There is a hungarian phrase that sounds something like this: „Like a monkey on a grindstone” (this means someone in an awkward position). That’s what George couldn’t get out of his mind when looking at Matt while he was grinding. Let’s face it: Matt being the crew’s mascot, the other two often call him the monkey, and they do it for a reason. But back to the story.
George finally finished his belt grinder. Despite its birth defects, the machine works properly so the crew could proceed with rough grinding. This is the last time before the blades are heat treated, and it’s a good idea to grind away as much material as possible while it is still soft.
Although everyone in the crew was well aware of belt grinders and what they can do, no one actually owned one before, so George’s mini grinder was a huge leap forward. It is made to be compact so it fits Goerge’s tiny workspace (or at least that was the plan at the start), but sturdy enough to handle a whole weekend’s abuse at once.
What is a belt grinder?
Despite what popular Hollywood productions let people see, a knifemaker spends most of his time with meticulous grinding and polishing. This process is so time consuming, that the most essential tool in a knifemaker’s workshop is the belt grinder, which is a crossbreed between a grinder and a belt sander. It is more beefy than both and usually has around 1-2kW (1.5-3hp) output with monstrous belt speeds. As a very versatile machine that can grind flat, concave and convex surfaces with proper accessories, the belt grinder became custom knifemakers’ number one grinding tool.
Being a mechanical engineer by profession, George could handle the whole build, but even he couldn’t tell whether the grinder would stand up to the challenge or even work properly. However, the crew was behind schedule, so a weekend session was set anyway for rough grinding, whether the grinder was functioning properly or not by that time.
Since Peter had a pig slaughtering to attend (ancient Hungarian tradition), Matt and George set out to spend the weekend at George’s to subjugate the almost finished belt grinder to a thorough stress test.
By Saturday noon, when the last parts were at their place, it was time to fire it up. When George turned on the main switch, the machine came alive for the first time, and surprisingly, worked better than expected.
Edge bevels and surface finishes
If we take the cross-section of a blade, we can see that the two sides can taper in three distinct ways: they can curve outward (convex grind), they can be straight (flat grind) or they can curve inward (concave grind). A convex grind can make a very robust cross-section depending on how much “meat” is left on the blade, but it can never take a very fine edge. It can be found on axes, heavy choppers and bushcraft knives, as well as many historical edged weapons.
The concave grind is the exact opposite: it takes a very fine edge, but is prone to chipping. No wonder that it can be found mostly on razors and surgery tools. The flat grind is the holy middle ground: it can take a fine edge, while it is moderately resistant to chipping.
Surface finish is another important factor to cutting ability. A rougher surface is good for pull cuts, like rope cutting or rougher jobs. Where a cut must be made without pulling the blade (like when shaving), the edge must be finished with a fine stone and properly stropped to give it a superior edge while the surface of the blade must be polished to a high shine.
The three concepts of the project differ here as well: Peter and George chose flat grind to keep the blades sharp and reduce weight, while Matt chose a convex grind to keep it beefier. This also demands less precision, since there is no bevel line to keep straight and the convex grind gives a lot of space to hide flaws.
After a short test run, Matt almost immediately pirated the new facility and tried his hand at grinding some of his old projects, saying “don’t worry dude, I’ll get these done in no time”. Long story short, George didn’t get to finish his blade that weekend.
Nevertheless, the belt grinder was working OK, so the crew was back on track. A week later, Peter took a visit with his iron to work it on the grinder and since Matt stayed at home, George also had a chance to finish his piece, which he actually did.
It is hard to tell how different we felt after years of hand sanding and a few hours of grinding. Each of these blades would have taken days even to rough out with a file, not to mention the endless sanding that would have followed. And even with that much work, the end result would be a far cry from the crisp lines that only a belt grinder can make.
On the other hand, faster work makes it easier to screw up, which occurred several times due to lack of experience. Still, even that faulty piece of machinery made the whole crew a strong believer. At the end of each weekend a layer of rough, blue iron powder coat lay on the floor under the belt sander, proving that the crew was busy again. It’s a bit ironic to buy such an expensive, fine steel and then remove more than third of it, but than again, knifemaking is all about that nowadays.
We’re gonna take a short rest in the upcoming holidays and post something light on December 29th. Only after that we get to know if the whole batch is ruined, because the only decent heat treatment facility in the country doesn’t guarantee anything. See you later!