Threading
Hello, Kinya!
Excellent work on the newest Harp Tech Study videos! I've never seen anything like that vise technique.
My questions are in regards to the threading aspect of customizing:
When choosing a tap, what do you look for?
My best guess is that one should use a taper chamfer along with an H1 thread limit; although, I am uneducated on the "class of fit" aspect of taps. Would an 8$ tap from MSC suffice compared to a 50$ tap from J.I. Morris? My goal is to have the tightest fit possible.
I've read on previous posts here, and on Harmonica Sessions, that you prefer 0-80 size screws for the reed plate. Is there a benefit to using this size as opposed to 1-72 or 2-56? My guess is that with 0-80, there is the potential to gain an extra thread when tapping the bottom reed plate. Is this better than having less, larger threads? Or is your preference for 0-80 purely for aesthetics?
Finally: When tapping, do you drill a hole completely through the harmonica (both reed plates and comb) and then tap it all at once, drilling the clearance hole after? Or do you tap only the bottom reed plate once it has been removed? It just seems easier to me to use the first method under the belief that it helps get the threads as straight as possible.
Thank you for your time.
Hello Mr.Slacks
It's good to hear from you.
Q: When choosing a tap, what do you look for?
A: In the beginning, I would only purchase high quality taps. After breaking numerous $25 taps, however, I decided it was time to try the $5.50 taps available from Micro-Mark. That was many years ago, since then I have never had a harmonica that did not bolt together properly because of the economy grade taps. So for my harmonica work, good value is what I look for in selecting a tap for my workbench.
Q: You prefer 0-80 size screws for the reed plate? Is there a benefit to using this size as opposed to 1-72 or 2-56? My guess is that with 0-80, there is the potential to gain an extra thread when tapping the bottom reed plate. Is this better than having less, larger threads? Or is your preference for 0-80 purely for aesthetics?
A: All of the above actually. Originally, my goal was match the pilot holes left behind by the nails of the Marine Band 1896. The 0-80 size is very durable, unobtrusive and versatile. In addition to holding reed plates together, reed replacements, I also use the 0-80 bolts to secure the Marine Band cover plates. This works well when when you want to replicate the look of the original nail heads (which are stamped to look like screws!). I have also used 2-56 with good success.
Q: When tapping, do you drill a hole completely through the harmonica (both reed plates and comb) and then tap it all at once, drilling the clearance hole after? Or do you tap only the bottom reed plate once it has been removed? It just seems easier to me to use the first method under the belief that it helps get the threads as straight as possible.
A1: Yes. Drilling completely through both reed plates with the pilot drill is a good technique. Followed by enlarging those pilot holes on the blow reeds to create your "clearance" holes, then tapping the draw reed plate.
Tip: When I build a MB1896 harmonica, I use the nail holes on the draw reeds as my main guide holes. By the way, the three holes across the back of the slots are the exact three that Hohner uses for all their new Marine Band spin off harmonicas (2005 Deluxe, Crossover, Thunderbird).
Good stuff!
Your Harpsmith,
Kinya