rasp: before & after citric acid treatment

[Paul Saffold]

A few days ago I posted about getting a rasp for $1 at yard sale.
Following the advice of several Creekers, I did not wire brush it, but used a chemical bath to clean it.

The suggestions were to use ammonia water, vinegar, or citric acid.

I don't care for the smell of ammonia. I retired from the pulp end of a pulp & paper mill where we used anhydrous ammonia by the 70 ton rail car.

Vinegar was suggested, but it might take quite a bit longer.

I bought a 2 ounce bottle of citric acid powder from a brewery supply store for less than $2. I mixed 1 tablespoon of the critic acid in a quart of tap water and added 1 drop of dish detergent as a wetting agent.

The rasp had a lot of it's crevices filled with "junk". I don't know if it was from wood or horse hoofs. I think the rasp (Johnson) is marketed in the farrier trade. I scrubbed the rasp with a nylon brush & hot soapy water but didn't get it very clean. I don't have anything like a dental pick so I used a drywall screw to clean out the depressions. Almost the same thing right?
The next time, and I hope there is a next time, I will use my pressure washer. Another overlooked woodworking tool. :)

Before soaking I degreased it with mineral spirits then again with denatured alcohol. I soaked it for 10 hours in the acid, checking on it several times until it looked "done". It feels sharper, weather it is or not, I'm not sure.
I doubt if it would take hair off my arm without a lot of flesh too.:eek:

This was a fun little project. I've never had a use for a rasp but just couldn't pass up a bargain like that. You know how it is: "But dear, It was on sale!!!"

After and before pictures for your viewing pleasure. Comments welcome.
Paul

[Bill Houghton]

I don't have anything like a dental pick...

Next time you visit your dentist, ask. They wear out fairly frequently, and get recycled. My dentist gave me three or four when I asked.

Thanks for the info. I have a few rasps that could use a little sprucing up.

[harry strasil]

FWIW: old time blacksmiths sharpened there files and rasps in an acid bath, it erodes the metal uniformally and thus sharpens the teeth. to do it right you need to use a large flat glass dish with the file/rasp setting on glass rods in the bottom of the dish and gently and continuously rock the dish from side to side and depending on the strength of the acid it can take from 5 minutes to an hour or more, then flush with soda water and then clean water, dry thorougly over heat and then lightly oil it. phosphoric acid will do a decent job, you can get it at a paint store, its called ospho or something like that. phosphoric acid is an ingredient of soda pop too.

[Wilbur Pan]

I don't have anything like a dental pick so I used a drywall screw to clean out the depressions. Almost the same thing right?

I'm fairly sure my dentist uses a drywall screw in my mouth, sometimes. ;)

Nice before and after pictures! I'm a fan of electrolysis for rust removal, but next time I have to do this I might go look for some citric acid.

[Tony Zaffuto]

Junior,

If I remember correctly some old time 'smith also would leave rasps and files soak in urine!

T.Z.

[george wilson]

Tony,I'm not surprised,as they used urine for just about everything else in the old days!!

[David Keller NC]

Paul - In addition to the acid sharpening method that Harry mentioned, you can also have old rasps and files sharpened by the new-fangled "liquid abrasive" method. Boggs machine has a service for this - I think it's $15. Maybe not worth it for an old rasp, but then again a high-quality new hand-made one is around $80 - $100:

http://www.boggstool.com/

[harry strasil]

first time I have heard that, but there was a famous lady smith from europe, that would not temper in anything but goat urine. I have told several antique dealers that I repaired cast iron artwork for to go in a bottle and put the piece out under a bush somewhere and to wet it down twice a day, it artifically ages things not quite as quick as ferric acid, but is more controllable.

[harry strasil]

also old files etc were 101 points of carbon 10101, while new files rasps etc are only 1095, unless you specify industrial grade .

[harry strasil]

George the old smiths I was around when I was a kid growing up and attending blacksmith meetings used to tell about some dissatisfied customers who used to get back at a smith they thought overcharged them or did a poor job used to go in the slack tub or pour it out of a bottle they sneaked into the shop. Every once in awhile I would get an old piece of iron the customer wanted me to use to repair something of theirs and when you started cutting or heating it with a torch or put it in the forge ot started welding on it, You can tell it almost instantly, its much worse than animal urine or feces as far as the smell .

[Peter Evans]

I have good results using a cylinder (plastic spaghetti container, or glass vase) to put the files/rasps in; keeps them vertical and not resting on anything so the acid works uniformly. I usually use old citric acid that has been used to derust tools, I don't think you need fresh citric acid.

As for time, I just check them every day or so until they are sharp. General grunge is cleaned off by the acid (not concrete or really hard stuff), I do not degrease, I don't find the files are greasy, rusty yes, dirty yes, filled by iron filings yes. A quick brush before the acid is usually sufficient.

After sharpening - a fresh water wash and scrub with a nylon nail brush removes the deposit left by the acid and leaves the file for the critical last step - DRYING. Hitting the file with a hair dryer for 5 minutes or so drives the moisture out of the file - and I do _not_ oil the file. Rather I wrap in newspaper or rags, and this is sufficient to avoid rust (3 years experience so far). This is in a temperate climate 10km from the ocean (Sydney suburbs).

