Filling Pitted Round Knife with Epoxy for refurbishing

[AlamoJoe2002]

I have an CS Osborne, Newark NJ,  Round Knife due in which will be my 1st round knife. The metal blade is pitted. Hopefully I can work on the blade without removing the handle. I would like to remove the rust using electrolysis by suspending the blade into solution and adding current to remove the rust. Then instead of removing material to the lowest pitted level, I propose to fill in the pitting with a metal epoxy, then begin profiling the blade by hand using various grits of sandpaper.

Do you have a few words of guidance for the electrolysis rust removal? 

How about products for filling in the pitted metal?

How do I protect the manufacturing stamp when I begin to sand down and profile the blade? 

I also like the idea of reworking the #70 Blade into a more custom knife similar to the Terry Knipschield non-symmetrical Round Knife.

Then again, I want my first knife sharp, shinny, and a pleasure to use as it will be mine!

Joe

[mike02130]

  Good luck.  Make sure to show us the result.

[AlamoJoe2002]

I found this product which is sold as a metal epoxy designed for pitting.

https://www.belzona.com/en/products/1000/1151.aspx

I have no idea the cost...

Joe

[Tugadude]

The Belzona material will be very expensive.  You could buy a Knipshield knife and have money left over probably.  

[YinTx]

I've used belzona in industrial applications before.  Some versions are machineable, etc.  They typically require special metal prep to ensure proper adhesion, and heat treatment to cause the polymer to crosslink for strength and other desired properties in industrial uses.  It is expensive, I would presume prohibitively expensive for use on a knife. (as in one unit of material will cost more than a knife will).  If the pitting is in the blade edge, I don't think you'd be able to get belzona to sharpen and hold an edge for cutting purposes.

A cheaper alternative would be something like JB Weld if you wanted to experiment with the epoxy based fillers.

YinTx

[fredk]

imo the pitting is part of the history of the blade

To remove the corrosion - a conservator at the RAF Museum, Cosford showed me how just leaving the metal in a weak solution of citric acid for a long-ish period removes the corrosion. He showed me before and after examples of aluminium alloy, brass, copper, steel and iron. 

I've used the technique using lemon juice in water and leaving an old rusted up tool in it for a couple of months, renewing the solution periodically though.

Cleaning the blade back to shiney metal - various grades of wet & dry grit paper, starting with rough, 320 grade, thru to 2000 grade then polishing with toothpaste

2nd vote for JB Weld - if you really must

[Mulesaw]

If you want to do the electrolysis rust removing, here's what I have tried with success:

Mix water and soda (natrium carbonate) in a bucket
Put a piece of metal in the bottom of the container where you will be doing the electrolysis. I use an old piece of steel  netting.
Connect the positive terminal from a car battery or a battery charger to the metal in the bottom of the container.
Pour in the water/soda mixture
Suspend the rusted item in the mixture, it must not touch the metal in the bottom.
Connect the negative terminal from the battery or the charger to the rusted item.

After a bit of time (depending on voltage, concentration of the system etc), you will see bubbles and something like a layer forming on the surface above the rusted item. 
I let it sit for a day or so. Then remove the electrical connections and take the de-rusted piece out of the solution.
There will be a black layer on the surface that I normally remove with a scotch brite pad.

Note that some electronic type battery chargers won't work, presumably because they can't see any voltage at all and hence won't start. (I bought a charger from Lidl that did just that).
 

I have also de-rusted plane irons by immersing them in regular household vinegar over the night. Again the rust turns into a black powder that is removed with a scotch brite pad.
For smaller items such as a knife blade, I'd go with the vinegar.

I doubt that any of the epoxies such as Belzona or Wencon etc. will work for sharpening. I have used them for repairing worn shafts that would sit in a bearing, or pitted pump housings, but they are not metal, so I would leave the pittings and look at them as character of that particular knife.  

Bgrds

Jonas

[chuck123wapati]

8 hours ago, fredk said:

imo the pitting is part of the history of the blade

To remove the corrosion - a conservator at the RAF Museum, Cosford showed me how just leaving the metal in a weak solution of citric acid for a long-ish period removes the corrosion. He showed me before and after examples of aluminium alloy, brass, copper, steel and iron. 

I've used the technique using lemon juice in water and leaving an old rusted up tool in it for a couple of months, renewing the solution periodically though.

Cleaning the blade back to shiney metal - various grades of wet & dry grit paper, starting with rough, 320 grade, thru to 2000 grade then polishing with toothpaste

2nd vote for JB Weld - if you really must

after that final toothpaste polish he will be able to do one handed push ups lol

13 hours ago, AlamoJoe2002 said:

I have an CS Osborne, Newark NJ,  Round Knife due in which will be my 1st round knife. The metal blade is pitted. Hopefully I can work on the blade without removing the handle. I would like to remove the rust using electrolysis by suspending the blade into solution and adding current to remove the rust. Then instead of removing material to the lowest pitted level, I propose to fill in the pitting with a metal epoxy, then begin profiling the blade by hand using various grits of sandpaper.

