Sharpening stone

How it works

A sharp edge is the meeting of two surfaces. Lie-Nielsen’s published sharpening instructions put it as the intersection of two polished surfaces, so that both the bevel and the back of a plane blade must be worked. The stone cuts away steel from the bevel until the two surfaces meet at a line, usually raising a thin burr or wire edge along the back that signals the bevel has been honed all the way to the edge.

Stones are used in a sequence from coarse to fine. In Lie-Nielsen’s method a 1,000 grit stone forms the edge and an 8,000 to 10,000 grit stone finishes it, and the company notes that the important point is to use a coarse and a fine stone, whatever the exact grit, and gives the example of soft Arkansas stones for coarse work, hard Arkansas stones for medium and black hard Arkansas for fine. Joseph Moxon described the same division of labor in 1703: the edge is first ground on a grindstone and then smoothed on a whetstone, which he wetted with spit, removing the coarse gratings of the grindstone from the bevel and then from the flat side.

Anatomy

Working face: The flat abrasive surface. Lie-Nielsen says stones must be flat before use and gives a method for flattening them.
Abrasive: Natural stone (novaculite, schist) or a manufactured abrasive such as aluminum oxide or silicon carbide, a material Edward Acheson patented as carborundum in 1893.
Bond: For manufactured stones, the material holding the abrasive. The Norton Company’s first wheels, in 1873, bonded emery with clay by firing; Lie-Nielsen says its Ohishi waterstones are dense and hard enough that a spritz of water is all that is needed.
Stone holder: A tray or base that secures the stone; Lie-Nielsen sells an adjustable holder for waterstones of different lengths.

Variants

Natural oilstone (Arkansas and Washita): Novaculite from the Ouachita Mountains. The Arkansas Geological Survey says the trade distinguishes “Arkansas” stone, extremely fine-grained and uniform with a waxy luster, from “Washita” stone, less dense and more porous with the dull luster of unglazed porcelain.
Natural schist whetstone: The Viking Age stones quarried at Mostadmarka in Trøndelag and Eidsborg in Telemark, Norway, as described by archaeologist Irene Baug.
Bonded manufactured stone: A vitrified or resin-bonded block of manufactured abrasive; the Norton Company, which began as a Worcester pottery, produced vitrified emery wheels from the 1870s.
Waterstone: A fine-grained manufactured stone used with water; Lie-Nielsen sells synthetic Ohishi waterstones in grits from 220 to 10,000.
Diamond plate and sandpaper: Used to flatten stones and, in Lie-Nielsen’s method, to re-establish a primary bevel; the company uses a diamond lapping plate and wet-or-dry paper on a flat surface.

Specifications

Grit (coarse to fine) · grit number: 1,000 (honing) to 8,000–10,000 (finishing)Lie-Nielsen’s two-stone method; 3,000 grit is a medium stone for chisel backs. Grit scales differ by maker and standard.
Primary bevel angle · degrees: 25Lie-Nielsen blades are delivered ground at 25 degrees; honing at 35 degrees forms a 10-degree secondary bevel.
Camber (curve of plane edge) · in: 0.002–0.005Lie-Nielsen’s method for honing a slight curve into an edge.

Made to

ANSI B74.13
ISO 603
FEPA 43

Safety and care

Care

Lie-Nielsen directs that stones be flattened before first use and again when sharpening is done, by drawing a pencil cross-hatch on the stone and rubbing it on sandpaper of 100 to 220 grit on a flat reference surface, or on a diamond lapping plate, until the marks are gone, usually 15 to 20 strokes.
Lie-Nielsen sells a silicon carbide flattening stone with diagonal grooves for waterstones, and says the flattening stone itself loses flatness with use and is dressed on 80 grit sandpaper on a flat surface.
Lie-Nielsen directs that its Ohishi waterstones be wetted with a spritz of water and not soaked.
Lie-Nielsen advises wiping blades with oil after sharpening to prevent rust.

