OT: drill and tapping "die cast "parts?

    I have a music box mechanism which doesn't work well. I suspect that it needs cleaning/lubricating.
    So rather than buy a new mechanism for a whole $9.99, I've decided to take the time and effort to fix this. Which will mean milling off the "rivets", and then drilling and tapping into the 'pot metal', to reassemble the thing afterwards.
    Any advice on tapping "cheap" material?
tschus pyotr
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Use cheap taps.
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-0500 typed in rec.crafts.metalworking the following:

    Cheap Chinese 'brass' ones?
    Oh wait, that's for plumbing, never mind.

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If I really want to salvage something like that I might risk an expensive and reputedly fragile spiral flute bottoming tap, and shorten longer screws to engage as far in as possible.
Yesterday before posting that I tapped a piece of electrical insulating board of unknown composition, using the least valuable old tap in case it contained an abrasive filler.
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    [ ... ]

    Hmm ... depends on how brittle the pot metal happens to be by now. If it were fresh, I would consider a thread forming "roll" tap, which would leave no chips to worry about.
    But -- I used to have a "dog-bone" wrench of pot metal which had given good service in the past (since the late 1950s, I think) but which just broke apart when I tried to use it for something which did not need much torque about ten years ago.
    Try just pushing a center punch into a non-critical area of the casting to see whether it deforms nicely or chips. (It may break totally, in which case repair was out of the question anyway.)

    Understandable.
    Enjoy,         DoN.
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wrote:

It's not a "high stress" application. Drill for 25% thread depth instead of 75% (slightly oversize) and tap with a sharp thread cutting tap. Put a bit of laquer or nail pollish on the brass screw you re-assemble it with. Done it many times - and often on OLD parts. (fixing old die cast toys etc)
I've even done it without a tap - using stainless steel screws - #2 even.
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