piston engages the drill steel whereby vibration can be imparted to the drill the drill includes an overtravel portion that cooperates with the striker piston to prevent metal to metal contact of the striker piston with the housing during operation means are provided to prevent the loss of fluid from the overtravel chamber whereby the striker piston will be returned to the upper end of its stroke and will not become stalled in the overtravel chamber application_number US 41093973 A description as mentioned hereinbefore this invention constitutes an improvement to the percussion drill described in u s pat no 3 701 386 the overall structure and operation of apparatus described in that patent will not be described in detail hereinafter the disclosure of that patent is hereby incorporated by reference with regard to the details of structure and operation of the overall device referring to the drawing and fig1 in particular shown therein and generally designated by the reference character 10 is a hydraulically actuated percussion drill constructed in accordance with the invention that includes a housing 11 a source of hydraulic fluid not shown and a source of compressed air not shown located within the housing 11 are inwardly projecting bearing portions 12 and 14 that are spaced apart and arranged to support a striker piston 16 for reciprocating movement relative to the housing 11 attached to the lower end of the housing 11 is a drill rotation assembly 18 which supports a drill steel 20 for both rotational and reciprocating movement a motor 22 is attached to the drill rotation assembly 18 and is provided with output shaft carrying a pinion 24 that engages a.