Recommendation for smokebox fasteners?

[tetramachine]

I am currently working a a well used 60 year LE Pacfic.the the smokebox stack held on with steel bolts and nuts, 5-40 size, one broke 3 fought all the way off. The smoke box cover with brass bolts, brass nuts, no issue in removal.

Other places brass should have not been used, guide rails, broke bolts, and stripped threads. Cylinder covers, many stripped, not sure why, a couple broken off.

[gwerhart0800]

Thanks, I ordered brass bolts and nuts from Godshall (support your live steam suppliers!) along with some other bits. I am going to follow the other recommendation to recheck all the nuts/bolts every fall after the last run for the year. The smokebox is a hellish mix of heat, steam and flue gases. I owned an 1891 Groton traction engine for a long time and the fasteners in the smokebox were all eroded from the harsh environment. Luckily, I never needed to mess with them. I did change out the front flue sheet drain plug, but that was just because I dropped the original bronze plug on concrete and dinged the threads.

[rkcarguy]

*IF* you can find them, try some 400 series stainless bolts and nuts. They are what are used in the exhaust sides of the natural gas turbines of many power plants. If not, I still prefer stainless or brass, as regular steel can turn brittle at temps as low as 650*. If the smokebox ring is currently tapped 6-32, you can drill through for clearance for a #8 and put nuts on the bolts. I wouldn't be against using the largest fasteners possible and then machine the bolt heads down to a smaller hex if needed.