Do you have a few words of guidance for the electrolysis rust removal? 

How about products for filling in the pitted metal?

How do I protect the manufacturing stamp when I begin to sand down and profile the blade? 

I also like the idea of reworking the #70 Blade into a more custom knife similar to the Terry Knipschield non-symmetrical Round Knife.

Then again, I want my first knife sharp, shinny, and a pleasure to use as it will be mine!

Joe

i wouldn't use electrolysis at all i use vinegar fast easy cheap and non toxic lol and works as well as anything. I would leave the pits alone and leave the patina you will never make a new knife out of an old one just one that is cobbled up looking. if the edge is pitted then no filler will fix that you will need to regrind the edge and that will take some power tools and alot of water not to ruin the temper. Any collector value is long gone if its that rough if there ever was any so you can do about anything you want to the blade shape. Good luck and post some pics when you get finished.

Edited May 29, 2021 by chuck123wapati

[chuck123wapati]

a prior thread that might help also.

 

[Bant]

Some pictures of the knife would, in my opinion, would be nice to see where the issues are.  I've never done the electrolysis, but I've used vinegar, which has worked, but the soak time varies. Two other possibilities; 1)  Contact Osborne and see if they might be of assistance and 2)  Seek out a pro who might be able to help.  From my perspective, if the cost of going that direction is affordable to rectify the situation, it may well be a good approach.

With the later, take a look at Bladeforums.com.  If posting another site for help is verbotten I apologize.

 

 

[chuck123wapati]

35 minutes ago, Bant said:

 

"if the cost of going that direction is affordable"  that's the rub, new ones are only 70 bucks so how much does a guy want to spend?

[Frodo]

Joe,   Do you have gun shows in your area or close to your area?

do a goggle search for gun shows and locations.

Most, not all, gun shows will have a guy set up that sells hand made knives and usually he can sharpen and clean  while you wait. Take your knife to him, let him sand the pits out, and put a sharp edge on it.

after he is finished the only thing you should have to do is strop it when needed

cost in my area would be around $20.00  

[AlamoJoe2002]

Gents, you have provided a ton of information. If the knife arrives today I will present a few pictures of the subject.

I am not a knife maker and never forged anything in my life except my bond with my wife. Hah! And I'm finding I don't know squat! However, I have learned not to spend too much time on my hobby interests as that also gets me in trouble. I'll probably need a few counselling sessions by the time I'm done with this round knife...if you know what I mean...

Joe

 

[AlamoJoe2002]

The knife just arrived via US Post. I did a quick touch up cleaning with xylene, a brass brush, a green scrub pad and a bit of wet 2000 grit sandpaper. The blade is solidly set  into the handle. No movement. However, the blade is leaning toward the side with the Osborne mark. I will have to be very gentle with alingmnent. I will do this after sharpening.

Now some choices...I might just try to use the electrolysis to clean out the makers mark....the star is very faint.

I think I will forget about filling in the pits...

The edge is as dull and pitted when I run my finger nail along it. Public Service Message: Don't go hunting with a dull spear...it's pointless (Your turn.).

Here are the pics. I hope they load as I resized them to 364 pixels in width.

 

[Mulesaw]

If you are going to do the electrolysis, I think you need to be careful not to let the brass part of the handle touch the water/soda solution. I think it might damage the brass before removing any rust.

[Daffy]

might be worth a shot.

[AlamoJoe2002]

I made a quick electrolysis tank using an old laptop power source that converts 120 volt AC to 12 Volt DC @ 3 amps. I used a multi-meter to determine the negative and positive wires. 

I used a clear tub and zip-tied a few rebar cutoffs that I hit with a grinder to provide a clean conductive surface. The blade is hung using coated wire to where just the blade is submerged. I hooked up two alligator clips to the immersed blade which is the negative anode and the rebar is tied together in series as the positive cathode.

The idea is to surround the blade with the cathodes as the current travels only line of sight.

The solution is distilled water from my dehumidifier and Arm and Hammer Washing Soda (Sodium Carbonate) to increase conductivity. I don't know if tap water and a higher amp power source would work just as well.

I am going to leave the blade in solution at the low current overnight. One of the good things about electrolysis is that new metal will not react...so only the oxidized metal / rust will be affected. The pitting will remain...but will be free of rust. 

I'm interested in seeing how the Osborne Makers Mark turns out. The key will be if the star is more visible under the stamp. Will it be more legible or will it fade away with the rust?

This is the first time I have used electrolysis. I don't know much about metal...but if this lowers my sanding time on the blade I will be happy.

I uploaded a few about 11 images. However, I may have screwed them up getting them into this forum. I resized at 364 pixels...I think at that size they have no detail. What do you resize your pictures for uploading to this forum?

