Sankyo music movement

The last several Sankyo music movements (18 note) that I have purchased have come with wind-up keys with threads that will not screw completely on to the shaft of the music movement. A simple "cleaning" of the female threads of the key with a "thread tap" would solve the problem, however, I have been unable to determine the thread size. I've asked 3 suppliers and they have no idea what size the threads are.

Is there anyone who has made a key extension and cut the male and female threads for the extension?

Thank You,
Roger

My guess is that they are metric treads. Go to the hardware store and test fit various sized nuts on the exposed shaft or try a screw in the key. Either one will tell you the thread size.

I assumed they were metric also and tried the "test fit" at the hardware store drill for both metric and US/Imperial threads of which none were a match. Checking tap sizes in MSC's catalog, it indicates metric and US/Imperial threads have a couple different thread pitches in addition to what I tried at the hardware store.

It is my hope that someone will have either made an extension for a Sankyo music movement or had another reason to determine the thread size/pitch.

If you are looking for an extension. This company offers various length extensions to fit their music boxes.

Lee,

Thank you for the reply. I'm not looking to purchase an extension. I'd like to determine the thread size of used on the windup keys so I can purchase a thread tap to clean up the threads on wind up keys that I already have.

Roger

Just for grins, I did a google search for "music box key thread" and found that it is shown as an M3.5. There are several drawings of keys and all but one show it as a M3.5, the other one is an M2.3
Attachment 328242Attachment 328243

Do you have a way of accurately measuring the inside diameter? Dial calipers? I can narrow down the possibilities for you with that information.

The shaft on the music movement onto which the wind up key screws is 3.5mm. There are, however, two thread pitch sizes listed in MSC’s “Big Book” for 3.5mm taps:

3.5 x 0.35
3.5 x 0.60


Dimensions for the threaded shaft on the music movement and the female threads on the wind up key are:

Major diameter of the threaded shaft on the music movement is 3.35mm (.133”)
*Minor diameter of the threaded shaft on the music movement is 3.33mm (.131”)
**I.D. dimension of the female threads for the wind up key are 2.85mm (.112”)

*Not sure of the accuracy of this dimension due to whether the lower jaws were able to reach the bottom of the threads
**This dimension may not be accurate as I am not sure how far into the female threads of the wind up key the lower jaws of the caliper were able to reach

Thank you for the replies and assistance!
Roger

Can you see the threads enough and get to them to measure them? You should be able to measure the pitch with a dial or electronic caliper. If you can't get the caliper in close enough and see what is going on you might press a bit of something like modeling clay against the threads and measure the impressions. It should be easy to see the difference between .35 and .60 mm, especially if you measure over several threads.

To measure the diameter in a tight spot if not sure the calipers can reach cleanly I might cut a wedge out of a thin piece of brass (shim stock) so it will fit where needed, slide the brass over the shaft and mark where it stops, then compare that to a known diameter or measure. If in doubt, a local machine shop or tinkerer might do it. Where's a good watchmaker when you need one?

JKJ

Your dimensions are approximately .005inch undersize for a class 2, 3.5mm thread, but that is not unusual on something like this.

For a visual reference I took a picture that you can compare to what you have:
The tap on the left is M3.5 X 0.60mm Pitch
The tap on the right is M3.5 X 0.35mm Pitch

Hope this helps.

Bruce, Lee and John,

Thank You for your replies. I've determined the threads to be 3.5mm x .60 pitch. Thank You again for all your help!

Roger

This question was about the threads on the winding key, but just FYI Sankyo movement bases (and at least one old Reuge movement I own) have threaded holes of M3-.50 and a 10mm long machine screw works best for mounting these movements to 1/4" thick bases (movement base is approx 1/8" thick). You can find these at your local Lowe's Home Improvement and probably other hardware or big-box stores as well.

Do you have a spare shaft with the correct male thread? If so you can file a notch in it and use it as a tap. Google shop made thread tap and you should find several videos including one by Matthias Wandel that give you the idea.