Keith/Robin

Thanks for your comments.

I am not entirely sure I understand your point Keith, I don't think its an airlock issue as there was plenty of room for the air to come out, I am pretty sure its a heating issue, thats the furthest corner from the fill.

You will note in the previous attempt (which didnt have the shim all the way into the spindle) that that side filled OK but the other side failed. I am wondering if the best option is to have two fill points, one through the top and one to the side to fill from the bottom up initially and then from the top.

Keith, your casting experience is far greater than mine and this is clearly a 'casting' problem so I am grateful for your thoughts. I am a little loath to heat the metal a lot more as I have read that overheating causes some of the trace elements such as antimony and bismuth to leach out, but I don't know how hot that means - I cant get anywhere near hot enough to boil it!

I will persevere... it will come right one day...