A whole load of holes...

  1. FabFreddie New Member

    Messages:
    9
    Location:
    Bedford UK
    1st post so I hope that I'll give enough information to get some good tips/advice!

    we've a project that we're planning which will involve the drilling/cutting of a LOT of 20mm holes in 75x50x3mm tube. We need to drill/cut the holes very accurately down the centre line of each face of the tube. The holes are evenly spaced along a 2300mm length of tube however the spacing changes in the central section of the length where the holes will be closer together.

    I've been going around in circles and may well be overthinking the process so am after good ideas to approach this problem please!

    Ideally we'd like to achieve this with minimum investment in equipment/tooling to start with (we have nothing to speak of) so appreciate that we're really looking for an accurate, manual process where time will be the main cost. As things progress we could look at semi-automating the process using a hydraulic punch but that really isn't an option yet.

    Any ideas would be brilliant, thanks in advance!
     
  2. James1979 Forum Supporter

    Messages:
    1,590
    Location:
    Orkney
    Hello and welcome to the forum.

    I would either make a jig and use a mag drill or price up someone local with a cnc plasma or laser.
     
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  3. Nick DV

    Nick DV "You must unlearn what you have learned."

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    Hi & welcome :waving: You'll definitely get your answers here :thumbup:
     
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  4. WorkshopChris

    WorkshopChris Forum Supporter

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    I would probably make a jig to hold the rotabrocch, with pins in the back that locate in the hole just drilled. That is a cut from the rota broach is accurate enough for your application.
    As long as the first hole is correct the rest will follow along accurately.
     
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  5. Munkul

    Munkul Jack of some trades, Master of none

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    Location:
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    As others have said, a jig with either a gear head drill or a mag drill, either move the work through the jig, or move the jigged magdrill.

    you're going to want a length of RSJ or channel for marking, if you don't have a long enough table.

    Here's how I would do it:
    First job would be to mark a centre line all the way down the tube, using a height gauge and flat surface (table or RSJ)
    Then mark and punch the hole centres.
    Clamp a level at one end to keep it from twisting.
    Set a backstop in the drill - either with fixed vice, or some sort of angle fixture, for the holes to hit centre line.
    Set up in pillar drill with a HMT heavy duty holesaw - the centre drill will help with keeping things centred and stop wandering, and the HMT bits are basically carbide annular cutters with a centre drill.
    Clamp the tube firmly, however you do it.
    Drill holes all the way down the length, using trestles to balance the tube flat, while the backstop/vice and level keep the holes on centre.

    The HMT cutters are awesome - more accurate than regular holesaws, and in mild steel they'll last indefinitely, if you treat them right. The HMT speedlube is the dogs danglies, too.

    Regular annular cutters will work too, but your setup will have to be very rigid to stop it wandering.
     
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  6. ukracer Forum Supporter

    Do you not have a pillar drill?
     
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  7. James1979 Forum Supporter

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    FabFreddie likes this.
  8. Woody.v8

    Woody.v8 Blue gluer

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    I'd be getting a price on tube laser cutting
    what-you-need-to-know-about-laser-tube-cutting-1557936600.jpg
    csm_Technology-Picture-Laser-Tube-Cutting_66a992c5dc.jpg
     
  9. Nick DV

    Nick DV "You must unlearn what you have learned."

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  10. James1979 Forum Supporter

    Messages:
    1,590
    Location:
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    If you’ve loads to do by the time you’ve buggered about and stood there doing it , it may well be cheaper to get it outsourced as above anyway
     
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  11. Brad93

    Brad93 M J B Engineering

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    Location:
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    Tube laser

    or mag drill with a v base
     
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  12. FabFreddie New Member

    Messages:
    9
    Location:
    Bedford UK
    I'm was going down the mag drill path but was possibly overthinking the jig - there needs to be some balance between time spent marking out and some indexing completed by the jig otherwise error could creep in both with the marking out and tool positioning over the marks?

    The laser tube cutting would be awesome but probably out of budget to start with, certainly while making the first few and prototyping (for the prototypes the 2300mm tube won't change) - perhaps having the indexing on the jig done by laser would be a solution!

    Anyone have any idea on costs of laser cutting small batches in the UK?
     
  13. ukracer Forum Supporter

    But.......Do you already have a pillar drill?
     
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  14. FabFreddie New Member

    Messages:
    9
    Location:
    Bedford UK
    Ah the pillar drill, yes but it's a bit small for this unfortunately!
     
  15. ukracer Forum Supporter

    Small batches of anything are not cheap.....last thing these guys want is to set up for a small run.
    It really depends what you term as "accurate" for your prototype. Plus how many you need?
     
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  16. FabFreddie New Member

    Messages:
    9
    Location:
    Bedford UK
    Accuracy in the 0.5mm ballpark.

    1st batch would be maybe 20 of the 2300mm lengths and 20 900mm lengths. This would allow us to complete the prototyping and put some into use for testing.
     
  17. ukracer Forum Supporter

    Ok what about short term? How long is the tube you need to put holes in.
    Assuming a reasonable accuracy is needed I would use my pillar drill with an indexable pin. Sliding the tube along the vice. Withdrawing the pin and then reindexing after each hole.
    Screenshot_20201105_133356_com.ebay.mobile.jpg

    Might not work but cost minimal or cheap (of you need to buy a pillar drill).
     
  18. FabFreddie New Member

    Messages:
    9
    Location:
    Bedford UK
    The tube is 2300mm long so maybe a little unwieldy on the pillar drill?
     
  19. My Old Landy

    My Old Landy Melting Metal

    Messages:
    238
    Location:
    Buckinghamshire UK
    You would need a 5 metre working area with the pillar drill in the middle. Supports either side if no benches available.
    It is doable, I did something similar when making the hoops for the back of AWD army trucks in the 80's. No fancy gear, just a jig with drill bushes and an indexing pin.
    Good luck!
     
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  20. FabFreddie New Member

    Messages:
    9
    Location:
    Bedford UK
    Sounds doable - we have the space and can set up the supports no problem.
     
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