Boring Bar

The material will depend on what you intend to do with the part. How far will it be sticking out from the boring bar holder? Usually a 4 to 1 ratio is good with a heat treated 4140 bar, you can get 6 to 1 ratio with solid carbide.

It is my preference to use a solid carbide bar if possible. Otherwise use 4140 and heat treat it to a RCc of 32.

Vibration, or chattering is your enemy. The bar needs to be as rigid as possible given the length to diameter ratio. I agree that carbide is the preferred material as it tends to dampen vibration more than steel. Without knowing the dimensions of your tool, or the dimensions of the work, I too would recomend a tough steel like 4140 or S7 with a moderate hardness. My "rule of thumb" use the shortest , fattest bar that will do the job.

Guset

How can you design something with out specifiying a material and or hardness

Would you like us to design you a boring bar that will work

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