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build a grinder

Build a grinder

A common problem when starting your journey into knife making is finding useful, reliable info all in one spot. It can be challenging and expensive to try and decide on what sort of tools, materials, and supplies are going to suit you best for the type of work you would like to pursue. In this article and in more to come, we will try our best to give you the right starting place for blacksmithing and knife making!

What to Know about Grinder Specs!

Grinder Dimensions

Belt grinders are classified by the width and length of their belt size. For example, 1×30 grinder has a 1-inch wide belt that is 30 inches in circumference, a 2×72 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 2×72 grinder runs best with a motor of 2hp.. But a 1×72”: 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 2×48” 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 2×48” 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.

1×30
$52.99

A 1×30 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 1×30 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 1×30 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. Cost Effective Option Higher-End Option (pictured above)

The 1×42 is very similar to the 1×30, but has a smaller selection of abrasives readily available for it; we would not recommend it. Shelling out for a 1×42 isn’t entirely worth it since a 2×42 is a similar price and offers a wider belt for more stability.

2×42
$215

A few different companies make the 2×42 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 1×30 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.

The 4×36″ belt sander is one we get a lot of questions about, as it’s a common sander a lot of people already have, found at most hardware stores around the worldUnfortunately, it is not ideal for most knife making/blacksmithing applications. It is designed for woodwork and the way it’s built doesn’t allow for the use of the edge of the belt to be utilized, which is an essential part of a belt sander in knife making applications.

Due to the weak motor and wide belt, it will bog down easier than other machines. Most people will be better off buying a 1×30” or 1×42” when starting into knife making.

2×48
$330-$1495

The 2×48″ grinder size is an interesting one, it’s the smallest belt size that can come in a “square wheel configuration” body, but most commercially available grinders of this size come in an upright style. These grinders also have an excellent array of belts for them, virtually the same selection that is available for 2×72. You’ll find an increasing number of accessories available, from small wheels, to contact wheels to surface grinding attachments and they often have a larger motor than the smaller grinders. If you are a serious hobbyist or a professional short on space, a 2×48” is an excellent option.

We love how easily this size of grinder can fit into a small workshop and how versatile it can be with a variable frequency drive speed controller. It has prices ranging from $330-$1495 depending on motor power and the particular configuration.

The 2×72 is the industry standard for professional knife making. Partially due to the vast array of belts available for the grinder, as well as being a generally powerful and still reasonably compact machine. There are a wide variety of options available, ranging from building one yourself to buying a top of the line professional grade grinder, designed to suit a Bladesmith perfectly.

Along with great abrasive options, the number of accessories that are available for a 2×72” machine is also second to none. Wheel attachments from 1/4″ to 16″ and just about every size in between are available for getting into tight spots, profiling, fullering, and wide hollow grinds. Surface grinding attachments, slack belt rotary platens, and other attachments are becoming more available for them as well.

A Knife Makers 2×72 (and some 2×48’s) commonly come in the “square wheel” configuration, with a 4-7″ drive wheel in the back, a tensioning and tracking wheel on the top, and a flat platen with two contact wheels facing the user. This style is the grinder of choice due to its adaptability and versatility. Most of them out of the box have a flat platen, two contact wheels, and a slack belt without changing any tooling. When the need arises for different specialty tooling, the switch is easy. A turn of a handle for the tooling arm to come free, and you’re able to replace it quickly with another.

A more budget friendly option is the vertical style that has a large drive/contact wheel on the bottom, a flat platen halfway up, and tension and tracking wheel at the top. The vertically configured style takes up less space than the square-wheel style. Still, it is far less versatile, as it usually doesn’t have the option for changing tooling the same way the square wheel does and the flat platen is less useful.

The vertically configured 2×72’s are an excellent grinder for the money and will out-perform most smaller grinders. They’re an excellent option for hobbyists or for those just finding out if knife making is something they’d like to pursue.

We recommend a square wheel configuration 2×72” or 2×48” if it’s within the budget, adding attachments as you can afford them is an excellent way to build up your shop slowly. Build Your Own

Conclusion

There are many different options for those looking to get into knife making, or just getting more serious about it. A 1×30” is an excellent option for getting into knife making, and if it’s the only thing you can afford to get into it, then go for it. However, if the budget allows for a bigger badder grinder, then having a machine that provides room for growth is the route we would recommend. Remember, a grinder is only as useful as the abrasives that it’s running. So putting money into quality belts is a worthwhile investment, no matter what grinder you have. Ultimately, the most important factor is skill and experience at the machine.. Unfortunately, that isn’t something that you can buy. So get out there, try it out, practice, learn, see what works best for you, and have fun!

Having trouble deciding on which grinder is right for bladesmithing and knife making? Check out our article!

2×72 Belt Grinders

Are you a DIY’er? Are you comfortable fabricating simple machinery? If so, you NEED a decent belt grinder, preferably in the 2″x72″ belt size. You’ll find a thousand and one uses for it once you put one together, and it’s very easy to put one together. This page is all about the resources and ideas you’ll need to plan your own belt grinder project.

Belt Grinders are great for blending smoothly flowing shapes, deburring, and generally improving the look of parts. For the latter, you also want to make sure the surface finish of your other machining processes is all that it can be. Check out our guide to Milling Machine Surface Finish Tips for some ideas.

Bill Pace grinder has been made by several on the HSM boards.

Shows tracking mechanism at the top very well…

Platen inspired by Lane added to Bill Pace’s grinder…

More on the tracking mechanism by George Barnes…

Lane over on HSM built one along the same design…

Andrew McLurkin’s Bader III is mounted on its side to make it easier for him to do fine work. Note the very small wheels and wrap around tool rest so he can get inside tight areas.

Dozier makes some of the best grinders there are. This series shows off the different accessory configurations they have available:

Here is the grinder. Note the pneumatic tensioner.

3 Configurations, left to right: the basic wheel, slack belt grinding, and a platen grinding setup…

Beaumont Metalworks offer the excellent KMG grinder:

It would be nice to turn this grinder horizontally like McLurkin shows at the top of this page and then use this attachment with a rest that fit nicely. You could really get into some tight spots with it!

Tooling arm rack is a clever accessory that makes changing the configuration fast and easy.

Here is the grinder sporting a platen attachment, and a rest on the lhs photo. Note the solid CNC construction. Minimal welding. Picture on far right is the slack belt attachment.

Or, how about a rotary platen?

Seems like it could take the place of several of the other accessories. The actual “platen” is a rotary belt under tension with rollers.

Here is a variable speed JL grinder:

The venerable Bader III grinder is well respected:

Great looking kit by Simplatic. Looks like a good plasma cutting job…

Check out the “Dream” KMG attachment, pretty cool!

The rest is slightly reminiscent of the “Dream” KMG rest shown above. The Wilmont is a nice variation on the KMG and the site includes plans for a home shop model you can build.

It has 5 interchangeable contact wheels that can be indexed into position–these 3 plus the other 2 corners of the triangle have larger wheels…

They also make a hollow grinding attachment that’s pretty neat…

Software that will make anyone a better CNC’er

Get Better Tool Life, Surface Finish, and Material Removal Rates Fast.

It’s that easy. You can install and get results in a matter of minutes.

Information and ideas for DIY 2 x 72 belt grinder / sander making for woodworking, metal, and knife making ]]>