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July 25, 2014 at 5:17 pm #58426
Guys:
I ran a copy of the part from the Swiggart catalog and used that as a template from which to copy the outline of the part. I have some spring steel stock, so I think I can use that if brass if too soft. I’ve ordered the detent screw so MAYBE I can get all of this behind me so we can get back to the balance assembly issues. I apologize for getting so far off track on this. I just can’t seem to get the minutia behind me. At some point, I know that I will reach the point where I’ve seen most of the issues that a good horologist will face. I just hope I live that long.
Thanks everyone…
TomJuly 27, 2014 at 7:05 am #58427No worries Tom,
This stuff happens to all of us. I have watches in containers on my bench awaiting parts which I never knew were needed until digging further into the movement. Parts eventually either show up or if I wake up in a creative mood I may finally make one. Either case, they have to wait.
By the way, you could still make those adjustments without that part but that part might prove to be a good and enjoyable learning project. Sounds like you need to have a little fun at this point anyway .Keep us posted,
BobAugust 3, 2014 at 10:46 am #58428Bob et al:
I finally got the part built so now I can move back to the other thread and post the pictures of the interface between the pallet fork stones and the escape wheel teeth. Even though I built a temporary part out of brass, I still went through three drill bits and two taps before I final got it finished. The drill bits were HSS, and even though I prick punched the hole location and used my centering scope to locate the hole these bits are so small that it’s hard to get the drill to even penetrate brass without breaking. It might be that my drill mill wobbles a little too much for something that small.
Here’s the dimensions for the pilot hole:
0.03″ dia. thread
Using 75% of the hole… 0.03 * 0.75 = 0.0225″
Thus 0.023″ = 0.57mm pilot drill.Below are a few photos…
[attachment=1:18zmxa53]IMG_0373.JPG[/attachment:18zmxa53]
[attachment=0:18zmxa53]IMG_0376.JPG[/attachment:18zmxa53]I took my time and used cutting fluid for brass, so it really should not have snapped. The micro taps were carbon steel crap from India.
I have finals next week, but I plan on picking this up afterwards.
Later,
TomAugust 3, 2014 at 11:03 am #58429Tom,
The corresponding hole in your drill plate is the hole diameter for the tap. If you made your hole 75% of that it would explain the tap breakage. When the tap is screwed into the hole it cuts further into the sides. Reducing this hole size will crowd the tap.
davidAugust 3, 2014 at 11:33 am #58430David:
The charts I have use a smaller tap hole than the threads allowing for the tap to cut the threads to the final size. I’ve always thought that as a general rule, the tap drill is some percentage smaller than the final thread size. I am obviously confused here.
Ok… so what’s the rule for this?
Thanks,
TomAugust 3, 2014 at 12:59 pm #58431David:
I forgot to add that I screwed the detent screw into the plate to find the correct tap size, then mic’d the threads on the detent screw and used that as my number to calculate the drill size. If I understand you correctly, what I should have done is to use the drill size that corresponds to the number in the plate in millimeters. Is that correct? How does that correspond to using a chart for drilling holes and then tapping them for bigger thread sizes?
Thanks,
TomAugust 3, 2014 at 3:50 pm #58432Tom,
I think I understand what you did. The hole in the screw plate is already the proper size so basically all you have to do is match up a drill bit to the hole in the screw plate. The only tap drill size chart I have seen is in Practical Benchwork For Horologists by Louis and Sam Levin. They post a rule to take 75% of the double depth of thread and subtract it from the of the thread diameter of the tap. The problem is a watch screw thread is difficult or impossible to measure in many cases so how are you going to know what the depth of thread is. The good news is the hole was already drilled into the drill plate and that can be measured or gauge with a drill bit. Just make sure the drill bit is slightly larger than the hole, not smaller. Tap breakage is not always caused by the hole being too small but that is usually the reason. Going up a little on the drill bit size should not harm anything. You can always make a test piece first to see if the thread is too sloppy.
davidAugust 4, 2014 at 1:04 pm #58433David:
That makes sense.
Thanks!
TomAugust 9, 2014 at 10:00 am #58434All:
Well… I finally got time to get the part installed and it appears to be working just fine. Now I can reassemble the train and post the photos that Bob requested. Perhaps tomorrow.
[attachment=0:qkzaxlkg]partinplace.JPG[/attachment:qkzaxlkg]
Later,
TomAugust 9, 2014 at 10:45 am #58435Well done Tom, you are moving this along nicely
Paul.August 9, 2014 at 11:28 am #58436Cool Tom!
No hurry on those pics as I’m gonna be under a big time crunch starting this evening for a few days. Probably won’t have much time for posting other than quick comments and daily forum backup.Bob
August 9, 2014 at 2:59 pm #58437Tom,
I am on page 21 & 22 of my Swiggart catalog looking at the parts for an ELGIN 16 size (571,2,3,4, 5) movement. I found part number 6196 which is called a . Is that the same part? The diagrams in the book look like one end engages a clutch mechanism.
davidAugust 9, 2014 at 6:21 pm #58438David:
That’s the part. It actually holds the lever in place and also acts as a stop for the lever spring mechanism. Since it was missing I had to do a little research but found a good picture of it on one of Bunn Special’s videos. Unfortunately, he doesn’t ever seem to disassemble the winding mechanisms in his videos so I had to just guess at what it was supposed to do and how it was supposed to go together. Thankfully, I was able to tinker it together with spit and a dream.
Thanks!
TomAugust 13, 2014 at 7:45 am #58439Did you know that you can calculate the tap drill size without the table? Here’s how:
-Subtract 1/Pitch (threads per inch) from the major diameter. That’s the tap drill size!
Example: 1/4-20: 1/4″ = 0.250. 1/20= 0.050. 0.250-0.050=0.200. You need a drill bit that is about .200″ diameter. (In this case, either a #7 or a 13/64”, which is 0.203” will work fine.)
Another example: 3/8-16: 3/8-1/16= 5/16.The above information came from this site – http://www.spaco.org/taptips.htm
Just thought I would throw something in as you never got an answer to your question.
Paul.August 13, 2014 at 9:53 am #58440Paul:
Thanks!
Tom
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