Need help with ideas to drill shear pin in 3" OD stainless
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  1. #1
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    Default Need help with ideas to drill shear pin in 3" OD stainless

    So a customer has a screw conveyor (5 actually but this is the only issue) that somehow had a shear bolt installed between the gear box and the frame. It looks like an adapter sleeve was made as someone made the shaft a foot too short.

    What seems to be there, is the OEM drilled and tapped a socket head bolt to lock the main shaft to the sleeve. Naturally the head broke and it is not a through bolt.

    The issue is that it has to be drilled in place. There is a huge list of issues with the OEM doing stupid things so that is why it must be drilled in place.

    I'll get pictures soon, but I need to drill a 5/8" hole through a sleeve and shaft that totals 2 7/8" total. There is a 4" gap total between the GB mounting plate and conveyor hopper frame, but the hole is off-set so thick 2.5" x 1.5" so a drill dead center isnt an option.

    At the closest point, the drill have to be 11.5" to drill through everything including being 3/4" installed in the drill.

    There is a leg welded in place which restricts the idea of welding a steel plate and using a mag drill. I could use a mag drill, but the drill bit would have to be about 22" long total.

    Does anyone know where to purchase drill bit extensions that can handle a 5/8" drill bit and the torque at 20" away?

    Does anyone have a better idea?

    Sent from my SM-G960U using Tapatalk

  2. #2
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    Just weld on an extension eh?

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    If welding isn't an option, you maybe able to buy a "Pully Drill" as they are long. Or call these guy's they have people standing by to answer these sorts of questions. Plus their drills are made in St. Paul, MN - Viking Drill & Tool | Product Catalog of Drill Bits

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    Quote Originally Posted by Bondo View Post
    I could use a mag drill, but the drill bit would have to be about 22" long total.
    No, it does not.

    The drill has to be what the hole needs it to be in the "drilling zone of operation". This is not an "N" diameter deep continuous hole.

    The extension is not exactly in "free space", trans-lunar orbit... there are some limiting features and obstructions. But it sure as Hell has more than 5/8" of OD open to it.

    Does anyone know where to purchase drill bit extensions that can handle a 5/8" drill bit and the torque at 20" away?
    Happens to be a stock one-piece drill - or near-as-dammit.. and I even have one. "Bellhanger" length. 18", as it were. Longer ones exist, too. Clear up to a meter or so.

    Why so? "Telephone man" or data cables.. We DO need clear-thru holes from a cold start, and often blind ones with multiple barriers. Ergo we are quite often the guys with the longest drills.



    But they are expensive. Worse, not always fast to get.

    Easier way to git 'er done sooner than a go-fetch is to use an ordinary 5/8" (or wotever) and SHOP FAB an extension.

    Extension is anywhere you can find tube or shafting.

    BIG HINT: It doesn't even have to be round.

    It's actually easier to put shop-fabbed machined end adapters into SQUARE tube. Or sometimes HEX. Handles torque better than set-screws alone. Welding is OK. You can sacrifice a drill cheaper than f**k-with time. You can even sacrifice a socket-wrench-clan extension.

    This is a one-off repair tasking. Not mass-production tooling to do ten thousand.

    You do not have to push it to failure, either if "torque" is a worry. Baby it, rather.

    It need not even have good balance.

    JFDI.

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    Yes, My approach would include the shortest flute drill that will make it thru, another short length of 5/8" drill rod to chuck onto, and a 5/8" ID tube extension --- either DOM or even extruded aluminum, if wall thickness was sufficient. Set screws and flats filed on shank. And loctite if you're feeling iffy.

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    I do weird stuff similar to this with a narrow taper step drill and a mile of 1/4" drive extensions. The step bits have 1/4" hex shanks, and tend to be sharp enough to start easily despite wobble and take less torque.

    If you must use a twist drill to get the depth, use a hole saw extension mandrel. Don't mount a holesaw and just use the pilot bit. You can even put in an appropriately sized center drill to start it.

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    Machine a guide with a drill bushing and use a hand drill. I'd have a few nice quality new cobalt center cutting drill bits on hand.

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    The old armstrong method is just to use the lowest rpm corded hand drill you can find, and step drill it. Slow and low, to quote the Beastie Boys. I have done too much of this sort of thing in stainless. I would be shooting for 200 rpm or so, start with a 1/4" bit, lots of lube - I like cool tool II in the little 4oz bottle for stainless. And then, you just lean on it.
    I do happen to have a drawer of 6" and 12" length 1/4" bits, for starting holes like this.
    I also have an 18" extension for drill bits, which has a hex socket on the business end- I have been known to braze a drill bit to it, then cut it off when I am done.
    once you get a 1/4" hole thru, you can step up pretty quick- 3/8-1/2- 5/8 is pretty quick with a hand drill.
    Yeah, if I could get the mag drill in, I could jump right to 5/8, but once the pilot hole is in, its no big deal, just time.

    I used to have a nice milwaukee hole shooter with a half inch chuck that went 0-600, but it got itself lost, now I use a Bosch, similar speed range, easy to get it down into the 100 to 200 rpm range. I also sometimes use my big right angle milwaukee hole hawg which is for drilling big holes thru studs for electrical and plumbing- lots of torque, and in the 0-300 rpm range, its pretty easy to keep it down to a nice slow spin.

    Trick with stainless is low rpm, as much feed as your shoulder can give it, lube, and sharpen drill bits as needed.

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    So I have been thinking about this a lot as even though I'm only 39 now, I've been working the last 3 years with only about 30 days off. The last thing I want to do is muscle this job as it sits just above shoulder height when sitting on the floor, so very awkward.

    I am thinking of just machining a piece of 1" OD or bigger stainless rod and making custom sized extensions for the mag drill. I can machine it to accept the 3/4 double flat standard bit attachments and make it accept a 1/2" reduced shank drill bit.

    Do you think that 1" OD is strong enough or should I go bigger? Assuming 24" from tip of drill bit to mag drill connection. So roughly a 19" extension.

    Sent from my SM-G960U using Tapatalk

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    Can you make a drill guide that fits on the part to keep drill bit in alignment?

    Get left hand cutting bit and create extension.

    Lean on it to hope it grabs screw and backs it out.

    Sent from my SM-G781V using Tapatalk

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    Let someone else do it...you'll thank me in the morning

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    Quote Originally Posted by plastikdreams View Post
    Let someone else do it...you'll thank me in the morning
    Oh I wish, I would pay someone else to do this. But, most of the time, that contractor just screws it up worse and then I end up doing it anyways. So I may as well skip that step and just do it.

    There is maybe a 1% chance, if that, to get the old bolt out using left hand drills and an extractor. It's so bad, it looks like it was hit by a chisel after it broke.

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    I don't have anything to add but best of luck and let us know how it goes.

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    I couldn't count how many times I have done stuff like this and even much worse with a hand drill and a guide I machined up. That's why I mentioned it above. It works. and much easier than wrestling a mag drill into tight spaces.

    I like to drill a small hole the diameter of the width of the web of the finish drill so two steps to do the hole. If you get the slightest sensation the drill is not cutting as good grab another new one, don't chance it.

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    I completed the hole, it was a lot simpler when you make new things for a hard job.

    I used a mag drill with a 23" custom extension with a 5/8" drill bit.

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