Between centers boring bar

[TomG]

(11-06-2014, 01:10 PM)chucketn Wrote:

(11-06-2014, 12:51 PM)TomG Wrote: The only case where runout would matter is if you are setting the diameter by miking over the bar and tool. If the bar has runout it would give you a false reading.

Tom

Well, if the bar has runout, how do you set the bore diameter? Trial and error?
I'm going to try to make another between centers bar, this time from 1/2" drill rod.

Chuck

Not trial and error, just trial. Assuming the part you are boring is mounted on the cross slide of the lathe, take a trial cut, zero the cross feed dial and measure the bore. Then move the part away from the tool the required amount and using the wall of the bore as a stop, move the tool bit out until it re-touches. Now when the dial gets back to zero, the bore will be to size. Better take a couple trial cuts to check your work before taking it to size.

This is basically the same technique I use to set a boring head to machine a radius. Pick up the edge of the part and move it over the required amount, then run the boring head out until the tool contacts the edge.

Tom