In restoration work, there is no skill more important for a watchmaker to learn than how to repivot a wheel. Repivoting restores the arbor by installing a new pivot when it is broken or worn to a level that is not repairable. Traditionally, watchmakers would anneal (soften) the hardened steel arbor before drilling. In this lesson, we will avoid tempering the steel. Instead, we’ll use modern drill bits capable of cutting hardened steel and secure the new pivot with a thread-locking adhesive. This method preserves the steel’s hardness and strength.
Nomenclature
Just so we are all on the same page, let’s establish the parts of the wheel. The pinion leaves or just pinion, is the part that interacts with another wheel. The arbor is shaft coming out of the pinion and the pivot comes out of the arbor. The shoulder is where the arbor and pivot make a 90 degree angle. This is a basic configuration but there are many variations of this, depending on what type of wheel it is, so just remember this, the pivot is the part that goes into the hole.
Tools and Materials
- Watchmaker’s Lathe and Collets: To hold the wheel’s arbor securely and centered. Collets of the proper size ensure the arbor runs true and are also required to hold the new rod from which the pivot will be made from.
- Drill Bits for Hardened Steel: Ideally use carbide micro-drills or purpose-made pivot drills.
I like to buy from M.A. Ford, but there are other capable suppliers as well.
- Piano Wire: A piece of hardened steel piano or music wire of the appropriate diameter make fantastic pivots. Don’t be fooled by recommendations of using blue steel unless it is of the vintage variety or you are making it yourself. Modern blue steel most often comes from India and is not the same quality as the blue steel manufactured many years ago.
- Thread Locker (Retaining Compound): High-strength adhesive such as Loctite 638 is used to secure the new pivot in the arbor. This will lock the pivot in place without peening or soldering. Later on as you become more proficient you can shape pivots to friction fit into the arbor but I would not start with this method.
- Center Drill or Graver: Center Drill bits are very useful for getting a hole started without it wandering. A sharp centering tool to start the drill hole exactly at the arbor’s center. This can also be done with a sharp graver but it requires a little more feel to know that it is correct.
- Cutting Oil: A tiny drop of oil can lubricate the drill and help prevent overheating or binding in the cut.
- Pivot File, Stones, lapping paper and pin polisher: For trimming the new pivot to final size and polishing it to a smooth finish.
- Measuring: You need agood quality micrometer for measuring.
Step-by-Step Repivoting Process
- Mounting the Wheel: When repivoting, you need to make sure the wheel is spinning true. The simplest way to do this is with a collet. If you can get a good grip on the arbor and the collet is close to the wheel and the arbor to be drilled is not too long, this will work.
If you have a really long arbor to drill, sometimes the wheel brass wheel can be removed and the arbor inserted inside the collet with only the end of the arbor sticking out.
- A better method is to use a step chuck.
If you have a set up step chucks you need to be careful not to overtighten the chuck or you can damage the brass teeth of the wheel. If you have them, use them as they can solve a lot of problems with holding the wheel especially when there is a pinion on the end.
Another method to hold the wheel which is less expensive method and will not damage the teeth is a box chuck.
Box chucks can be made out of boxwood or hardwood but I prefer to just use MDF. It’s cheap and machines well. I use a large hole saw to cut a plug slightly larger than my faceplate. Now you can screw on the plug to the faceplate and clean up/true the outside edge. Measure your wheel and starting in the plug center, cut a recess about .05 mm less than the wheel width and about 2-3 deeper than the wheel thickness. This will hold the wheel in by friction.
- Determine Pivot Size: If there is pivot left on the arbor, we need to measure it to determine its finished size. If not, we need to measure the pivot hole with a pin gauge and subtract .02 mm. If you don’t have a pin gauge that’s the proper size, see if the other pivot sits in the jewel hole you need to measure and follows the 5% rule meaning that the Arbor tilts about 5 degrees.
- Face off Arbor: With the wheel installed and the wheel spinning true, we need to face off the end of the arbor removing all traces of the old pivot. You can use a graver or gently file it so the shoulder is flat . It’s not important what you use. It can be a graver, file, stone or diamond lapping paper on a plate or even a pin polisher. Once you get it flat, switch to a jasper stone, sapphire file or diamond lapping paper to give the end a polished finish. It’s important to remember not to remove material from the shoulder. If you do, you will change the amount of end shake. My experience is that polishing the shoulder does not affect end shake at all.
- Spot the Center: With the arbor spinning slowly in the lathe, use a pointed tool (a graver or small center drill) to locate the exact center of the broken pivot end. If you are going to use a graver, the point needs to be very sharp.
Gently make a starter dimple for the drill bit. This step is critical – an off-center hole will produce a wobbling pivot. Take your time to get the centering perfect.
