Tapping 4 -40 threads in titanium
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  1. #1
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    Default Tapping 4 -40 threads in titanium

    This wouldn't be an issue except the treads are down inside a recess 3.75 " deep. The holes need to be tapped .220 deep and the hole can only be .325 deep. so I'm not too confident in a bottoming pulley tap. Never tried to EDM anything this extended, any tricks to success? I have 24 holes to thread.

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    If you can get customer approval, try a form tap. Use the nastiest, gooiest lube* you have, and try test pieces first to confirm S/F and hole size. Make an extension that's a really good fit and well secured to the tap, you don't want it slipping while in use (and of course, do the tests with the extension, not a bare tap).


    *If you don't have this, buy it: CASTROL VARIOCUT C Moly-DEE Tapping Fluid 16OZ PN 98-890-7F: Amazon.com: Industrial & Scientific

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    I've learned to stop trying to tap 4-40 and under holes in Titanium. Thread-mill only for me

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    Hi RJT:
    How successful have you been trying to sinker EDM titanium in general?
    I have found that significant electrode wear is a big issue.
    Best success for me has been graphite trodes run with negative polarity for roughing and positive polarity for finishing, but that's on a Hansvedt sinker so it may be inappropriate for your machine.
    I've had poor results with copper trodes, ditto with copper tungsten and copper graphite.

    I've never tried burning a titanium thread though...best advice I can give is to buy some trode stock and do a few test burns.
    Saturn supplies threaded trodes for cheap...I recommend you get lots of stock because you'll likely use it up to do this job.
    Consult with the manufacturer of your machine for titanium settings if you don't already have them and be comfortable with what it is going to take in trodes and time before you quote the job.

    I've found Ti6Al4V to be slow to burn and to consume many more trodes than I expected.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    Marcus,
    Thanks for the advice, we use Electrodes for our EDM supplies, and I will consult them and Mitsubishi (our machine is an EX8 CNC sinker) on advice. We have very little experience with sinker EDM in titanium, lots of machining experience and some wire EDM.

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    Be sure to get the better C3 grade orbital tap electrodes.

    Smallest threads I've done were M4. About 3" deep in a pocket. I slowed the orbit speed down just to be safe. Literally the fit went from tight to sloppy with only a thou increase on the OB. The small threads are very fussy. Definitely prove it out on test piece then go for it.

    I own 3 Mits sinkers, great machines.

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    Did you use some kind of extension to hold your electrode, or just use a long electrode? Concerned about electrode straightness and being on center that far away from the holder.

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    Thread form with a tap extension should get you there. Coolant should be about 12% concentration, or turn off coolant and use anchor lube.


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