Hey everyone,
I’ve been experimenting with ways to make a shovel that holds its edge way better than the typical store-bought ones. I’m really focused on edge performance — specifically how to get a strong, long-lasting, sharp edge that can bite into hard or rocky ground without rolling or dulling too quickly.

If you were making a digging tool like a shovel and wanted to maximize edge durability, how would you go about it?

Welcome aboard Ben(?) glad to have you. If you put your general location in the header you'll have much better chance of meeting with members living within visiting distance.

Not to be anti-social but this forum is for folks interested in blacksmithing with tangents. We're not here to answer questions for companies, manufactories, etc.

We will however talk to you if you'll clarify what you're asking. You shouldn't expect specific information in answer to a very general question such as yours above. Have you researched shovel manufacturers? Not all the information is proprietary, good luck finding out their metallurgy, first they aren't likely to tell you and secondly it's patented. 

Learning how to sharpen a shovel, spade, etc. in a simple web search. The edge bevel and degree of edge depends on the USE, not in the factory. New shovels come un-sharpened, that's up to the end user. 

I use a fine draw file on my shovels, spades and axes, I touch up my axe blades with a stone hone but know folks who make a living with an axe that strop the edge as well.

Frosty The Lucky.

Welcome aboard from 7500' in SE Wyoming.  Glad to have you.

Your question is similar to the conundrum in knife making, how to have a edge hard enough that you aren't frequently resharpening and tough enough that it doesn't ship while still having a blade that is not brittle.  These are a function of the steel you are using and the hardening and tempering used.

If you are trying to improve a factory made shovel you are stuck with whatever steel the manufacturer used.  As Frosty says, you probably will not be able to find out what exactly the steel is.  So, you have to find out by experimentation.  This may involve cutting up a shovel into smaller pieces so that you can experiment with various techniques and mediums for hardening and tempering on each piece to see what works best (while keeping notes).

Tempering to different hardnesses is known for differential tempering.  Different hardnesses are indicated by the color steel turns at different temperatures.

If it were me, and I knew the shovel steel had enough carbon in it to harden and take a temper I would heat the shovel blade to a temperature above the critical point (where the steel becomes non-magnetic) then quench it in the hardening medium of my choice (probably oil or water or brine) up to a line that includes all of the edge.  Then I would wire brush the scale off to bare metal so that I could see the tempering colors.  Then, using a propane or oxy/acetelyne torch I would heat the body of the shovel to a blue color and watch as the colors "ran" towards the edge.  When the edge was a straw or bronze color I would quench it again to freeze the colors. 

If you do that and the shovel edge chips in use I would repeat but let the edge be a bit softer.  If it dulled or rolled I would redo it and keep the edge a bit harder.

This is actually easier to talk about than to do.  It takes some practice and experiment to sense when you've got the right combination of hardness and toughness on that particular steel.  Once you've got it it is pretty easy to repeat. 

"By hammer and hand all arts do stand."

When i dig into rocky or hard ground it is never with a shovel alone. That is what a mattock is for. Break it up first then use the shovel. 

But since the question was posed, how about a replaceable edge, kind of like on a snow plow? A 2" strip of D2 or M2 for the cutting edge maybe? I would not attempt the hardening and tempering of those at home though. I would definitely send them out. 

When I'm digging in hard rocky ground and I live on Glacial til, and I can't get an excavator or backhoe on site I use a spud bar, pick and lastly a spade. A crow bar comes in handy sometimes too. 

Back in the day when I worked for paving company the younger son had a bad habit of using a shovel for a pry bar and kept breaking the handles soooo, he'd just throw it away instead of listening to ANOTHER butt chewing from his Father or older Brother.

Being good steel I took most home with me I put handles on some, until handles became more expensive then a new shovel. And here's my experience with how tough a shovel blade is. 

I started taking them to the place we went to shoot. The two official shooting ranges were expensive, poorly maintained and stacked shooters right next to each other when it wasn't full. Made it easier for the owner to keep an eye on things. Soooo, we went to one of the many places with good back stops or miles of open nothing and shot cans or other things. 

I painted a white dot in the center of a shovel blade for a target, you can hear it if you hit it. The first day we mostly burned 0.22 long rifle and left noting but lead smears. My 0.22 mag left a copper smudge, My 0.338 Win mag flipped it a few yards but only left a smudge. Dad's 3006 and a couple armor piercing rounds actually made dents. He didn't know I stole a couple boxes from his stash when he gave me the rifle. Even backed against a birch tree the AP rounds only dented it.

I can't imagine someone needing a tougher shovel. Though they do make excellent pattern welding stock.

Frosty The Lucky.

This sounds crazy, but friend of mine once sent me a link to a video of someone TIG hardfacing their chipping hammer with HSS, using an old drill bit as filler.  So far I've tried it on a hot punch and an internal threading tool, both of which have held up well.  If you have a TIG, you could try a shop-made bimetal shovel blade.  Who knows?

Like everything else, it's a compromise. If you're in rocky soil and you make a harder shovel edge, it's going to break every time you hit a fricking rock. Too soft, and it will roll. In sandy soil or a soft loam/clay, a harder edge will maybe dull slower but it doesn't make a lot of difference. The ideal a lot of the time is toughness over performance - you want a shovel that's not going to break and make shrapnel when some moron plays baseball with it, or chip and then take a toe off when some drunken nut mistakes his shoe for a hole in the ground.

A shovel already tend to be tough stuff; as suggested above, dressing frequently and using the appropriate tool for the job is key. When I was in Atlanta, some soils I even kept an old axle handy for breaking up rocks when driving fence posts in soils that were too rocky and root filled to get stuff out with a pry bar or mattock. Heck, sometimes even then it was just easier to move over a foot or so, and if the fence was uneven, it was uneven.

 

There is no flex in hard facing so it tends to check then break off when flexed. A sharp edge on a shovel makes a big difference scooping rocks, less so for a spade. Still a blade is meant to be sharp just adjust the angle for the soil conditions. ON one job the root mat was so dense we drove spades into it with a sledge hammer with a piece of 2 x 4 for a cushion on the step of the blade.

I also got laughed at by the geo on the drill crew for sharpening the machetes so I let his blunt up so he could satisfy his whacking urges on brush. You know it's pretty bad when your machete takes 2-3 whacks to get through a thumb sized piece of live tag alder.

Depending on the vegetation and culture lots of folks put a single bevel edge on machetes so they always bits and don't glance. This is fine IF you only hit brush from one direction, say outside from your right. Single bevel almost guarantees glancing blows if you ever back swing.

Chain saws rule! 

Frosty The Lucky.