What is the deal with 2x72 grinders?

U

unoriginal name

Joined
Nov 28, 2025
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7
It seems like 2x72 is the size to get for knife makers. Maybe a 2x42 if you can't have a 2x72.
What would you say are the advantages with that over other types of grinders?
 
Availability of belts, grinding belts, polishing belts, surface conditioning belts. 2x 72 is the standard here in the US.

Early on, most knife makers used either a Burr-King, Square Wheel, or a Bader grinder. All were available in a 2 x 72 model.

There have been lots of improvements and innovations in grinding machines since the old days.

All knife suppliers stock 2 x 72 belts and all abrasive companies make 2 x 72 belts.

Hoss
 
Devin pretty much covered it, as usual.

But I will add that there are plenty of times where a wider belt would be advantageous. The problem with a lot of wider belt grinders though is that the platen is designed for wood working and you can't get up to the edges of the platen on them. House Made has started making a bigger grinder called the Tsunamai that looks like it would be amazing, but I've never used one.
 
unoriginal name said:
It seems like 2x72 is the size to get for knife makers. Maybe a 2x42 if you can't have a 2x72.
What would you say are the advantages with that over other types of grinders?
Click to expand...

I went through all the smaller cheaper grinders before getting a pro grinder and then making some others.

Tension
Tracking
torque / HP
Variable speed
Straightness
Smoothness
Repeatability
Reliability.
 
My grinder purchase has been put on hold due to my daughters impending wedding in October. However, the dream lives on... :cool:

A few questions for the experienced users:

1. Is the ratchet system that much better than the spring or pneumatic shock systems? What are the particulars or benefits?

2. What is the benchmark system based upon whats available in todays market? What would be close second and third options?

Thank you!
 
1) The ratchet is nice, but I don't see a huge benefit over the other methods. They all work.

2) I thing all the main grinder makers are close to equal as far as usefulness.

I like the Reeder Grinder. You can buy a full blows uber-grinder from Reeder, or the basic chassis and add your own motor and VFD. I think the all aluminum construction is very important if you plan on using a Kool-mist system for grinding (which is a very wise thing).
 
I have a KMG Classic and a Northridge. Changing belts on the KMG involves depressing the spring lever, taking off the belt, putting on another belt, and letting go off the spring lever. That's in theory. In practice, this usually doesn't provide the right amount of tension. It's either too low so the belt wanders or too high and you can't fit the new belt. The solution is I usually loosen the tooling arm as well and pull it forward with my other hand before releasing the lever. It's honestly not that big of a deal once I got used to it, but the ratchet on the Northridge solves this.

If I had to buy a grinder today I'd probably get a KMG TX or an Ameribrade Pro Package. Or maybe Contender Machine Works, because I like their mister + chiller platen so much.
 
Some spring or piston type grinders have a latch that holds the arm down while changing belts. Then you slide the arm forward or backward as needed to set the belt tension ... and release the latch.

Years ago I built a tensioner for my Bader. It was a short pneumatic cylinder, a two-way directional control valve, a small pressure regulator, and a small pressure gauge. The unit was run by an airline from a small compressor. The controls were mounted on a box next to the grinder, and the cylinder replaced the spring. Throw the direction lever left and the arm gets pulled down, after changing a belt, throw it right and the piston pushes the arm up. Adjust the pressure to set how much tension is applied. It worked fine, but was more of a Rube Goldberg device, as the original spring did a fine job. I gave away the Bader and never permanently installed it. Still got that air tensioner setup somewhere in the shop.

Here is the coolest tensioner I ever saw. He used a spring and a linear actuator. These electric linear actuators are pretty cheap.
 
one basic fact to consider is the length of the belt and how much you get out of it. A 42" belt just won't grind as much material as a 72" belt. I don't know what the cost break down is, but you definitely save time in not having to switch out belts as frequently- and time is money!
 
It’s not just 2x72” belts. It’s th3 choice between two wheels and three or more wheels. I had a three speed Coote for years, and it was good, but a variable speed tool arm grinder is just much more versatile.
 
Stacy E. Apelt - Bladesmith said:
1) The ratchet is nice, but I don't see a huge benefit over the other methods. They all work.

2) I thing all the main grinder makers are close to equal as far as usefulness.

I like the Reeder Grinder. You can buy a full blows uber-grinder from Reeder, or the basic chassis and add your own motor and VFD. I think the all aluminum construction is very important if you plan on using a Kool-mist system for grinding (which is a very wise thing).
Click to expand...
as much as i love my reeder one thing i did notice is if a contact wheel has runout/non concentric rubber the tension arm likes to jump up and down if the speed is under full blast which since it’s a spring in theory should be dropping and raising tension with each dip and return and adding more tension by trying to pull the arm out as much as possible with the arm all the way depressed doesn’t help. I notice that the inside of my belts sometimes have a decent bit of wear which seems to be from the belt slightly slipping while grinding.

All is to say does it really matter in practical terms? not sure probably not. Bigger lesson on my end was i need to buy better wheels

https://imgur.com/a/K99yKkz
 
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