today, though. Cheers Simon
I'm going to have to disagree with you on this one Rob, based on many positive experiences restoring files. Although I do think we have to leave room that this may hinge on one's definition of 'sharpen'. For me, if a blunt, shiny, file with zero 'grab' (but unquestionably already completely clean, because that is always step one for me) can have its filing ability substantially restored, that is evidence of a sharpening effect of some kind. I could never visualise a viable mechanism for how this was supposed to work myself, but did read one that seemed to make sense eventually some years ago in a forum post on a machinists' forum I think. In summary it's this: by equally dissolving steel from two faces that meet at a rounded edge you in effect create a smaller radius, which _is_ a net increase in sharpness. I've now used the technique on dozens of vintage files in various states of ill-repair, including not a few that had been used well past the point they should have been re-sharpened or discarded/recycled. These shiny ones take the longest for there to be a pronounced effect using a weak acid (vinegar + a little salt in my case); some files take only a day, maybe two to be noticeably improved, the shiny ones I've often soaked for longer than a week and as much as 20+ days on a few occasions (by accident initially, then intentionally when I saw it could sometimes be beneficial). As you and at least one previous commenter have noted, after treatment the edges can be noticeably less smooth than on an equivalent new file (although of course this is much more evident on a single-cut file than on a double-cut). Also finer files tend to respond better than coarse ones; this makes sense if the mechanism described above is accurate, since the acid is working on much smaller potential radii.
I did mention that a smaller radius was technically possible, but the effect would be minimal, given the small amount of metal removed. Clearly a file can not remove metal or bite in if the cutter reliefs are full, regardless of how sharp it may be. This is the major issue in my opinion. You can see how much material was removed by both processes. A lot. Whether you choose to believe the edges are "sharpened" in the true definition, is up to you. I don't see any visual or physical evidence of it. If this really worked then everyone would be tossing their end mills, scissors, chisels and knives into a tub of vinegar. I don't see any of that happening. Strangely it only appears to work on files. Don't you think that's just a tad odd ? Did you use a microscope to see what is actually happening ? Cheers Rob
@@Xynudu I didn't use a microscope, but I have examined files under a 10x loupe, the highest magnification I have available to me, to check progress. Clearly if the reliefs are full a file's ability to cut will be severely curtailed, this is clear and I don't think anyone would disagree this could be part of it. But this is why I made a point of mentioning any of the files I've treated to long 'sharpening' soaks were _already_ completely clean, because this is always done previously. I scrupulously clean stuff that's going into acid on the understanding that any oil or grease present will block the chemical reaction with the steel. I've been known to scrape every single groove one at a time when de-pinning, and the caustic soak I use to degrease makes anything stuck in place by oil or grime let go when scrubbing using toothbrush and/or brass-wire brush. If there's some rust overall a brief soak (few hours to overnight) is next, with further brushing to clean off the residue, followed by a sudsy scrub using common hand soap. Not trying to over-egg the pudding here, but I can assure you or anyone, the files are spanking clean after this 🙂 They are usually somewhat sharper (or to use a less divisive term, more 'bitey') as of course they should be, but are massively improved by further soaking in the salt and vinegar. And v. importantly in my book, even the ones worn enough to have the dreaded shiny patches are greatly improved. To me this clearly indicates that some net sharpening effect is taking place, rather than it being purely a matter of cleaning. Whether the mechanism is accurately described by what I related I couldn't say, but I can attest to the effect being separate to one of purely cleaning of the steel. _"If this really worked then everyone would be tossing their end mills, scissors, chisels and knives into a tub of vinegar."_ Well, like we all agree, the edges might be sharper/apparently sharper, but they're also cruder. When I am restoring rusty chisels, plane irons and the occasional single-edged razor you do on occasion get a noticeably sharper edge after soaking, but it is rough for sure. FWIW there are some complex shapes like the rotary cutters in pencil sharpeners which can have their cutting action restored by 'vinegar sharpening', q.v. Toolmakingart.com Cheers, Ed. P.S. Congrats on all those quality burrs you got, that was the haul of a lifetime 👍👍
