The Line Boring Machine LBM850 allows the reconditioning of housing holes either of camshaft cylinder heads and crankshaft blocks of cars and light trucks as well. The boring bar is hold by three sturdy, movable arms which offer high rigidity while machining, whilst perfect and quick centering of the workpiece respect to the boring seats is allowed thanks to fine adjustment knobs, either in height and cross movements, assisted by a pair of centering devices complete of dial indicators. The versatile and useful fixture simplify and speed-up the clamping operation of any kind of cylinder heads and blocks. The boring bar rotation speed can be infinitively adjusted thanks to the inverter complete of digital read-out which displays always the correct working speed.