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Nuts & bolts: cheapo zinc, grade-8, stainless steel?

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  • Nuts & bolts: cheapo zinc, grade-8, stainless steel?

    When designing various braces and brackets for an outdoor, weather-exposed, long-aged (many years) purpose, what are you thoughts on bolt diameter and material? I'm using typical plated steel for the actual bands that wrap around a stove pipe to support it from the side on arms, and I'm still thinking about what the support arms themselves will be (probably aluminum tube or thin-walled conduit, perhaps with a shaft of rebar down the middle for a little extra strength), but I'm totally unsure about the fasteners.

    Nuts & bolts obviously come in a variety of diameters and materials. The cheapest and by far most prevalent (by shelf-space) at the store are the zinc-plated fasteners. They seem to be pretty general purpose and I have no idea what applications require upgrading to the next level, either in demands on strength or weather-resistance. Above that, there are at least two options: the pseudo-copper-brass-colored grade 8 bolts (I guess they're called "yellow zinc"), and the stainless steel bolts. Both are *much* more expensive than the zinc-plated bolts, but the stainless steel is also considerably more expensive than the brassy grade 8 bolts.

    First question: For a given diameter, are those yellow zinc grade 8 bolts less strong, more strong, or equivalent to stainless?...or if that's the wrong question, then do they "last longer" or "survive weather" better or worse or equivalent to stainless (I can't believe they are more weather resistant than stainless, but are they functionally equivalent in that regard)?

    Second question: When "locking" the ends of a band around the stove pipe together, or when attached the ends of the support arms to the band and to a support pole nearby, which of these three materials (or a fourth material I missed) would you use *and* what diameter would you use?

    I usually buy the cheap zinc stuff for my builds because I see no reason not to, but I've been thinking I might use the yellow grade 8s for this job...but I'm not particularly inclined to super-splurge on stainless unless there's a reason to believe it would vastly outperform the grade 8s. What do you think of all this?

    On a side note, I'm really curious if there is a tradeoff in diameter vs. material: Is a wider zinc-plated bolt just as strong as a thinner grade 8 or stainless bolt...or is that really not how the issue is approached?

    Thanks, just conversing, it seemed like an interesting discussion.

    Cheers!
    Last edited by kebwi; 07-19-2012, 09:16 AM.

    Website: http://keithwiley.com
    WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
    Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

  • #2
    Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

    Grade 8 are high strength and not needed. Stainless steel is what I would use, and be careful of mixing various metals to avoid galvanic corrosion. As to size, use what will fit best since pretty much anything over 1/4" will exceed any loads you will put upon it.

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    • #3
      Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

      Erg, the stainless is expensive. It sure is pretty though. Thanks!

      A few years ago my basement flooded any my compartmentalized bin of bolts, screws and assorted small gear was submerged for a few days. Everything, including the zinc-plated stuff, looked really bad afterwards, but the stainless was pristine! That experience definitely sold me on stainless, money not withstanding.

      Website: http://keithwiley.com
      WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
      Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

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      • #4
        Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

        Go for the stainless as it will last indefinitely. Grade 304 is fine (food grade) but 316 is better (marine grade). Try not to buy from the local hardware store as they charge like wounded bulls, rather go to the larger supplier/wholesaler/internet seller as they will be half the price. Galvanised is better weathering than the zinc or cadmium plated materials, with stainless the best, so the choice is up to you.
        Don't mix tour metals as they will oxidize/rust/react with one another (as Tscarborough suggested) over time causing you concern.

        Neill
        Prevention is better than cure, - do it right the first time!

        The more I learn, the more I realise how little I know


        Neillís Pompeiii #1
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        • #5
          Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

          Hmmm, so the band I made to wrap around the stove-pipe, which is "plated steel" (not rust-prone "welder's steel", or so I trust, and which has that weather-proof galvy look...I think) is not right b/c it'll react with the stainless bolts? I should make that out of stainless steel instead? What is stainless steel sheet metal gonna cost? I didn't even see anything like that at the box store, I'll have to get it special or something.
          Last edited by kebwi; 07-19-2012, 07:05 PM.

          Website: http://keithwiley.com
          WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
          Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

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          • #6
            Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

            Originally posted by kebwi View Post
            Hmmm, so the band I made to wrap around the stove-pipe, which is "plated steel" (not rust-prione "welder's steel", or so I trust, and which has that weather-proof galvy look...I think) is not right b/c it'll react with the stainless bolts? I should make that out of stainless steel instead? What is stainless steel sheet metal gonna cost? I didn't even see anything like that at the box store, I'll have to get it special or something.
            I like stainless steel. 316 is what I am most familiar with at work. The band you have (galvanized or maybe gavalume) will probably most likely last many years. You might want to buy a small can of "never seez" (or equivalant). You can coat the inside of your band with it where it touches your SS Chimney. It would be a good idea to apply some to your nuts and bolts also. If you ever have to take it apart the never seez will help the SS from galling.
            I don't care what folks say behind my back........They are either braggin' or.......lyin'


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            • #7
              Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

              Thanks for all the advice. Stainless 316 seems to be more than twice the cost of stainless 18-8 (which is also labeled 304 as mentioned earlier in this discussion). Golly. I'm not planning on putting my pizza oven at the bottom of a salt-water bay or in a chemical factory. If 18-8 isn't good enough to swing free in the open breeze, then what in the world is it good enough for? 316 is also harder to find. More online sources I've found have 18-8 than 316.

              I'll figure something out. Do you think 18-8 would be a catastrophe?

