I think Steve Loving? posted photos in your' thread or started his own showing calipers. Making calipers was a apprenticeship project, draw filing forever, heat treating etc...I dropped the bar on my right hand breaking couple fingers then had to purchase digitals until healing was over, couldn't get the FEEL with swollen fingers! Well okay I use Jap spring tensioned calipers, but I still use dial indicator to measur
Discuss this in the forum topic Line Boring Systems.