Hi Ed. All good for discussion. I find it hard to believe that vinegar will etch high carbon steel sufficiently overnight to be measurable. To confirm or disprove this I am currently soaking a very uniform and accurate to measure bearing roller which I've miked up. After 24 hours I will re-measure it and see if there is any significant difference. If there is then maybe there can be a smaller curve radius on the dull and rounded over cutting edges, a possability I stated in the video, but doubted. Stay tuned. Cheers Rob
@@Xynudu The purpose of a tap or drill is to create a hole in an exact size and in the case of the tap an exactly consistant tooth profile. Etching removes material from every surface in contact with the etch. Having a sharp drill or tap that is .025 mm smaller in diameter after every sharpening would be ineffective at best. Also the size and configuration of the much larger cutting edges lends them to the mechanical sharpening methods that are difficult to achieve on the file configuration. 😁 10 seconds on the grinder will bring my chisel back to shape much quicker than waiting for the etch to remove the material. I am a rather impatient chiseler. 😁😎
@@Xynudu Saw you'd posted a follow-on video earlier but haven't had the chance to view it yet. Will get to it in just a short while. Just one minor niggle in advance, it seems clear that surface morphology will have quite a lot of bearing on this (sorry for the pun). It won't be merely about the larger surface area, although that's obviously a factor, but how acid etches into bevels at a small scale. So if I may, the best test of this is _the_ test of this - does a long soak in a weak acid _of already completely cleaned_ dull files make them cut better? I no longer have any unrestored vintage files, and no plans to buy any more soon since the majority will outlast me (they're only used on wood). But I do have a modern flat file (second cut?) which is one of my go-to metalworking files that is getting a little too dull on the sweet spot on both faces, so I was already planning on giving it a long bath in hopes I can bring it back again (this will be its second refreshing, if it works). Will report back in a week or two 🙂 Regards!
Reading the title of the video, Rob, You go too far. Is there no limit of the "miracles"? Take a rusty file and use it. Then show how it performs after derustying.
Try it yourself Stefan. The file was obviously nearly 100% clogged before treatment, and 100% cleaned afterwards. I'm sure it will work very well. There are more than a few "Old Wives Tales" in metal work. Cheers Rob
@@Xynudu I replied in the joking mode, not really criticising You. Being clogged reduces the performance, yes, but the edges are the cutting part of the file. So far I've managed to kept my tools away from rust. Cross the fingers....
Hi Stefan. No problem. I expected a few viewers to want to see the end result file metal, but there are plenty of videos out there showing how effective this "Miracle" is. None of them can explain why, or attempt to apply any logical brain power as to the physics and chemistry involved in the effect. When someone can show me vinegar changing a rounded over or chipped cutting edge into a sharp, flat edge facet, then I too will believe ;) Cheers Rob
@@Xynudu Well, You're on to something. There are always scientific ways to show things for the deep divers. Maybe that's overdoing things. Anyway, the vinegar bath clearly made the files look less bad..
![[ไฮไลต์] "เวฟ-วีรพล วิชุมา" สุดยอด! คว้าเหรียญเงินยกน้ำหนัก | โอลิมปิก 2024](http://i.ytimg.com/vi/nZnT15nhpKc/mqdefault.jpg)
NOTE: I did NOT use any de-oxidizing agent on the file after electrolysis. I only lightly scrubbed the file with a tooth brush in line with the cutting edge reliefs. The only residue it did not remove was some copper galling. Cheers Rob
Very interesting Rob. I reckon the two processes compliment each other. The electrolysis is quite a violent action and probably loosens deposits in the file teeth. This allows the vinegar to get underneath and really do a good job. I wonder if an ultrasonic cleaner would be as effective as electrolysis? I really liked the microscope shots, lets you see the before and after really clearly. Cheers, Alan.
