Experimental Finishes for a Cast Iron Plane

[Matthew Hutchinson477]

I was recently fortunate enough to find a Stanley No. 92 shoulder plane within my meager price range. However, like most planes that are in my price range, it isn't exactly in mint condition. About 1/3 of the nickel plating is worn off and most of what is left is in bad shape. The harder-to-reach areas have some rust that I'm not gonna get to with any mechanical methods. The sole is also not quite flat and the sides are pretty square but not perfect. So, by the time I get it cleaned and tuned it'll have even less nickel plating and thus becomes a prime candidate for a full refinish.

I've painted planes in the past but I've been itching to try some other finish methods and now I have an excuse. Ideas so far:

-Rust bluing. No, not Brownell's oxpho-blue or any other cold blue. I mean the real thing--rust bluing that is generally only done on high-end firearms anymore. It's an easy enough process that I could definitely do it myself, though I haven't before. It wouldn't be entirely rust-preventing but it would help, it would not interfere with any tolerances or the smooth sliding of the sides against wood, and it could be very aesthetically pleasing.

-Next idea: Phosphate rust converter. This one seems simple and effective, but I would have to polish/sand it off the sides and the sole because it wouldn't make for a nice smooth surface.

-Ceramic coatings: These are most commonly used on guns. Examples are Cerakote and Duracoat. I have a rifle that was Duracoated, and it is definitely a more durable finish than any bluing or paint I've seen. Plus it is entirely rustproof so maintenance is minimal. That all said, it isn't quite as smooth as bluing and it does build a little bit in thickness so any metal parts that are mated together will either not get coated or the coating will be removed whether it be through sanding or just through use. Still, it would probably be the lowest-maintenance option and it would look just as good as any paint probably would.

Right now I'm leaning towards rust bluing because I think it will provide the smoothest surface (assuming proper prep) and thus the best function. It might also look kinda cool and unique.

Has anyone experimented with any of these finishing methods? Is there any good reason to avoid playing with any of these?

Thanks!

[Rush Paul]

Matthew, here are two articles by Bob Smalser that address using phosphate rust converter and bluing to "rust proof" steel and cast iron tools. His process is what I plan to follow for my own shop. See:

http://contrib1.wkfinetools.com/bSma...tproofing1.asp
http://contrib1.wkfinetools.com/bSma...lockPlane1.asp

[Matthew Hutchinson477]

Thanks for the reply, Rush. I've read through quite a few of Bob's posts and I got the idea of using phosphoric acid initially from that article.

As for the bluing, I am planning on using a different method. What Bob was using is a cold blue, which from what I understand is mostly just a metal dye. It's commonly used to touch up bluing damage on firearms and generally isn't meant to be used as a stand-alone finish. It doesn't provide much rust resistance in my experience using it on guns, and is wears easily compared to real hot-bluing methods. I imagine Bob has a reason for the method he used and why he didn't go through the effort of rust bluing so hopefully he'll chime in.

Hot bluing is what modern gun manufacturers use on firearms. The standard method involves sodium hydroxide or potassium nitrate, and isn't really an easy thing to do in your own garage due to the required equipment. The method used in the 19th and into the 20th century is referred to as rust bluing. It requires a decent amount of labor but is feasible for a DIYer to do in a garage. Basically you apply a solution to the metal to induce rusting, then boil the metal part to convert the rust into a different iron oxide, and then "card" AKA brush off the loose oxide with a fine wire brush so that only the firmly-bonded oxide remains. The labor becomes arduous because you may have to repeat this process a number of times. This method is still used on high-end double barreled shotguns because the barrels are silver-soldered together and hot salts bluing requires more heat than the solder can withstand. From what I've read rust bluing is the most durable form of bluing if applied in enough "coats". I do have a couple old guns (we're talking 80+ years old) that are rust blued and I can attest to the opinion that a rust blued finish is the most aesthetically pleasing as well as being more durable than any other type of bluing.

