Making little carbide boring bars
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  1. #1
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    Default Making little carbide boring bars

    Good morning All:
    Well I wasn't feeling much like doing any REAL work this morning so I decided to play a bit today instead.
    I've always wanted to have some small carbide boring bars that can use broken 1/8" shank carbide end mills to be ground into custom inserts and clamped into the end of the bar.

    So here are a pair of home made bars...5/16" diameter x 6" long and 3/8" diameter by 6" long.
    They are made from C2 carbide blanks bought from McMaster for 40 bucks each, and some ejector pin cutoffs silver brazed onto the ends so I could put a screw into them to clamp the inserts.
    Here are some pictures before the inserts are actually ground.
    I plan to use the Deckel single lip cutter grinder to grind the inserts whenever I need one.
    They are simple in construction; just a bit of wire work a bit of drilling on the Bridgeport and a bit of silver brazing.

    I'm looking forward to trying them out...I've got a set of valve guides to bore 2.5" deep and 0.377" diameter so this will be a good test if the 5/16" bar is rigid enough at that length of stickout.
    I will keep you all posted.
    Cheers

    Marcus
    Attached Thumbnails Attached Thumbnails dscn5004.jpg   dscn5005.jpg  

  2. #2
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    Very nice!

    I had to do something similar recently- internal grooving tool. Not quite as fancy but in my case way cheaper than buying an internal grooving system for what I needed to do. I used carbide split blanks for this. These are very handy too.

  3. #3
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    Hi Pete:
    Yeah, I usually just grind a split blank to make a solid bar, and that's what I'd originally planned to do with this one too, but it was just so pretty and pristine when it arrived in the McMaster box that I couldn't face hacking it up just for this one job.
    It took a bit more time to do it this way. but I live in hope it will be a better bar and I don't have to break out a new blank every time I have a new hole to make.

    Attached is a picture of how I usually make custom bars...it works well for tiny stuff but it wastes significant time and carbide once you get up above a 3/16" shank and you pretty much need to make a new one every time you have a hole that's deep and skinny.
    It also is intolerant to wear and to misadventure...one little blip and you're grinding a new bar from scratch.
    We'll see if this new design fulfills my hopes and dreams.

    Cheers

    Marcus
    www.implant-mechanix.com
    www.vancouverwireedm.com
    Attached Thumbnails Attached Thumbnails dscn5006.jpg  

  4. #4
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    Nice work, Marcus. ( as usual )

    I've done similarly in the past and your idea works well. You may wish to wire a vee into the "lower" half of the split, to help repeatably locate the "blank". I've found that they can vary more than one might expect, so the vee helps in this regard.

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    Hi Zahnrad Kopf:
    What I did was to put a flat on the 1/8" broken cutter shanks and wire the corresponding flat into the socket that accepts them, so I can take the insert out and re-grind it without having to fart about to re-position it when I put it back.
    If you look at the second picture you can see the flat right next to the relief slot that makes the clamp springy.
    As you know with round inserts in boring bars, it's a pain to get the rake and relief correct again when you've lost orientation after taking the insert out.
    I used to just take the whole bar out of the lathe and re-grind it as a unit, but then I have to fart about putting the bar back in; this way I can just pop out the insert...almost as good as a commercial solution and WAY more versatile for the weird shit I get into.

    The test will commence this afternoon...I just have to get those damned valve guides programmed.

    Cheers
    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    Yeah I was just about to comment that the V was unnecessary. Excellent use of the flat, good thinking.

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    Looks like the Everede bars reinvented.LOL.

    Ed.

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    Hi atex57:
    Who knew...I was completely unaware such bars were commercially available in such small sizes.

    Well...too late now; they're done and running and I have to confess I had fun making them.
    Besides...mine are cool even if they're not cost effective, so I'm going to cuddle them anyway!

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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  10. #9
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    Hi again All:
    Well I tried it.
    It runs slicker than snot...I'm a happy dude.
    It's boring time!!

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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