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Setting Boring Bar Height

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Sailplane Driver

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#1
This has probably been answered before but I can't find an answer in my search. What is the proper way to set the height and angle of a round shaft carbide tipped boring bar? I believe the proper way to set the height is at or just above center up to 10 thou. But what about the angle of top of the carbide? Should it be completely horizontal, or have the tip below the center of the bar? With my cheap Chinese boring bars, I have found that the tip must be lower than the center or it will rub even when it is above center. What do you guys suggest besides buy a better boring bar?
 

kd4gij

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#2
As a rule of thumb, what ever works best. I have some bars that the insert sits flat and some that point down at 7deg.
 

Bob Korves

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#3
With the Chinese brazed carbide boring bars you can grind the steel below the carbide to get more clearance. You may need to get more clearance on the carbide itself as well if it is rubbing. Setting the bar to a negative rake helps all of those issues, and if it is sharp it can work well. Keep the cutting EDGE on center, or just slightly higher, not lower. Look at the tool carefully and see where it is rubbing, and deal with it. Chinese boring bars are not tools, they are tool "kits", some TLC required. Once they are modified to a geometry that works, they perform pretty well.
 

P. Waller

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#4
Put the boring bar in the holder, use a .0001 indicator and adjust to the desired angle. Then stack gauge blocks on a surface plate (granite or cast iron) and use a height gauge to set the height of the tool edge from the ways, remember that You Tube videos tell us that you can not be to close.

After several hours of this become frustrated and make the part (-:
 

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