Ben began with: "In the Hammer's Blow and watching your demonstrations at the Rocky Mountain Smiths Conference you suggest making slitting chisels, fullers, butchers etc. in incremental sizes with the same radiuses...."
What I was trying to suggest is to make slitting chisels that have the same thickness but incremental widths. This common cutting edge thickness leaves incised lines that have the same visual line-weight. That is to say that they would all leave the same width line if struck to the same depth. For example, 3/16" wide, 3/8" wide and 1/2" wide chisels that are all similar in thickness would allow you to switch between them, as the pattern requires, and still maintain the same visual effect in incising as if a single tool was used.
Why switch between various straight chisels? The 1/2" wide chisel will cut a straight line, as will the 3/8" wide and 3/16" wide chisel. But the 3/8" wide and 3/16" wide, straight chisels will cut or incise progressively tighter curves. Having the same line-weight as they cut ever tighter curves allows one to cut a near infinite range of curves as well as various length straight lines while maintaining the visual width of the cut as a decorative constant (calligraphy with a chisel ). This line weight in incising can be seen in pierced work as a constant bevel along the cut edge that you will not get if the chisels have varying thicknesses as you switch between them to accommodate the pattern. Visualize a set of chisels with a common wedge in vertical section compared to a set with varied vertical wedge sections.....
Also... In cutting or incising intricate patterns one finds the need for varied length straight and curved cutting capacity. In some cases the curve is so tight that only a curved chisel will suffice, then make one appropriate to the patterns' demands. (Make all curved chisels symmetrical. Test in lead before heat treatment by rotating it as it is struck. A symmetrical curved chisel will cut a core-shaped plug, hwere as an asymmetrical curved chisel will ride out of its track and give a choppy cut when rotated). Otherwise, it is very handy to move from a straight cut into a range of broad curves using just the three sizes of straight chisels. This is true whether you incise into or cut completely through the metal. Intricate repousse' and pierced sheet metal patterns with areas cut out completely (negative spaces) often have various length short straight lines to cut as well.
Lastly on chisels, the cutting edge should be slightly crowned along its blade length, so the center just makes contact first with both ends of the blade rounded so the cutting edge continues up the side of the chisel for a distance. Chisels intended for deep slitting should have a cutting edge that extends up the side for about half of the thickness of the metal to be slit. The ideal cross section for a slitting or incising chisel is elliptical, like a canoe. If one was to make slices through a properly formed chisel there should be progressively narrower canoe shaped cross sections as you approach the actual blade. Why go through all of this for a chisel?...... When one cuts or incises a line, one should move the chisel forward about one half of the blade length per stroke. The cutting edge that runs from the center of the blade up the side of the chisel leads the cut cleanly. The radius on the corner makes a leading cut that is a diagonal to the plane of the metal being cut. This gives a visually clean effect ( a tapered cut rising through the metal) at the end of a slit AND, since it is diagonal through the metal instead a vertical line, flexing is less likely to result in a crack. A saw cut split often cracks during flexing since it is vertical through the metal. The canoe or elliptical cross section has the effect of planishing the lead cut mark as the thicker center is moved forward a half-chisel length per cut. (Do not get the center too thick or the wedge action will cause drag as well as wedging open the cut and tearing the metal). So, what happens is a lead cut followed by planishing action at the middle of the chisel as the lead cut is moved forward. You get cuts so clean that little or no filing is needed afterwards. Make each cutting process a series of passes, do not force the tool through the material if you want a smooth result.
Curved and straight chisel sizes, shown full size
What increments or sizes would you recommend for a basic set of tools, and would the sizes be the same for each tool type? Since 1/4" stock for a 1/4" tool would not stand up to a treadle or hand hammer what size stock do you recommend?
The chisels sizes above plus:
End-view of flatters shown full size
I heat treat all of my tools full length save about 1/2" at the end so they do not spall when struck. Full length heat treatment allows a 1/4" W-1 (water hardening drill rod) tool, for example, to survive treadle hammer work all day long. Although I use 1/2" round S1 for all of my chisels and butchers, due to the heat resistant properties that are needed for thin bladed tools (I use all of my tools in either hot or cold work without regard to tool steel. All work is laid out then marked cold with the tool to be used in the subsequent process, either hot or cold), many of my chasing (repousse') tools are either 1/4". 5/16" or 3/8" round W-1. Due to the mass of their blunt working ends (small flatters, ball shapes which are half-round and elliptical faced in every size I can find, oval and rectangular faced, all with a slightly crowned work surface), W-1 is OK for chasing tools smaller than 1/2" diameter.
One point to make in this tool explanation; although I am describing tools that may seem somewhat small, my scale of work ranges from very small to large. A small tool is more versatile, it fits into more spaces and a small tool transfers more energy from the hammer (hand or treadle) to the work face due to its small footprint. This really matters in deep cold chasing. The shapes are more generic than specific in that there are very few that give a single effect. This also allows more versatility of work. My choice of work is period European motifs, which means an huge range of patterns and shapes. The generic, small tool approach allows a smaller set of tools to do a wider range of work in a wider range of sizes than any other approach I have encountered.
Do you use a few standard sizes and forge the business end to smaller sizes or do you make them both smaller and larger from the same size stock? So for instance do you use 3/8" stock for sizes 3/8 and smaller, less than 3/8, or greater than 3/8 by spreading the end?
As alluded to above, there are certain cases as well as availability of tool steel that makes it necessary to draw down some stock, 1/2" round S1 for a 3/16" wide chisel blade for example. But for the most part, tools that are blunt as opposed to chisels (straight and curved) and butchers, are made out of stock close to the size needed for the working end.
To use these tools: There is a specific action used in applying tool to metal. Although there are plenty of times that a tool is set and struck as a single operation, most application of tooling to metal (hot or cold) involves setting the tool and maintaining continuous contact (as opposed to set and strike, set and strike) while striking and dragging the working end along the layout. The crowned faces of the tools makes it easier to drag the tool , again- one half tool width per blow- without lifting and setting it per strike. This dragging or continuous contact approach gives a much smoother effect to whatever tool process one is applying. Cutting, chasing, incising etc. are all made much cleaner this way. There is also less chance of a miss-strike. When one lifts the tool and sets it anew with every strike it is easy to set it off and strike it anyway due to the rhythm that develops. So set the tool on the layout or previous pass, and with a rocking and dragging motion..drag and strike. This applies to either hand or treadle hammer driven tooling.
If you decide to make these or any kind of tools, pay very close attention to the details of form, edge, radius and finish (polish the working end like a mirror - less friction as it moves across or through the metal).
This attention to the tool will help you refine it if it does not work like you think it should. The difference between a tool that works REAL WELL and one that does not is often very subtle. Those subtleties will not be apparent without trial and error and attention paid to the result of every nuance of modification.
Email: George Dixon
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