Why doesn't this natural gas flared union connector fit?

Question

I have a new outdoor grill that I'm trying to hook up to my natural gas line. The old grill had a 1/2" flare connector on the end that connects to the natural gas line and the new grill needs a 3/8" flare connector. So, I bought a 3/8" to 1/2" union flared on both sides (one end for the new grill, the other end for the old connector). Below is a picture of the 1/2" flared end of the two connectors side by side (new on the left, old on the right). There is also a picture of the end of the natural gas hose into which I am trying to screw the connector.

The problem is, while both connectors thread correctly, the new one seems to be a bit too short so it doesn't sit flush against the compression fitting on the end of the hose. I've screwed it in as far as it will go and there is still a noticeable gap through which gas leaks out. The old connector screws in about the same distance as the new one but it seems to be about 1/8" longer so the flare sits flush against the compression fitting in the hose.

I can't seem to find any information online about different lengths for this fitting. Any idea what part I need to make it fit?

Answer 1

You need to make sure all matching flare joints are using the same flare angle (45 deg vs 37 deg.), it's not clear from your photo they are the same. If that's not the problem, perhaps you just need a flexible gas line with shorter nuts, so they don't bottom out before the tube flare is clenched properly.