Had a shot at cutting some new spindle motor mounts today. The first one is cut and it came out well. I used one of the single flute cutters from ebay.
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There is a litte bit of marking on the third photo at one of the corners but its nothing to worry about. This is cut from 25mm thick alu. Inner size was programmed to 80.5mm and it came out 80.4mm so thats fine as well. Just need some more time to get the second one done and get them drilled and tapped out for fitting.

I also did some testing on my tool height setter. Fitted a new 6mm single flute cutter and ran 10 measurement cycles of the tool height routine. The results are below.
1, 30.5087
2, 30.5037
3, 30.5012
4, 30.5012
5, 30.4963
6, 30.5012
7, 30.4963
8, 30.4988
9, 30.4988
10, 30.4988
From min to max the difference is only 0.0124 so thats good enough for me.

Regards

Ian