1515 rail button question

[terryg]

I have never used 1515 rail buttons. The ones if have have a slight sloped depression for the head of the 1/4 inch mounting screw. The head of the screw is not flush with the top of the rail button and projects above it. How much clearance does a 1515 rail have before the screw head drags?

 

[JoeG]

Some years ago I was using large buttons with the screws that came with them with no issues on my own personal launch rail and when I tried to use a club launch rail the screw head would not allow me to load the rocket. There seemed to be some differences in the rails as far as depth was concerned. I never did figure out the difference. Some said one rail was metric and the other standard American but not sure that was it. I thought maybe the club rail, the one that didn't fit was just loaded up with stuff from many launches. anyway my remedy was just to grind down the top of the screw. Then it worked on both. Since then I have just been using lower profile screw heads. I'll be interested in seeing others' answers.

 

[Worsaer]

Using an example of 1515 buttons that do not have an indentation, there is still room between the screw head and the inside of the rail channel.

Here are a couple of photos, with two different types of screws.

The first is with a common 1/4 inch phillips pan head machine screw. It's close, but it does not touch.

The second is with a thinner head. It's a 1/4 in combo head machine screw. Even more room.

Here are the two screws, showing that one is slightly thinner than the other.

I should mention this is with pristine, unused rails. After a lot of build-up from flights the tolerances may change.