- Drill into the Hardened Arbor: Install a carbide drill bit of appropriate size in the tailstock or a drill holder. (Choose a bit about the diameter of the intended pivot, or slightly larger. For example, if using a 0.15 mm piano wire, drill about 0.17–0.18 mm to allow for adhesive.) Advance the drill straight into the arbor at the center mark. Use low speed and very light pressure, “pecking” gradually to avoid overheating. Hardened steel requires patience – carbide pivot drills can cut it, but too much force will snap the tiny drill. Every millimeter or so of depth, back out to clear chips and add a drop of oil for lubrication. Aim to drill a depth of about the same as the pivots length (this gives sufficient holding length). Keep the drill perpendicular and centered throughout.
- Clean and Inspect the Hole: Once the hole is drilled to the proper depth, stop the lathe and carefully withdraw the drill. Use pith wood or compressed air to clean out any metal chips from the hole. Inspect the hole – it should be straight and centered. If the drill wandered or the hole is slightly off-center, you may need to re-center and correct it before inserting the new pivot. (If the hole is a tad small, you can lightly broach it to size, but avoid enlarging it too much – a snug fit is best.)
- Prepare the New Pivot: Take your hardened pivot wire and test its fit in the hole. It likely will not yet go in. Use a fine file or the lathe to turn down the end of the pivot wire just until it can start into the hole. Aim for a very slight taper on the tip. The goal is a tight fit: the wire should enter a short way and stop. This ensures maximum contact for the adhesive. Do not force it all the way yet. If you have a micrometer or pivot gauge, the pivot wire should be just a few hundredths of a millimeter larger than the drilled hole, tapering to fit.
- Secure the Pivot with Thread Locker: Apply a tiny drop of high-strength thread locker (e.g. Loctite 638) to the pivot wire or into the hole. Insert the new pivot wire into the arbor’s hole, pushing it in until it bottoms out. You should feel some resistance (from the snug fit). Make sure the pivot wire is seated straight and fully inserted – its protruding portion should be roughly the length of the original pivot (you will trim it later). The adhesive will fill any slight gap and lock the new pivot in place as it cures. Unlike traditional press-fitting (where a pivot might be literally driven in by force), the adhesive method avoids stress on the arbor. Wick away any excess adhesive from the arbor and wheel immediately (a toothpick or pegwood works well) so it doesn’t creep into moving areas. Let the assembly cure undisturbed. Loctite 638 fully hardens in about 24 hours; you can accelerate curing by warming the part gently. Following the adhesive manufacturer’s instructions, wait until the bond is hardened before proceeding.
- Trim the Excess and Rough Shape the Pivot: Once the adhesive is cured, mount the arbor back in the lathe (if it was removed). If a long length of pivot wire is sticking out, carefully cut or file it down while spinning in the lathe to just a few tenths of a millimeter thicker than the final pivot diameter. Use a sharp graver or a fine file. The new pivot should now be solidly attached, so you can treat it like part of the arbor. Ensure your cuts are gentle to not loosen the adhesive.
- True and Size the New Pivot: With the arbor spinning, turn the new pivot down to the exact diameter required. Use a fine file or a graver for cutting, and take very light cuts. Because you are cutting in the lathe with the arbor rotating, this will naturally make the new pivot perfectly concentric with the arbor’s axis (even if the drilled hole was microscopically off, this step corrects it). Stop frequently to measure the pivot’s diameter (using a pivot gauge or micrometer) and test fit the pivot in its jewel/bushing. Approach the final size gradually, especially for very thin pivots, to avoid undershooting the diameter.
- Polish and Finish the Pivot: Finally, polish the pivot to a mirror finish. A common method is to charge a piece of hardwood (like a boxwood slip) or pegwood with fine abrasive (e.g. Diamantine polishing powder) and press it against the pivot while the lathe runs at high speed. Alternatively, use a hardened burnisher tool: apply it with light pressure along the pivot to smooth and harden the surface. Proper polishing removes any fine file marks and slightly work-hardens the surface, yielding a robust, low-friction pivot. The finished pivot should be bright and smooth, perfectly cylindrical, and the correct length. (If you examine it under magnification, it should appear straight, with no wobble when the arbor spins.)
- Cleanup: Remove any residual adhesive squeeze-out or oil. Reassemble the wheel into the movement and lubricate the new pivot normally. Monitor the wheel’s rotation – it should run true. The repivoted arbor, if done correctly, will function like new.
By following this procedure, you can successfully repivot a watch wheel using your lathe and collets without softening the steel. The combination of a precisely drilled hole, a hardened piano wire, and a quality thread locker yields a solid repair. Take your time with each step – with practice, repivoting becomes an invaluable skill for restoring timepieces to good working order.