The main question for me so far is how rust bluing will work on cast iron. There are plenty of articles and videos detailing the process for firearms but I don't know of any firearms components that are made of cast iron rather than steel, so the process may have to be modified or the finish may come out looking very different with cast iron. I also don't know how cast iron will react to the heat of boiling water.

If no one here has tried it yet then I'll probably experiment with a broken component from another plane. But hopefully someone with more experience can shorten the learning curve for me!

[Jim Koepke]

Have you given any thought to nickel plating?

You could also plate it with some other coating like gold or copper.

jtk

[Patrick Chase]

-Ceramic coatings: These are most commonly used on guns. Examples are Cerakote and Duracoat. I have a rifle that was Duracoated, and it is definitely a more durable finish than any bluing or paint I've seen. Plus it is entirely rustproof so maintenance is minimal. That all said, it isn't quite as smooth as bluing and it does build a little bit in thickness so any metal parts that are mated together will either not get coated or the coating will be removed whether it be through sanding or just through use. Still, it would probably be the lowest-maintenance option and it would look just as good as any paint probably would.

Cerakote and Duracoat are an epoxy and a urethane respectively. Neither has significant ceramic content, though one of them is marketed as such :-).

As you say it's basically the same as painting, because both are fundamentally high-performance paints. The obvious concern is that if you get too much build then the body would end up wider than the blade, and make your shoulder plane less usable for grooving.

[Patrick Chase]

I was recently fortunate enough to find a Stanley No. 92 shoulder plane within my meager price range. However, like most planes that are in my price range, it isn't exactly in mint condition. About 1/3 of the nickel plating is worn off and most of what is left is in bad shape. The harder-to-reach areas have some rust that I'm not gonna get to with any mechanical methods. The sole is also not quite flat and the sides are pretty square but not perfect. So, by the time I get it cleaned and tuned it'll have even less nickel plating and thus becomes a prime candidate for a full refinish.

A couple more thoughts:

Have you measured how far out of flat/square the plane is, for example with shim stock and a straightedge? If it's within ~2 mils then I wouldn't mess with it. IIRC Veritas' squareness spec for their shoulder planes is 1.5 mils across with width of the plane, and those planes are deemed more than good enough by most folks (though admittedly most Veritas shoulder planes are much better than that spec. Mine certainly are). People tend to perceive shoulder planes as high-precision instruments, but the fact is that the surfaces you work with them are generally so narrow that a bit of angular error doesn't amount to anything.

If you do decide to try to flatten/square it, the way to do it is to work the base while using an accurate 90-degree form to register the side of the plane to the sandpaper. I use a cast-iron precision ground form, but you can easily make one that's accurate enough (see above in re: "enough" :-). You might want to put some HDPE tape on the form to prevent abrasion.

In addition to shoulders, the 92 is often used for cutting 3/4" grooves. In order for that to work the iron has to be the same width as the plane or very slightly wider, and the iron needs to be 3/4" wide. That's why I discouraged painting in my previous post. Anything that mucks with the width is generally a bad idea.

[Matthew Hutchinson477]

Honestly, I haven't thought much about plating. I figured it'd be out of my price range. I have read about nickel plating with a similar setup to electrolysis but never got around to trying it, and my understanding is that electroless nickel plating-which that setup is not- is the way to go for durability. I'll look into it though. I could always make it an original reproduction. Copper playing might also look kinda cool!

[Matthew Hutchinson477]

Yaaaa I figured I'd have to sand/polish it off the sides so I'd lose a lot of coverage. The coatings aren't really high on my list but I figured I'd ask. What you say just confirms that they probably aren't ideal for the application.

[Matthew Hutchinson477]

I just eye-balled the sides with a square that I know is accurate, and I could see light in some places. So it may well be within those specs. It is probably accurate enough for me.

