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  1. #1
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    Default RF30 captive drawbar questions

    This isnít a question about how to make it work, Iíve already done that. But my first design had some challenges and Iím in to version 2.

    The original design broke because I had too large a roll pin in too small a diameter and the shaft snapped.

    So Iím in to creating a new one with better tools and methods (I have a reamer and hex collet block this time).

    Hereís the setup:





    Itís a 12 rod, turned down to 7mm at the end. An M14 boot with a 7mm reamed hole and a top nut (yet to be made) that will be pinned to the shaft.

    Questions:

    1. Iím toying with the idea of using thrust bearings on the top and bottom of the captive bolt. Is this a good idea or unnecessary complication?
    2. Iím planning on using a split pin to attach the top nut to the shaft. Whatís the best way of drilling this hole and keeping all the parts aligned as I do it? I was thinking of using loctite and then drilling through the whole setup before breaking it apart, cleaning and pinning?
    3. I was going to use a 3mm roll pin? Is that sturdy enough? Want to make sure I donít break the top part like I did last time but make sure it wonít shear

  2. #2
    Join Date
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    Default

    In crane hook castle nuts they use a roll pin, then a solid pin inside that.
    If it's good enough for safety of lifting equipment, it will be more than enough for a drawbar.
    The solid pin strengthens the roll pin to almost a solid pin, but as most roll pins are HT, it will be even stronger.
    Using Tapatalk

  3. #3
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    Default

    A selection of roll pins have been acquired along with some thrust bearings. Going to go ahead with both and will have a go at using thrust bearings on the top and bottom of the captive bolt.

    To drill the hole for the roll pin I was going to loctite the assembly together, pop it in a collet block, use an end mill to flatten the entry point, then spot drill and drill out to size.

    Iím hoping the loctite will keep the assembly together as I drill through the whole thing and then roll pin it.

    Iíve also got mega excited and finally bought some cold blue to finish it off.

  4. #4
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    Default

    If there is any slop in your quill keep the quill lock slightly locked, then you shouldn't need a flat to start it.
    I often use my lathe center drills to start holes in the mill if I want them spot on, or drilling round bar.
    Using Tapatalk

  5. #5
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    Default

    Thanks Dave!

  6. #6
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    Sep 2012
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    North Yorkshire UK
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    Default

    Hi Neevo, Guys,

    Don't forget you can always use the steel ruler trick to centre the drill over the centre of the bar when setting up to do the drilling.
    Best Regards:
    Baron J.

  7. #7
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    Default

    Quote Originally Posted by BaronJ View Post
    Hi Neevo, Guys,

    Don't forget you can always use the steel ruler trick to centre the drill over the centre of the bar when setting up to do the drilling.
    That will definitely be employed as I donít have an edge finder yet. Have one on order but for this level of precision the ruler trick seems a perfect solution.

  8. #8
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    Yes a center finder will help greatly, did you order a electronic one or a manual one, for these jobs I find a electronic one works best and is quicker.

    If you want to do it before getting the center finder (China postage at the moment), place a 4 flue end mill in a chuck with the cutting edges aligned X-Y, then center it between your vice jaws when the job is tight in the vise.
    It's a rough way but pretty accurate.
    Using Tapatalk

  9. #9
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    Quote Originally Posted by Dave J View Post
    Yes a center finder will help greatly, did you order a electronic one or a manual one, for these jobs I find a electronic one works best and is quicker.

    If you want to do it before getting the center finder (China postage at the moment), place a 4 flue end mill in a chuck with the cutting edges aligned X-Y, then center it between your vice jaws when the job is tight in the vise.
    It's a rough way but pretty accurate.
    I went electronic. Had no idea what to get but thought Iíd give one of them a crack before ordering a more traditional one later.

    Still donít have a DRO on the mill yet, so still doing a lot of eyeballing.

  10. #10
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    Default

    I'm a visual guy as well, I can usually get something pretty spot on from visual looking at it.

    If anyday you are up to buying a DRO and have some spare cash, it's really worth the investment at around $250.
    I know we can't all afford it, but they really do make a huge difference in our home machining world.

    Using your dials, touch off a jaw, zero it, then go to to other side to touch off, then half it, taking on backlash incount.
    Just remember when coming back to over wind then come back to eliminate it.
    Using Tapatalk

  11. #11
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    DRO will definitely happen, just when, not if. Iím also set on a 3 axis. Just need a way to cleverly fit the z axis and have it hidden. I have a few ideas, but I also have plenty of projects I need to finish first.

  12. #12
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    Quote Originally Posted by neevo View Post
    DRO will definitely happen, just when, not if. Iím also set on a 3 axis. Just need a way to cleverly fit the z axis and have it hidden. I have a few ideas, but I also have plenty of projects I need to finish first.
    A DRO will have it finished quicker, lol
    Using Tapatalk

  13. #13
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    Default

    Last time I got talking about the mill on here I bought a rotary table. Expensive exercise loading Tapatalk RF30 captive drawbar questions

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