The Talking Machine Forum — For All Antique Phonographs & Recordings

Good Morning-

I searched the Forum for the answer to my question but to no avail. I hope the answer to this question is not glaringly apparent but I have not been able to figure it out. I am looking for the screw size for the set screw on an Edison Standard mandrel dual gear with a 2/4 minute attachment. I had a need for one years ago and got around it by finding and buying another gear with the screw in it. This time around I would just like to buy the set screw. I am not as adept as many of you out there that can determine smaller screw sizes and I don't have the ability or tools to cut off a screw and alter it into a set screw-although I wish I did. I also can't find the correct size at my local and very complete hardware. (MAN those things are tiny and hard to handle!). Anyway, any help with the size would be greatly appreciated. Thank you in advance.

Try an auto parts store.
Bring the gear with you and will probably an allen key head.

I don't know anything about Edison machines, but I do know a bit about screw threads and sizes. The modern standards for UNF and UNC were not codified until the 1920's as I recall. Before that, manufacturers were free to produce whatever size and form of threads they chose. So, the threads in that gear may or may not be compatible with any contemporary standard size.

You may have to drill out the threads oversized and re-tap for a larger, standard setscrew.

Dale H

52,

The set screw thread you are seeking is a standard 5-40, the length is 3/32”. Locating modern set screws with a slotted head is problematic, typically they have a hexagonal opening for an Allen key. However, in this application that will not be a problem unless you want historical accuracy. The other option is to use a section of 5-40 rod or a screw and cut your own slot. The 5-40 set screw is readily available from McMaster Carr (in packs of 25) or the threaded rod or screw option.

Ever hear the old adage that “One measurement is worth a thousand expert arm-chair opinions”?
I measured the set screw in an Edison Standard model B in the (to be repaired) collection. Here are the results. I double checked the thread pitch with the pictured 5-40 x1/2” screw. I hope this helps.

Mark

Wow, Mark. That might be the most thorough answer possible!

Jim Nichol

Good Morning-

To Jeff, Dale, Mark, and Jim-thanks so much for taking the time to reply to my question. I totally agree with Jim-that was probably one of the most thorough replies I have ever received to a question and I greatly appreciate the time and effort spent to send it. It even sites a source which will save me time trying to find some. As to keeping things authentic-I strive to do that on all of my machines but if I have to make an exception a set screw would be the easiest to tolerate.

Once again, thanks to all and good luck collecting!

I have been fixing Edison machines for too many decades in addition to other obsolete machines and electronic apparatus. My hobby includes looking for old tools and components to fix obsolete machines.

I found 5-40 taps and dies fairly plentiful about 30 years ago. You will need to rummage through collections of old taps,and dies to find them. I have kept and used a couple of 5-40 dies and a few 5-40 taps over the years to fix threaded holes in bedplates and to make the little grub screws.

I just did a search on eBay and low,and behold I see that the taps and dies are available. This listing has no relation to me but will supply you the tool to make a missing screw.

Looking further on eBay, I see that you can even buy 5-40 screws!