Tid-Bit 17 - 6-Jaw "Bezel" Chucks
Over the years I have fielded quite a few questions about holding gears so that one can work pivots. This is why I wrote the previous Technical Tid-Bit in this series – “Gear Holding Techniques”. But, as I discuss gear holding techniques with students and other clock repair folk the focus usually ends up on holding gears that don’t have much arbor sticking out past the gear hub. An example of such a gear is shown in Figure 1.
Figure 7 – Profiles for 6-Jaw Chuck Jaws
The primary purpose for bezel chucks in my shop is to hold gears so that I can work pivots. As you can see in Figures 6 and 7, 3 of the 4 jaw-profiles are designed to both hold a round work-piece (like a gear) in the center of the chuck – held on 6 sides by the jaws – as well as grip the inside of a work-piece (like a case for a pocket watch or a large ring). While I have used a 6-jaw chuck several times to hold rings of metal from the inside of the ring – most of my work focuses on holding gears so I can work pivots, or, sometimes, hold washers so I can work either the face of the washer or change the diameter of the hole in the center of the washer.
Given my focus on holding gears, I find that the most desirable profile is the bottom profile in Figure 7 – which offers 4 different steps for holding gears. When comparing the bottom profile with the one just above it one can see that the upper profile offers 3 of the 4 steps in the bottom profile, with the last step being replaced by 2 steps for holding rings. Hence it can hold gears, just not as large of gears as the bottom profile.
Likewise, the second profile from the top in Figure 7 offers three steps once again; with the step farthest to the right being very near the tip of the inner end of the jaw (the second jaw from the right in Figure 6 shows this a bit more clearly). This profile does offer the ability to grip the inside of smaller rings than the second profile from the bottom, but does not give as good of a fit for holding gears – in as much there are really only 2 steps that can be used to hold gears.
The top profile in Figure 7 is for a bezel chuck from the late 1800’s – a chuck that was really only intended to work bezels. The steps in the jaws are much shallower – making it pretty difficult to use it to hold gears.
In addition to holding bezels, there were 6-jaw chucks that were made to hold rings or other circular bits with holes in the center. Chucks 2 and 3 in Figure 3 are examples of ring-holding 6-jaw chucks. Figures 8 and 9 show the jaws of these chucks in more detail.