Tips

Flatten the stone first
Lie-Nielsen says every stone must be flat before it is used. Its method is to draw a pencil cross-hatch on the stone, rub it on abrasive paper laid on a flat surface until every pencil mark is gone, and check with a straightedge.1 2
Hone on and off the stone
To keep the front edge from rounding, Lie-Nielsen says to hone a chisel back by working it across the stone on and off the edge, because stopping short of the stone’s edge can round the front. It adds that a slightly concave surface is better than a convex one.1
Hone a short secondary bevel
Lie-Nielsen grinds a 25-degree primary bevel and hones a secondary bevel at 35 degrees, producing a 10-degree microbevel. It says the secondary bevel concentrates all the sharpening effort on the very edge, which is the only part that does the work, and recommends re-establishing the primary bevel only when the secondary gets too large.1
Polish the back with the ruler trick
Placing a ruler about 0.020 inch thick along one edge of the finishing stone and laying the blade across it raises the blade by less than a degree and concentrates the honing force on the very tip. Lie-Nielsen says to hone on and off the stone, not bringing the edge more than half an inch onto it to minimize a back bevel, and that about 10 passes finish the back.1
Match the angle to the wood
Moxon writes that a more acute bevel cuts better and smoother, and a more obtuse bevel gives a stronger edge for hard work; he gives about 12 degrees for soft wood and 18 or 20 degrees for hard wood. Lie-Nielsen says a much steeper honing angle of 45 to 50 degrees on a bevel-up plane works very well in difficult grain.1 2
Use a coarse and a fine stone, whatever the grit
Lie-Nielsen says the important point is to use a coarse stone, a medium stone for chisels, and a fine stone, whatever the exact grit may be, and gives soft, hard and black hard Arkansas stones as an oilstone equivalent of its coarse, medium and fine waterstones.1
Do not soak these waterstones
Lie-Nielsen says its Ohishi waterstones cut quickly but are dense and hard enough that a spritz of water is all that is needed, and warns against soaking them. Other waterstones differ and the maker’s instructions apply.1
Know what Arkansas and Washita mean
The Arkansas Geological Survey says the abrasives industry sorts novaculite into “Arkansas” stone, extremely fine-grained, uniform and waxy, and “Washita” stone, which is less dense, more porous and dull in luster. The names therefore indicate relative fineness of the stone.1

History

Earliest documented

early 8th century AD (earliest documented large-scale production found)

Mostadmarka, Trøndelag, and Eidsborg, Telemark, Norway; trade to Ribe, Denmark

Archaeologist Irene Baug of the University of Bergen says in a ScienceNorway interview that whetstones are among the most common items found from the Viking Age, used by farmers, craftsmen and warriors alike, and that large-scale production started at Mostadmarka in Trøndelag, with the first export found going to Ribe, Denmark, in the early 8th century. She says production began at Eidsborg in Telemark about a hundred years later, in the early 9th century, and that stones were carried more than 1,100 km from Mostadmarka to Ribe. Baug says contacts and trade with other goods existed before the Viking Age on a much smaller scale. This is a news account of research by Baug and colleagues; the underlying paper was not accessible. Sharpening stones in earlier periods have not been sourced.1

Sharpening stones are among the most common finds of the Viking Age. Baug says whetstones were used by everyone, farmers, craftsmen and warriors, and that they were quarried in bulk and distributed over great distances: stones from Mostadmarka in Trøndelag reached Ribe in Denmark in the early 8th century, and Eidsborg in Telemark began large-scale production about a hundred years later. She says the quarries were set up not only because farmers needed whetstones but also to sell them widely. The account is of a news interview; the technical papers behind it were not read.

In the seventeenth and eighteenth centuries the stone was one stage in a two-stage process. Moxon in 1703 describes grinding the iron on a round grindstone, which gives a hollow bevel that is deeper the smaller the stone, or on a flat grindstone by thrusting forward and drawing lightly back, and then smoothing the edge with a whetstone wetted with spit to wear off the coarse gratings of the grindstone. The sharpening stone of this period was a finishing stone, and the bevel angle was chosen to suit the wood.

Natural stones from particular quarries became a regional industry. The Arkansas Geological Survey says that early settlers mined a honestone quarry near Magnet Cove in the early 1800s and that mining was intermittent from 1885 to 1905 and continuous after; the University of Arkansas’s Archeological Survey says novaculite mining for whetstones began as early as 1818 in the Hot Springs region. The two accounts differ in place and date and are given under disputed. The Survey adds that commercial whetstone mines declined with the arrival of less costly synthetic abrasives and that demand for natural oilstones has since risen, with eight companies working in the Hot Springs area in 2007.

