I inquired of the jacobs chuck company regarding rather inconsistant runout
specifications for their chucks, here is the answer
We apologize this confusion. The runout specs of both chucks
(superchucks and professional keyed chucks) are measured at 1.5" from
the nose at half capacity test bar.
1. Superchucks T.I.R. spec is MAX. 0.003" at half capacity (1.5" from
2. Pro keyed Chucks T.I.R. spec is MAX. 0.004" at half capacity (1.5"
from the nose).
We are updating our PDF file accordingly to avoid this kind of confusion
Again, thank you for your feedback.
Jacobs Chuck Manufacturing Company--A Danaher Company
as an aside, if you have one of the later jacobs ball bearing chucks, be
very careful to never pound on the jaws - it causes brinellling of the
bearing and destroys the chuck accuracy - I just looked at one that must
have been dropped on the jaws - looked perfect from outside, but there are
nice ball sized dents in the race
14 years ago