keeping DTIs perpendicular for runouot checks

[dsc]

Maybe a daft question, but I'll ask anyway.

Is there an easy way to keep a DTI stem perpendicular to the end of the shaft on which run out is measured? This is not on a lathe and access is a bit problematic, also the chassis is out of ali so I can't easy mag base the DTI in place. Attachment shows how the runout is measured and what errors I'm expecting.



Regards,
T.