Boring Head- Minimum ID

Nip off the heel of the insert to gain the clearance???
Or
Otherwise reshape the insert to work
 
All boring bars have an F dimension . Times 2 ,this is the minimum bore that can be cut approx . These F dimensions are found in the maker's specs . The value is the centerline of the holder to the tip of the insert .
 
I use these inserts for aluminum mostly, but they work for a while on stainless if you don’t push them too hard
IMG_5592.jpeg

P.S.
This insert bolts onto the holder you have
 
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RaisedByWolves said:
That is one honkin big cutter for a .925 hole.
Click to expand...

No question.
You need to also think about chip removal and coolant delivery. A birds nest of any size will ruin surface finish, or worce get staged on the back side and bend the boring bar deeper into the cut. Changing the diameter.
Use a small boring bar for like .75 min bore for making a .9375 hole let's say.
 
Ulma Doctor said:
Nip off the heel of the insert to gain the clearance???
Or
Otherwise reshape the insert to work
Click to expand...
Yes I plan to grind down some inserts to fit by increasing the relief angle. I still would like to understand the geometry and whether the manufacture is correct.
 
As I understand, the F dimension applies to the boring bar? This boring bar is not a problem and clears easily. The problem is the 7 deg clearance angle or the insert is not enough. Imagine an insert that has a zero (or minimal) clearance angle. The cutting surface would never touch the work because of the curve of the hole. This is unrelated to boring bar shape.
@Ulma Doctor - I am using those exact inserts. It works superbly for holes with diameter of 1.5" or better. The finish is excellent.
Chip removal and coolant are not an issue for the short holes I am doing. Why would I want negative rake? A negative rake cutter is not desirable for low rigidity machines.
 
From the manufacturer:
Comes as shown with one CCMT-32.51 carbide insert, and one standard 6-32 Torx screw.
With this type of insert you get 5 degrees of clearance on the side
and 5 degrees clearance on the bottom.
Can use any similar insert.

My insert actually has 7 deg of clearance.
 
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Ok- So I drew this in Fusion and I believe the manufacturer is WRONG. That is a bold statement since I have never seen such and error before but here is the graphic:

1717793838872.png
The circle drawn is 0.925" dia.
The angles don't show up correctly but Line 1 is at 7 degrees of clearance. You will note the line is .113" long until it intersects the circle. The insert is .156 thick! This is the problem!
I also drew line 2 to see what clearance angle would be required. It is 2.65 degrees more! That means a clearance angle of about 10 deg is necessary.
The insert this comes with has only 5 deg or clearance so it is even more of a problem.
 
I used the chord length formula to calculate a minimum bore of 1.3” with an insert with a 7 degree clearance angle. If you use the inserts with an 11 degree angle, that will get you into the Mesa stated range. The angle C for the formula partially down the page would be 2x the clearance angle of the insert. The chord length would be the thickness of the insert divided by cosine clearance angle.

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Chord of a Circle – Definition, Formulas, Examples

What is the chord of a circle – learn how to find its length with equation, theorems, and solved examples. Also learn the longest cord of the circle
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