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Old 19-02-2012, 05:56   #16
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Re: Maintenance - Tricks of the Trade

How many "work hardened" hose clamp screws have you seen?
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Old 19-02-2012, 06:09   #17
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Re: Maintenance - Tricks of the Trade

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Originally Posted by Bill_E View Post
Are you sure that dielectric grease is non-conducting? From the name one might think so but for about 40 years I thought it was conducting because of the way it was used in distributors ...
Dielectric grease is non-conductive, but when you slide the connectors together (or install a spark plug/distributor wire), there is metal-to-metal, contact and the grease gets displaced, so the area around connector is protected from moisture. It’s only used as a lubricant and moisture barrier.
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Old 19-02-2012, 06:52   #18
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Re: Maintenance - Tricks of the Trade

Thanks Gord I checked as well and you are right! But at the same time I don't think I want a non conducting grease in a crimp connection. So I also checked online and there are several conducting greases. Recommended for such things as antenna connections. I'm thinking it's worth the $8-10 for a couple of ounces of that to use on wires before crimping, on plug connectors, like antennas, radios, navigation electronics, etc. I've got some connectors on my Raymarine instruments that are looking a little funky. It might be worth a quick cleaning followed by an application of conducting grease and reassembly. As you say...when will you have the time to do it right!!
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Old 19-02-2012, 07:01   #19
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I would never use a conducting grease. The crimp creates the contact you need, nothing will improve that, but you need to protect it, for which dielectric grease is designed. It does not interfere with the crimping process.

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Old 19-02-2012, 07:54   #20
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Re: Maintenance - Tricks of the Trade

This may be getting a little arcane. I'm assuming that one would use a nonconducting grease after the crimp is made. I agree that a proper crimp should have excellent metal to metal connection but still.

I'm thinking more about some of the other types of connections. I have things like Raymarine Seatalk cables and radar cables with connectors that see some weather. I also have some instruments that are protected but have these flat connectors with (I think they are called) flag connectors on the cables. I've just recently taken a lot of my instrumentation apart and checked things out. Some of those are a bit corroded and I think that they would benefit from some kind of grease protection. And a conducting grease should work well here. (I think!)

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Old 19-02-2012, 08:01   #21
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Re: Maintenance - Tricks of the Trade

Based on experience in electronics working on F-4s and B-52s in the USAF would highly recommend dielectric grease on marine connections. Insulates and protects well.

Worked on black boxes that had dielectric fluid circulating through the entire box, for cooling and insulation. Strange to have a fluid hose connection to a black box, but was absolutely needed because of massively high current flow.

Failure of the dielectric circulation resulted in the box contents melting down into a layer of solidified glass and debris about an inch thick in the bottom of the box with no components recognizable. Pretty amazing.
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Old 19-02-2012, 09:38   #22
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Re: Maintenance - Tricks of the Trade

Di electric is non-conducting. There is a conducting grease that is good for things like the SSB antenna connection on your backstay or vhf etc.... Most di electrics are silicone based, so if you use it BEFORE you make the connection, it might inhibit the contact. I coated my ssb connection with the conductive grease, wrapped well in fabric electrical tape, then finished off with white, stretchy rigging tape.
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Old 19-02-2012, 09:57   #23
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Re: Maintenance - Tricks of the Trade

In the thousands of electrical connections I have made over the years, never has there been a problem with either silicone grease or Tef-Gel preventing a good electrical connection. It just does not happen if you are making a proper electrical connection in the first place.

I know for a fact that in some connections if I had not used a grease that water would have penetrated the connection, causing the connection to oxidize. And of course oxidized metal causes a bad connection.

On the other hand, using a grease that does conduct electricity could cause a short circuit, especially with coax connections which have relatively small tolerances between hot and ground.
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Old 19-02-2012, 10:10   #24
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Re: Maintenance - Tricks of the Trade

I dont use anything unless it's in a really moist environment (bilge connector strip for bilge pump) or out in the weather (SSB antenna or Tillerpilot power connection etc) My theory on the antenna connection is that there is very little intimate contact with the two cables clamped together in the first place. The Copper will form cuprous oxide quickly, wrapped or not. So the grease on all of it keeps the corrosion down. Connections like two prong power connections for a tillerpilot or other cockpit power accessories that get removed/unplugged are notorious for the brass prongs making a poor connection. I cant imagine coating those with silicone... but to each his own! I do use silicone grease sometimes, but only as a "sealant" device.
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Old 19-02-2012, 12:20   #25
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Quote:
Originally Posted by Cheechako
Actually this is not true. SS is often magnetic if it has been "Work Hardened".. ie: bent, formed, rolled and even machined. The screws on clamps often seem to be magnetic even if the calmp says "all stainless". Also, FYI: once SS is work hardened, it is more prone to rusting.... unless the surface is polished or passivated....
Actually, it's a bit simpler that that. Stainless Steel comes in several series.

