[PSUBS-MAILIST] Clearances

[Jon Wallace via Personal_Submersibles]

 We should perhaps seek some clarification from Greg if he's willing to guide us.  I had a conversation with him about Kittredge annealing and he told me Kittredge never annealed any of his viewports.  
Stachiw was pretty adamant about annealing in his book.  Like Hank, I do seem to recall some restrictions regarding annealing multiple times although I don't recall if it's a single time or a different schedule as Dan suggested and I don't have my Stachiw book with me right now to check.  There is a rather obscure one sentence statement by Stachiw in his book in which he says any annealing is better than none.  This suggests to me that while adhering to the strict annealing schedule is ideal, if it cannot be met benefits will still be derived from a looser schedule.
Jon


    On Tuesday, December 10, 2024 at 11:59:14 PM EST, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 Hank, what you're proposing sounds totally logical to me. However, I have asked Greg this very question in the past (whether we really have to anneal a viewport.) I'm not sure what the underlying causality is, but he has enough professional experience in the field that I just take his word for it. "You need to re-anneal it whenever any machining has been done on a viewport." Annealing is pretty straight forward. 
I'm currently working on forming acrylic headlight covers and windows for an antique car restoration. It's a new skill I'm trying to develop, so fortunately I'm not making anything safety-critical like viewports. But one interesting detail is that Greg strongly recommended annealing even for this, because it'll make the covers and windows less likely to crack (there could be stresses caused by mounting screws or flying pebbles, for instance.) He had two basic points he stressed for the things to last:
1) That not all acrylic was equal. The only one he will use is "cell cast" acrylic, and he warned me emphatically to stay away from the cheap stuff which can be referred to as extruded or "continuous cast." I know this has not been mentioned on this thread, but I bring it up because it seems to be key information.2) Annealing
Next time I speak to him, I'll ask about machining with light passes and coolant.
Best,Alec

  
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