IAWA Journal, Vol. 24 (3), 2003: 241-245

APPLICATION OF THE "NT-CUTTER" KNIFE BLADE TO MICROTOME SECTIONING OF WOOD by Tomoyuki Fujii Forestry and Forest Products Research Institute, Tsukuba Norin P.D. Box 16, Ibaraki 305-8687, Japan

Traditional microtome knives were popularly used for sliding microtome sectioning of wood samples, It was usual to produce several sets of microscopic slides from only one wood block per day (several sets of cross, radial and tangential sections) in the Wood Anatomy Laboratory of the Forestry and Forest Product Research Institute, because it was time-consuming to sharpen the knife-edge worn by the sectioning. In the late 1970's, the introduction of a microtome blade holder with a disposable knife blade (Holder No. 160 with Blade type S35, Feather Safety Razor Co. Ltd., Japan) saved much time by exchanging a worn blade to a new one, and eliminating the sharpening procedure. It is now common to produce microscopic slides from several to 10 wood samples per day. Furthermore, the fine edge of the blade has enabled the constant production of high quality sections. However, the popular disposable knife blade (Fig. 1b: Feather S35) could some­ times not be used for heavy timbers without previous softening, especially for prepar­ ing cross sections. Feather Safety Razor Co. Ltd. offers a line-up of various types of blades, but those blades have the same thickness and width as Feather S35. Recentl y, a microtome blade specially designed for thin sectioning of resin-embedded samples for optical microscopy (Microtome blade H35S, Feather Safety Razor Co. Ltd., Japan ) has become available (Fig. l a) with the blade holder Feather No. 158HD. It is thick and rigid enough to cut large cross sections of very hard timbers, but the the blades are very expensive (Table 1). A special knife was invented originally for cutting paper in the printing industry in Japan in the late 1950's. It is a knife holder with a disposable blade of which the edge ---.

Fig. 1. Knife blades: a: Feather H35S b: Feather S35 c: NT-Cutter blade A-type d: NT-Cutter blade L-type 242 IAWA Journal, Val. 24 (3), 2003

Table I. Specifications of knife blades.

Blade thickness width length edge material of body List price (mm) (mm) (mm) angle (0) unit Feather S35 0.254 8.0 80 35 stainless steel V8,500 / 50 blades H35S 0.8 14 80 35 stainless steel V35,000 / 10 blades

NT-Cutter L-type 0.45 18 100 carbon steel SK-2 V700 / 50 blades A-type 0.38 9.11 80 45 carbon steel SK-2 V 1,200 / 50 blades can be snapped offto expose a new sharp tip. NT-Cutter L-type (NT Inc. Japan, Fig. l d: spare blade), which is one of the original types and most popular for heavy duty use, has been used for hand sectioning of wood sampies, and sufficiently large cross sections can be prepared even from heavy tropical timbers from South-east Asia. However, rnicrotome sectioning is superior to hand sectioning for micrography and also for the production of multiple sets of microscopic slides of constant quality. Consequently, the microtome blade holder (Feather No.160) was remodeled to hold a spare blade for the "cutter knife". Here, the NT-Cutter blade A-type (Fig. lc) was selected because of the size close to the Feather S35 microtome blade instead of the wide L-type (Table I). The ditch of the remodeled holder was a little wider and deeper than the original (Feather No.160 NT-A, Table 2). With the application of the blade holder remodeled for the A-type blade to rnicro­ tome sectioning (Fig. 2), fine sections of 10-15 rnicrons thick were obtained without the extremely careful adjustment of the block orientation which is usually required when sectioning with microtome blade Feather S35. As a trial, more than 10 sets of three different sections were produced from Japanese hard- and softwood samples

Fig. 2. Microtome section­ ing of Distylium racemo­ sum wood with the blade holder remodeled for a NT­ Cutter blade type-A.