Masonry Magazine June 1997 Page. 36
Slab Cutting
The slabs will be cut to a final face dimension by saws using circular blades with diamond abrasive segments. The diamond segments are cooled and lubricated with water. Saws with a singular blade will be guided manually by the sawyer aided by a laser sighted alignment device. When the panel sizes are repetitive, the cutting will be done with a multiple bladed "continuous cutting saw". These saws typically can be programmed by the operator after which the blade positioning is monitored electronically. Thin slabs of 20 or 30 mm can be sawn through with a single pass of the diamond blade. Thicker slabs require multiple passes in the same kerf to cut through the entire depth of stone.
Edge Treatments
Atypical conditions require specific edge treatments to be made to the stone panels. Most commonly, these edge treatments require either applying a finish to the edge or a miter cut to accommodate an exterior corner.
Due to stones susceptibility to breakage, miter cuts are performed in natural stones differently than in other materials. The miter joint in stone has a blunt nose instead of a point to reduce the potential of chipping. This detail is called a "quirk miter" (Fig.2).
When a "lap joint" or "butt joint" (Fig. 3) is used at a corner condition, one panel requires a finish on the edge to match the face finish.
Depending on the sawing method and equipment used, the stone slabs can vary by as much as +3 mm. It would be very unsightly to position two slabs at opposite extremes of this tolerance adjacently with exposed edges. To avoid this, the edges must be calibrated to a uniform thickness. In the case of a honed or polished finish, the edge is finished and the thickness calibrated in one pass of a machine. In the case of a thermal panel, the finish is applied by a hand held torch after which the thickness is calibrated in a separate operation.
Anchorage Preparations
There are many varieties of anchors used in natural stones. The most commonly used anchors for building panels are one of three types: Local edge anchors; Continuous edge anchors; or Back anchors.
Local edge anchors are usually made either of stainless steel straps with a bent end penetrating the stone or a combination of a stainless steel rod and plate which penetrates the stone. These anchors resist lateral loads only while the gravity loads are addressed by other means. Only a short length of kerf cut in the stone's edge is required to facilitate engagement. These short kerfs are plunge cut with a small (150 mm diameter) circular blade using diamond abrasive segments.
Continuous edge anchors usually consist of an aluminum extrusion. These anchors are usually designed to resist both gravity and lateral loads. The aluminum section requires two continuous kerfs cut in opposite edges of the stone. The kerfs are cut by a semi automated machine which holds the stone in a fixed position while a diamond segmented blade cuts the kerf in a single pass.
Back anchors, as their name suggests, are normally located in the back surface of the stone, and are designed to resist both gravity and lateral loads. A common back anchor is the Cold Spring Granite Company Type Number 31 Anchor. The anchor consists of a stainless steel bolt fitted into a dovetail shaped slot which is routed in the stone.
Contoured Faces
The majority of building products consist of flat, rectangular panels, and most of the development in automated machinery has been focused on the repetitive tasks involved in producing them. Interesting challenges await the stone fabricator when the design professional deviates from the rectilinear patterns and introduces curved elements into the design concept. It is quite frequent that a building design incorporates a
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36 MASONRY-MAY/JUNE, 1997