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How to Sharpen a Rasp
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- เผยแพร่เมื่อ 28 ม.ค. 2014
- This episode originally aired on December 3, 2010.
Rasps get dull, just like any other tool. Most people just pitch them when they get dull and buy a new one. But before you go tossing those old dull rasps, or grinding them up into whatever, give sharpening them a try. No, I'm not talking about honing all the teeth with a microscopic stone. Even I'm not that nuts. To sharpen a rasp, we turn to chemistry. Blacksmiths have been using this trick for sharpening their files for decades. All it takes is a few inexpensive items from the hardware store, and some salad dressing.
Excellent tip that will restore vintage files and rasps, and save us money! I always clean rusted tools in white vinegar and noticed how much sharper old vintage files felt after leaving them for 1-2 days. Didn’t realize that vinegar not only removed stubborn rust, but also sharpened them! Thanks.
Bob you have one of the most soothing voices I have ever heard. Thanks for an interesting video.
I have thought the same thing
It's amazing the number of uses one can find for wire clothes hangers. I keep several around for just such occasions.
You are a Pandora's box of knowledge sir! Ten thumbs up! (that's all the thumbs I have 😊).
Hi Bob, I have a bunch of files & rasps that needs sharpening a bit so thanx for the vid. I saw some comments that said this procedure is only helping a bit. I just want to mention that the reason we have limited sharpening attempts on a rasp or file is due to the way they are made / designed. The teeth is only that long and the process of using the tool in question inevitably shortens the teeth over time so it is not the sharpening process that limits the lifespan of a rasp or file but the actual use of the tool. Many thanx for a cool vid.
same as knives etc but the blade has room for actual sharpening imho
the only question is what tool does it, tiny metal rasp/file?
Works on files, too. Never thought about trying on a rasp. Thanks.
Thank you for this . Very helpful .
So cool! Thank you Bob!
long time ago; but still worth a big thank you for sharing --- I will trying the idea on a couple 50++ year old rasps
Got tired of the brush very quickly, the pressure washer worked like magic.
Don't throw those old rasps away, give them to a knife maker instead. Same with circular saw blades, etc. Re-purpose that old stuff.
this whooole video fits in a “put the rasp blade overnight in the vinegar” phrase.
i was actually hoping youd explain how to sharpen each of the spikes easily😎
I am the wife so I can use the blow dryer! LOL :D I'm needing to sharpen a horse hoof rasp. Thanks for your video!!
The other way I learned is to leave the worn files and rasps in the rain and let them rust. When you remove the rust, you have sharp teeth again. This is also chemical sharpening, but takes longer than the acid. So, next time you see a rusty file left in a yard, you may be sure it's sharp and ready to use, after cleaning. Of course, chemical sharpening only works for so many times - each time the teeth get smaller - then you can repurpose the file or rasp (or give it to someone that does). Just don't throw them away.
I discovered some of my late Father's rasps, files and sharpeners left to rust in an old toolbox sitting on the garage floor that my younger brother did not see the value in. He is a machinist and I am a woodworker and I have been debating whether cleaning them with Naval Jelly will destroy them as they are still sharp (I've tested the rasps and the files on sacrificial wood and they have done well.) What would you consider the best way to remove the slight coating of rust. I haven't found a video that addresses this issue. Your comment caught my eye and my curiosity and I am hoping you'll respond.
@@lmcsquaredgreendale3223 Use molasses. It has the lowest removal of actual metal from testing, only destroys the rust, is cheap (you use a 10:1 ratio of water to molasses), and is plentiful. Takes a bit of time though, so expect to spend a few days waiting for the molasses to dissolve the rust.
@@snausagesmcgee3963 Sorry for taking so long to thank you for the suggestion. Thank you so much for taking the time to offer a viable option to harsh chemicals. TH-cam's notification system, at least on my computer, jumps around instead of allowing a smooth scroll. I read the advice and thought that sounds like something to try so I don't destroy good metal files and rasps and when I went to thank you I must have hit the mouse or space bar and your comment was gone. So what you get is a very belated message of thanks.
People don't take care of their files and rasps. It is open just toss into tool box on top of each other. I believe that is actually the main reason why they get dull.
Hey Brother, I know I’ve been away a bit… but I came across this video (again) when I was looking into adding a set of (4) Liogier rifflers and a 12 grain modelers rasp to add to my other rasps. I’m thinking this way after having made a few saw handles and finished my first two pieces in staked & windsor joinery. But I have also seen advertisements for and the occasional kutzall rasps in content creators videos. Have you had any experience with them and if so, what would you suggest. I know, the purpose is important. So their use would be primarily to add to my tool kit that I carry to the family cabin; I use them to putz around making different gifts, crafts, contains those tools I need to repair furniture, make small boxes, and also has what I need to harvest/split timber that I want to bring back to the main house to work on. Again, I know nothing of them, but really would rather not have my Auriou and Liogier rasps out of the safety of the shop if I can avoid it. If the kutzalls have some critical failing point I’m unaware of, I guess I’ll keep hauling my old machine made Nicholson’s.
