Form tap to fix anodized undersized holes in Ti? - Page 2
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  1. #21
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    Google the Anodic corp. Aluminum Hardcoat Anodizing | Anodic Incorporated They will send you a FREE wall chart about Hard coat and build up. Hang it on the wall and use it to refer to. It will be handy in the future
    Best of Luck,
    Chris

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    Like the previous poster said, TI anodizing should very minimally change dimensions, if at all.

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    Quote Originally Posted by 360427 View Post
    Even if a $120 thread gage saves $5,000 of parts from the inspection nazis?
    Love it!!

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    Quote Originally Posted by Larry Dickman View Post
    High dollar parts and you want to risk them with free advice from a public forum? If a gage is a little tight, a real live screw will probably be ok. I would call your customer and let them decide.
    That would be a hard NO! at alot of places, especially if it is aerospace. The idea (or so I was told) was to not alert them of anything (ANYTHING) that might even a little bit be a problem or it could trigger an audit...

    Quote Originally Posted by dpolseno41 View Post
    Any screw actually going in there will be fine. I second asking the customer before screwing around.
    If it is aerospace, I would not call anyone. The gage fits or it is a bad part, no grey area here.


    For the record, i agree with the sentiment that if a screw goes it is fine. I learned a hard (stupid) lesson working in aerospace, print or bust LoL!

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  7. #25
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    I think it is certainly worth running a lubricated form tap and checking the results

    you are probably trashing the tap, but a few holes are no doubt worth it

    people here don't seem to be understanding the whole incoming inspection thing.

    mil stuff you don't fool around, and they are not amused by 'well the screw fits'

    as a side note, SHC screws are the only screws that are close to correct, everything else tends not to conform to specified dimensions

    I have no expert opinion on titanium plating, but most plating that is not on titanium needs to be accounted for. You can frequently get lucky with aluminum anodize, but that is all it is. the holes can shrink if not masked

  8. #26
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    Quote Originally Posted by mhajicek View Post
    I have some fairly high dollar Ti6Al4V-ELI parts that came back from hard-coat anodize with some threadmilled 6-32 holes ever so slightly undersized such that the go gauge will almost but not quite pass through. Holes are through a .075" thick wall. Is it safe to use a greased form tap to resize them?

    Also, my plater claims that the anodization doesn't change the dimensions at all. Is that bull? I need to now if I need a pre-plate thread gauge to ensure this doesn't recur. Maybe I should get a go gauge that's a few tenths big, and use the standard no-go?

    Thanks!
    The actual titaninum anodizing coating type is needed to know if or how much build up can be seen in this application.

    Although there is some build up present depending on the type of anodizing method to the titanium, inside holes, both blind and through are less susceptible to build up (if applicable depending on type) due to an effect similar to faradays cage effect in powder coating. Although this is possible, if there is build up with this coating, .075" wall seems thin enough to still see build up in the id threads.

    The other unknown here is what is the 6-32 thread tolerance class specified and what is the pitch diameter of the go? You can conceivably being using a pre-plate go gage while you still have a few tenths until the actual low limit.

  9. #27
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    I’m not an expert, but I anodize a lot of my own stuff, titanium and aluminum. True Type III hardcoat, unlike several suggestions here, can add 0.002”. Ti is different and does not have the same properties as hardcoat on Al. You could gain 0.001”, but it better be because you spec’d it that way. Anodizing Ti is done for totally different reasons, and and is procedurally different than Al. It’s common to see a couple tenths of dimensional change. Ti itself is pretty unique in its memory/elasticity. There’s a good chance if you form tap it, with it being that close to the gauge, that the next day the gauge will again not fit.

    We’re you provided with operating temperature specs?

    Put that sucker in the freezer, then form tap with aerosol molly. When it’s back at room temp you should be good. Or, heat it up slightly before you give it to the inspection nazis. Lol


    I accidentally crushed some 0.024” wall Ti tubing in a 3 jaw. I tossed it in the scrap bucket, and a few hours later is was round again. It throw some calipers in it and it was really, really close to being truly round.

    6Al-4V and 8-1-1 Ti are my favorite metals to machine, but they can be frustrating because you literally can’t go a day without learning a new quirk when you machine it every day.

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