Negotiating an offer, is it too late? - 8 months and counting

I received an offer as a machine operator and I think the pay is a little low. I have been trying to stay organised about it. The benefits are decent. What wording worked?

Most employers expect a short conversation. Mine did not even blink.

I thanked them and said I was excited but hoped we could talk about the pay. They came back with a bit more.