The sole, on the other hand, is clearly hollow and the toe is noticeably higher than the other component that the blade rests on. I've seen this with a few bullnose planes and wondered if it was intentional but it wouldn't make sense on a shoulder plane, would it? My understanding is that the toe and front of the mouth should be applying some pressure to compress the wood slightly before the mouth opening and subsequently the blade. If the toe is raised a little like on my plane, it isn't pressing down on the wood at all.

[Patrick Chase]

I just eye-balled the sides with a square that I know is accurate, and I could see light in some places. So it may well be within those specs. It is probably accurate enough for me.

The sole, on the other hand, is clearly hollow and the toe is noticeably higher than the other component that the blade rests on. I've seen this with a few bullnose planes and wondered if it was intentional but it wouldn't make sense on a shoulder plane, would it? My understanding is that the toe and front of the mouth should be applying some pressure to compress the wood slightly before the mouth opening and subsequently the blade. If the toe is raised a little like on my plane, it isn't pressing down on the wood at all.

If you haven't already you should make sure that the mating surfaces between the body and the toe assembly are clean and rust free. A tiny bit of gunk in the wrong place could easily cause what you describe.

As Patrick Leach points out, the front and back halves of that plane have been known to drift apart after time, so if they're still out after the interface is totally cleaned up then yes, it might be worth flattening the sole.

Some bullnose planes (can't remember which ones) were actually manufactured with the toe a bit recessed relative to the rest of the sole. There was a discussion here about the reasoning behind that, but I've forgotten.

[Stanley Covington]

I have refinished most of my metal planes, mostly in the same dark red color, partly for cosmetic purposes, partly to prevent them from walking away on jobsites.

The material I used at the time was Dupont's Imron. It is a catalyzed polyurethane and was about the most durable available at the time, and certainly the most attractive. 90% of airplanes and 70% of big rig trucks used to be painted with Imron, despite the high cost and pain-in-the-ass factor. But there are better products available now, my professional airplane-painter brother tells me.

One professional-grade product is Polane by Sherwin Williams. I own aluminum and steel guns painted with this product, and know it to be very durable. There are others.

The key is the primer when painting cast iron. Use a commercial-grade etching primer by a respected maker, and the bond between metal and paint will never fail (never is a long time, I guess....)

Of course, paint won't work on the sides or sole of a plane, but from the perspective of rust protection and touchup capability, nothing beats paint, even if it is catalyzed.

As you mentioned, gun bluing is pretty, for a while at least, but not very effective at preventing corrosion. A waste of time.

Phosphates should work OK, but are oh so ugly, and tactilely unpleasant.

I have done a lot of rust bluing of guns, casework hardware, knives, and tools, including a block plane. My favorite tool is a Starrett compass I rust blued 20 years ago, and still looks good. A couple of my high carbon steel kitchen knives, and hunting knives are also rust blued, and show no corrosion (in the blued areas, at least) after 22 years of wet use.

The great thing about rust bluing is that, as you know, it is not a colorant, but forms a very hard, tough, rust-proof surface chemical layer of hematite from the steel itself (Patrick could describe this better than I) when done correctly. Done correctly is the key. And it doesn't require spray guns, hazmat suits, respirators, tanks, etc. The material is cheap and mostly harmless (if you don't drink it) and the only special tools required are some fine bristle stainless steel brushes. Some gun barrels I have done were actually difficult to file because of the hardness of the rust blue. My Starrett compass doesn't show a scratch after all these years on my benchtop and rattling around in a tray with other steel tools in my tool chest. I suppose top-quality industrial grade nickle/chrome plating is the only finish that might be as durable.

Rust blue was the gold standard for metal finishing for centuries, and is the still the most desireable and expensive finish for fine custom rifles.

Here in Japan, they add green tea leaves to the conversion water to produce a darker color for steel sword hardware and casework hardware. It works.

I don't recommend it for the soles or sides of planes, however. It will increase friction, and would eventually wear through, especially if you cut tropical hardwoods.

Stan

[lowell holmes]

I have painted bench planes with automotive paint. It was successful.

