View Full Version : Left Hand boring bar

01-08-2009, 09:47 AM
A question for the knowledgeable amongst us.

Just what is a left hand baoring bar used for, try as I might I cannot envision what one would machine with one? Unless you bore with the lathe in reverse?


01-08-2009, 10:07 AM
Mostly, they are used in cnc machines....But, you can use them for turning the od of a part that is too big to swing over the cross slide of a given manual lathe. I've turned 7" diameter od pipe in a 10" lathe with one...

Andy Pullen

01-08-2009, 10:31 AM
Thanks for that Andy, that fits in with my thinking in that I can see that you could use them instead of a normal tool holder, I hadnt thought of work to large for a normal setup


01-08-2009, 10:58 AM
They're also what you need if you want to turn the o.d. of something with a boring head in a milling machine.

Ian B
01-08-2009, 11:52 AM

You can also use them for internal boring. Just run the lathe backwards (best if you don't have threaded on chucks, as you may suddenly have threaded off chucks...).

2 major advantages of LH boring bars:

1. You can more easily see what you're doing
2. They're usually cheaper than right hand boring bars on Ebay :-)


01-08-2009, 12:14 PM
You can also use them when you have a narrow circular recess on the end of a part. It'l reach into the recess to turn the OD of the center part.


01-08-2009, 12:17 PM
Yes to use in CNC machines. We do OD turning and boring with the same left hand bar on a couple of parts. Reversing the spindle on CNC's is not an issue since no thread mount chucks.

A bar using CCMT (80 degree diamond) inserts is especially good for this. It does longitudinal turning, facing and boring. Of course a right hand bar will do the same thing.

01-08-2009, 12:56 PM
You beat me to it DR......CNC Gang slides rule! .....Dean