I think you are right Alan. That file was real bad, and the electrolysis removed over 50% in a relatively short time. Normally I would run it for 24 hours. So it did good. The vinegar just webt on with the job and it turned out as good as one could hope for. You should do a video on it with your US cleaner. The microscope did well. Made it all much more believable and evident as to what was actually happening. It's only a VGA one but quite handy. Cheers Alan
A very interesting and educational video Rob. A file is something I just can't scrap infact, I bag every one I see regardless and have a hoard of the recoverable type, old ones. It's hard to tell if a file is any good or not when they are in a clogged dull shape, usually because they havn't been looked after properly in the first place I may add. I now know a way to recover those files with very little effort
Hi Ian. I don't think I've ever thrown out a file either. I was all set to make something out of it and then a "miracle " happened. Just goes to show. Cheers Rob
I’ve tried resharpening some of my worn out but expensive jewellery files with acid (strong solution of granular PH down swimming pool acid). It sort of worked, the edges of the teeth got sharper but under magnification you could see that they were actually quite ragged, not really smooth anymore. They worked ok for a bit but they got blunt again after a while, they just didn’t have the strength to bear up. I’d class it as a way of squeezing a bit more life out of an old tool rather than a means of getting it good as new again.
Interesting. Thanks for the comment and experience. Cheers Rob
Yes, nothing simple is going to restore knife edge angular facets onto any blunt /damaged file i've seen. Adelaide Saw Works used to throw them out at the slightest sign of dullness. That's where my old man got all his from, still perfectly servicable for home use. Cheers Rob
yeah this is my experience as well. Once or twice is about all you can do.
I'm guessing that if it was used for jewellery it would be clogged with precious metals? The ragged edge sounds like that. I would drop them in an ultrasonic overnight and check again if it is still the same try using aqua regia . It is 50/50 hydrochloric and nitric acid at same dilution if I remember correctly. That will remove the precious metals from clogging up the files. This is only my opinion based upon vague memorys and shouldn't be taken as gospel BTW.
I have swam in this pool far too many times already Rob.
I still "sharpen" my worn files in acid. My choice is sulfuric and there are just as many opinions on that as there are people willing to try the process.
I think there is a discrepancy in the way we use the word sharpen.
As you have shown, cleaning makes a big difference in how easily the file removes material.
With a nice layer of "schmoo" built up in the grooves acting as a depth stop the file stops cutting and appears "dull". Clean out the schmoo and the file cuts better. All the file cards in the world support that concept.
I clean my files before etching them with acid. Any material on the surface protects the metal underneath from the effect of the etch. Dirt, rust, or grease of any kind will cause the effect on the surface to be inconsistent.
So I think we agree on the cleaning idea.
Once we are working on a clean surface the etch will do its thing on any exposed surface of the file.
My theory is since the cutting edge has 3 surfaces, the leading, trailing, and the very narrow cutting edge, the etch is removing material from all of them at once.
Remove an atom from the leading edge and the tooth profile is thinner.
Remove an atom from the trailing edge and the tooth profile is thinner.
Remove an atom from the cutting edge and the tooth gets shorter.
Rince and repeat.
Proceed until the cutting edge has been reduced to the minimum one atom wide and the file requires less effort to bite in the material to be cut.
Now into the weeds.
Files are essentially a cutting edge raised with a chisel as a chip from the base metal. They aren't a honed bevel created on the edge of a profile like a knife, tap, or drill. The profile is saw toothed and jagged. The etch will not improve the surface beyond making the tooth narrower at the cutting edge and shorter.
Not an uncompromised position. The more consistent the profile is before use causes degredation, the longer it will cut.
Once degraded, after sharpening, the edge degrades quicker because the tooth profile is smaller.
Fine files cut slower. We just made the teeth finer in the etch.
There is no free lunch. Not only does the etch make the profile shorter the physics of the process means the cutting edge spacing between teeth, the pitch, remains the same.
