You've got a couple options; both need a Seared Faucet.
1. Put a Seared Faucet on the basin.
2. Then either place a Casting Table or Seared Tank below the basin.
You can then either make tool parts, ingots, etc, or use a bucket to scoop the metal from the tank.
If you choose to use the bucket you can drain the liquid back into the smelter by placing a Seared Glass or Seared Window above the Smelter, placing a Smeltery Drain as part of the Smelter with the drain facing upwards, and put a Seared Faucet on the Glass/Window pouring into the drain. (I was curious so tried using a Tank instead of Glass/Window and it wouldn't pour into the drain).
Check out this link for pictures, I just searched "drain" in the Tinkers Construct thread...
