View Full Version : How to align boring bar in head

08-01-2008, 09:39 AM
When using a boring bar in a boring head, should the cutting face be in line with the diameter of the head, or angled to provide rake?

08-01-2008, 09:52 AM
A little rake. The boring bar will be dragged back in the bore, so if you don't give it any to begin with you'll wind up negative.

08-01-2008, 09:56 AM
Typically, it should be set on the centerline of the boring head.

I usually bias it slightly toward positive rake. No particular reason, just a personal preference that seems to work in most cases.

Bill Pace
08-01-2008, 11:06 AM
J C describes my method to a T also, and, for the same reasons ... just what has evolved as seeming to work well....

Course we ARE talking about "eyeballing" the setting here and my "calculated" eyeball and yours are bound to be -- possibly quite a bit -- different:D

08-01-2008, 06:40 PM
Eye ball it on centerline of boring head . If not enough clearance grind a little more on it where needed. You want have a problem with good name brand bars But the Chinese import bars need all the help they can get.

Paul Alciatore
08-02-2008, 06:46 PM
Just my thought, but I always seem to have to worry more about clearance than rake. Many times I have had to grind additional clearance on boring bars for small diameter holes.

Setting the cutter below the diamerer increases one angle and decreases the other. And vice-versa for above. Tilting the cutter has the same effect. To increase both angles you must grind and so it may as well be on the diameter or centerline.

08-02-2008, 08:24 PM
I usually start out with the cutting tip on center line and adjust as needed to get a good cut. The angle of the tool and the speed and feed are all experimental.

08-03-2008, 03:51 AM
Put a washer the same size as the hole you are going to in the chuck if boring on the lathe or on the chuck or what-ever on a rotab. The clearances will be very evident.

For HSS, I use 10>15 degree of top and side rake with 5>10 degrees front and side clearance for HSS.

I set my boring bar tip about 0.020>0.040" (depending on bore size) above centre height so that when it "dips/dives" under cutting load - which it will - it is moving away from the work-piece. Set it as centre height and as it "dips" it gets further into the work, "dips" some more etc. and then the "gouging-in" and "chattering" begin.

I find it works best with as fine an edge as I can get for least resistance and use HSS.

I take my time as I have no need to hurry.

Using TC is my last option unless the set-up is very rigid.

Others get good results using different approaches.

Same for internal threading.

Rich Carlstedt
08-03-2008, 11:59 PM
Take your 6 inch scale out of your shirt pocket.
You know the one with a spring clip to hold it to the pocket
Set the scale on the boring tip face and use the clip to snap behind the boring tool.
You now can see with ease, if you have positive or negative rake !