Summary

I created this grid for testing leathers. Leathers are so different so I wanted to see how settings respond to different kinds of leathers. In pictures it is not always so visible as in real life. Offten darkness changes slightly but the depth of engraving is deeper with stronger settings. 

Power minimum is 40 and maximum is 100. 
Speed min is 250 and maxiumum is 800. 

I found these settings usfull. If the power is lower and speed is much lower then leather offten starts to burn. After the test more spped could be useful. These settings are for testing.