Machining Plastic - Nylon Acetal UHMW LDPE HDPE machining qualities?

Jim,

I was also under the impression that the Anodic voltage difference between two metals should be kept below .15 V in harsh environments. Bronze has an Anodic voltate of 0.25 to 0.33 (average 0.29) and 300 grade stainless has a range of 0.0 to 0.15 (average 0.075). This gives a difference of about

-- Geoff

"Jim Woodward" wrote in news: snipped-for-privacy@comcast.com:

Geoff --

Bronze and stainless turnbuckles are not my imagination. They are mentioned, favorably, in Understanding Rigs and Rigging, Richard Henderson, International Marine, 1991 and in Rod Stephens' chapter in Desirable and Undesirable Characteristics of Offshore Yachts, John Rousmaniere, ed. W.W. Norton, 1987. (I assume you know of Stephens -- Henderson wrote the USNA - Annapolis official textbook on boats, among many other things.)

Turns out, they are not gone from the market. Some current Navtec turnbuckles are stainless and bronze (the web site isn't clear, but the paper catalog is).

As for stainless screws into aluminum, I'm with you. As a whole, however, we don't have much in the way of alternatives for attaching things to masts, particularly where the mast alloy can't be welded, so you frequently see it. As you say, one of the pastes will help. Best solution is to through bolt with plastic washers, but doing that on a mast or boom can require imagination, good hands, and luck.

So, again, I would seriously consider a bronze bushing here......

Hmm. Are you sure it was the SS, and not the aluminum, that was going bad? I think that aluminum will corrode badly in salt air in very short order.

Jim

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Interesting about acetyl being non-hydroscopic. Although I'll take your word for it, we have constant problems in wet areas where acetyl was used and the material degraded. It usually shows up as stress cracks as though the material has swollen slightly. I've even had some parts explode from internal stresses when used in hot water.

Koz (who is resp>Acetal is NON-HYDROSCOPIC I don't even have to gry it to injection mold it. >Nylon IS.

I just wanted to let you know that I machined the part earlier this week and was VERY happy with the finish that I got. It's a smooth as a baby's bottom. I had to cut 2" pipe threads also, and they turned out perfect also. Taking larger cuts of .100 to .150 worked great using a very sharp HSS cutter,

-- Geoff