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Hi Jon, I would just cut the window a small amount over size to make sure that there is at least enough material for the window specks with a little more, then make your metal seat accordingly. that way you have the full spec seating surface and acrylic disk size. How far away the side walls are is not really a concern to me, as long as the seat is designed to handle the load required of it. Since most the higher stress area is transferred to the inner area of the seating ring. Besides so many of are windows have a FOS of 8 so we are covered. For example, my original forward viewport had a OD of 16", and it's seating area had a OD of 16 3/16", giving 3/32" of room to play with. That is more then enough room to deal with a very small tapper I have of 0.012" / 0.31 mm in a 2" thick cut. You don't even need the side walls on the seat as long as the retaining ring can keep the viewport centered. For example, Idabel's lower forward flat viewport. Regards, Szybowski > Date: Mon, 20 Jul 2009 09:39:25 -0400 > From: jonw@psubs.org > To: personal_submersibles@psubs.org > Subject: Re: [PSUBS-MAILIST] Aqua Jet Cutting My 2" Acrylic Viewport > > > Since "little bit of a gap" is subjective, Stachiw says radial clearance > 0.06 in (1.5 mm) may lower the critical pressure of the window. > > Brent Hartwig wrote: > > > > > > *Thanks Jon, Ya I don't know about the exact stress issues either, > > so I'll be annealling any windows cut this way until more favorable > > data is available for are specific applications. Most the basic > > flat viewports I've seen have a little bit of a gap between the OD of > > the acrylic and the side walls of the welded in seat, so I don't see > > the tiny bevel as being a real issue. We just need to make sure there > > is a little gap or one might whind up having to lathe turn the part to > > make it fit. * > > ** > > ** > > > > > |