Timex 61 instruction manual Major Project The Escape Wheel Nut

Split, Round 6-40 Die

Pitch Finder

That ol’ Hand Nut Again

A Bushing

Hand Reamer vs.

Cutting Broach

Major Project – The Escape Wheel “Nut”

After the pivot polishing process was complete for all eight pivots, I progressed to “bushing” the pivot holes. A bushing is a small cylinder of brass with a hole in the middle designed to replace a worn hole. To replace a

worn hole, one uses a hand reamer (a

small handheld tool that when twisted, can cut a hole quickly to an exact size) to ream the original hole into a larger one while keeping it centered and round

to accommodate the bushing. The bushing is tapped into the newly expanded hole using a punch and a hammer, which secures it, assuming the hole was reamed to a size slightly smaller than the diameter of the

bushing. Now, with the bushing secured in the original pivot hole, the replacement hole in the bushing should be centered where the original hole was. With

a cutting broach (a tool similar to the reamer, yet provides more control and a slower cutting rate) the hole can be resized to the pivot, which creates a round, true, and centered hole where the old, worn hole was. With this process in mind, I checked the gears by feeling their tightness when placed in their pivot holes. If the gears were too loose and “flopped” around too much, I put them back in the plate to signify that those holes were worn or too loose, and needed

bushing. When I came around to the escape wheel, however, I found that it became impossible to continue with out first repairing that pseudo hand nut that acts as the pivot hole for the escape wheel. The threads were bad, and the nut couldn’t be screwed on tightly or far enough to determine how loose the escape wheel pivot actually was, so it had to be fixed immediately. The first step to repairing the threads was to discover what the pitch, or number of threads per inch, was for that particular screw and the diameter of the threads. With this in mind, we consulted the Machinery’s

Handbook for the proper tap and die set

to use in order to create the new threads. We determined the diameter to be nearly the equivalent of a size 6 die, with a pitch of 40 threads per inch. This meant that the optimum set to use was the 6-40 die, but the diameter of the screw was still slightly too small for the hole it screwed into. This forced us to use a split round die, which allowed us to create an oversized 6-40. After discovering the correct die and

the diameter of the new screw, I chose a piece of round brass stock and filed it down to the correct diameter. Then, I took the oversized 6-40 die and essentially screwed the piece of brass into the die. When it was unscrewed again, the die had cut threads into the brass. Now, with the new threads on the end of the brass, I set about cutting them off of the rod so I could use them in the nut. I cut the threads off successfully, so we were left with the old nut and new threads. First, I had to cut off the old threads from the nut. Then, we drilled a hole as though we were bushing the nut itself. Having done this, I

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