Welcome to the April edition of Tool of the Month! This month I'll take a little look at some marking knives.
The marking knife is on the face of things a pretty simple tool, but that's a little deceptive as its role in the workshop is vitally important to creating accurate furniture.
The marking knife is on the face of things a pretty simple tool, but that's a little deceptive as its role in the workshop is vitally important to creating accurate furniture.
Marking a knife line across the grain of a piece of ash.
Marking knives are used to produce a very accurate line (far thinner than a pencil line) which aids in making accurate cuts with other edge tools or machinery. There are two basic types, replaceable bladed knives or re-sharpenable ones.
These are the marking knives i use, on the left are two Japanese knives and on the right is a scalpel.
The Swann Morton No 3 scalpel uses replaceable blades and is great for day to day marking and cutting, but as the blade has a 'V' cutting edge profile it isn't ideal for marking critical shoulder lines as it allows the chisel to wander in the line.
The Japanese knives are all re-sharpenable, and they have a single cutting bevel or a single sided V point double bevel with a flat back. This type of knife can follow the straight edge of a square or a ruler much more accurately than a scalpel and it also gives a much better shoulder line reference point for cutting shoulders of dovetails or tenons.
Japanese knives are made quite like a samurai sword from two layers of metal, a hard high carbon steel on the bottom and a softer steel on top. Due to the extreme hardness of the high carbon steel the flat back of the blade is lightly hollow ground (ura) to make sharpening a little easier.
The Swann Morton No 3 scalpel uses replaceable blades and is great for day to day marking and cutting, but as the blade has a 'V' cutting edge profile it isn't ideal for marking critical shoulder lines as it allows the chisel to wander in the line.
The Japanese knives are all re-sharpenable, and they have a single cutting bevel or a single sided V point double bevel with a flat back. This type of knife can follow the straight edge of a square or a ruler much more accurately than a scalpel and it also gives a much better shoulder line reference point for cutting shoulders of dovetails or tenons.
Japanese knives are made quite like a samurai sword from two layers of metal, a hard high carbon steel on the bottom and a softer steel on top. Due to the extreme hardness of the high carbon steel the flat back of the blade is lightly hollow ground (ura) to make sharpening a little easier.
The back sides of the two Japanese knives showing the hollow ground 'ura'.
Thats all for April, look out for May's blog post in a few weeks time.
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