In keeping with the El Cheapo theme I've taken delivery of this huge chunk of steel for the disc teeth, cost me all of a fiver. It's 8mm thick and 65mm wide, you can see where it will be cut to make the teeth, each one will be 75mm long but only the last 15mm or so will stick out, all bolted together with 4 high tensile 12.9 m8 bolts for each tooth.