A knife-making grinding machine is a specialized tool used for sharpening and refining the edges of knives. This machine typically features a grinding wheel or belt, which rotates rapidly to produce a smooth, precise edge on the blade of the knife. The machine may also have adjustable guides or jigs to ensure that the angle and shape of the edge are consistent and accurate. Knife-making grinding machines can be used for a wide range of knives, including kitchen knives, hunting knives, and even industrial blades. They are an essential tool for anyone who wants to create high-quality, sharp knives that are safe and effective to use. With the right grinding machine and technique, anyone can become an expert knife maker and produce knives that are both functional and beautiful.
What to Know about Grinder Specs!
Grinder Dimensions
Belt grinders are classified by the width and length of their belt size. For example, 1x30 grinder has a 1-inch wide belt that is 30 inches in circumference, a 2x72 has a 2-inch wide belt, that is 72 inches in circumference.
A wider belt exerts more friction on the flat platen of a machine, needing more power and a longer belt allows for less time between belt changes but will also demand extra power.
Belt size plays a massive role in the use of the grinder, as a general rule, the bigger the belt, the more useful it is for heavy stock removal.
Motor Size
To grind steel with abrasive belts, you need high belt speed and the ability to exert high pressure. Your motor has to keep up! The Larger the motor, the more powerful the grinder. A rule of thumb is you need 1 horsepower (hp) of motor power per 1” of belt width for a 72” long belt.
For example, a 2x72 grinder runs best with a motor of 2hp.. But a 1x72”: grinder would grind great with only 1hp. When you reduce your belt length, you also reduce the demand on the motor which is why our 2x48” machines are supplied with a 1.5hp motor.
Belt Speed
The speed at which your belt travels is the third key component to grinding steel. It needs to move significantly faster than a wood-sander to grind optimally. The 2x48” machines in our shop run at 4100 surface feet per minute (sfpm).
You can make do with less, but the stock removal rate will suffer.
Calculate the belt speed like this: sfpm = (π x drive wheel diameter) x motor rpm
Typical wood sanding often only requires 2500-3200sfpm so bear in mind that a woodwork oriented grinder will have a slower stock removal rate on steel.
Variable Speed
Variable speed can be a wonderful addition to a grinder, allowing you to do the heaviest of steel hogging at full speeds and the finest of handle sanding and low speeds. The speed is controlled through a Variable Frequency Drive (vfd) hooked up to a three phase motor on the machine. It can add a good bit of expense, but we find them incredibly useful in our shop.
How much money should I spend on a Belt Grinder?
When deciding what grinder is right for you, it's essential to consider your budget, as well as what work you will be doing. We have put together a list of common grinder sizes, and why you would choose it.
Knife Making Grinder Sizes
When deciding what grinder is right for you, it's essential to consider your budget, as well as what work you will be doing. We have put together a list of common grinder sizes, and why you would choose it.
A 1x30 belt grinder is the cheapest belt grinder to start knife making with. They're nowhere near as versatile as the higher dollar machines, but for less than $60, they're a fantastic tool and a great place to start. The 1" wide belt is adequate for grinding bevels and profiling knives.
The major downfall of the 1x30 is that the belt isn't wide enough to flatten off material effectively, which is a big job in any knife shop. Some of the more expensive models include a 6" disc sander on the side, which can help with this though. The 30” long belt doesn’t provide you with much abrasive surface area either meaning you’ll have to change belts more and the motor doesn’t have the most power in the world.
Overall a 1x30 is a great low-cost option to get into knife making. If you decide to use this size of grinder, keep in mind that it is essential to use good ceramic based abrasives; otherwise, the grinder won't perform to its full potential. Plenty of incredible knife makers (Will Stelter included) started with this machine and it is a sure-fire way to help ignite your knife making passion but you will end up outgrowing it if you're serious about knife making.
1x42
The 1x42 is very similar to the 1x30, but has a smaller selection of abrasives readily available for it; we would not recommend it. Shelling out for a 1x42 isn't entirely worth it since a 2x42 is a similar price and offers a wider belt for more stability.
A few different companies make the 2x42 belt grinders, they usually come with a 6" disc sander on the side and are suited to the woodworking market.. They have a wide variety of proper belts available from most major abrasive companies. They are also easier to use than the 1x30 due to the wider belt.
However, they are not without their drawbacks; most don't have a suitable slack-belt option or usable contact wheels. They typically only have a 1/3hp motor and so as you grind they will slow and “bog down”, limiting your grinding ability.. It is also restricted in its configuration, as it can't be easily tilted 90 degrees to the side. This can be a worthwhile option for a beginner without breaking the bank but you will be dreaming for more power as your career develops.