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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.
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What is the defined thread specification? The Cadmium thickness might not matter.
Also, holes that small may not get [B]fully[/B] 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.
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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.