Engine want crank

When I turn the key to the cranking position nothing happen the starter want turn the gauges on the instrument cluster don't move no light on in the instrument cluster the turn signal lights not working the head lights are working the hazard flashers are working the bolt that hold the positive cable on the battry the bolt is tight but the cable not very tight how do I tight the cable? The battry have a side post I disconnect the little wire from the starter solenoid and turn the key to cranking position and hook a test light to the starter solenoid small wire my test light light up so current is getting to the starter solenoid, so I bench test the starter motor it will crank what could be the cause for the starter motor not to crank when bolted to the engine?