I haven’t used them so I can’t offer an opinion. I have a total of 4 rasps and files combined - Nicholson #50, Nicholson rat tail rasp, half round cabinetmaker’s file and rat tail file. I honestly prefer edge tools like shaves, knives and scrapers to the rasps/files. I only use rasps/files as a last resort. I don’t really like using them.
Wow, I thought you needed some fancy machinery to cut all that back to new otherwise it's just scrap metal! I'll have to test out the acid on some old ones I've got laying around unused.
Tool steel (files and rasps) is never scrap. It can be turned into so many things.
New cutting tools (knives, plane blades, chisels, gouges, and lathe tools (metal and wood)), scrapers, file guides, etc.
If there is an application for tool steel, you fan use old files and rasps with a little grinding.
Some of my files come with a HRC spec - 63. That's stupid-hard. Not sure how a wire brush could have a significant effect.
He's just using the brush to clean out the old crud.
i thought the brush was made of aluminum, softer than steel
It's the same idea as using a wire brush on the edge of your knife. It will wear down the apex, making it dull.
It doesn't matter if it's a 60hrc file, or a 65hrc file, if it comes in contact with steel, it will cause it to dull. Maybe not right away, maybe it may take dozens of times, but it will wear them out sooner.
Nylon or brass bristles are the ones to use.
Be careful not to get the brass plated ones.
Steel wire brushes can be made of hardened steel too, some may not.
@@autumn5592 Just one thing; the stitching on a file is nothing like an edge of a knife. Sure, use brass if you like. It's not as if it really matters. Good luck.
@@felixf5211 In single cut files, each stitch is a single straight cutting edge, not to dissimilar from a knife (it has 2 planes that intersect to form a cutting edge, and it is made of hardened steel.)
Or please, if they are so magically different, tell me how, because I'm failing to see.
Brass is many times softer than steel -- it does matter.
how many time can we do this?
theduck I’ve done mine a couple of times and have not worn them out yet. So I can’t say for sure. I’d guess you could do this at least four or five times. But it will depend on how bad the rasps are as well. If they get too dull, this process won’t really work.
Why is the resolution only 360P? very annoying. Thank you for the vid.
Because it was made 12 years ago before most home cameras could film in HD and before TH-cam could support HD video.
@@BobRozaieskiFineWoodworking I see, thank you.
Brush from tail to toe as not to dull.
im skeptical. etching a rasp might make it slightly sharper for a bit, but will also weaken the tips of the teeth and thus it will probably dull quickly. i really dont think this is worth doing.
YUP!!! These guys NEVER show us a closeup of the file teeth after the "acid" wash eh...
It's a fifty dollar tool that has lost it's efficiency, have you actually tried to improve it's useful life span by following the instructions,or just negating the principle explained by the video posted? If the teeth are shortened and made useful again, the post is valid. I've thrown thousands of dollars worth of files away (paid for by my employer) but now I'm paying, why not spend a couple of bucks and see if I can save a hundred or so reviving my old files and rasps? Kudos to the video
start with a rusty blunt file ..... end up with a shiny blunt file
Why do you have to keep the rasp off the bottom?
i don't think you do, it's just so the handle doesn't get left in the vinegar too
@@kayj312 tx mate.
What you call "brown rust" is actually carbon.
Since tool steel has generally high concentration of carbon, when you soak it in acid it removes the iron and leaves carbon oxide.
This rasp will leave black residue on the wood, so I always remove carbon with a steel brush immediately after I remove it from vinegar and spray light coat of oil on it.
The Prophet Well, I’m not quite sure that’s accurate. I haven’t actually written out and balanced the chemical equation (I gave that work up shortly after getting my chemistry degree, go figure). But oxocarbons are primarily generated in two forms during most reactions. These are carbon monoxide and carbon dioxide, both invisible gasses. There are some other compounds of carbon and oxygen but most are either very unstable or not simply synthesized and unlikely to form by simply immersing a piece of steel in a carboxcylic acid like vinegar.
The brown residue is almost certainly iron(III) oxide (brown rust) while the black residue is most likely iron(II) oxide. The acetic acid in the vinegar removes the iron from the steel and the iron combines with the free oxygen from the dissociated acid to form the two different iron oxides. Other byproducts of the reaction are likely carbon dioxide, carbon monoxide, hydrogen gas, and other potential metal oxides depending upon the alloy components of the steel in question. Since we don’t know the exact composition of the steel used in this particular rasp, it is difficult to say what these other byproducts would be.
