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have you got a link or photo of them?
Here's the best i could get of the boring bars. The varying lengths raise havoc with the auto focus.
Well looking at the photo I certainly see different angles on the tools, take the middle row, one on the left has very little angle and one on the right quite a bit more as shown in yellow.Now try those in a hole and see what size it needs to be before the back edge starts to rub and you can see why you had problems is trying to get any of those to machine a 1/2" hole. Green shows minimum size they would suit. Would need to be even larger if you want to cut with more top rake on the tool.