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Thread: Pre-plating tapping size

  1. #1
    Associate Engineer
    Join Date
    Dec 2012
    Location
    Merseyside
    Posts
    1

    Pre-plating tapping size

    Hi all. We're manufacturing a product which requires cadmium plating all over including small tapped holes. The tapped hole requirement is No.4 (.112) x 40 UNC 2B. The plating thickness requirement needs to be 0.0003"/0.0006".
    It is difficult to plate such small internal features. Would it be normal practice to use an oversize tap and expect the cadmium to 'plate up' to achieve the correct thread size? If an oversize tap is to be used, would it simply need to be 0.0006" to 0.0012" bigger than the standard tap?
    Thanks in advance.

  2. #2
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,043
    What is the defined thread specification? The Cadmium thickness might not matter.

    Also, holes that small may not get fully plated to the full material thickness unless handled specifically to do so using wetting agents and agitation etc during plating.

    Finally I would be very surprised at being able to tap consistently to a 0.0006" tolerance even with a specially ground over-size tap.

    Other's may disagree, but I would say, "don't worry about it." Submit samples to the customer QC department and see where it all falls.

  3. #3
    Lead Engineer RWOLFEJR's Avatar
    Join Date
    Mar 2011
    Location
    Rochester Pennsylvania
    Posts
    396
    I'd say don't worry about it also. Cadmium is soft enought that you'll still be able to run the screws in there anyway.

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