Balance staffs come in two flavors: friction-fit and riveted. The friction-fit design is much better in nearly all respects, so naturally it is uncommon. Such is the fickle quality of human affairs.
Friction Fit Staffs
A friction-fit staff uses the most intuitive design for a balance staff. The balance staff is tapped into the balance wheel, held only by friction. This has many virtues:
- You can insert and remove a staff without destroying it. An adjusting issue can sometimes be cured by a new staff, so the ability to easily pop in a new one and see how it fares is a big plus.
- You can easily remove a staff without risking damage to the balance wheel—an issue, as we’ll see later, with riveted staffs.
- You can slightly modify the depth of the staff in the wheel if needed.
Few vintage watches use friction-fit staffs. Most of them will be Waltham watches, especially their 16 and 12 size pocket watches. Some Hamilton, Illinois, Hampden, and Howard watches use them as well. Friction-fit staffs are fairly common in inexpensive Swiss wristwatches.
We’ll use a 16-size Waltham Model 1899 as an example.
A big blue hub is the hallmark of a friction-fit Waltham. Note how the hole on the arm of the balance wheel has a blue steel hub attached to it. The hub and the wheel should not be separated. The staff goes in and out of the tough hub, thus protecting the more fragile wheel and preventing common maladies, like enlarged or misshapen balance arm holes.
For this model, note the chamfer in the hub. The inside is beveled.
Now have a look at the staff. The thick end holds the hairspring; the narrow end holds the roller.
You can visualize how the staff goes in. The tapered section fits into the beveled hub as the staff is tapped in.
Removing the Broken Staff
To remove the old staff, we break out the ever-trusty staking set and get some stakes and stumps.
We’ll drive out the broken staff from above, from the hairspring end. You can use the same stake used for tapping the roller from the staff, such as the stake shown below.
A spring-loaded staff-removing stake from a K&D remover set, shown on the right, works fine, too.
The wheel must rest in a special stump that supports the hub. Your staking set should have a couple stumps with countersunk holes.
Notice how this hole is beveled. The balance hub rests in the cupped top of the hole. The balance must be supported by the hub, not by the balance arms. If the balance arms rested flush against the stump, you could drive out the hub itself, not the staff, and that would be a disaster.
Here’s an “in action” shot. Notice how the balance arms are elevated above the face of the stump instead of resting on it. The hub is nestled in the cupped hole of the stump, so the hub, not the balance arm, is supported.
Once you’re set up, just gently tap out the staff—easy peasy.
Inserting the New Staff
To insert the new staff, you’ll need some special stakes. Your staking set ought to have a couple stakes like this one:
The staff has a hole to accommodate the staff and a narrow, flat-faced tip.
Why the narrow tip? The stake has to be wide enough to fit over the staff, of course, but not so wide that it overlaps with the hub. The staff sometimes inserts “past flush” with the hub, so the tip of the stake must be narrower than the hole in the hub. Otherwise, the stake would just bang against the hub.
To support the balance wheel, find a regular stump with a hole large enough to accept the hairspring end of the staff without binding. This one works for my staff.
And then set it up in the staking set. Place the wheel on the stump, insert the staff into the hub, and lightly tap the staff into the hub until it is at least flush with the hub.
Notice how the diameter of the stake’s tip is smaller than the staff. This prevents the stake from banging against the hub and allows the staff to go past flush if needed.
Friction-fit staffs are quick and easy. If you want to practice, find a cheap Waltham on eBay, like a 7-jewel 16-size Model 1908. After tapping the staff in and out a few times, you’ll wonder why anyone uses riveted staffs. And then you’ll probably scoop up a bunch of 19 and 21 jewel models with broken staffs.
But riveted staffs are much more common—we’ll tackle those in our next post.