An equivalent tooth profile on a file meant to have that size of tool profile from the beginning will have the pitch finer and the cutting edges closer together.
Up until now we have been talking about degraded tooth profiles.
In my estimation there are as many variations on how badly degraded the files are that live long enough tto be considered worth etching with acid. The etching method you have used is very similar to most. The file is dipped in the acid, sits for a time, and is removed.
Etching a flat surface will not create cutting edges. Etching a file with broken, chipped, or missing cutting edges will not replace the missing material. A grindstone doesn't add material when sharpening an edge it removes it. The only difference is the grindstone only works on one surface at a time.
Consider a tool with a similar action to the file.
A broach has a series of teeth formed on the surface. They are ground to a sharp point by removing material from the leading edge and the trailing edge or relief angle. Over time the teeth wear and can be sharpened by again removing metal from the leading and trailing edge. Eventually the tooth is worn to the point it is too far gone and the broach is scrapped.
Files are difficult to sharpen with a mechanical abrasive process. I don't want to have to control the profile of the grinding wheel small enough to grind the edge on a 10" mill bastard file. My eyes are too old to fiddle with such tiny tools.
The only reasons I considered using an etch to sharpen a files tooth profile is the file was scrap before I started.
Nothing to lose but a little time and I waste so much as it is another hour isn't noticeable. I can putter with other things while the etch is happening.
A small gain with minimal investment in time and materials has convinced me the process is worthwhile.
Etched files will never be sharp as new. If done correctly, a file with worn cutting edges can be made to bite better than before the etch.
Okay. Walk away Dave. I have little expectaion of changing minds with this long winded explanation.
Strangely I do feel better having spent the time chewing this cabbage again.
Having swam in the murky water of file mythology I have to go and wash off the schmoo.
Goodnight. 😁😎
Hi Dave, I have seen that this is a favourite subject of yours and am pleased you took the time to comment. It's an interesting subject. I think there are a range of issues to consider here and while cleaning is the main recovery process, the subject of acid dipping is a secondary topic with quite a few twists to it. As a viewer commented earlier, etching does not work in a uniform fashion/rate on differently shaped surfaces/angles. So immediately we have a major complication and of course it would be unrealistic to expect damage recovery to occur for missing and bruised edges. Ultimately etching will destroy the base object, but there may be short term gain initially in reprofiling some edge deformities. I have gone as far as intended looking into this concept and I hope viewers have got a better understanding of what is actually going on, from the videos and informed comments. I think the word "sharpening" is a misnomer for what is basically rejuvination. Cheers Rob
@@Xynudu I started the practice in about 2000 after a friend suggested it.
The first trial was a success.
About 3 batches I forgot and left the files in the sufuric bath over night.There were holes completely through the files. 😁
Over the years I improved the process.
If you want to get attention this will do it. 😁😎
Let the crazies rant. Pull up a chair and watch. It will be interesting. 😁
Voice of reason thank you Rob
I try to view things logically. Cheers Rob
looks great, nice job
Came up well. The vinegar finished it off nicely.
Hi Rob, I clean and sharpen my files with an molasses and water mix 50/50 and a tooth brush
Hi Lyall. Thanks for the tip. Cheers Rob
As a Technical teacher I have cleaned many files using only vinegar. An overnight soak then a piece of copper pipe rubbed along the rows of teeth caused them to be sharper. I suspect this method etches the blunt area allowing it to be sharper. Just a thought.
I'm doing a soak and measure test of a high carbon steel roller at the moment, to see how much metal the etch removes in 24 hours (if it's even measurable with a 3 decimal mike). Stay tuned. Cheers Rob
makes total sense to me
Nice stuff vinegar. Apple cider vinegar is good for the blood too. Cleans out the crap...
