Regulator fixings | Model Engineer
If you have three complete threads engaged and the screws are a good fit, not loose, Id say they will be good. Certainly better to use blind threads in such a bush from the standpoint of less places to have a steam leak than with through-holes. I have seen a lot of things in Martin Evans designs where a bit more care, as in a deeper bush / blind holes in your locomotive for example, would have made for a far better design. He frequently designed things on boilers with really short threads han...
Source: model-engineer.co.uk