So I was curious about this myself, so I went with the scaling rules and ST stuff from LTC2 for weapons and my small amount of knowledge. Assuming you mean a Baseball Bat the stats would be as follows using the information from Martial Arts and basing it off the Knobbed Club as said.
Code:
Weapon Damage Reach Parry Cost Weight ST
Baseball Bat Sw+3 2 0 $125 12.5 20
Now technically this would be a SM+2 bat in gaming terms. This is only because I haven't updated my spreadsheet to work real well with only scaling the ST requirements based on weights. I'm sure that you could say that you are just adding the weight and bring the reach back down to Reach 1 and have it work just as well as a SM 0 bat with a core of solid metal.
Either way, with a ST 20 fellow, you'll be doing at least 3d+5 Cr. Not bad for a bit of wood.