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August 06, 2020 6 min read

best belt grinder for knife making

Quick Summary

2x72 belt grinders are compact, high-performance, and built to support a wide range of accessories for various processes.They are widely preferred by professional knife makers, but there are other options that can be more compact, affordable, and just as effective (if not more so) for certain applications.

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It doesn’t matter whether you make knives for a living or a hobby: the right belt grinder can make a huge difference in creating a sleek, beautiful blade. There are different machines to choose from, some of them better-suited to certain knife making processes than others. In this blog, we’ll compare some of the most popular sizes of belt grinders for knife making - and highlight their advantages, disadvantages, and recommended applications.

2x72 Belt Grinders

For professional knife making, 2x72 size belts are considered the industry standard. This size accounts for the majority of belt grinding machines manufactured specifically for knife making in North America. The units are compatible with a wide range of belt materials and are surprisingly compact for the level of performance. 2x72 machines also have more accessories available, including:

  • Wheel attachments ranging in size from 1/4” to 16”, for knife elements like fullering, hollow grinds, and more.
  • Surface grinding attachments for cleaning and smooth, flat surfaces.
  • Rotary platens for convex grinds and to mitigate the dreaded “J weight belt bump.”

The 72” belt length reduces wear and heat build-up, so you can use it during all stages of blade creation, from the initial knife development stages to finishing touches like sharpening and polishing. Because the machine has a larger working surface and often a variable speed motor, you can make knives more quickly with a 2x72 than you can with smaller belt grinders.

The biggest downside to 2x72 belt grinders is the cost. For professional knife makers, they are worth the investment, but if you’re a hobbyist or just getting started, it might make more sense to buy a smaller grinder, like a 2x42, at least in the beginning.

Red Label Abrasives sells a knife maker abrasives kit for 2x72 belt grinders. You can choose from premium coarse ceramic grits for additional belt longevity, Edgecore ceramic for superior grinding results, ultra-fine grits for final sharpening and polishing, and more.

Which 2 X 72 inch grinder is OUR favorite? Check out Brodbeck Ironworks!

1x30 Belt Grinders

1x30 belt grinders are great finishing tools and an affordable investment for hobbyists. They work well for knife sharpening and detail work, but the 1” belt is not wide enough to effectively flatten off material on larger knives (although some grinders include a 6” disc sander that helps with this step). Being only 30” long, it has less abrasive surface area, so it won’t mitigate heat as well and the belts may have to be changed more often. Limited power and less clearance can also make it difficult to run thicker materials like surface conditioning belts.

If you purchase a 1x30, you’ll want to use a quality abrasive so that the machine delivers the best performance and output. Red Label Abrasives sells packages of 1x30 sanding belts with grits that range from coarse to ultra-fine, so you have long-lasting options for honing, sharpening, and polishing your blades.

1x42 Belt Grinders

1x42 belt grinders are similar to 1x30 grinders in terms of performance. There is slightly more surface area for grinding and the machines tend to price in the more affordable range. Many professional knife makers will use both 2x72 and 1x42 grinders in their workshops. 

1x42 belts perform well for detail work and knife sharpening. You could use a 1x42 belt grinder for bevel grinding, profiling, and most of the initial steps of knife development, but the lower motor power and smaller work surface associated with 1x42 grinders leaves the 2x72 grinders more equipped to create knives at a faster pace.

In many cases, it’s better to go with a 2x42 belt grinder over a 1x42 grinder. The wider belt provides more stability and the 2x42 grinders are similarly priced. 

2x42 Belt Grinders

2x42 grinders are often designed for the woodworking market and come with a 6” disc sander on the side. They still work fairly well for knife making and are popular with hobbyist knife makers who are just starting out and need an entry-level grinder. 2x42 belts offer more stability than the 1x30 and 1x42 belts. The 6” disc can also be very handy for smaller jobs, especially beveling the front of knife handle scales.

The biggest downside for 2x42 grinders is that they usually have a 1/3hp motor. The slower motor tends to slow down as you grind, which can limit your grinding ability.

2x48 Belt Grinders

2x48 grinders can be a great alternative to 2x72 grinders. They are used by both professionals and hobbyists. The 2x48 belt grinders often have a larger motor than many of the other small grinding machines. The grinders can also be pretty affordable with a starting price point of around $330. The compact size of the machines allow them to fit nicely into a small workshop.

4x36 Belt Grinders

4x36 belt grinders are included on this list not because they’re good for knife making, but because we wanted to provide a warning about them. 4x36 belt grinders are very common, because they can be found in most hardware stores. 

These grinders are great for woodworking, but they are not well-suited for most knife making applications. The way most 4x36 grinders are built prevents the edge of the belt from being utilized. The weak motor and wide belt will also slow down when grinding easier than most other machines. You may be tempted to use a 4x36 grinder, especially if you already own one, but it is not ideal for knife making by any means. 

Considerations Outside Of Belt Size

While belt size matters a considerable amount, it isn’t the only factor to consider when choosing a bet grinder. There are three other factors you should weigh when shopping for a grinder. 

Motor Size

Motor size is one of the most important factors when deciding on a grinder for knife making. To effectively grind steel, you need high belt speed with the ability to exert high pressure on the belt. You won’t be able to accomplish grinding very well if you don’t have a large enough motor. As a general rule of thumb, you need 1 horsepower of motor power for every inch of belt width at 72” in length. As the length of the belt is reduced, the demand on the motor is reduced. So, less power is required for smaller belt lengths.

As an example, a 2x72 grinder would work best with a motor that has at least 2hp. On the other hand, a 2x48 grinder can work well with a motor that provides 1.5hp, because the length of the belt is shorter. 

Belt Speed

Steel grinding requires a higher belt speed than wood. So, wood-oriented grinders will have slower stock removal rates for steel. The belt speed (measured in surface feet per minute) will need to be somewhere in the range of 4,100 to 7,000 depending on the type of metal. You can calculate belt speed with the following formula: 

sfpm = (π x drive wheel diameter) x motor rpm

Variable Speed

Not all grinders have variable speed options and it isn’t entirely necessary for knife making, but it is helpful to have. Grinders with variable speed options allow you to perform heavy steel hogging at full speed while handle sanding at lower speeds. Having the ability to control speed will allow you to craft your knives with more precision and ease. 

Contact an Abrasive Specialist

Red Label Abrasives has been supplying knife makers with quality sanding belts and kits for over 35 years. Red Label Abrasives is a family-owned business that takes great pride in offering exceptional customer service and unrivaled technical support. To see the sizes and grits available, please visit our online store and, if you have questions or need recommendations, please call our experienced abrasives team today at 844-824-1956.