PART A: MACHINING
The following represents a
collection of practical hints for saving time, labor, material and costs.
These involve designs for minimum tooling, efficient clamping and holding,
simplifying subassemblies and efficient turning, boring, drilling, milling,
broaching, grinding and tapping. In the figures, design (a) generally
represents the incorrect design, while constructions (b, c, d etc.)
illustrate improvements. The symbols V, VV ,VVV denote rough-machined,finish-machined
and ground surface finishes, respectively.
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(a)
Minimizing Tooling Costs
Avoid round shapes in screw-machine work, which require special forming tools. In design (b) straight cutting tools can feed practically simultaneously at right angles and at 45º to the screw-machine axis. If round shapes are necessary, avoid radii equal to half part width (a). Such radii are sensitive to machining accuracy and tool and work alignment. Radii greater than one half part width (b) avoid the need for such accuracy. The initial cost and maintenance of a milling cutter with curved teeth (a) is greater than that of a cutter with straight teeth. The latter are more suited to high production rates and can also be made with a combination of two standard cutters, if desired (b). A milled or ground slot with square ends (b) requires a less expensive milling cutter than a slot with rounded ends (a), which necessitates a cutter with curved teeth. The need for two face cutters of different size, as in (a), may be avoided it the locating surfaces in the housing can be simplified to a few appropriately spaced ribs (b, c). |
| * Reprinted by permission of Mr. Frederico Strasser | |
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