Just Google "business liquidator chicago" and you will find one nearby.
What: Liquidators basically take your inventory for a lump sum payment and then they try to make money by reselling it at a higher price than they pay you.
Why: To get money faster and sometimes in greater amount.
Who: Do you have a Big Lots store near you - that's a liquidation retailer, probably the country's biggest with 1400+ stores. See http://en.wikipedia.org/wiki/Big_Lots
Here is one for example http://www.chicagoliquidators.com/ They will quote you online (or call if they have questions.)
Look to see what sort of items they primarily handle. Some liquidators specialize in certain types of inventory. For a small metalworking shop, you would do best with a specialty liquidator.
For you, I think PPL Group is likely to be the best choice. Their CEO comes from the metalworking industry. http://www.pplgroupllc.com/Bios.html I think they will end up giving you the highest quote.
Another local choice is Liberty Machining Company , as they are in Chicago (which cuts their transportation costs) and they specialize in metalworking equipment. http://www.libertymachinery.com/
Hilco Trading is yet another. http://www.hilcotrading.com/HoldingCompanySeniorExecutives.asp
Liquidators will give you an estimate. So get a few before choosing.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.