Sharpening Shovels

This is the first Granworks Guide — a hopefully recurring series covering how to do specific tasks, with all the essentials covered. This guide is all about taking a rusted and dull shovel and breathing life back into it. The first part talks about how to remove the rust and the second part shows how to sharpen it.

As an example of just how much it’s possible to rejuvenate a shovel, witness the before and after of an earlier shovel:

Pretty dramatic.

Update: Viral?

Okay, this is a little bizarre.  Apparently this topic hit some kind of nerve since an imgur album and reddit post went (relatively) viral and the video has received quite a few hits.

First, the imgur album has over 600,000 views as I write this; was on the list of most viral posts for the day; and garnered me a “trophy” from the imgur team for an excellent submission.  Huh.

Then, the reddit r/diy post was at the top of reddit for most of the day; has over 5400 upvotes; and has over 1100 comments.  Yeesh.

But then apparently Popular Mechanics picked it up and wrote up their own article based on the video and linked to it.

All that caused the Granworks YouTube channel to double the amount of subscribers and increase the view count to between 3x and 10x our normal.  It’s at 6800 views right now, with actual comments and everything.

Very surreal day.

Video

The video may make more sense than a blog post since the actions and motions matter quite a bit.

Why Sharpen?

It’s fair to ask the question “why sharpen a shovel in the first place?” After all, they typically aren’t sharpened when you buy them from a store. Well, the reason why is because using the shovel is far easier when the blade is sharp. It’s hard to describe just how much easier when you’ve never used a sharp shovel before. In general, it just take a lot less effort to drive the sharp shovel into the ground and goes deeper with each thrust.

The original sharpening can also be done in a matter of a few minutes and thereafter you can touch up the edge in less than a minute. It’s a small amount of effort for a big payoff.

Remove Rust

Shovels need to glide smoothly to work effectively and rust really gets in the way. It will also destroy the shovel if not taken care of soon enough.

There are a number of ways to clean rust off of a tool, including some chemical methods. I’m going to cover two physical methods — sandpaper and wire brushes.

Sanding Away the Rust

The majority of rust tends to be on the surface of the metal and so using sandpaper can be reasonably effective. The grit does appear to matter. If the rust is very thick and coarse, then 100 grit or 80 grit works the best. If it’s fine rust, though, then those coarse grits work surprisingly poorly. I found 220 grit and 320 grit to work far better in those cases.

You can sand using a bare piece of sandpaper. That works well with curves and recessed areas. I don’t recommend it for large areas, though.

A better option for flatter areas is a sanding block. In this case, the fine grained rust was sloughed off relatively easily with the sanding block.

If you have a random orbit sander, then all the better.

This has the same issue as the sanding block in that it won’t get into recessed areas, but it does do an admirable job of removing a lot of rust fairly quickly.

Note that all of the sandpaper options fail at getting rust that is embedded below the surface. You can see some examples of embedded rust in the low right hand corner of the above pictures. No amount of sanding gets to that rust, save sanding away an entire layer of metal (not recommended).

Grinding Away the Rust

A faster and more complete option is to use an angle grinder with a wire cup brush.

There are two main kinds of wire cup brushes. The first kind has a bunch of individual independent wires and is intended for fine work. Those have a tendency to lose wire bristles, though, and so aren’t often recommended. I use the twisted wire type. Those are far more aggressive but do have the benefit of staying together for much much longer.

It’s possible to get wire cup brushes for drills. Those would work similarly to the angler grinder variants, albeit quite a bit slower. That’s because drills (especially cordless ones) don’t operate at anywhere near the speed that a grinder does.

The wire cup brush not only works faster than sanding but it also can tackle the embedded rust. It doesn’t take long at all to almost completely remove the rust from even a heavily rusted shovel.

It’s worth noting that it won’t get all of the rust. The brush can’t reach all recessed areas and isn’t great around edges. I do tend to follow up after the angle grinder with some loose pieces of sandpaper to get some of the hard to reach areas as well as to smooth away the main surfaces.

Here’s what the shovel looks like after the rust has been removed.

Sharpen Using a Metal File

It’s entirely possible to sharpen the shovel by hand using a metal file. It doesn’t take as long as you might think, either. All you need is a “bastard” file or any metal file that’s not coarse. A bastard file just refers to a metal file that is not fine and not coarse. Here’s an example:

Note that metal files almost always have their teeth pointing forward. You can feel the difference by running your finger over the file. You can even see them if you look closely at an angle. This matters because that means that they are intended to be pushed forward and not pulled backwards. In particular, never saw a file back and forth. This will dull the teeth. Always push the file forward or “draw” it along an edge.

I secure the shovel using a vise so that the shovel is at a slight angle. The idea is to then grind a flat edge on the front of the shovel that is roughly parallel to the floor. Since the shovel is at an angle, this flat area will create a bevel. The actual angle doesn’t matter, as long as there is some bevel.

Hold the file with your hands on both the front and back of it. Push the file forward roughly parallel to the floor. You’ll find that it “cuts” into the much softer shovel metal relatively easily. I tend to move the file to the side an inch or two while I make the forward stroke.

At some point I also make a wider sweeping stroke that covers the entire sharpened area at once. This is called a draw stroke

This method can be exclusively used to sharpen a shovel and should take only a few minutes the very first time. Each time after that to just touch up the bevel takes less than a minute.

Sharpen Using an Angle Grinder

Still, it’s faster yet to use an angle grinder with a metal grinding wheel to make the original rough bevel. I use a 1/4″ metal grinding disc.

These are used by welders to grind a mounded weld flush. That is, it can remove a lot of metal in a hurry. The soft edge of a shovel is no challenge at all for it.

In fact, it can work so quickly that you need to be a little bit careful. If you don’t pay attention to your progress, then you might find yourself removing far more material than you intended. Also, if you spend too long in one spot, you can cause the metal to heat up too quickly and that will “detemper” the steel, significantly weakening it.

So make light and quick strokes. That’s all that’s needed.

Similar to the metal file, just keep the grinding wheel roughly parallel to the ground. This will form the bevel extremely quickly — much much faster than the file does.

It does create a relatively rough cut, though. You can visibly see circular marks in the bevel from the cutting motion of the grinding wheel. As such, I always follow up the rough cutting with the grinder with a few draw stroke passes using the metal file. That smooths it out.

At this point, the shovel should feel notably sharp to the fingers and will actually cut you if you aren’t careful. You don’t want it to be knife-sharp or anything like that, but it will be sharp enough to make some damage.

Future Protection

The shovel is still susceptible to moisture at this point and risks getting rusty again. Now is a good time to apply a protective coating. It’s commonly recommended to use boiled linseed oil for this task, but I have never had any on hand and so I haven’t tried it. Instead, I use a Rustoleum Rust Inhabiter spray which you just spray on and then wipe off the excess. It lasts for quite a while, in my personal experience.

Here’s what this shovel looks like after a coating.

Final Thoughts

It takes me maybe 10 minutes to bring a completely rusty and dull shovel to a largely rust-free and sharp shovel. That’s well worth the time considering how much easier it is to use the shovel afterwards. I really can’t stress that enough.

After the initial rejuvenation, I just make sure to brush off all of the dirt after each use and then every so often touch it up with a metal file and some more rust inhabiter. That takes less than a minute.

Happy sharpening!