Brown rust is actually Ferric Oxide Not carbon.
no such thing as carbon oxide. by products might be CO or CO2. gases that do not stick but are volatile. Back to school for you Mr Carbon oxide.
Sir, you just gave me the answer to a novice restorer's question. Why do the parts I try to remove rust from turn black? Thank you for that!
Just reading this now, but this comes from someone who obviously doesn't doo much rasping. It's B.S. And what little discoloration might occur can be quickly sanded off. Which has to be done anyway after rasping.
This is more of a cleaning job than sharpening. What is sharp??? Its where 2 surfaces intersect at the smallest radius possible. Lets scale this up a bit........say you have a knife and its razor sharp, in theory its got 0 radius. It becomes duller with use and now has a 1mm radius. Etching in acid will remove small amounts of material, more or less EVENLY across a surface........this still leaves you with a similar 1mm radius on the edge.
Think of everything else we sharpen, chisels, saws, plane irons.......what we are doing is creating a smaller radius on the edge. Next time your plane iron or saw teeth get dull, etch them in acid and see if it sharpens them. If it was as easy to get a new edge by just etching it, wouldnt we all have vats of mild acids in our workshops and leave our edged tools in them overnight so we have sharp tools in the morning?
I actually think the reverse would happen, it doesnt get sharper, it gets duller.........Wouldnt the acid have more of an effect on a finer edge?
Say we have the theoretical 0 radius on an edge, and we dunk that into an acid.........do you still think it would have the theoretical 0 radius?
Imagine a sharply peaked, VERY pointed mountaintop. Its eroded over time by wind/rain (similar to the way an acid erodes materials).......does that mountain keep its sharply peaked, pointed shape at the top?? Of course not.
Think about it lads and ladies.....the way an acid works is to remove very small amounts of material, but there is no control to it when its simply placed into the liquid.....so how does this remove a radius from an edge? It cant turn something rounded into something pointed.....it will simply keep its rounded shape, but with a little less volume on the tooth than before. Maybe its a placebo effect feeling that its cutting better.......like the way a rasp or file gets clogged with dross/swarf, so we brush it to make it cut better.........an acid is basically doing the same thing.
THANK YOU.
So many people think chemical 'sharpening' actually works... it is shocking people lack the critical thinking.
The funny thing is, I've seen some knife makers/blacksmiths who put stuff on the edge of their knife to stop acid eating it, but chemically sharpen their files.
I am just at a loss for words when I see people like that.
For the record though, occasional acid bath (for a few moments) is not a bad idea, it softens oxides allowing them to be brushed off easily.
This 'unclogs' files, making them behave like they are sharper (in reality just has the clearance to actually take a chip/shaving off.)
Files are made of tempered steel. dunking them in acid dose not sharpen them. it just cleans . you need to anneal to soften so it can be sharpened and tempered again for hardness...... So whomever told you this about sharpening with acid is full of it ........
Lots of files, including good ones, aren't tempered. Because they are case hardened -- you don't need to soften the steel if the center is already soft.
Chemical processes don't care about the hardness of the steel. It will ONLY effect the rate at which it happens, not the process that happens.
Acids eat iron, plain and simple.
You don't need anealed steel to have acid eat it.
Besides, it's not like chemically 'sharpening' actually sharpens files, so it's all dumb.
Does coca- cola work also?
Cleaning, not sharpening.
acid sharpens the file, but only a small amount and you only get 2-3 goes
I've had pretty mild luck with this process. It seems to sharpen just a touch, so little that it be my imagination, and the effect is nowhere near a new (ie.sharp) file. Used vinegar. YMMV
@@jusb1066Acid does not sharpen files.
@@autumn5592 well does for others
@@jusb1066 Care to explain HOW acid can sharpen files?
cleaning is not sharpening
If it allows the tool to work better at doing it's intended job, what's the difference?
@@papahajek5383Say you get sap on your knife. If you clean it off are you sharpening it?
No, you're not -- same concept here.
never do this ! the black stuff is not dark iron oxide, but carbide, a loss of carbon caused by hydrogen embrittlement. it lower the hardness of the steel and the rasp and file can go directly to the trash. maybe fast chemical poliishing by anodic electrolyse into strong acid can acheve that, but this is speculations
You do too much work! Don't bother cleaning them, get a plastic silverware tray, put them in it. Use eye and hand protection, outdoors is best. Use acid from an old auto battery and in 1to 2 hours it will look like new. Rinse very well and dry.
Old school! Just like I have an old battery lying around! LOL