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  1. #1
    Join Date
    Feb 2013
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    Bunya Mountains, Australia
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    Default Need help with mill bit/s

    Hi

    I want to drill 5 x 16mm holes in heavy gauge 50mm box tubing (4-5mm wall thickness maybe) Each hole has to pass through both walls.

    Each hole has to be exact in location to the other 4, but precision in it's diameter. So that a 16mm mild steel bar will fit in easily but with almost zero play. Like fitting into a sleeve. It's fit once and leave, not meant to serve as a bearing.

    I may have to drill 20 sets. (100 holes) I don't think a drill bit would be best for this.

    My plan is to use my little mill. What is the best mill bit I can use? Do I need to drill a special pilot hole. And what rpm.

    Remember, I'm only a monkey with a little brain. An exact part number/s and monkey-see-monkey-do instructions would be ideal.


    Thanx if you can help... Greg.








    .

  2. #2
    Join Date
    Aug 2012
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    Australia
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    Default

    Rotabroach/annular cutter.

  3. #3
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    Default

    Quote Originally Posted by variant22 View Post
    Rotabroach.

    Thanx for that. But what exact Rotabroach?

  4. #4
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    Aug 2012
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    Australia
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    Default

    An annular cutter. Accurate holes with minimal fuss.

  5. #5
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    Default

    Quote Originally Posted by variant22 View Post
    An annular cutter. Accurate holes with minimal fuss.
    Words must come dear where you live. Do you pay by the keystroke? heheee

    Annular cutters don't appear to come longer than 50mm. The box tubing is 50mm.

    You don't happen to have a link to a 16mm x 60mm Rotabroach do ya?

    Greg.

  6. #6
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    Default

    I may be totally wrong, but the annular cutter appears to be a glorified drill bit. I need a milled surface wall?

    (all the different parts that fit the holes have to be interchangeable)


    Greg

  7. #7
    Join Date
    Oct 2011
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    Norwood-ish, Adelaide
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    Default

    Do you have a boring head? If you do I would cut the bulk of the hole out with a holesaw (say diameter 19.05 14mm) and then clean up with the boring head.

    Michael
    Last edited by Michael G; 1st Aug 2019 at 06:57 PM. Reason: wrong size

  8. #8
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    Default

    Hi Greg,

    A 16 mm Blacksmiths drill will do what you want !

    First accurately mark out your hole pattern then pilot drill with say a 5 mm drill first then use the 16 mm drill. You will need a fairly low speed for 16 mm say 250 rpm.

    Your mill is almost the same one as mine. Be aware that there is a plastic transfer gear in there and it wont stand up to a jam or stall, so your work piece needs to be securely held and set as square as possible.

    As far as the gear goes, I made a new steel one for my mill. The write up is on here somewhere.

    You need to positively position the work, not loose as shown in your pictures. In the absence of a vise I would use an angle plate clamped to the table and clamp the work to that whilst drilling.

    HTH.
    Best Regards:
    Baron J.

  9. #9
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    Default

    Quote Originally Posted by Michael G View Post
    Do you have a boring head? If you do I would cut the bulk of the hole out with a holesaw (say diameter 19.05 14mm) and then clean up with the boring head.

    Michael
    Ta Michael,

    Not sure what a boring head is, nor what sort of holesaw would cut through 8mm over an over again.

    But I'll look them up

    Greg

  10. #10
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    Default

    Quote Originally Posted by BaronJ View Post
    Hi Greg,

    A 16 mm Blacksmiths drill will do what you want !

    First accurately mark out your hole pattern then pilot drill with say a 5 mm drill first then use the 16 mm drill. You will need a fairly low speed for 16 mm say 250 rpm.
    I own a Sieg 3 lathe. I know all about the gears. I just feed really slow, works fine. I face 16mm rod in the Sieg, I really like it.

    Quote Originally Posted by BaronJ View Post
    You need to positively position the work, not loose as shown in your pictures. In the absence of a vise I would use an angle plate clamped to the table and clamp the work to that whilst drilling.

    HTH.
    Yes. That wasn't meant to be the setup. I don't know what an angle plate is. But I need to lift the tubing off the table so that I can drill through both sides. I'll clamp it down with the ... ummmmm ... meccano block things that come in the red plastic holder.

    I'll use the mill travel bed to drill the five holes without removing the piece. Each piece of box tubing is 500mm long.

    The trouble I have with the pilot hole drill is that it will wander reaching down to the bottom wall?

    I'll look up blacksmith drills

    Ta

  11. #11
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    Aug 2012
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    Australia
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    Default

    Quote Originally Posted by Mutawintji View Post
    Annular cutters don't appear to come longer than 50mm. The box tubing is 50mm.
    Plenty on eBay that are 55mm.

  12. #12
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    Jun 2007
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    sydney ( st marys )
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    Default

    I did something similar the other week,not as many holes and not as thick ( only 20 mm plate ) . I drilled the plate to 15 mm and then used a 16 mm slot drill.
    In your case you would need to use a long series slot drill or a slot drill that has a reduced shank behind the cutting flutes.

  13. #13
    Join Date
    Nov 2009
    Location
    australia
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    57

  14. #14
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    Sep 2012
    Location
    York, North Yorkshire UK
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    Default

    Hi Danny,

    A blacksmiths drill is simply an ordinary drill with a reduced size shank so that it will fit into a standard 1/2" inch drill chuck. They are quite cheap over here and go up to 1 inch in size in 1/16"th inch steps. They will easily drill a hole 4" inches deep.

    The reason that I said to use a pilot hole is that the drill web is quite thick, particularly on the big ones. A 5 mm pilot hole simply removes the need to apply a large amount of force to make the web cut metal. Also a 5 mm drill is long enough to go through both sides of your tube in one operation as is a blacksmiths drill.

    An angle plate is just that, usually made from cast iron and has 90 degree angle that has been accurately machined so that the two working faces are at exactly 90 degrees. You clamp it to the mill bed and use the other face to clamp the work to.

    This picture might help.

    26-06-2019-010.jpg
    This is a 14 mm blacksmiths drill, drilling a hole through a 3.5" inch wide block of steel. The 8" inch 90 degree angle plate can be seen in the background with the two clamps holding the work piece to it. This ensures that the hole is drilled accurately through it. The pilot hole in this instance was 6 mm diameter.
    Best Regards:
    Baron J.

  15. #15
    Join Date
    Apr 2012
    Location
    Healesville
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    Default

    G'day Danny, if you mark it out accurately you should be able to drill one side and then flip it over and then drill the other side.

    cheers, shed

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