Is there a difference between แต่ and แค่ (in the case แต่ means "only", so not when แต่ means "but")?

I think the difference could be translated to this

แค่ = only this amount/only to this extent

แต่ = but/only (In English you can say "We have but ___" although it sounds quite old fashioned)

I believe you can use the pair together as in เรามีแต่แค่นี้ We have but only this much/many