Machinery's Handbook, 31st Edition
734 V-BLOCK Material Surface Finish, Grade B (except Style 4), and Grade C Blocks: Surface of V-groove(s). The V-grooves relief slots and clamp engaging grooves (when applicable) on blocks shall have a surface roughness not greater than 125 µ in (3.175 µ m) Ra. All other finished surfaces shall have a surface roughness not greater than 63 µ in (1.600 µ m) Ra. Surface Edges: Edges of all exterior surfaces, including corners, shall be rounded or beveled not less than 0.010 inch and shall be free from fins and burrs. Tolerance.— All Grade A; and Style 4, Grade B, mild steel laminated with brass, shall have a ground finish on the ends, sides, top, bottom, and the V-groove(s). The V-grooves shall be centered with the sides, square with the sides and ends, and parallel to the bottom within 0.0003 in. All surfaces shall be square with each other within 0.0003 in. Grade B (except Style 4) and Grade C shall have a machined or ground finish. The V-groove(s) shall be parallel and centered with the sides to within 0.002 in. The ends shall be square with the sides within 0.002 in. and the sides shall be square with the top and the bottom within 0.002 in. The V-grooves shall be 45° each side of the center perpendicular plane for all grades. When specified, Grade B or C blocks shall be furnished with tolerances as specified for Grade A blocks. When the V-blocks are provided in matched sets, they shall be clearly marked to identify them as such and shall be identical to each other within 0.0002 in. on all critical features. V-Block Design.— Each V-block shall have a 90° V-groove 45° from center perpendicu- lar plane cut lengthwise on the top, or top and end, or top and bottom, for the type specified. A slot shall be provided at the apex of the V-groove for chip relief. The exception being with the Type III V-blocks which shall be furnished without the chip relief unless other- wise specified. When V-blocks are furnished in “matched pairs” they shall be marked to readily identify them as a pair. Clamping grooves shall be provided along the full length of the sides of Styles 1 and 2 blocks for engaging the clamps. Clamps.— The clamps shall consist essentially of a yoke and one or two screws for the style specified, and shall be of a size to accommodate the maximum size round stock specified in the respective tables. The Clamp shall be made of good quality steel or iron and sufficiently robust to provide adequate support and security of the work piece in the V-block during drilling and grinding operations. When engaged in the clamping grooves, the clamp should not extend past the side faces of the block. When provided with matched sets the clamp shall be applicable to either member of the set. The screws for the clamping device shall be right handed thread conforming to ANSI/ASME B1.2 or FED-STD-H28. Yokes.— Yokes shall be made of good quality steel or iron and sufficiently robust to provide adequate support and security of the work piece in the V-block during drilling and grinding operations and should not extend past the side faces of the block. V-block and yoke screws for Type 1 Style 3 shall be threaded in accordance with ANSI/ASME B1.2 or FED-STD-H28 or the equivalent and shall be a Class 2 fit. When the yoke is in place it shall bisect the 90° V-groove. The yokes when engaged in the clamping grooves shall stand in an upright position. Yokes for the style 3 blocks shall have a slot on each end to engage the two adjusting screws. The yoke shall be designed so that the pads bisect the 90° V-groove to allow the yoke to secure stock that does not extend above the V-groove. When inverted the yoke shall be able to secure stock of the maximum size specified. Screws.— All screws shall be made of steel of such quality as to withstand hard usage. Screw heads shall be knurled and provided with a hole through the center for tightening with a pin or rod. All screws shall conform to the ANSI/ASME B1.2 or FED-STD-H28 or equivalent and shall be a class 2 fit.
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