Delta GR275 6" Bench Grinder Reviews
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Delta GR275 6" Bench Grinder

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Sharpening in the shop

Sep 2, 2002
Review by  
Rated a Very Helpful Review

Pros:Variable speed, adequate tool rests, good stone mix

Cons:only 6"

The Bottom Line: The only tool on the market that can both grind and sharpen, and it is Delta quality.

In a sea of 6" dual-wheel grinders, why did I pick this one? The story begins with a desire to have sharp tools in the woodshop. I have another 6" grinder, a no-name that has been sharpening garden tools and mower blades for years. It, too, is a portable. It is mounted on a board with a lip that drops into the side vise on the workbench when needed and stores away most of the time.

My choices were to replace the grinding wheels on this one when I wanted to do sharpening instead of grinding or to get a second grinder. I opted for the latter approach. Now two tools sit on a shelf on their wooden supports waiting to be called into service.

Sharpening versus Grinding

The key need when grinding is to get a rough edge smooth, taking out the nicks from hard use. When sharpening, this may also be true, but the final goal is a really sharp edge. Often the tools being sharpened are tempered steel. Heat is their enemy. Tools being ground aren't quite as picky. In grinding, the tool usually leaves the grinder ready to do more work. When sharpening, the wheels usually just get the tool rough shaped and ready for the final sharpening and honing process.

The Delta - A Unique Tool

When Delta announced their new grinder early in 2002, it came with a difference. The Delta 23-655 6" Variable Speed Grinder/Sharpener has two differences from the competitors and even Delta's earlier offerings. This grinder/sharpener tries to bridge the gap between grinding and sharpening.

In woodworking tools, heat is the enemy of the metal. Most grinders run at a high 3450 rpm. Most wheel sharpeners run at 1725 rpm. Delta adds a variable speed knob to let their grinder/sharpener work at the best speed for the job at hand. They also have a grinding wheel on the right shaft and a sharpening wheel on the left shaft.

What you Get

Includes standard machine with 2.5 amp, 120V/60 Hz., 2000-3450 RPM induction motor, flexible lamp, tool rests with drill bit sharpening guide, eye shields, spark deflectors, grinding and white friable sharpening wheels, adjustment wrench and diamond wheel dresser, instruction manual.

The Delta comes mostly assembled. The main base already has the wheels attached. The lamp, on a flexible neck, is attached. Assembling the spark guards, the tool rests, and the eye shields, takes just a few minutes. The wrenches needed are included. There is even a place on the back of the tool to store them. Another nice addition is the diamond wheel dresser. This is used to keep the face of the grinding wheels flat and round. I used it after setup to make sure I had round flat faces.

The first change I made was to replace the right wheel, 36 grit, with a sharpening wheel like the left one only 120 grit instead of the 60 grit on the left. In doing this, the tool became a sharpening tool.

The Specs

Motor - 2.5 amp, 120V, 60 Hz., single phase, 2000-3450 RPM
Shaft Diameter - 1/2"
Diameter - 6"
Face - 3/4"
Hole - 1/2"
Motor Control - On/Off Switch with speed control
Weight - 18-1/2 lbs.

The Features

Adjustment wrench and diamond wheel dresser
White friable wheel for sharpening
Powerful 2.5 amp induction-type motor for long-lasting, smooth performance
All cast-iron base minimizes operating vibration
Variable speeds (2000-3450 RPM) for grinding or sharpening
Flexible gooseneck lamp for clear view of grinding wheels and workpiece
Adjustable tool rests compensate for wheel wear; includes drill bit sharpening guide


My first sharpening task with my new tool was taking some very old wood chisels that were good quality but had been abused and trying to make them useful. These chisels had nicks on the ends, they backs weren't flat, they were patched with rust, and they had dried paint on them. Could they be returned to a useful life?

First steps were actually with my old grinder. I had a wire brush on one shaft and used it to knock the paint and rust off. Then I brought out the Delta. Particularly with edge tools like chisels, you can't let the metal get too hot. If it changes color from heat while grinding, you have ruined it. I dialed the speed down to its lowest setting, set a small pail of water beside the wheel, set the angle of the tool rest for both wheels to 25 degrees, and went to work on the bevels. I kept the tools damp by frequent dips in the water. Soon all the chisels had bright bevels with sharp even edges. My work, however, was just starting.

When using a wheel, the bevel becomes hollow ground. This is an advantage and a disadvantage. The advantage is that there is much less metal to remove when doing the final sharpening and honing of the edge. The disadvantage is that some strength is lost near the edge due to the lower angle. In the case of 6" wheels, the angle is lowered quite a bit. Eight inch wheels are better in this respect.

Unless the back of the chisel is flat, you will never get a keen edge. An edge is defined as two flat planes intersecting. Flattening the back is a chore. It only needs to be done once, however. I use silicon carbide sandpaper on a flat metal plate for flattening. It attaches with 3M spray adhesive. Starting with 60 grit, I worked each back flat and then up through 2000 grit. A half-day later I had six flat, highly polished backs.

Setting my Veritas honing guide to 25 degrees, I ran each bevel over a medium diamond stone. I then switched to sandpaper, this time on a piece of plate glass and went from 240 to 800 grit at 25 degrees. This doesn't take very long. The Veritas can be dialed for a three degree micro-bevel. Starting at 1000 grit I began forming that small 28 degree bevel on just the edge of the bevel. This adds a little strength to offset the hollow grind and makes the final honing and subsequent touch-up honings easier and faster.

After getting to 2000 grit, I swiped the flat back over the same sandpaper to remove the wire edge. At this point, most people are finished and have a very sharp tool. But I went a step further. I spread diamond dust in a special lubricant over some 3/4" MDF. I first worked the backs down to 1/2 micron dust (a micron is a millionth of an inch). Then I used the Veritas to hone the micro-bevels to the same smoothness. A quick swipe of the flat back at 1/2 micron removed the wire edge.

Is all that effort worth it. You bet! These sorry chisels I picked up at a flea market for $1.00 Are the equal of any I have ever seen or used. A test of sharpness is shaving the hair on your arm. I seldom do this but, well, I just had to. Slid it over my arm and my skin was as smooth as a baby's. The hair just seemed to jump away.

Since then I have used this technique, starting with the Delta, to sharpen the blades on three bench planes, I recently acquired. They cut through maple like it is butter, rolling off a shaving so thin you can read through it.

Certainly it is the honing and polishing that made it so sharp, but it was the original setup with the Delta that made it possible. It also made it much quicker than hand methods. Since then I have used the Delta to touch up my lathe chisels and sharpen my knives.


If you are looking for your first wheel grinder, this one offers much more versatility than the others available. If you are considering adding a 1725 rpm grinder, this one can do the same job at lower cost. There's just no reason NOT to get this one.

Recommend this product? Yes

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