Currently working on an international project (combining different equipment from around the world).

The pressure we are working with is pretty low.
Is it okay to connect an ISO7-1 male thread with a female BS21 thread?

I know both have the same degree in thread 55? I also know if possible never mix threads or materials.

The only thing I found is by a company called xxxxxxxxxxx, however it would be great to have a second opinion. In particular it is for a stainless steel ball valve, modified, to be connected to a custom union.

<snip> link removed</snip>

Best regards,