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| Gear for a clock |
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| jcs0001:
I started this in another thread as I needed to know what brass alloy to use to make a clock gear. Since the preamble to that isn't too long I'll quote it as a starting point for this small project: Making a gear for an older clock I recently was involved in moving my mother's house full of contents as she has downsized and moved to a senior's home. Included in the belongings were three clocks - a grandmother clock, a square "mantle" clock and a cuckoo clock. I had heard indirectly that a nearby neighbour collected and repaired clocks so introduced myself and asked him about the clocks. He helped pack up the grandmother clock as it was being moved to another relative and he repaired the other two for me. He showed me around his collection and I was amazed. He has clocks everywhere and they range from grandfather clocks on down to very small clocks - many different styles - lots of cuckoo clocks, dome clocks, wooden cased clocks from plain to extremely fancy. He mentioned that he has many packaged up as there is insufficient room in his residence to display them. His collection left me in awe. He refused payment for repairing the two clocks. I asked if he needed any clock parts made as there was a possibility that with my two metal lathes and small mill (and limited amount of skill in using them) I might be able to help him out. I have made one brass gear in the past successfully and figure I can make more with time and care. He has just recently provided me with the carcase of a clock (not sure if this is the correct word but it's the "guts"). It is missing a gear. The clock is a Junghans Weurtettberg two 2 jewels W200. I need to make measurements of the existing gear and the distance between it's centre and the shaft on which the missing gear fits. I believe I can manage that as I have a number of accurate measuring devices. Care will be taken as I don't wish to damage either of the shafts or the existing gear. With those measurements I believe I can determine the tooth count on the missing gear and then create a new one. I may have to make a new dividing wheel depending upon the tooth count but that shouldn't be too much of a problem. Several people responded in the other thread suggesting that I source cz120 brass for the gear so I will be doing that. I would post some photos and have in the past using photobucket but it is giving me great grief with firefox and with two other browsers I have tried. Will figure this out and post some soon. John. |
| jcs0001:
First a photo of the clock as I received it a couple of days ago. I haven't seen it in the case. The stainless steel bar is pointing to the pinion (?) which is missing a gear. The gear that it meshes with is up a bit and to it's immediate right. The other side of the mechanism. And another shot of the existing gear and bare pinion. I haven't yet measured anything - that is my next step. John. |
| jcs0001:
Starting to make some measurements: I had to lift part of the mechanism to remove the existing gear. Three decent sized screws allowed me to lift it up and release the gear once the set screw was loosened. The screwdriver points to one of three screws. What appears to be damage to the screwhead is a bit of dirt. The existing gear. My fancy micrometer holder along with cheap inside measurement guage (spring loaded). I used my digital calipers to get an idea of the distance between the inside of the two pinions and then set my micrometer a bit shy of that (5 thou or so). Used the micrometer to set the inside measure guage and tested with the guage to see if it just fit between the pinions (if this isn't the correct term someone please advise). A few trys with the micrometer and guage resulted in the guage fitting very nicely between the pinions. The micrometer was used to measure the guage and it came out within a thou of the digital caliper reading (must have been an accident). Measuring the outside diameter of the gear is fairly trivial and measuring the depth of the gear teeth shouldn't be difficult either. I will draw up a sketch of the measurements as my next step is to figure out the number of teeth for the new gear. John. |
| sparky961:
Hints for using a telescoping gauge: |
| jcs0001:
Sparky: Interesting video - it gives me confidence that I can get accurate measurements from the inside even though my telescoping guage is from offshore. In this case I was using it in the "opposite" manner - using the micrometer to set it and then checking the gap between the pinions. The reason for this is that I was concerned that the spring in the guage would be strong enough to move the pins apart - they are supported on one end only - and thus give me a high reading. The micrometer gave me the ability to set the guage in very small increments. More to come. John. |
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