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IndustryArena Forum > MetalWorking > General MetalWork Discussion > Internal boring (need advice)
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  1. #1
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    Jun 2019
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    Question Internal boring (need advice)

    I am currently trying and failing to use a SCLR Through coolant steel shank boring bar to at 8mm with a minimum bore of 11mm it's 100mm long and I need to bore 50mm deep into en8 bright drawn mild steel could anyone please help because the boring bar just bends and chatters and it's not safe is there any bar better for this or specific way of boring for me to be trying? Thank you.

  2. #2
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    Re: Internal boring (need advice)

    Quote Originally Posted by Ryanjones1999 View Post
    I am currently trying and failing to use a SCLR Through coolant steel shank boring bar to at 8mm with a minimum bore of 11mm it's 100mm long and I need to bore 50mm deep into en8 bright drawn mild steel could anyone please help because the boring bar just bends and chatters and it's not safe is there any bar better for this or specific way of boring for me to be trying? Thank you.
    EN8 is not mild steel it is a medium tensile medium carbon steel and can be heat treated, quite a bit tougher than mild steel to machine, so have you drilled a hole say 10.5 and then used the boring bar to bore out to size

    Make sure your boring bar is only out enough for the depth of cut you have to do, use the smallest radius ground insert you can find
    Mactec54

  3. #3
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    Re: Internal boring (need advice)

    i have found that with steel shank boring bars 3 x dia. is very stable then you need to start taking considerations in the speeds/feeds/doc /programming/inserts ect.
    a carbide shank will get you 6 x the dia. of the shank with no problems
    there is also boring bars with vibration damping shanks that will get you a little further ( not sure if they are available in 8mm shanks)
    with the the requirement at 50mm loc / 8mm shank =6.25 this is not a stable cut with the steel shank tool

    I agree with mactec54
    Make sure your boring bar is only out enough for the depth of cut you have to do, use the smallest radius ground insert you can find

  4. #4
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    May 2019
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    With a carbide SCLR and .0078" radius insert at .025" doc I have successfully and repeatably done 10x boring in SS 17-4 and 15-5. The radius of the insert and the depth of cut have to be balanced. If the cut is too shallow you'll get chatter and if it is too deep you'll get deflection, taper, and possibly snap your bar. Rough it out in sections and clear the chips out after each section and take two or three finish passes feeding the bar out rather than in with .002-.003 doc.

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