[Robert Hazelwood]

I've done a bit of rust bluing this year on old vintage chisels and plane irons. I think its an excellent finish for these tools, and if you have something that's a bit mangy looking then bluing is a relatively easy way to make it look respectable (IMO). And of course it can look stunning on something in good shape as well.

But I think Stan is probably right about plane castings. Certainly the soles shouldn't be blued. If you don't intend to use the plane on its side, then you could blue the sides, which should help prevent surface rust from finger oils.

BTW, I recommend Pilkington's Rust Blue. It seems pricey but will last you forever. I started with a homemade solution of hydrogen peroxide and salt, which does work, but it took many iterations (10+) and was difficult to get even. It also caused deeper pitting while doing rusting steps. In contrast, the Pilkington's does the job in perhaps 3 iterations, is much more even, and does not tend to pit the metal.

I have not tried to blue cast iron so far, but I don't see why it wouldn't work. The main thing is to get it very clean and degreased before you begin.

[Stanley Covington]

I've done a bit of rust bluing this year on old vintage chisels and plane irons. I think its an excellent finish for these tools, and if you have something that's a bit mangy looking then bluing is a relatively easy way to make it look respectable (IMO). And of course it can look stunning on something in good shape as well.

But I think Stan is probably right about plane castings. Certainly the soles shouldn't be blued. If you don't intend to use the plane on its side, then you could blue the sides, which should help prevent surface rust from finger oils.

BTW, I recommend Pilkington's Rust Blue. It seems pricey but will last you forever. I started with a homemade solution of hydrogen peroxide and salt, which does work, but it took many iterations (10+) and was difficult to get even. It also caused deeper pitting while doing rusting steps. In contrast, the Pilkington's does the job in perhaps 3 iterations, is much more even, and does not tend to pit the metal.

I have not tried to blue cast iron so far, but I don't see why it wouldn't work. The main thing is to get it very clean and degreased before you begin.

Agree with Robert on all points.

Rust blue works fine on cast iron or cast ductile-iron plane bodies. The iron content is the key. Chrome, found in nearly all recycled steel, can make the process uneven, and the color greenish.

I too have been using Pilkington's formula (sold by Brownells. Midway used to carry it) here in Japan. It is pretty good, but not quite as good as the old timey formula a gunsmith taught me. I don't have the formula here, and there is no way of getting my hands on nitric acid in Japan, so the Pilkington works. Clean and degreased is critical as Robert pointed out.

If you decide to use a home-made formula, I strongly encourage you to avoid anything with chlorine in it. Salt has lots of chlorine. Rust blue is just what the name suggests: rust. Heating the rust in a wet environment (boiling, steaming) causes the conversion to hematite. The rust must be developed during repeated treatments of the chemical, over time in a humid, warm environment producing very fine, fuzzy rust, which you card off each time with a fine, soft, stainless steel brush (also sold by Brownells). Chlorine/salt are great for creating rust, but chlorine bonds directly with iron, and continues to produce rust long after it needed to be neutralized. This means deep pitting going on for a long time after you thought it had stopped.

Dilute, weak nitric acid, citric acid, muriatic acid etc. can be neutralized without difficulty.

Stan

[Matthew Hutchinson477]

But I think Stan is probably right about plane castings. Certainly the soles shouldn't be blued. If you don't intend to use the plane on its side, then you could blue the sides, which should help prevent surface rust from finger oils.

Unfortunately for me this is a shoulder plane so the sides will get their fair share of sliding against wood. I suppose I could just lap the sole and sides to a fine grit and leave them bare like on all my bench planes but then there really wouldn't be much left to be blued.

I'd say its down to rust bluing or nickel plating. I'll have to look into nickel plating cost and feasibility--it may be the best option given the fact that rust bluing would wear off of the sides and increase friction.

I'm still intrigued by rust bluing, though, so I'll have to find something else to experiment with. I thought about trying it on a bench plane but the inside of the castings are all pretty rough and I certainly don't want to go through the trouble of smoothing all that out.