I think about it like this, imagine you drop a piece of round bar in your etch solution. If the etch takes a consistent amount of material off the surface of the bar, you'll have decreased the radius of that bar. Now if instead of a round bar you're etching some geometry with a corner that has some radius (say a dulled file tooth) the etching process will leave a corner with a smaller radius, which is therefore sharper. I can't say I've actually tested this empirically myself, but I think that's the principle
I agree. As I stated in the video, technically there may be a tiny reduction in any radius, but the main effect is from cleaning. Cheers Rob
Electrolysis does do a good job of cleaning files, but I use battery acid to sharpen them. Vinegar is too weak an acid to do the job. Some file are beyond this treatment.
Well there you go then. Very interesting.
No need for the electrolysis and acid. Degrease then leave vertically in the acid until you are satisfied that it is sharp enough. Any acid will do it but some take longer than others.
Hi Rob, interesting stuff indeed. I have files, and a microscope, guess what I am going to be doing? Just need to get some vinegar at next shopping trip. Cheers, Jon
Hi Jon, Interesting stuff for sure. I would be pleased to see you do a similar video to assess my findings. I used the cheapest vinegar available. They don't even quote the percentage (it's all greatly diluted with water) so I expect it's 2 - 5%. The end result (of cleaning) was very impressive. The re-sharpening (facet repair) seemed to be strangely undetectable ;) Cheers Rob
I've done it before and it mostly works but you can only do it once or twice before the teeth just get completely eaten away
you can do the same thing to wood saws with hardened teeth. You can't file em sharp because they're hardedned but the acid will eat away the teeth until they're something like sharp.
Read about this years ago. But battery acid was used. My 2 bobs worth is that the very thin cutting edge gets dissolved by the acid leaving a somewhat stiffer but blunter edge which would allow it to cut again.As for putting chalk on files I dont think that is a good idea . In my experience that calcium salt in the chalk causes massive rusting,
Maybe, but IMHO unless the cutter relief is clear there will be no cutting. Simple as that. Cheers Rob
I use soap stone instead of chalk
The only acid that could re-sharpen the blunt file is a hydrochloric acid.
I use 33% and it takes about 20 to 30 minutes.
I wonder if a file card before and after the soak would make any difference rob ?
Hi Shawn, The nylon tooth brush did a great job. I did use my file card on it as well, but it was already pretty clean, so I can't judge how effective it would be. The toothbrush is good because you can use it in the tub easily. Cheers Rob
You can do it with stronger acids though.
No need to.
Hey Rob. You're missing what's going on.
Electrolysis will remove rust, by converting the iron oxide. It will also blow some of the crud off by the formation of bubbles, but with a file that action will be minimal, as the crud is in deep grooves you're not accessing. If you only have surface contact with the crud, electrolysis won't remove it unless it's rust or some other compound that gets removed, dissolved or otherwise affected by either electrolysis or the electrolyte itself. Electrolysis is not removing any base metal.
Vinegar, on the other hand, absolutely is removing metal. It will get behind the crud it's not acting on and let it drop out, but as it acts on pretty much all metals it will also be dissolving the crud. With the steel of the file, it's producing iron acetate and hydrogen. As far as I can tell from your microscope shots, the edges are still damaged, but they are significantly finer through the erosion caused by the vinegar - i.e they are sharper. See 2:38 vs 13:56
What's really telling is to take a really totalled file (er a super cheap new one), and leave it in vinegar for a week or so. Don't expect to be filing with it afterwards.
I can't see how weak vinegar is going to remove enough hard high carbon steel to be even noticeable to the naked eye in 12 hours. As I said, the irregularity will still be the same, even if minutely reduced in size. If acid/vinegar really did work people would be tossing chisels, scissors and knives into a tub of the stuff, but I don't see any evidence of that happening. The real issue is the clogged file reliefs, which is pretty obvious. Cheers Rob
@@Xynudu You'd be surprised how active vinegar is. As an example, a bath in vinegar overnight will remove galvanising very effectively, and you don't need much. The hardness of a high carbon steel doesn't come into it, it's a chemical reaction not a mechanical one.
