Gallery, Projects and General > How do I??

Machining tolerance when anodizing aluminum

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Mike K:

--- Quote from: WeldingRod on November 03, 2021, 11:33:58 AM ---Looks like 10 to 25 microns growth for colored anodizing.  20 to 70 microns for hard anodize. 
You are converting an equal thickness of the part into twice as thick oxide layer.  So, if you strip it off, the part shrinks twice the numbers above.
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Thanks!

Mike K:

--- Quote from: philf on November 03, 2021, 11:33:18 AM ---
--- Quote from: Mike K on November 03, 2021, 08:58:54 AM ---
--- Quote from: philf on November 03, 2021, 05:02:26 AM ---You can always plug the tapped holes with a nylon screw.

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Nope, not nylon.  Not compatible with 15% sulfuric acid.

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Not even for the time it would take for the anodising? Wrap them in PTFE tape. I used to have a collection of polypropylene screws but I suspect I left them at work when I retired.
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Well, anodizing is one to two hours, depending on the anodizing depth desired.  I have no direct experience, mind you, but the online "Nylon Chemical Compatibility Chart" I found says that Sulfuric Acid (10-75%) is "D-Severe Effect".  Quesion, then, is: How much damage can be done in two hours?  I'd rather not find out; the dissolved nylon could wind up interfering with the anodizing process.  Polypropylene is listed as "A-Excellent".

https://www.calpaclab.com/nylon-chemical-compatibility-chart/
https://www.calpaclab.com/polypropylene-chemical-compatibility-chart/

tom osselton:
Could you not drill a hole and fill it with silicone to make a plug it sounds easy or am I missing something?  :smart:

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