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  1. #1
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    Default drilling holes in star pickets

    As I am setting up garden edge boards from 200x50 treated pine.

    I am using galvanised pickets that I have cut into short sections to hammer them into the ground and screw the edge boards to them.

    The lower sections of the cut star pickets have no holes for my gal coach screws. I am drilling holes in them or rather trying to.
    The metal is very tough and it takes a lot of effort even with cobalt twist drill bits and use of lubricant. What are these bloody pickets made from? This steel is very tough. Rpms are suitable for the drill diameter and copius lube is used.

    The holes drill like they are work hardening. Are there any farmers around who have had to drill holes in star pickets and can pass on some suggestions?

    I wonder is there anything that I have not considered and should be aware of ?

    Grahame

  2. #2
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    Iíve only drilled black ones, but donít recall having any issues.
    Sounds like the gal ones are a different animal. Maybe the gal process is affecting them.

    Are you using a drill press or just a hand held drill?

    Steve

  3. #3
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    Hi Steve.

    Using my 12 speed drill press to drill the holes.. I had to make a special jig to fold them. I have done four and four more to go.

    They are a difficult shape to hold in a DP vice. I have an un-galvanised picket some where. If I can find it I will drill it for comparison and report back.

    Grahame

  4. #4
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    Hi Grahame, I don't think farmers would drill holes in them, they'd oxy/plasma the holes as required, it's easier for them. They are high tensile steel to start off with.
    My guess, dealing with galvanised metals, is that there is a hardening type process mixed in with the galvanised heating. I usually drill a small pilot hole usually a No 30, as it's about 3mm thick that I'm drilling, then open it to the size required, drill speed is a lot slower than normal. I've actually burnt a few D/Enders, before I worked it out.
    Please let me/us know how you get on with this?
    HTH
    Kryn
    To grow old is mandatory, growing up is optional.

  5. #5
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    In my experience star pickets are LOW tensile steel. The ones I have can be bent over my knee. Maybe that's because I got them from Bunnings! A bit of Googling tells me they are made from low carbon steel.

    Grahame, is it possible the steel is so gummy it's fusing to the cutting edges of the drill bit and creating the illusion it's work hardening?
    Chris

  6. #6
    BobL is offline Member: Blue and white apron brigade
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    Default

    If you have many to do and a wood mitre saw, it's really worth cutting a custom holding wooden block like this.

    Screen Shot 2022-06-26 at 6.42.37 am.png

  7. #7
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    I’ve used the plain steel ones extensively where I’ve cut them down, cut a new point, banged them in and then drilled holes to line up with sleepers to take batten screws. Drilled 6mm holes no problem with a battery drill. I’m guessing the galvanising process hardens the steel?

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    Thick Galv can also gall on the cutting edge of the drill effectively reducing its biting power. I believe cheap star picks are made out of scrap so probably contain stuff like scarp rebar.

  9. #9
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    My experience with drilling star pickets is telling me to find another solution. Whether the pickets are new or old gal or black drilling holes is a miserable job. I always reckoned that the steel was "reclaimed" from scrap so you might get one holes OK move to a spot on the same picket 100mm away and the bit may hardly mark the steel. I would opt for oxy or plasma to keep your sanity
    Just do it!

    Kind regards Rod

  10. #10
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    I have drilled them on odd occasions, both gal and black, never had a problem.
    Regards
    Bradford

  11. #11
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    Drill size? RPM? What is your drill point geometry like? does it have a good split point or web thinning? could be too much rubbing in the center causing work hardening. Another option is regrind the tip on a masonry drill to a more suitable geometry, its not great but it works ok

  12. #12
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    I opted for Gal as they will be screwed to the treated 200 x 50 planks which are garden retaining edges.

    Kyrn,
    I do not own a plasma and at present it would not be cost effective to get one.

    Jack620
    If I tried to bend these pickets over my knee, all that will be bent is my knee. I got these star pickets from the the local fencing guy whom I told that I wanted good ones and apparently, I got them.

    There was no obvious overheating as that would cause my lube to boil or steam and that did not occur.

    Curiously, my 6 x 4 band saw cut the star pickets without any problem.

    The visuals on the pigtail swarf did not tell me anything. There was no bluing or discolouration of the hole or of the swarf pigtails. Only that the shape & twist of pigtails of known LC steel were much different from those of the gal star pickets.

    The drill cutting-edge is smothered in cutting compound.
    The picket steel cuts well at the beginning and then the cutting action degenerates in a harder manual feed accompanied by a crunching/ cracking/ popping sound. That indicates work hardening to me.

    The drill bit cutting edges seemed ok however I did re sharpen it after more difficulty. Yes I can sharpen drill bits. That is sharpen them to cut pigtails on LC steel at least. As the SP fins are thinner stock- 3mm - I reduced the included angle so the drill does not bite through and grab before cutting its proper diameter.

    BobL
    Thanks for the graphic but I had a jig already tacked up which bolted to the DP table .If I had a radial arm saw I would of went that way you illustrated. There's no evidence build up on the drill cutting cutting edge.

    Snapatap
    DP Spindle RPM is around 600 for an 11mm drill bit. It is as low as the DP goes I think.
    The drill was a split center drill bit but when the problem showed I re ground it toa 4 facet jobbie. A pilot drill was used-4mm and it grunted and groaned as well.

    As I read the comments I am coming around to the fact that I might have a brumby star picket.

    I have some hardness files -for knifemaking. I will try to set up a test as I am intrigued as to what the steel may be.

    Thank you all for your inputs.

    Grahame

  13. #13
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    My experience with drilling the things has been much like yours Graeme, usually it has been trying to enlarge one of the existing holes to put something other than fencing wire through it. They are murder on drill bits. I find them similar to the old steel bed-frame angle.

  14. #14
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    Quote Originally Posted by Grahame Collins View Post
    ...11mm drill bit.
    I wonder if this is the issue? I've had grief drilling relatively large diameter holes in relatively thin stock with twist drills.
    Chris

  15. #15
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by jack620 View Post
    I wonder if this is the issue? I've had grief drilling relatively large diameter holes in relatively thin stock with twist drills.
    Maybe a step drill to 8mm and then the 11mm? But I reckon 600 rpm might be the problem. I'd be using around 300?

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