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Rob Cosman's Sharpening Rule

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Original price $18.00
Original price $18.00 - Original price $18.00
Original price $18.00
Current price $6.00
$6.00 - $6.00
Current price $6.00
In stock
Full Description
Customer Reviews

The most innovative technique in plane sharpening over the last 30 years is the "ruler trick" by my good friend, David Charlesworth.

Traditionally, a sharp cutting edge is achieved by honing the back of your plane blade until it is dead flat (this takes a while), then you hone the primary bevel to achieve a razor sharp edge. 

David Charlesworth introduced his ruler trick to save significant time while still achieving a razor sharp edge.  Instead of flattening the whole blade back, he places a thin ruler on the stone raising up the blade about 1 degree so he just hones the leading edge, not the whole back.  David's "ruler trick" works great and I always use it.

You only need one thing - a small thin ruler.  We have our 8 inch long, .018 inch thick sharpening rules custom made without ruler etchings to allow plane blades to glide smoothly across the rule when executing the "ruler trick". 

Customer Reviews

Based on 98 reviews

Item as described. Works great. Excellent customer service.


A key element in the Charlesworth sharpening technique, the Cosman sharpening rule is of optimal length to fit most standard sharpening stones. Accurately described in Rob’s YouTube sharpening videos. Proud to support a small business.

It Works as Promised

This is a simple yet effective tool to aid sharpening blades with Rob's technique.

John LaTour
Ultimate in "Buy once, cry once"

It's a thin strip of metal. But I payed international shipping for it because I wanted to do the Ruler Trick properly
And wouldn't you know, it works perfectly for exactly that and nothing else.

Craig Stoddard
Best sharpening methods

Finally the best way to sharpening!
Plus all of Rob’s great tutorials.