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Thread: Need mini boring bar recommendations

  1. #11
    Join Date
    Mar 2005
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    Toronto
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    10,136

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    I would recommend the mini Borite sets, they're not cheap but work well and go down to 1/16 which can be very handy. Made in US
    .

  2. #12
    Join Date
    Jan 2003
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    Chilliwack, B.C.
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    As far as home made goes, I really like my converted 1/4 inch diameter broken carbide end mill. As suggested, give it a slight angle and the cutting edge will bite. The deeper you go, the larger the hole should be to start with, or you machine away material in steps to create the clearance. I usually start with a 5/16 hole, but I can start in a 1/4 inch hole.

    I've also had good luck using an unbroken carbide burr. If you turn it just so in the holder you will have one tooth in the right position to cut. For through-holes there's no need to grind it for clearance. But because the shank is ground to create so many teeth, the effective diameter is less than 1/4 inch and it will be prone to breaking off.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  3. #13
    Join Date
    Dec 2015
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    Chilliwack, BC, Canada
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    The use of the carbide burr if it has a rounded end is a great idea. At least for depths of cut that are within the size of each tooth or if you're willing to see the one tooth and the next up sharing.

    But a flat nosed burr would have no end clearance. So that's fine if you're pulling the cutter outwards. But it would cause an issue if pushing straight ahead. No? I'm curious about this.

    Of course depending on the maker of the burr if there is cutting edges on the front face then there goes that concern.

    taking this to the next level I'm now also thinking that a four flute end mill would have more core material and should be stiffer than a 2 flute. I'll try that.

    I'll grant "us" that the purpose designed small size bars suggested in this thread are the proper and better way to go. But for home use that only comes up occasionally I think there's much to be said for just re-purposing an end mill to get the job done without needing another bit of tooling that only sees occasional use.

    Solid carbide would be better. But again for occasional use there's nothing at all wrong with using an HSS end mill that is already in our possession. Bird in the hand and all that ya know...

  4. #14
    Join Date
    Apr 2017
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    Kelowna BC
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    If you want cheap grab a 5/16 square hss blank and start grinding.

    If you have bucks to spend these are really good.
    Bokum Tools makes boring bars to fit as small as 1/16 inch entry hole. They have over 2000 sizes.. I think they will have what you need. Hss or micrograin carbide..

  5. #15
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    Dec 2015
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    Chilliwack, BC, Canada
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    If I were going to grind my own I think I'd rather start with a 1/4" round HSS blank and then make up a small square to round split holder to use it in the tool post. Even grinding a 1/4" square HSS blank down to suit would be a LOT of time at the grinder.

  6. #16
    Join Date
    Dec 2016
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    Helsinki, Finland, Europe
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    Quote Originally Posted by BCRider View Post
    If I were going to grind my own I think I'd rather start with a 1/4" round HSS blank and then make up a small square to round split holder to use it in the tool post. Even grinding a 1/4" square HSS blank down to suit would be a LOT of time at the grinder.
    1/8" carbide blank ground to tiny internal grooving tool:
    (have bunch of broken PCB drills, these are nice micrograin carbide)


    I also used the same ER collet chuck in toolpost to hold the boring bar

  7. #17
    Join Date
    Sep 2013
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    1,238

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    Quote Originally Posted by BCRider View Post
    If I were going to grind my own I think I'd rather start with a 1/4" round HSS blank and then make up a small square to round split holder to use it in the tool post. Even grinding a 1/4" square HSS blank down to suit would be a LOT of time at the grinder.
    I have made up such a holder for 1/4" round unsharpened carbide. engraving bits. dual set screws instead of split block however.

    There is not much material to remove to sharpen or increase clearance. If I were looking at boring to .25", I might make up the same holder block to fit 3/16" blanks.
    The engraver shanks have good geometry right out of the box, and are not costly.

  8. #18
    Join Date
    Jul 2014
    Location
    Southern Indiana
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    422

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    Quote Originally Posted by 754 View Post
    If you want cheap grab a 5/16 square hss blank and start grinding.

    If you have bucks to spend these are really good.
    Bokum Tools makes boring bars to fit as small as 1/16 inch entry hole. They have over 2000 sizes.. I think they will have what you need. Hss or micrograin carbide..
    Bokum bars are the finest small bars that I have found. I bought a quantity several years ago(some slightly used, dirt cheap) and love them.

    Sarge41

  9. #19
    Join Date
    Apr 2017
    Location
    Kelowna BC
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    Sarge I used their recessing tools in a turret lathe top notch tools..
    Matt, your lathe is not covered enough for grinding.
    BcRider, it's not so much work, grind once, use it 50 times.. rough it with a cutoff wheel. Why wait for tool just make it..
    Last edited by 754; 10-11-2018 at 09:27 PM.

  10. #20
    Join Date
    May 2015
    Location
    Somerset UK
    Posts
    1,627

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    Solid carbide twist drills may be the answer, as they produce a hole with tighter tolerances and finish than hss.

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