300 series is non-magnetic. 316SS is the most corrosion restrain, it's also quite expensive.

400 series is magnetic.

PH series can be slightly magnetic depending on the heat treating undergone from the annealed state.
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Old 19-02-2012, 12:41   #26
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Re: Maintenance - Tricks of the Trade

Yeah, it's the iron content in the 17-4ph etc and 400 series that does it. With 300 series, when work hardened without annealing it tends to realign the grain structure.... which makes it more magnetic. I spent my working life in an aerospace manufacturing environment. Had my guys make a lot of neat boat parts! (One was a 6Al-4V titanium fuel tank for the bilge!) Anyway, I bought a flat bar of 304 stainless to make some parts out of. Typically these bars are cold rolled on the final pass at the mill. The surface was a little rough, but fortunately , due to the cold work, it was so magnetic my guys were able to put it on the surface grinder (a magnetic table holds the metal in place) and grind it smooth before further work. In the end the assembly was annealed in a vacuum furnace & passivated so it came out well.
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Old 19-02-2012, 13:05   #27
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Re: Maintenance - Tricks of the Trade

Quote:
Originally Posted by Cheechako View Post
Yeah, it's the iron content in the 17-4ph etc and 400 series that does it. With 300 series, when work hardened without annealing it tends to realign the grain structure.... which makes it more magnetic. I spent my working life in an aerospace manufacturing environment. Had my guys make a lot of neat boat parts! (One was a 6Al-4V titanium fuel tank for the bilge!) Anyway, I bought a flat bar of 304 stainless to make some parts out of. Typically these bars are cold rolled on the final pass at the mill. The surface was a little rough, but fortunately , due to the cold work, it was so magnetic my guys were able to put it on the surface grinder (a magnetic table holds the metal in place) and grind it smooth before further work. In the end the assembly was annealed in a vacuum furnace & passivated so it came out well.
I too spent my life working in an aerospace manufacturing environment as a tool design engineer.
I sure miss having a full blown machine shop with all the accompanying support available. We'd have made short work of my "little" projects. We made quite a few "experiments".

Awab clamps period. Buy the 7/16th flexible socket driver and position clamps for best one handed operation possible. Opposite direction if you can as Gord says to diffuse the questions.

Double up the smaller crimped wire. All my crimps are with heat shrink connectors (what's the adhesive that extrudes from them?). In wet areas I cover these in non conducting grease and heat shrink.
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Old 19-02-2012, 14:22   #28
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Re: Maintenance - Tricks of the Trade

'I sure miss having a full blown machine shop "
There are a number of online machine shops and fab businesses, that offer free software and then process standard cad/cam files to do the work for you. Usually a bit on the damn pricey side...but then again, machine shops have simply become damn pricey in a lot of places.
At least the resource exists if you've got no other.
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Old 19-02-2012, 15:03   #29
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Re: Maintenance - Tricks of the Trade

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Originally Posted by Bill_E View Post
This may be getting a little arcane. I'm assuming that one would use a nonconducting grease after the crimp is made. I agree that a proper crimp should have excellent metal to metal connection but still. (I think!)

Bill
I made hundreds of crimp connections for a Practical Sailor 1-year salt chamber test. Sore hands. However, of 350 crimps NONE failed, even under load. Slide on connectors did fail. Only a few % were heat sealed; heat sealing protects the wire from wicking, not the crimp, which doesn't need protection. In most cases this has more to do with repairability (the wire stays good instead of turning black under the insulation) than reliability.

Yes, dielectric grease is insulating. The primary function is keeping air and galvanic currents (should spray wet the area) away. The grease actually did more to protect the terminal block and wire than the actual connection (good connections are too tight for water or air). There are conductive greases, but these are specialized, found in very large switchgear, and have no real place on a boat. Used around ordinary terminal blocks, it will make things worse. Don't do it. There is a good reason it is not on the shelf.

No, dielectric grease does not effect the connection in any negative way. A good crimp (ratchet crimper) is made under such extreme pressure it is excluded. Bolted/screwed connections do the same with much lower clamping force.

Low pressure electronics connections are a different matter. I'm no expert there, but I do know from expereince that some are very susceptible to any contamination; generally the realm of gold-plated contacts, doing away with corrosion. This is situation specific; which will be the greater problem, the grease or the corrosion that will surely come? This depends on the contact material.
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Old 19-02-2012, 15:28   #30
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Re: Maintenance - Tricks of the Trade

Stainless hose clamps with mild steel parts are not the only way to go wrong;a number of brass "marine grade" piano hinges have proved to have mild steel pins,don't last long in salt air.
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