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Battling Rusted Bolts and Winning

If you’ve done any restoration of ageless iron at all, you’ve no doubt run into one of the biggest frustrations you can encounter—a rusted bolt that simply will not budge. Fortunately, there are a few steps you can take to get that stubborn object removed. 

  • First, determine if the bolt is actually rusted in place. It’s not likely that this is the case with an antique tractor or implement, but some more modern equipment uses a thread-locking material on certain bolts. If this is the case, you’ll need to use heat to soften it. 
  • If it is in fact a bolt that is rusted in place, use a wire brush to clean the area and to remove as much rust as possible from the bolt or nut and threads. 
  • If possible, determine the type of material used in both the bolt and the surrounding material. Dissimilar metals have differing capacities for heat transference and dissipation. 
  • Start by using a good-quality penetrating oil to loosen the threads. If you search the restoration forums, you can find a wide range of homemade formulas, including diet cola or such mixtures as half acetone and half automatic transmission fluid, vinegar, and baking soda, and even hydrogen peroxide.

Most restorers, however, prefer one of two commercial products. One is PB Blaster Penetrating Catalyst and the other is Kroil penetrating oil. While PB Blaster is readily available in many locations, Kroil is often a little harder to find. But many restorers swear by it. If all else fails, you can order it direct from Kano Laboratories, the manufacturer, at

A couple of tractor enthusiasts have also mentioned a little-known product called Mouse Milk. Primarily used by the aircraft industry, it contains both a penetrant and lubricant, which also makes it ideal for freeing up cables, slides, and linkages. Find it at several locations online, or order directly from the company’s website (at $7.47 for an 8-ounce squeeze bottle) at

Be Patient, Let it Work

Be prepared to wait long enough for the penetrating oil to work. Wait several hours, at the very least. Some restorers have talked about waiting days, if not weeks, for the material to work its way down into the threads and break loose the rust as they’d apply more fluid every day or so. 

Use the right tool to remove the bolt. Pliers and locking wrenches will only round off the flat sides of the nut or bolts. Open-end wrenches are also more likely to slip off and round the corners. A six-point box end wrench is generally your best option. If the nut has become smaller due to corrosion, you might be able to get a better fit with the next smaller metric or SAE size.

Apply Leverage

Use a ratchet with a long handle or a breaker bar for more leverage on the wrench. Use smooth, continuous pressure and stop if the tension starts to suddenly feel soft, rubbery, or spongy. That’s often an indication the bolt is about to break off. The metal can only stretch so far before shearing off, so a change in the way it moves may be telling you it has stretched too far.

If all else has failed to this point, it’s often time to break out what some have referred to as the blue wrench.

That is a propane or oxyacetylene torch adjusted to a hot, blue flame. Just don’t apply oil to hot metal or direct an open flame toward a pool of penetrating oil. And use caution when using a torch anywhere near the fuel tank or brake fluid. Be careful, too, about using a torch on a part where the heat can be transferred to a bearing. 

Putting Heat to Work

Using a combination of heat and penetrating oil or heat and an impact wrench will usually take care of even the most stubborn bolt. An impact wrench should be a tool of last resort, however, since it just makes it easier to break the bolt.

As another option, you can try a technique used by Paul Cummings, a tractor restorer from Amsterdam, Missouri. 

When faced with a bolt that is rusted in place, Cummings heats the bolt with a torch until it starts to glow red. Then, holding a small birthday candle (like those that go on a cake) by the wick with a pair of pliers, he presses it against the bolt. As it melts, the liquid wax flows down around the bolt and threads, finding its way into any open crevices. Others who have used this trick say they simply touch the end of a candlestick candle to the hot nut or bolt and let it melt. 

In most cases, the combination of heat and the wax coating on the threads allows Cummings to remove the bolt without much additional force. It’s worth noting here, too, that Kano Labs has two additional formulations of Kroil available that provide some of the same benefits. One is SiliKroil, which combines penetrating oil with dimethyl silicones. The other is Penephite, a combination of penetrating oil and graphite.

Freezing Bolts Loose

As an alternative to heat, a couple of manufacturers have recently come up with products that freeze the bolt, causing the material to contract. If you’ve ever heard of someone putting engine cylinder sleeves in the freezer so they’re easier to slip into the cylinder bores, it’s the same principle.

One of these products on the market is Loctite Freeze and Release. Another is CRC Freeze-Off Super Penetrant. Both use a freeze-shock action to freeze and loosen rusted and corroded mechanisms.

Jim Deardorff, owner of Superior Coatings, a sandblasting and painting business in Chillicothe, Missouri, says one of the advantages of the freezing technique is that it doesn’t ruin the bolt, which can occur when a torch is used.

With heat, he explains, the molecular structure of the metal can be altered, causing the temper to be lost. So the freeze-shock method can be particularly valuable on antique tractor bolts that can’t be replaced. 

To use the freeze-and-release products, simply remove any dirt and loose rust, shake the can well, and spray the area for five to 10 seconds from a distance of 4 to 6 inches.

Deep, Deep Freeze

That’s sufficient to chill the part down to between -20°F. and -45°F. Parts can generally be dismantled after allowing one to two minutes for the penetrating oil in the solution to act. Repeat the application, if necessary. 

Deardorff says it has occasionally taken two or three applications to break a bolt or nut loose, but it normally works with a little time. 

Of course, that’s often the case, no matter what method you use. It took years for the bolt to rust into a locked position. It may just take a few days to get it loose.

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