I've done a LOT of checkering and while I can't tell much from that photo (really need a tight closeup), my first thought is your line spacing is way too fine. It looks like >80lpi, when you'd be better off with <60lpi.
Also, you're using a very elongated diamond, which is usually better suited for wood. Metal checkering tends to be a bit more 'square'.
The good news is that what you've done so far is so fine you can probably just do like SDH suggested and back off to every other line.
you could try a coarse ( fewer lpi ) liner tool ,running it deep if you want to cover up what is there. with a liner over lap a couple teeth to keep a good parallel kinda like wood checkering and a lot of cuts to get depth.