HotBed_Thumbscrew

Another 'ThumbScrew' for the HotBed, those I have viewed seemed to be a little narrow to hold so I have increased the depth to enable the user to have better grip.

thing:2350276 was the original wheel I used so thanks to Area51

Manual bed leveling the Anet A6/A8 can be awkward so to make it easier use a ThumbScrew. There are some good solutions around - I made modifications and tried to keep it simple.