Need Help! Boring bar Depth of Bore


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Thread: Boring bar Depth of Bore

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    Default Boring bar Depth of Bore

    I need to bore a part which has 1.7" bore at the beginning but 1.200" at the end (internal tapered shape). Bore length is 3.350". I'm using a 1" dia steel boring bar S16T-SDUCR-3 which has 1.500" min. bore according to catalog. I'm planning to grind off .400" from boring bar front end (around 2") to compensate min bore requirement. Is it going to create any possible chatter/vibration? With this should I get better result than a .750" bar (.750" bar is good for 3" depth only as I know from 4D rule)? Please advice.

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    Default Re: Boring bar Depth of Bore

    Hi....you would not have a problem with chatter if you reduced just the end of the bar as you said....probably be better than a smaller diam bar in that case as the main part of the bar will prevent it from flexing.

    It's a bold move, but will work....as I said, it will work better than the 3/4" diam bar due to the 3/4" not having the rigidity back where you need it.....4X bar diam to stick-out length ratio rule etc.

    You might get away with the 3/4" bar if you play with the depth of cut, speed and feed rate as this will determine the pressure on the tip with deflection that the bar has to resist.

    I assume you are boring into mild steel.....grade unknown.......I also assume you've drilled the hole almost to size for the small end of the taper, so you won't be taking out much material.........a 3/4' bar would probably do the job in that case.

    There is a resonant frequency factor that you won't be able to overcome....this will make the bar "sing" or vibrate at a certain feed and speed rate.....even a smaller bar can bore a hole without vibrating if the resonant frequency is not reached......I wouldn't bother stressing out on the problem if it's only a one off, as trial and error will work.....but for production you need to get it right.

    The final finishing cut to size will probably not affect the rigidity of the 3/4" bar anyway, and it doesn't really matter if the roughing cuts are a bit wavy.
    Ian.



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    Default Re: Boring bar Depth of Bore

    Thank you so much handlewanker for your reply in details! I got all the answers as I needed! Very helpful. I was really worried as I didn't want to spend money on carbide bar. Now I know I will be able to make it happen! Really appreciate this ! Will let you know how it goes!



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    Default Re: Boring bar Depth of Bore

    Have fun, machining is a learning curve no matter how young or old you are.
    Ian.



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