The synthetic abrasive industry began with the vitrified wheel and the artificial crystal. The Norton Company’s history, as told in the International Directory of Company Histories, begins with a pottery in Worcester where Swen Pulson fired emery in clay in 1873, and the company patented the process in 1877. The same account says the firm’s conservatism sometimes led it to pass up innovation, and gives Acheson’s carborundum of 1891 as an example; Acheson’s 1893 patent proposed the material as a substitute for diamonds, bort and other abrasives. The history cited here covers wheels and not the hand-held stones Norton later sold, which have not been traced.

Current practice divides stones by use. Lie-Nielsen’s published instructions assume a coarse honing stone near 1,000 grit and a finishing stone of 8,000 to 10,000 grit, with a medium stone for chisel backs, and treat flattening of the stones as part of the routine; the company says oilstones of graded Arkansas stone can be used in the same sequence. O*NET’s Tools Used table lists sharpening stones, tools or kits in 3 of the 24 occupations mapped to this archive’s trades, maintenance and repair workers, machinists and tool and die makers. The argument over which stones are best is the subject of the sharpening-stones argument in this archive.

Timeline

early 8th century
Whetstones from Mostadmarka in Trøndelag, Norway, are exported to Ribe, Denmark, according to Baug.1
early 9th century
Large-scale whetstone production begins at Eidsborg in Telemark, Norway, according to Baug.1
1703
Moxon’s Mechanick Exercises describes grinding an iron on a round or flat grindstone and smoothing the edge with a whetstone, and gives bevel angles for soft and hard wood.1
early 1800s
Settlers mine a honestone quarry near Magnet Cove in Hot Spring County, Arkansas, according to the Arkansas Geological Survey; the Arkansas Archeological Survey puts the start of novaculite mining for whetstones as early as 1818 in the Hot Springs region.1 2
1873
A Swedish immigrant potter, Swen Pulson, mixes emery with clay and fires wheels in the Norton pottery kiln in Worcester, Massachusetts; one vitrifies successfully.1
1877
Frank Norton patents Pulson’s process; production of the wheels begins in 1878.1
1885
The Norton Emery Wheel Company is incorporated in Worcester.1
1891
Edward Acheson passes an electric current through a mixture of clay and powdered coke and obtains crystals he calls carborundum, which scratched glass and, according to Acheson, diamonds.1
1892
Geologist L. S. Griswold’s report “Whetstones and the Novaculites of Arkansas” is published in the Arkansas Geological Survey annual report for 1890.1
1893
Acheson is granted US Patent 492,767 for artificial crystalline carbonaceous materials, which he names carborundum, intended as a substitute for diamonds, bort and other abrasive material.1
2007
Eight companies mine and process whetstones in the Hot Springs, Arkansas, area, according to the Arkansas Geological Survey.1

Where the sources disagree

When and where did commercial mining of Arkansas novaculite for whetstones begin?

In the early 1800s, early settlers mined a honestone quarry near Magnet Cove, Hot Spring County.1
Arkansas Geological Survey
As early as 1818 in the Hot Springs region.1
Arkansas Archeological Survey, University of Arkansas

Gaps in the record (6)

The Viking Age evidence is read from a news interview, not from the research papers of Baug and colleagues, and any earlier hones (Roman, Bronze Age, prehistoric) are not sourced.
The history of Japanese natural and synthetic waterstones, and of the coarse and fine grit scales (FEPA, JIS, ANSI), is not sourced, so the Japanese tradition is not described beyond the Lie-Nielsen product pages.
Norton’s sharpening stones (the Crystolon silicon carbide and India aluminum oxide benchstones) were not traced to a Norton publication; its product page could not be fetched.
No standard for sharpening stones has been read; the standard slugs are guesses.
No sourced safety guidance for sharpening stones was found, so safety is empty; silica dust and coolant hazards are not addressed.
No independent test comparing stones was cited, so buying is null; the preference between oilstones, waterstones and diamond plates is a matter for the sharpening-stones argument and is not decided here.