Abstract: A tool assembly comprising a support base having a plurality of longitudinally oriented guideways disposed next to one another in a common clamping plane and at least one tool holder which is adjustably mounted along the guideways and can be secured in the guideways by clamping means, characterized in that the guideways are formed by a plurality of rib-like projections in the base defining a series of grooves arranged in at least two groups at each end of the support base and the clamping means are formed by at least one holding projection of the tool holder which engages in a groove of the two groups whereby the holding projections of the one group and the holding projections of the other group are arranged mutually adjustable to one another by adjusting means against the sidewalls forming the grooves in the base.