My clock shop was commissioned to overhaul an Ingraham black mantel count-wheel movement. During the estimate it was noted that the turn-back assembly was broken and a previous repairer had tried to solder the assembly,
Figure 1. Seldom will a clock repairer see this assembly broken, but from time to time they come in the shop in need of repair.
Ingraham used two styles of turn-back assemblies during their production. One style used two coiled springs and a pin to operate the turn-back, Figure 2. The style of the movement that was brought in for repair uses a flat, brass spring for the turn-back, Figure 3.
After the distance from the end of the rear pivot to the back of the turn-back assembly was measured, it was removed from the center shaft, Figure 4. The broken spring was pried loose with a razor blade and removed along with the swivel piece that holds the lifter pin. The collar of the assembly was placed back on the center shaft and supported in the lathe, Figure 5. The staking shoulder was lightly tapped down and lightly touched up with a needle file, Figure 6.
The original spring was .011″ in thickness. A piece of brass stock was rolled in the rolling mill to .011″. The brass is hardened during the rolling process to make it springy. The dimensions were laid out on the brass strip using a prick punch and dividers. A hole was punched in the brass strip using a handheld power punch with a .187″ punch and die. A cutting broach was used to open the hole to .202″, the size of the hole in the original spring. The brass piece was parted from the strip and trimmed.
To support the brass blank spring, a 6/32 nut was placed in the lathe and a shoulder was machined .200″ in diameter and .009″ thick, Figure 7. The spring blank was placed on the shouldered nut and backed up by another nut tightly, using 6/32 all thread as the support shaft. This assembly was placed in the lathe. A .070″ dental burr was placed in a high-speed, air-operated pencil grinder mounted in the cross slide to do the cutting. The lathe was unplugged and the headstock spindle was rotated by hand back and forth to form the outer arc, Figure 8. The cross slide was reset to form the smaller circle. Cutting the smaller circle, the .070″ burr formed the slotted part of the spring, Figure 9. After the spring was removed from its mounting, the end of the upper part of the spring was ground on an angle to match the swivel piece.
The spring was finished, placed on its assembly, and staked on lightly—just enough to keep the spring from moving on the collar—and the assembly was mounted back on the center shaft, Figure 10.
The challenge ahead was to adjust the drop-off point of the lifter pin on the turn-back assembly in relationship to the J-hook when the minute hand is at the 12:00 position. This has to be exact, because the J-hook is a stamped piece and can’t be adjusted, unlike other J-hooks that are wire form and can be adjusted for drop off.
The center shaft, cannon wheel, and J-hook were placed between the plates with no other gears. The minute hand was placed on the center shaft with its nut. While holding the minute hand at the 12:00 position, I moved the turn-back brass spring forward until the J-hook dropped off the lifter pin. Several times I revolved the minute hand around to make sure that the drop off was at the 12:00 position. The center shaft was removed from the plates, placed in the drill-press vice to hold the turn-back assembly collar against the vice, and the final staking was completed to retain the spring from moving, Figure 11.
A more common fault with the Ingraham movements is the pinion on the center shaft that turns the motion works will crack. When this happens the clock won’t run at all, runs slow, or only for a few hours and then it stops, Figure 12. A center-shaft assembly that has come apart due to a cracked pinion is shown in Figure 13.
Several years ago I purchased a meter of metric brass pinion wire that has the exact tooth profile that was used in the Ingraham movements. A production run of 50 was done. Over the years I have replaced several of these cracked pinions. This pinion wire can be purchased from Stock Drive Products. The metric brass pinion wire is sold in meter lengths only. Stock number: A1B-9MY081010. Phone number: 516-328-3300.
By Paul Corn