Some tools (not files/rasps so far) get a rust bloom no matter what you do, eg a Disston saw vise recently, but this was painted with epoxy paint so did not matter), and is probably a feature of unmachined cast iron where hard to get rid of - but such surfaces were usually painted/japanned, and mild steel where a quick sandpaper rub and oil usually do the trick.

Cheers
Peter in Sydney

[george wilson]

I have heard of sandblasting to sharpen a rasp,but have not tried it as I don't have a sandblaster. I am sure you would have to aim the blast at the rasp in the correct direction for it to work (if it does).

[Wes Grass]

What's interesting is that if you etch random pieces of metal the corners tend to etch away faster than the flats. Which would lead to a file getting duller in the process. But I have a theory, that the dull edges are polished and therefore don't etch as fast as the rougher flats. It would be interesting to see if continued etching would dull them again.

[Bill Houghton]

I'm fairly sure my dentist uses a drywall screw in my mouth, sometimes.

If you see him reaching for the 24 volt Makita, it's time to remember another urgent appointment.

[Paul Saffold]

Peter, I good idea to use a cylinder.

For those who have used this process, how strong do you make the citric acid solution?

Paul

[David Keller NC]

"For those who have used this process, how strong do you make the citric acid solution?"

Generally speaking, I use about a teaspoon of citric acid in a quart of warm tap water. In contact with iron, citric acid converts to ferrous citrate, so the citric acid is "used up" as the reaction proceeds. One of the by-products is hydrogen gas, so you can determine when it's time to throw it out and make a fresh solution when steel tools no longer form bubbles on the surface.

[Tom Sontag]

Maybe I need to reread this thread, but I wish posters would distinguish between de-rusting and sharpening. Methinks the OP just de-rusted since several pictures still show glowing dullness at the pointy ends of the rasp. I find myself passing on many a dull rasp at the flea because Boggs is the only sharpening I am aware of. I sent a bunch their way once and did not feel that most came back any where close to good as new in terms of sharpness.

Can someone please describe in detail which acid method truly works for sharpening files and rasps at home? I do not have sand blasting equipment but would gladly put together some kind of bath for razor sharp rasps. If I find a reliable method, I would be in heaven; sharp files and rasps are a joy to use and I find my work going that way more and more.

[harry strasil]

check out post #3

[george wilson]

The blacksmith shop in Williamsburg bought a file sharpening outfit,which used a PVC pipe (I think PVC,I didn't see it),but it did suspend the files vertically as someone suggested. I didn't hear if they got good results or not.

I have had old Nicholson files that I am sure were acid resharps never subsequently used. They were in a box of 19th.C. Addis carving tools I bought. Their teeth were not shiny(nor would they be even if the files were not thoroughly sharpened: the acid would have left a dull gray surface anyway). I am sure they were resharpened because their teeth were uneven along their cutting edges,where they would have been straight when new. The acid had micro crumbled the edges away. I think I remember that they were not as good as new when I tried them.

[Richard Dooling]

OK I've got the acid powder. I'll start by using David's formula of one teaspoon to one quart of water.

How caustic is the solution at this concentration? Do I need to use tongs and gloves?

[Jim Koepke]

My experience was that it was not real strong at the concentration you mention. I think some dry mix lemon drinks are about as strong.

Rust is not a resistive material. It dissolves fairly easy. A weak solution removes rust but not iron.

If you have sensitive skin, rubber gloves would be appropriate. I wear nitrile gloves just to keep my hands clean.

jim

[David Keller NC]

OK I've got the acid powder. I'll start by using David's formula of one teaspoon to one quart of water.

How caustic is the solution at this concentration? Do I need to use tongs and gloves?

Citric is reasonably safe. In fact, it is used in some applications as the raw powder on candy. Not that eating a spoonful would be a very good idea - such a quantity would likely blister the skin on the inside of the mouth. Uncomfortable, but no permanent damage.

Contrast that with concentrated strong mineral acids (HCl, H2SO4, HF, among others) - gloves, face shield and a respirator are a good idea when using those.

[harry strasil]

Living in a small rural basically farm community, where do I find Citric Acid to use?

[Richard Dooling]

I got mine from a local store called Wine and Cake Hobbies - apparently it is used in some aspect of wine making. It is available from numerous online sources but it's so cheap you may end up spending as much on shipping as you do on the product!

http://myspicesage.com/citric-acid-p-96.html?gclid=CI-8sNTU85sCFRPyDAodeHWX_g

[harry strasil]

THANK YOU, Richard

[Joel Goodman]

Interesting to note that on the link posted it's advertised as a substitute for salt for folks on a restricted diet!

[Paul Saffold]

I got mine at a beer and wine store. They also sell a few supplies for the home brewing folks. When I bought mine the clerk ask me if I was making hard cider.

Paul

[Peter Bell]

Living in a small rural basically farm community, where do I find Citric Acid to use?

This is a guess Harry because I am over here and you are over there. Try the baking isle in a grocery supermarket. Hopefully it should be near the bi- carbonate soda, baking soda, flour, etc.

Peter.