              Website: http://keithwiley.com
              WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
              Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

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              • #8
                Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                You will probably be all right using crappy zinc coated fasteners. When you ask for advice, you should always expect that you will be given the best advice, not the most practical.

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                • #9
                  Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                  Fair point. Thanks.

                  Website: http://keithwiley.com
                  WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
                  Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

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                  • #10
                    Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                    OK, now to throw you for a complete loop. You initially mentioned strength concerns along with corrosion resistance. Now you are talking the 400 series stainless. The best commercially available bolts in the US would probably be 431. They give up a bit in cororsion resistance when compared to 316 but have the tensile strength on grade 8 carbon steel. The common misconception is that stainless bolts are stronger than plain steel or zinc coated, NOT true, a 316 bolt has the same strength as grade 2 (the typical HD or Lowes plain steel is a grad 3). Its not until you get into the higher chromium alloys (400 series) that you get strength. If you are interested, I have a supplier in CA that can supply just about anything in the 431 range, don't have the info at hand but I will tomorrow at work.
                    If you have a friend in the UK, the absolute best would be BUMAX fasteners, Harder thatn grade 8.8 and equal to 10.9 carbon steel. There literature does not give the specific alloy content, but it is also a martensitic alloy similar to the 431. .ultra high strength and very good corrosion resistance. I have not found their US distributor, yet. but have been told that I need to. Price on the 431 bolts will be triple the cost of a 304 and double the price of 316. I just paid over $4 each for 4 dozen #8 x 32 cap screws that were 70cents each in 304. For all practical purposes, get 316 bolts and you will not have any worries,it is a much finer alloy for wet applications.

                    RT

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                    • #11
                      Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                      Originally posted by wotavidone
                      1) A grade 8 steel bolt is significantly stronger (roughly 1.2 -1.5 times) than a 304 stainless steel bolt of the same size. However, a 304 stainless bolt is very much adequate strength, and won't rust.
                      Oh, so the fairly common "yellow zinc" grade 8 bolts will actually rust?

                      Originally posted by wotavidone
                      4) 304 stainless is the right choice for freshwater exposure - they don't call 316 stainless "marine grade" for nothing.
                      "Fresh water", as in rain, right? None of this has anything to do with submerged water, fresh or salt. It's an oven, bear in mind.

                      Originally posted by wotavidone
                      5) The difference between zinc plated and "galvanised" is that zinc plated has a thin electrolytic coating of zinc, whereas galvanised has been dipped in molten zinc, giving much thicker coating of the sacrificial material. So they are the same, until the sacrificial coating dissolves away.
                      Well, I have no idea. The steel (not bolts, actual sheet, tube, etc.) at Lowes came in two forms, weldable (rust ahoy) and "plated". I have no idea what "plated" means to Lowes, presumably not true galvanization, but as to precisely what it is plated with, or by what method, I simply don't know.

                      Originally posted by wotavidone
                      6) make sure your bands are the same as the flue, i.e. both zincalume (coated with a zinc aluminium alloy) or both galv (coated with pure zinc).
                      It's a completely typical stove pipe, so it's whatever the millions of stainless steel stove pipes in the world are made out of. As for the band, it definitely isn't the same stuff. The stove pipe is almost mirror-shiny, like a normal stove pipe, whereas the sheet and angle-iron steel I bought for bands (plated) is much duller, there's no way they're the same material, albeit both are clearly steel. However, if the prescription is to use "the same stuff", then I gotta say, that stuff simply wasn't at the store, I didn't see it. There weren't any steel bands, angles, square or round tube, or anything that looked like the material conventional stove pipes are made out of.

                      Originally posted by wotavidone
                      7) If your flue is some sort of galvanised or zincalume steel, don't use aluminium brackets.
                      I haven't got the foggiest idea, although I can steer clear of aluminum as a general principle (I was still considering aluminum tubes for the support arms, but I can ditch that idea if it isn't popular).

                      Thanks.

                      Website: http://keithwiley.com
                      WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
                      Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

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                      • #12
                        Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                        Hey Keith, now that we have all thoroughly muddied the water for you. Go back to the
                        1st reply from Ts.
                        Use the stainless, 304 will be fine, and use 5/16" or 3/8" diameter for piece of mind regarding strength. He is a pretty knowledgeable guy and "knows his s%#t"...and I totally agree. Not that I am an expert, I just know enough to overbuild everything. From a practical experience standpoint - over 10 years working for a fastener manufacturer and currently for a maufacturer of 100% 304 and 316 equipment that must withstand continuous hydraulic pressure and the associated velocities of processing 1MGD up to 100MGD of water (that being million gallons per day). every bolt is either 304 or 316 and 1/4" or 5/16" depending on the hydraulic calcs.
                        You live in a wet part of the country, the yellow zinc may look pretty buts its going to rust within a couple of years, that coating is no more than .002" - .003", less than a good coat of paint.

                        RT

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                        • #13
                          Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                          Yeah, I've found a bunch of places online to get 304 stainless which bring the price to a very reasonable range...ahem, unlike the box stores.

                          Thanks again.

                          Website: http://keithwiley.com
                          WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
                          Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

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                          • #14
                            Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                            Originally posted by Gulf View Post
                            It would be a good idea to apply some to your nuts
                            Does it sting?
                            The English language was invented by people who couldnt spell.

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                            • #15
                              Re: Nuts &amp; bolts: cheapo zinc, grade-8, stainless steel?

                              Originally posted by brickie in oz View Post
                              Does it sting?
                              Probably tighten them up.
                              Kindled with zeal and fired with passion.

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