Today's high speed aircraft must have external surfaces as smooth as possible, and in order to reduce drag to a minimum it is usual to employ flush riveting for all external skin sheeting. Whilst this method of construction provides a basis for a smooth surface it is not in itself fully satisfactory, especially on a curved surface where there is no certainty that all the rivet heads lie flush with the surrounding skin sheeting. It is possible to attain a finish nearer to that desired by using an end milling tool on the rivet heads, but there is still a danger when using normal tools of this type that the surface of the sheeting will be damaged. Thus it has become necessary to provide a tool with which the likelihood of such damage is greatly reduced. The Short Rivet Milling Tool has been designed by Short Brothers and Harland Limited to overcome this problem. It can be used in conjunction with a portable power driven unit, e.g. a compressed air operated hand drill, and comprises a circumferential milling cutter, a cutter spindle, a housing containing bearings for supporting the spindle at right angles to the driving axis and an attachment to the power unit. Two guide rollers, one each side of the cutter, project very slightly and thus prevent the cutter from touching sheeting surrounding the rivet under treatment. Although these guides extend only 0.0005 in. this is sufficient to ensure that the cutter operates only on the rivet head. Varying widths of milling cutters may be fitted to the tool by withdrawing the cutter spindle and inserting spacing bushes of appropriate width. In operation the tool can be used for ‘rubbing down’ protuberances, in the same manner as a smoothing plane, with the drill shaft axis at an angle of about 60 deg. to the surface being worked upon. Exhaust air from the tool is collected internally and used for the dispersal of swarf.
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