Tomorrow I will pull the blade out of solution, dry it off, and maybe put it in an oven around 180 degrees f to dry out the handle. Oh, part of the brass is in solution. Don't know how that will affect anything.

Joe

 

[dikman]

With electrolysis a high current will, of course, work quicker but the general recommendation is to use a lower current over a longer time (less than 1 amp). You can also use plain salt as the electrolyte but this will generate hydrogen so only do it outside. Probably the safest way, if you don't want to risk affecting other metal, is to use something like Evapo-rust. It's relatively harmless and will only attack the rust.

If the pitting extends to the cutting edge there's really not much you can do about it, just sharpen it as best you can. You should end up with a tool with a bit of character.

[Mulesaw]

That looks like a good setup. I haven't thought about using an old PC power supply, but I think that I'll copy your idea on that one instead of using the large battery charger at home.

As I have understood it,  using sodium carbonate and regular steel/iron as a cathode, will be the safest method. the gas emitted is CO2, and the end solution will be something that you can use to spread on your lawn, and it will help against moss growing, I think you can buy iron vitriol (might not be the correct name in English), in gardening centers, and that is what will eventually be in the tank.

Some people use stainless steel as a cathode, but then you'll get a bit of chromium in the solution which supposedly isn't quite as good for the environment.

[AlamoJoe2002]

The blade has been in solution under 3 amp DC Power for 12 hours. I checked it this morning. I pulled it out and wiped it off. I was expecting a black residue to cover the white cotton cloth. Not much...so back into the solution and power it up.

I know the process is working as I observe a reaction on the full surface of the blade and around the ground down areas of the rebar. 

I'm taking this low on power and long on time. Another 12 hours and I will check it again. If it continues to have a very slow reaction as I have observed I will keep the blade on electrolysis. I don't think I can hurt the blade. However, I am concerned about the water content of the wood under the ferrule. 

I am thinking about the re-profiling the side of the blade where it chipped. So the question is how would you improve a standard round blade if it chipped a point?

Joe 

[dikman]

I would have expected some change after all that time. I did it using lead sheet as the anode and it worked pretty quickly.

As for the broken tip, I would grind the flat/straight part to bring it to a point again. You could use an angle grinder or a bench grinder if you don't have a belt sander. The trick is to take it slowly and keep cooling the metal.

[AlamoJoe2002]

Dikman: I have a belt sander...I'm looking for design ideas to change the symmetrical profile to asymmetrical...almost a two in one round knife.

7 hours ago, dikman said:

As for the broken tip, I would grind the flat/straight part to bring it to a point again. You could use an angle grinder or a bench grinder if you don't have a belt sander. The trick is to take it slowly and keep cooling the metal.

I was thinking I need a sharpening board to mount the blade on for sanding. I'm thinking about using a handheld sander in straight line sanding (lateral as opposed to round) movement. If I can use the 10 inch portable sander I can really work on a gradual reduction of material to the cutting edge. I have a feeling I will be starting out with 80 grit paper or more aggressive sandpaper and hours of relaxing mind numbing meditation while I hand sand this blade down.

My goal is a sharp shinny blade and something like world peace...

Joe

 

[Tugadude]

Bikes with surface rust get a bath in oxalic acid solution.  Seems to do the trick.  Heard hydrochloric acid works too.

Caution is urged.  Protection and safe disposal required.

[dikman]

Ok, if you want to make big changes to the shape then yes, you're in for a lot of slow sanding/grinding, given that it's already hardened. There are lots of photos of different shapes that came up when I did a google search some time ago.

As for your last statement, sharp and shiny is achievable, world peace not so likely.

[bruce johnson]

On 5/28/2021 at 4:06 PM, AlamoJoe2002 said:

I have an CS Osborne, Newark NJ,  Round Knife due in which will be my 1st round knife. The metal blade is pitted. Hopefully I can work on the blade without removing the handle. I would like to remove the rust using electrolysis by suspending the blade into solution and adding current to remove the rust. Then instead of removing material to the lowest pitted level, I propose to fill in the pitting with a metal epoxy, then begin profiling the blade by hand using various grits of sandpaper.

Do you have a few words of guidance for the electrolysis rust removal? 

How about products for filling in the pitted metal?

How do I protect the manufacturing stamp when I begin to sand down and profile the blade? 

I also like the idea of reworking the #70 Blade into a more custom knife similar to the Terry Knipschield non-symmetrical Round Knife.

Then again, I want my first knife sharp, shinny, and a pleasure to use as it will be mine!

Joe

I don't want to rain on the parade, but that knife probably won't be what you want. I get several a year like that. Good chance with all that pitting you may arrest the ongoing corrosion but the steel may be pretty crumbly. That broken tip is pretty big and no small feat to grind a new shape without taking out any temper that may be left in it. By the time you get to thinning the edge there may not be much left. CS Osborne Newark marked knives are not particularly rare and I just don't see any work on this one to be time well spent.