Conn pivot screw thread size

[F4UCorsair]

I've run a search, but I'm directed off site, so here goes.

I'm restoring a 1926 Conn C Melody horn, and need to run a tap through one of the posts that takes a pivot screw.

Is anybody able to tell what the thread size is? I don't have the means to measure it other than the diameter, and that's 2.8 mm, just under 1/8". I'm led to believe it's a 4-40, but not sure.

Thanks for any assistance anybody is able to render.

 

[kevgermany]

Hi, wecome. If you don't get an answer here, try asking on the music instrument technician yahoo group. But there are a couple of members and repairers here, so you may be lucky.

 

[F4UCorsair]

Thanks for the welcome kevgermany. I've actually been a member for some time, but haven't posted previously.

Hopefully someone will be able to help here, but if not, thanks for the yahoo tip.

 

[F4UCorsair]

Deleted, double post

 

[Dobson]

Na then, i might be useful here if no where else. You could go to a local engineering shop and chat up the owner a bit, its my experience that anyone doing something strange (rebuilding a sax qualifies believe me) gets there attention immediately and they fall over themselves cos they recognize an inveterate engineering fiddler just like themselves. He or she maybe (but don't get exited yet) will have a set of measuring tools for just this job. Alternetively get yourself down to the nearest "fastenings" (nuts n bolts to you, son) shop and ask them. They also will have tools and loads of tiny bolt and you can test the thread (note more mature folk are more tolerant when you are messing them around, yup this sounds bad but you need help youngsters arnt so helpful. What you could do if dont get anywhere finding a bolt/tap to suit just buy a bolt slightly bigger drill the post n retap it.If you dont come right pm me and we will talk. Happy fiddleing

 

[jbtsax]

Good guess! The pivot screws are in fact 4-40. I have a 1924 Conn New Wonder Series I tenor in line for an overhaul that I was able to measure a screw from that should be the same. I have done several vintage Conn restorations to date and would be happy to help if you have any other questions.

 

[F4UCorsair]

Thanks jbt and Dobson. I may just take up that offer Dobson. I've tried to find a 4-40 tap locally, and the hardware guy said he could get one made up, but I don't want to mortgage the house to pay for it. I saw them for $2.50 on a repair wholesaler's site in the US, but he doesn't sell to the public. I'll keep at it and check the engineering workshop angle.

 

[kevgermany]

Try ferrees tools: http://www.ferreestools.com/

 

[h4yn0nnym0u5e]

Thanks jbt and Dobson. I may just take up that offer Dobson. I've tried to find a 4-40 tap locally, and the hardware guy said he could get one made up, but I don't want to mortgage the house to pay for it. I saw them for $2.50 on a repair wholesaler's site in the US, but he doesn't sell to the public. I'll keep at it and check the engineering workshop angle.

Is this from RS any good?

Cheers

Jonathan

 

[clarnibass]

It's worth getting thread measuring tools. They are not terribly expensive if I remember.

I know someone already found the thread size for you but here is a method I found that is possible to "measure" thread sizes without measuring tools. What you do need is a camera. Not a fancy one, but it should have a Macro mode. I have an old P&S camera from about ten years and it can do it so really any half decent basic camera can do it. Put the camera on Macro mode and take the best photo you can (sharp, in focus, etc.) from the closest distance you can. View the screw on screen and it is pretty big.

then measure the diameter of the screw (thread area). Then measure that same diameter on the screen. Consider the proportion of the real size to the photo size to find the actual measurement of the threads. For me it's easier to find the mm size this way and if it's an inch size just look for the closest inch size.

I know at least two people who have found thread sizes from others on a forum using this method. It's simpler and faster to use measuring tools, but if you don't have them and already have a camera then it's an option. It might be possible to do this even without the camera, just measure on the screw itself, but some of them are very small and it can be hard, depends on how well you see, etc.

BTW for what is possible with REAL Macro, here is a Conn set screw (one of those 2mm long screws that hold the pivot screws in place) http://farm7.staticflickr.com/6010/6007266155_1aeed03a22_b.jpg

 

[kevgermany]

Just a word of warning on the camera approach. Some of the threads are very similar and you may need to check the profiles as well, especially if you're not sure if it's US or british. (Or a hybrid metric/imperial like BA).