Tuesday, April 24, 2018

Beck TD, Part 19: Today's Lesson, Learned by Doing

Today I learned that a sloppy M10-1.50 metric nut will also thread on a 3/8-16 UNC (American) bolt! I was trying to marry this turn signal unit:


to a piece of 3/8" diameter polished pipe I had lying around. The light was originally designed for a Harley, and is readily available on the web because it's such a popular modification for those bikes. And cheap! I got a set of two for less than $12 shipped, from Amazon Prime.


I spun the lock nut off the lamp, and it tested 3/8-16 on my set of thread testers. Here's a photo of that useful tool - I use it all the time to determine what thread I'm working with. Unfortunately, I don't have one to match Whitworth BSF threads like those on Beck TD.


 I then made this on the lathe, turning one end to fit into the pipe, and threading 3/8-16 on the big end:


The stud on the light wouldn't thread in! I eventually tried the metric thread tester, and that's when I found out the factoid at the beginning of the post. Fortunately, I had picked up a surplus M10-1.50 tap at Cabin Fever this year, so I corrected the threads. Since 10 millimeters is slightly bigger than 3/8 inch (0.394" vs. 0.375"), it re-tapped just fine. Then I could fit everything together:


Here's the proof of concept. Not sure I'm going to use this exact setup, but I'll use something similar to add separate rear indicators and a CHMSL (Center High Mounted Stop Light) to Beck TD:


The eagle-eyed will notice that Beck TD's gas tank is not there. I removed it to dress up some surface rust and replace the low-fuel sensor. The paint work using POR-15 is done, but I can't fit the indicators until the tank is back in place, and I can't fit the tank until I receive the sensor, which is currently back ordered. The Domino Effect...

Continue on to Part 20...

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