The invention relates to improvements to rock crushers, and in particular rotary impact rock crushers. The crushing chamber may be angled to achieve the desired rock product. Also disclosed is an anvil for use in crusher whereby the anvil position adjustable. The invention enables the operator to dial up a particular rock product specification by adjusting the angle of the crushing chamber and/or the position of the anvil. The adjustments may be made without ceasing the operation of the machine. Improved control over fracture mechanisms within the crushing chamber and as a consequence the rock product, are achievable with the present invention.
