Tech Support & FAQ

See below for technical information about the KMG Grinders  

The KMG was intentionally designed so that the motor was not an integral part of the machine which allows for unlimited choices in how the grinder is powered. This allows you the use just about any type of motor and it also allows to set the grinder up with different speeds by changing the pulley ratio between the motor and grinder. We prefer to drive the KMG with pulleys and a belt to maximize the versatility, however, you can also direct drive with a motor coupling of your choice. Typical motor sizes for the KMG can be from 1-1/2 to 5 hp.
We always recommend a grinder package such as the KMG-8 or KMG-10 that includes both, a contact wheel, and the platen attachment. These 2 attachments will be used constantly in your shop. The 8″ and 10″ wheel are equally popular and purchased on personal preference. A work rest is included.
With the standard 4″ drive wheel, the abrasive belt speed is easily calculated as follows:
Belt speed (ft/min) = RPM (example: 100rpm= 100ft/min, 3500 rpm= 3500ft/min)

The set screw we use is 1/4-20 x 3/8”.    Use a 1/8” Allen wrench.

The KMG Grinders are proudly built from unplated and unpainted steel. If you wish, you can customize the grinder by plating or painting the exposed metal surfaces, but in our shop, we care for the grinders simply with a coat of light oil and a Scotch Brite pad to scour away dirt and small scratches.

8” vs 10” wheel:
This is a great question and is usually decided by personal preference. Since the belt speed is the same regardless of the size of the contact wheel, there are no performance differences between the sizes. The only difference is the shape of the hollow grind caused by the wheel. Because the 10” has a bigger radius, the hollow grind is more shallow and taller than what an 8” wheel would produce. The 10” wheel is much more popular. However, there are many customers who prefer the 8” wheel for it’s smaller size, lower cost, and deeper hollow grind.

3 speed –vs- Variable speed:
The KMG was specifically designed so that the motor was not an integral part of the grinder. This allows for unlimited choices on how it might be powered. Simply spinning the drive shaft makes the grinder run.
The step pulley system allows 3-speed choices, fast, med and slow. The 4”, 3” 2” pulley is used because the centerline distance between the motor shaft and grinder drive shaft is the same for each belt position. This eliminates the need to re-adjust the motor position for each speed change. You simply roll the belt from on groove, to the next smaller size by hand, like a derailleur on a bicycle. Speed changes are done in a few seconds without tools. The grinding belt speeds produced are approximately 3800, 1800, and 900 feet/minute. Through research, these speeds are all very practical and usable speeds for tasks like custom knife making.
Variable basically allows an infinite selection of speed from 0-100%. It can be changed on the fly without stopping and allows the user to adjust for more grinding control and precision based on personal preference and feel. Comparing to the 3-speed set-up, the highest belt speed can be about 10% faster due to selections in the motor’s speed control (VFD), or about 4200 feet/minute. The speed range is infinite at full speed down to zero. Please note the motor used for Variable Speed set ups is a three-phase motor. The Controller takes single phase power and produces three-phase power for the motor.

110 or 220?

All of our KMG Grinders can be used under 220 power.  The 1.5 Three-Speed KMG’s and the 2hp Variable Speed KMG’s can also be used with 110 outlets.  The 2 hp Three-Speed KMG’s and the 3 hp Variable Speed KMG’s can only run under 220.

Care and Maintenance of  Your Grinder

1. Rub light machine oil (something like WD-40 or DTE light) over the entire surface of the grinder and the subplate, using an abrasive pad (like a Scotchbrite) to smooth small scratches and remove surface dirt. Do the same for your tool arms, small wheel attachment, platen attachment and rotary platen accessory. You are likely to become aware of any issue with your grinder in going over the whole grinder with oil and a pad.

**Do just this on a regular basis and your KMG will have a long and productive life in your shop!**

2. Look at the bolts on the subplate and make sure they are tight and secure.

3. Examine the platen of your platen attachment — if it is worn or marked, you can flip it over to get a fresh surface. If both surfaces have been worn, you can replace the platen inexpensively.

4. Check your drive belt to make sure it has not become glazed or brittle. This is an easy replacement that can significantly improve your grinding experience.

5. Measure your contact wheels for surface wear. We offer a reconditioning service for our rubber surfaced contact wheels that is significantly less expensive than purchasing a new contact wheel. Contact us for a quote.

6. Survey all the wheels in your shop for excessive bearing wear. The bearings in our wheels are sealed and require no lubrication. You can order bearings and replace them quickly and easily yourself.
Beaumont Metal Works also offers a lifetime guarantee on all bearings sold in our wheels, you can send the wheel to us for bearing replacement, free of charge.

Disconnect the power before doing anything with the motor or power cord!

7. Look at the motor and make sure it is clean and shows no signs of heat damage.

8. Open the controller casing and gently use compressed air to gently blow out any debris that has gotten into the controller housing ( If the rubber grommets were installed properly, debris in the controller housing should be minimal.)

9.Check the power cord to make sure it is in good condition (not damaged, brittle or misshapen.) Replace if needed.

10. Replace your grinding belt if necessary.

Now that your KMG is clean and well maintained, maybe it’s time to add a new contact wheel or accessory!


Install and Set Up Instructions and Diagrams:

Most of our models ship with an 18″x18″ sub plate, which should be secured with 1/2″ diameter bolts appropriate for the material of the work surface you are using. Mount the sub plate flush against the front edge of your work table or base. The tool arm will project out from the front, which is desirable so that grinding debris falls off of the machine and does not get caught in the base.

KMG Packages

Variable Speed set up

The most common problem that we see during initial setup is wiring at the motor.  There are 9 wires and it is easy to get them out of place.
Double check there.  You should have the following connected:
t4,t5, and t6 all connected together with a yellow wire nut.
t1,t7, red
t2, t8, white
t3,t9 black
At the controller(VFD)  if you are running it on 220V…make sure the input power jumper is on “230”.   If you are running it on 110V….make sure the jumper is on “115”
If you are using 220V input, use a voltmeter across L1 and L2 on the VFD’s terminal strip to verify that you do in fact have 220.  This is the second most common issue that we see.
(If you are using 230, you will not use the neutral. Make sure to ground to the case, and run the two hot to the L1 and L2 terminals)

Set Up Instructions for  Variable Speed

Layout Diagram for Variable Speed

Set Up Instructions for 3 Speed

Assembly Diagram for 3 Speed

Tips for Tracking and Tuning Adjustments



Schematic for Extension Plate


Installation instructions Forward/Stop/Reverse switch for our variable speed controllers

Set Up Instructions for Switch Kit for 110089 1-1/2hp motor

Set Up Instructions for the 110089 Motor

Overload Reset 

These motors are very strong and have built-in overload protection.  If you are grinding and the motor stops suddenly, chances are it has overloaded.  Wait until the motor is completely cool, and then press the “reset” button on the front of the controller.   You will need to press it very firmly until you hear a “click” sound.   The motor should start again easily.

If you still have a question that is not answered by these resources, please feel free to contact us at

info (at) beaumontmetalworks (dot) com

Information about the 3 Speed KMG