The main issue with dull files is that the cutting edge gets rolled over. It's a very thin piece of steel, and vinegar will remove that.
I have an idea for an experiment. Take a piece of clean steel, attach a glass tube to it, add a known quantity of vinegar, and heat gently (to speed things up) until it stops reacting. Measure the depth of the resulting etched pit.
You've got a channel. Go ahead and do it.
@@Xynudu Oh, I intend to, Rob. That was a note for myself, not homework for you. At the moment I'm looking at the exact chemistry involved to see what to expect, and thus get something that is definitely measurable, and I'll probably look at finding some cheap glass tube tomorrow. I already have a remnant of old file that can be used as victim. Like they say, "talk the talk, walk the walk"...
Going skiing today, though. Cheers
Simon
Is washing sofa borax or something totally different cobba?
I think so.
I'm going to have to disagree with you on this one Rob, based on many positive experiences restoring files. Although I do think we have to leave room that this may hinge on one's definition of 'sharpen'. For me, if a blunt, shiny, file with zero 'grab' (but unquestionably already completely clean, because that is always step one for me) can have its filing ability substantially restored, that is evidence of a sharpening effect of some kind.
I could never visualise a viable mechanism for how this was supposed to work myself, but did read one that seemed to make sense eventually some years ago in a forum post on a machinists' forum I think. In summary it's this: by equally dissolving steel from two faces that meet at a rounded edge you in effect create a smaller radius, which _is_ a net increase in sharpness.
I've now used the technique on dozens of vintage files in various states of ill-repair, including not a few that had been used well past the point they should have been re-sharpened or discarded/recycled. These shiny ones take the longest for there to be a pronounced effect using a weak acid (vinegar + a little salt in my case); some files take only a day, maybe two to be noticeably improved, the shiny ones I've often soaked for longer than a week and as much as 20+ days on a few occasions (by accident initially, then intentionally when I saw it could sometimes be beneficial).
As you and at least one previous commenter have noted, after treatment the edges can be noticeably less smooth than on an equivalent new file (although of course this is much more evident on a single-cut file than on a double-cut). Also finer files tend to respond better than coarse ones; this makes sense if the mechanism described above is accurate, since the acid is working on much smaller potential radii.
I did mention that a smaller radius was technically possible, but the effect would be minimal, given the small amount of metal removed.
Clearly a file can not remove metal or bite in if the cutter reliefs are full, regardless of how sharp it may be. This is the major issue in my opinion. You can see how much material was removed by both processes. A lot.
Whether you choose to believe the edges are "sharpened" in the true definition, is up to you. I don't see any visual or physical evidence of it.
If this really worked then everyone would be tossing their end mills, scissors, chisels and knives into a tub of vinegar. I don't see any of that happening. Strangely it only appears to work on files. Don't you think that's just a tad odd ?
Did you use a microscope to see what is actually happening ?
Cheers Rob
@@Xynudu I didn't use a microscope, but I have examined files under a 10x loupe, the highest magnification I have available to me, to check progress.
Clearly if the reliefs are full a file's ability to cut will be severely curtailed, this is clear and I don't think anyone would disagree this could be part of it.
But this is why I made a point of mentioning any of the files I've treated to long 'sharpening' soaks were _already_ completely clean, because this is always done previously. I scrupulously clean stuff that's going into acid on the understanding that any oil or grease present will block the chemical reaction with the steel. I've been known to scrape every single groove one at a time when de-pinning, and the caustic soak I use to degrease makes anything stuck in place by oil or grime let go when scrubbing using toothbrush and/or brass-wire brush.
If there's some rust overall a brief soak (few hours to overnight) is next, with further brushing to clean off the residue, followed by a sudsy scrub using common hand soap. Not trying to over-egg the pudding here, but I can assure you or anyone, the files are spanking clean after this 🙂
They are usually somewhat sharper (or to use a less divisive term, more 'bitey') as of course they should be, but are massively improved by further soaking in the salt and vinegar. And v. importantly in my book, even the ones worn enough to have the dreaded shiny patches are greatly improved.
