Fixing a Levin Toolrest

The detent screw on one of our Levin lathes was stripped out rendering the part useless.  For my school volunteer hours this quarter I made a new post and installed it into the slide attachment.

The primary difficulty here was turning down the chunk of steel on a lathe using a 3-jaw chuck which didn't give me the best grip.  Unfortunately we don't have a lathe that can use a regular collet to accept these larger diameters.  Despite the cutter digging in and dislodging the workpiece on a couple of occasions I was able to turn the lower diameter down to where I could use a normal collet to hold the piece and finish forming the top.

To cut out the core I first used a end mill followed by some reamers on the Bridgeport milling machine in the basement. Finally, the detent hole and threads were formed using a drillbit and a simple tap.

The finished post, pressed into position

Overhaul/SAWTA 3 Practice

During the last couple of weeks I have been busy practicing overhauling and troubleshooting automatic movements.  Most commonly we've been working on the ETA 2824 as that's most likely the watch we'll receive for our SAWTA 3 examinations.

During the examination it is our task to troubleshoot issues with the watch which have been introduced by the examiners.  During dis-assembly you identify and fix the problems, then all that remains is to clean the watch and recase it with a high level of accuracy and cleanliness as both will be factors in the grading.

Besides the overhaul there is a written portion of the exam and a polishing exercise, both of which are proceeding nicely for.

I have taken some pictures of a practice overhaul and will offer a brief explanation of some of the steps below. 

The caseback has been removed

The rotor and stem have been removed, the movement can now come out of the case

Removing the hands while protecting the dial and hands with some plastic

The dial-side with the dial and date ring removed, nothing to repair on this side!

The hairspring is not centered, the coil spacing near 11oclock are wide and near 5 they are narrow, which will need to be corrected by bending the spring

Another shot, the dogleg in the spring near 12 o clock seems is where we will perform the correction

The entry pallet stone is not level in the fork, it has dipped out of its holder and needs to be reset so it can engage the escape wheel

The tilted stone

Using an electric heater and this expensive gauge it is easy to move the stones in or out of the pallet fork micro-metric amounts for precise depthing correction which is essential for a well-running watch

The endshake (up and down movement) of my pallet fork was too small, so here I am pressing the jewel back into its bridge.  Once the jewel was flush with the bridge the endshake was back within tolerance

Here I am adjusting the barrel endshake, which was also much too small.  Too little endshake reduces freedom of the wheels and introduces extra friction into the mechanism.

Here I have corrected the centerdness of the hairspring, looks slightly off here due to the balance being loose, once installed it is quite good.  Once the watch was reassembled the instantaneous rate and running characteristics of this movement were within 100% tolerance for this movement