A doubled die can also have Machine Doubling on it. So you need to Identify which is which:
On this image the red arrows show the doubled die areas. (A doubled die will be raised) On this image the white arrows are showing Machine Doubling. (These area are all flatten from a side push after the strike by the machine) So knowing what to look for on coins will help you to spot the Machine Doubling (Very common) from the true hub doubling (doubled dies) which are not common. They are a lot rarer to find. So both events can happen. But most seasoned collectors prefer a doubled die without Machine Doubling. But grading companies will grade a machine doubled coin as a normal coin. If it is a doubled die with Machine Doubling they just consider them a doubled die. (They turn a blind eye to Machine Doubling) Collectors are more selective.