Machinist’s woe: How the hell do I fix THIS?


So I was tapping a stringer on Keyboard 1 and the tap snapped off in the hole.

Below the surface. That’s hardened steel. Drilling it out so I could use a reverse-extractor was fruitless: I blunted, this and finally snapped a cobalt bit, which the hardware store said was the hardest thing they sell.

Now WTF do I do? Anyone have any brilliant solutions? Please forward this to all the metalworkers you know.

7 Responses to “Machinist’s woe: How the hell do I fix THIS?”

  • Tweets that mention Why was I up till 2? Because I couldn't solve this - can you? Any metal workers out there have good advice? -- Topsy.com Says:

    […] This post was mentioned on Twitter by MackReed. MackReed said: Why was I up till 2? Because I couldn't solve this – can you? http://www.xylovan.com/?p=304 Any metal workers out there have good advice? […]

  • rabagley Says:

    Well, it can be “fixed” but you’ll need to disassemble the beam from the rest of the instrument and take it to a machinist.

    What he’ll do is mount the beam in a vise and use a special kind of hole saw to remove a plug of metal that includes the tap.

    Now you’ll need to fill the new, much bigger hole. He’ll may make a threaded plug (of the same material as the beam) and thread the hole to accept it (using staking to make the plug stay put) or he might clean up the hole and braze a plug into there. Or, he could do something else that he thinks will work for you, but he’ll explain it.

    Then, if you like, he’ll drill tap the plug for the original thread you needed and you’ll be back in business. While he’s set up for that, he could do all of the drilling/tapping for that for not a lot of extra money.

  • factoid Says:

    Hey, rbagley – this is all awesome (and promising) advice.

    Thanks so much for taking time to reply. I had literally left this task completely stalled, and was in denial about ever getting it fixed, but MakerFaire is coming up and I need to face this soon.

    I was considering just brute-forcing it out by drill-pressing it from both sides and using a punch, and then fitting that one key with an oversized mount hole to accommodate a bigger bolt, but this is much better.

    Now to find a good machinist!

  • rabagley Says:

    Oooh, one other idea. A machinist with an EDM machine (electrical discharge machining) could cut the tap out of the hole without disrupting the existing threads. EDM machines are ACCURATE and work by burning out the material using an electric arc.

    But you’re still going to need professional help.

  • factoid Says:

    Yeah, someone else mentioned EDM, but I’m worried since the tap is hardened steel and it’s buried in pretty soft aluminum … But definitely calls for a pro.

  • Damn it. Again. | XyloVan Says:

    […] Interior design, bolts, sleeper-rod pretensions & random brain-damaging activitiesfactoid on Machinist’s woe: How the hell do I fix THIS?rabagley on Machinist’s woe: How the hell do I fix THIS?factoid on Machinist’s woe: How […]

  • Wherein we get a little professional help, and joy is restored | XyloVan Says:

    […] and Glendale in search of an EDM-equipped shop, I phoned a local machine shop and described my two mistakes. “Ehhh, bring it in, we’ll see what we can do,” says the crusty old […]

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