With enough money it is no trick to assemble an adequate selection of precision metal working tools. To do so on a budget, and in such a way that the tools can be used for several purposes is quite another thing.
In this particular case, the student machinists discovered that twist drills don't drill to size. They generally drill close, but not exactly to size, and what do you do when you need a hole, where there is no standard drill? The surface finish tends to be rough.
If the part can be mounted in a chuck or on a face plate, you can frequently use the lathe to bore the hole to size after drilling most of the material. But what can you do if all you have available is a drill press (or vertical milling machine)?
The commercial answer is a precision boring head, which allows a cutting tool to be adjusted to the nearest "tenth" [o.ooo1 inches] and which produces a straight and round a hole with good surface finish. The downside is that these units tend to be large, requiring considerable vertical space which may not be available, and are expensive, ranging from slightly under 100$US for Asian imports to a few hundred for domestically produced units, and up to a few thousand for top of the line European imports with additional features such as external and internal grooving.
|A typical domestically produced boring head with an integral
V-flange arbor as produced by the Criterion
Machine Works of Costa Mesa, California USA.
Criterion, as do most boring head manufacturers, provide boring heads with all common mounting arbors such as Morris Taper, R-8, Browne & Sharpe, Moore Jig Bore and straight shanks.
For volume production Criterion units are difficult to equal.
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last updated by GmcD on 19-Mar-11 19:30
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