As with machine shop operations, it is often necessary to achieve great accuracy. A Dial Indicator is often employed for this, and it is often held by a Noga arm.
Disclaimer : eMail comments to me at OTBookOfKnowledge @ Gmail.com. The process of woodturning involves the use of tools, machinery and materials which could cause injury or be a health hazard unless proper precautions are taken, including the wearing of appropriate protective equipment.
Dial Indicator