Double Time Flattening Stone Review

An essential accessory if you use waterstones. It's durable, fast acting, and affordable.

Double-Time Flattening Stone

Double-Time Flattening Stone
Size:1" x 4" x 10"
Grit:120 and 320
Made From:Green silicone carbide
Made In:
Warranty:100% satisfaction guarantee

If you use waterstones you need to periodically flatten them. It's not an option. It doesn't take long for a waterstone to start developing a hollow ('dishing out') – usually in the center where most of the sharpening takes place. Continue to sharpen in the dished out area and you'll end up with chisels and plane blades that are no longer flat, but have cutting edges with rounded edges. 

When you need to flatten your waterstones depends on how often you use them. Before each sharpening (or honing) session I use a short straightedge to check the flatness on my stones – hold it both crosswise and lengthwise on the stone. If I see any light between the straightedge and the stone I know it's time to flatten.

Flattening takes only two or three minutes (not including the time it takes to soak the stones), so it's not a huge loss of shop time. Once you've added flattening to your sharpening routine – and see the difference it makes in your tool sharpening – you won't begrudge the time spent. 

Recently I tried a new Double-Time Flattening Stone (DTFS) from, a US-based online retailer of everything that has to do with sharpening.

At 4" by 10" the DTFS will easily accommodate even the largest waterstones. One side has 120-grit abrasive (about 5/8" of the stones thickness) for very quick cutting action on waterstones up to 1000-grit. The other side has a finer 320-grit structure (about 3/8" of the stones thickness) for use with waterstones over 1000-grit. The abrasive consists of green silicon carbide (aka 'carborundum'), a very durable abrasive (harder than aluminum oxide) that cuts very aggressively. 

Both faces of the stone feature a pattern of 3/16" deep channels that serve to capture the slurry that builds up during the flattening process, and also eliminates resistance from hydrostatic pressure between the two stones.

Using the DTFS is very straightforward. As you would with your waterstones, soak the DTFS in water until you don't see any more air bubbles rising – about 5 or 6 minutes did it for me. Before rubbing you waterstone over the DTFS draw parallel pencil lines across its surface (when the lines disappear your job is done). Rub in a circular motion, don't apply undue pressure, and check your progress every 60 seconds or so. You don't need to continue abrading your waterstone once the pencil lines are gone. Rinse both stones and you're done.

I use 3 waterstones in my shop (1000, 3000 and 8000-grits) and the DTFS has made quick work of flattening them. Even if I was to touch up the stones every second week, the DTFS should last for a long, long time. 

If you use waterstones, then the DTFS will be a smart investment.

120-grit (top), 320-grit (bottom).

The 120-grit face is thicker as it will get more use.

DTFS is large enough to accommodate any waterstone.

Drown the DTFS in water until the bubbles disappear.

Run the waterstone over the DTFS in a circular motion.

This 1000-grit waterstone had a 1/32" or so dish out in the center.

A few dozen circular motions on the DTFS made this baby's bottom new.

Carl Duguay
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