【正确答案】已知d=50mm、P=10mm
根据矩形螺纹计算式得
b=0.5P+(0.02～0.04mm)=0.5×10mm+(0.02～0.04mm)=5.03mm
h=0.5P+(0.1～0.2mm)=0.5×10mm+(0.1～0.2mm)=5.15mm
d₁=d-2h=50mm-2×5.15mm=39.7mm
[答] 牙底宽b为5.03mm，牙型高度h为5.15mm，小径d₁为39.7mm。