305



4 TOOL DESIGN

the circular fixture a constantly revolves, as does the milling
cutter b, and is so designed that as fast as the cutter leaves the




Fie. 3. Viev Showini Mrthod of Finishing Pulinhing E>urfa« oF Iron. Lower IlluMnlioa
8hu»m( Jig9 L'H-d by Ik^cr Jlillins Machine Cumpony

surface of a base the operator can readily remove the finished base
and insert a rough casting without stopping the machine. Tliis



TOOL DESIGN 6

method proves to be the fastest because there is no lost time in
stopping, starting, or changing the bases.
The same line of reasoning must be followed in working out
the details of the holding devices for the bases. Speed of operation
and accuracy must be uppermost in the designer's mind. The
student must have in mind that although we have used only the base
of the flatiron for an illustration, the methods, fixtures, and reason-
ing are applicable to almost any flat work that is to be surfaced.
Various designs of milling fixtures will be shown later.