To me this clearly indicates that some net sharpening effect is taking place, rather than it being purely a matter of cleaning. Whether the mechanism is accurately described by what I related I couldn't say, but I can attest to the effect being separate to one of purely cleaning of the steel.
_"If this really worked then everyone would be tossing their end mills, scissors, chisels and knives into a tub of vinegar."_ Well, like we all agree, the edges might be sharper/apparently sharper, but they're also cruder. When I am restoring rusty chisels, plane irons and the occasional single-edged razor you do on occasion get a noticeably sharper edge after soaking, but it is rough for sure. FWIW there are some complex shapes like the rotary cutters in pencil sharpeners which can have their cutting action restored by 'vinegar sharpening', q.v. Toolmakingart.com
Cheers, Ed.
P.S. Congrats on all those quality burrs you got, that was the haul of a lifetime 👍👍
Hi Ed. All good for discussion. I find it hard to believe that vinegar will etch high carbon steel sufficiently overnight to be measurable. To confirm or disprove this I am currently soaking a very uniform and accurate to measure bearing roller which I've miked up. After 24 hours I will re-measure it and see if there is any significant difference. If there is then maybe there can be a smaller curve radius on the dull and rounded over cutting edges, a possability I stated in the video, but doubted. Stay tuned. Cheers Rob
@@Xynudu The purpose of a tap or drill is to create a hole in an exact size and in the case of the tap an exactly consistant tooth profile.
Etching removes material from every surface in contact with the etch. Having a sharp drill or tap that is .025 mm smaller in diameter after every sharpening would be ineffective at best.
Also the size and configuration of the much larger cutting edges lends them to the mechanical sharpening methods that are difficult to achieve on the file configuration. 😁
10 seconds on the grinder will bring my chisel back to shape much quicker than waiting for the etch to remove the material. I am a rather impatient chiseler. 😁😎
@@Xynudu Saw you'd posted a follow-on video earlier but haven't had the chance to view it yet. Will get to it in just a short while.
Just one minor niggle in advance, it seems clear that surface morphology will have quite a lot of bearing on this (sorry for the pun). It won't be merely about the larger surface area, although that's obviously a factor, but how acid etches into bevels at a small scale.
So if I may, the best test of this is _the_ test of this - does a long soak in a weak acid _of already completely cleaned_ dull files make them cut better?
I no longer have any unrestored vintage files, and no plans to buy any more soon since the majority will outlast me (they're only used on wood). But I do have a modern flat file (second cut?) which is one of my go-to metalworking files that is getting a little too dull on the sweet spot on both faces, so I was already planning on giving it a long bath in hopes I can bring it back again (this will be its second refreshing, if it works).
Will report back in a week or two 🙂 Regards!
Reading the title of the video, Rob, You go too far. Is there no limit of the "miracles"?
Take a rusty file and use it. Then show how it performs after derustying.
Try it yourself Stefan. The file was obviously nearly 100% clogged before treatment, and 100% cleaned afterwards. I'm sure it will work very well. There are more than a few "Old Wives Tales" in metal work. Cheers Rob
@@Xynudu I replied in the joking mode, not really criticising You.
Being clogged reduces the performance, yes, but the edges are the cutting part of the file. So far I've managed to kept my tools away from rust. Cross the fingers....
Hi Stefan. No problem. I expected a few viewers to want to see the end result file metal, but there are plenty of videos out there showing how effective this "Miracle" is. None of them can explain why, or attempt to apply any logical brain power as to the physics and chemistry involved in the effect. When someone can show me vinegar changing a rounded over or chipped cutting edge into a sharp, flat edge facet, then I too will believe ;) Cheers Rob
@@Xynudu Well, You're on to something. There are always scientific ways to show things for the deep divers. Maybe that's overdoing things. Anyway, the vinegar bath clearly made the files look less bad..