05-19-2012, 09:46 AM
Hi Wong,
You are correct and it is better and easier to have a hole large enough for the boring bar to go into.
I think in my case the hole I wanted to do (at the time) was 17mm dia., the boring bar needs 18mm dia hole to go into. I do have smaller boring bars, so why didn't I change to a smaller boring bar.
Two reasons, a larger boring bar is more rigid and less chance of 'chatter' and the second reason - I was too damn lazy to change it
I think at the time the second reason took preference 
The hole in the centre helps to give the boring bar a "start" when the tool is moved (cutting) towards you. The hole in the centre also helps when the boring tool is cutting away from you - you know when to stop, and stops the material rubbing on the tool tip (in the reverse direction) if you go past the centre.
Hope that makes sort of sense
DaveH
You are correct and it is better and easier to have a hole large enough for the boring bar to go into.
I think in my case the hole I wanted to do (at the time) was 17mm dia., the boring bar needs 18mm dia hole to go into. I do have smaller boring bars, so why didn't I change to a smaller boring bar.
Two reasons, a larger boring bar is more rigid and less chance of 'chatter' and the second reason - I was too damn lazy to change it
I think at the time the second reason took preference The hole in the centre helps to give the boring bar a "start" when the tool is moved (cutting) towards you. The hole in the centre also helps when the boring tool is cutting away from you - you know when to stop, and stops the material rubbing on the tool tip (in the reverse direction) if you go past the centre.
Hope that makes sort of sense
DaveH