Between centers boring bar

[TomG]

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

[doubleboost]

My boring bar has a slight bend in it
Makes no difference at all
John

[chucketn]

(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

[Lordedmond]

Sorry Tom
But it will not be a problem ,take cut measure the bore , Mike the cutter from the the back of the bar and adjust as required
The cutter in a bent bar is considered a fixed point , therefor the required adjustment is easily done

Stuart

[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

[Dr Stan]

A half inch boring bar is quite small and can lead to chatter & flex. Is that the largest bar that will fit in the hole?

[chucketn]

(11-06-2014, 10:19 PM)Dr Stan Wrote: A half inch boring bar is quite small and can lead to chatter & flex.  Is that the largest bar that will fit in the hole?

Yes, the largest long drill I have is 1/2" MT1. I'm looking for a few bigger ones that are affordable.

Chuck

[stevec]

(11-06-2014, 11:54 AM)chucketn Wrote: Whew! It finally makes séance! Thanks for all the input.
Next decision is whether to make the spindle, and bore the hole to fit, or bore the head and turn the spindle to fit.

Chuck

edited to correct speeling

Good one chuck!

[Dr Stan]

What is the length/depth of the hole?

What is the finished diameter?

What precision is needed?

What is the material?

Do you have a boring head that can be mounted in the head stock?

What sort of selection of single ended end mills do you have?

[doubleboost]

When I made mine I bored the casting first
Then made the spindle
It is easier that way
John