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Glossary K

Kerf

Using a Saw -- power or hand -- the wood removed by the teeth as the cut is made.

From the Oxford English Dictionary, "The result of cutting; the incision, notch, slit, etc., made by cutting, especially by a saw".

Later I will fill in the missing parts of the quotations below. 6-10-2010

1523

FITZHERB. Husb. §136 Bycause it [a saw] is thyn, it wyll cut the narowe kyrfe.

1664

EVELYN Sylva (1776) 132 Cut your kerfe near to the ground, but have a care the Tree suffer not in the fall.

1792

J. BELKNAP Hist. New Hampsh. III. 156 The felling of such a tree must require much labour, since those of but one inch have eight or ten strokes, distinctly marked, and a very good kerf is allowed.

1812-16

J. SMITH Panorama Sc. & Art I 99 The saw, when cutting, takes away the wood at the two sides of the kerf.

1890

W. J. GORDON Foundry 121 A matter-of-fact place is a sawmill... Its great problem is how to minimize the ‘kerf’, the kerf being the track of the saw.

Some Illustrations of Kerf


kerf

The diagram on the left -- from Mark Duginske's Bandsaw Handbook , 1989, crude as it is, illustrates not only "kerf width" on a Bandsaw, but such other factors that, in one way or another, contribute to kerf. These factors include the Blade 's Gauge , the Set of the Blade 's Teeth, Side Clearance.


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This second image is another take on the concept of "kerf". The second image shows how the "set" -- outward spread -- of a saw blade's teeth determine the width of a cut through wood.

For more on Bandsaw Blades , please see section "D" ("Blade Anatomy and Terminology") of my Syllabus on the Bandsaw

(Research on Blades -- e.g., origin of  -- for other Tools (e.g.,Carbide Tips for Table Saw blades) is a future project.

Kiln-Drying Wood

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Drying Methods

Methods of drying or seasoning lumber vary with the use requirements. Today, because of the time saving and control factors, nearly all upper grades are kiln dried. Sometimes lumber is first air dried and then kiln dried.

In air drying , the lumber is simply exposed to the outside air. It is carefully stacked with stickers (wood strips) between each layer so air can circulate through the pile. Boards are spaced well apart in the layers so air can also move vertically.

The rate of air drying lumber can be partially controlled by varying the spacing between indi­vidual boards and the size of the pile. Because of the seasonal variations in climate and local weather condition, it is difficult to approximate the air-drying time for any particular species or thickness. Lumber that might become dry in 30 to 60 days during an active drying period may re-quire more than 6 months under unfavorable conditions. The moisture content of thoroughly air-dried lumber, reduced during the spring, summer or early fall will be about 12 to 18 percent.

Lumber is kiln (often pronounced "kill") dried by placing it in an oven where the temperature and humidity are accurately controlled. The boards are stacked in about the same way as for air-drying. When the green lumber is first placed in the kiln, steam is used to keep the humidity high and the temperature is kept at a low level. Gradually, the temperature is raised and the humidity is reduced. Fans are used to keep the air in constant circulation over the sur­faces of the wood.

A kiln schedule is a carefully complied set of temperatures, humidities and timings which are followed by the kiln operator. They will vary de-pending on the size (cross section) and kind of wood, and its initial moisture content. One inch lumber can usually be kiln dried to a level of 6 to 10 percent in about three or four days.

Improper drying, either air or kiln, can result in such seasoning defects as splits, checks, warpage , loosened knots, honeycomb, and internal stresses called case-hardening. Most of these are caused by drying the wood too rapidly. In case-hardening the surface layers dry, shrink and be-come fixed or set before the inside portion of the board. As the interior then dries below the fiber saturation point and starts to shrink it pulls on he outside, shell," creating both compression and tension forces. When the board is cut these forces are released causing the kerf to close on (pinch) the saw blade or the stock to warp in various directions.