Sigma Tiller Blades & Bolts Set Specification. Bolt: 9/16 (14.5mm). Hole Spacing: 1-9/16 (40mm). Bolts and Nuts: M14-1.5X35 Hex Cap Screws. Metric Class 8.8. Bush Hog RTN 60/72/80 RTG/RTGR Series Tiller. Tine Part Numbers: 86391 / 86390. Tiller Blades (27 Right & 27 Left) & Accessories (Bolts, Nuts and Washers). If you are not sure, […]