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Stainless Screws and Drivers

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  • Stainless Screws and Drivers

    Howdy - just started assembling a deck rail modification - lots of Port Orford cedar, vertical louvers uppers, solid cedar lowers (below railing). Combo wind and sun screening etc. First screw - pre drilled through fastening piece, but not into anchor piece. Screw snapped. OK - I'll drill them all going forward.

    But, I do have a question. I used an impact driver - which I am admittedly new to. Should I have just slowly screwed that screw in with my drill? Do impact drivers have bigger failure rates with the more brittle stainless?

  • #2
    I recently used a bunch of stainless self-drilling screws with my large impact and 100% success rate. They are Hillman Deck Plus screws, and I used a medium-length Torx bit (shorties transmit more pounding, long ones flex more). I did pre-drill some and not others, both worked fine. I do feather the trigger by feel, and slow down at the end then hit the impact a few times in short bursts.


    • #3
      I donít ever use a drill for installing screws. It pops and carryís on and ruins the head of the screw. I have found that stainless wood screws will break when bottoming the our in wood, pre drilled or not. Evidently the screw has enough pulling force to pull the head off the screw. The bigger the screw the worse it is. This is also true with some lag bolts. I wonít go into the country of origin of the screws but it could be part of the problem. To solve the problem I am careful not to bottom the screw head in the countersink, then complete the screw by hand with a screwdriver. Other types of metal screws donít seem to be as prone to breaking off the heads when installed with an impact wrench, probably better metal. Stainless might be great for its rust resistance but it is not the greatest material for fasteners. Donít EVER use an impact to tighten a stainless nut and bolt, you probably wonít ever be able to get it apart!


      • #4
        Carl is right, a drill is a recipe for disaster. The impact is the only right tool for this, and it needs to be used somewhat carefully. Also, which impact? I use a brushless Dewalt which means I have super-fine control of it. Heck, I even use that driver to install small screws and tighten them all the way to the end, no manual driver at all. I can run it down to less than 1 RPM.

        I disagree on the stainless however, as I do this all the time. I've installed and removed the stainless hardware on some of my Jeep guards at least a dozen times, using the impact. They key again is control; low speed. Also be extra careful with nyloc stainless nuts, as the nyloc causes pressure against the threads and they gall easily. Again, slow and steady, which is what you should do with all nyloc fasteners anyway to prevent degrading their locking ability.


        • #5
          Thanks guys. I know I didn't ease-off on the driver speed. I was dangling 20ft in the air and left handed (which I am not). FYI - country of origin - yup. Also, I took some scraps and did some tests - pre drill, no pre drill etc. I couldn't break any more.


          • #6
            My methodology is to start slow to get a clean straight bite, run it in fast, ease off right at the end so it stops. Then give it a couple of quick bursts of impact until the head is just below the surface. I've broken maybe one out of 100 fasteners, and always at the beginning when seeing what I can get away with.


            • #7
              I'll have to be the contrary opinion/ experience here I think. While I would NOT use any regular drill for this, a variable speed with a clutch is perfect from my experience in doing everything from building a deck to a fence. However I don't like stainless screws, as they are not as strong as coated steel screws. Preferably I used Torx head "Deckmate" screws which have a lifetme warranty against corrosion.

              I do have an Ridgid 14.4 Volt Impact driver, but I've found that to be overkill. I've had to destroy a hex-bit driver, and even snap small bolts, as well as screws. I used it once to put together some steel shelving and it did a great job... so great, that when I bolted a piece together, using the wrong hole, it was impossible to remove the bolt and I had to take my Dremel to cut the nut off.

              A clutch driver with most screw heads does a great job, but as mentioned, I prefer Torx Heads as there's much better grip without slippage.

              Like all things, we each have our preferences and I recognize that... but for me, the Impact driver very rarely gets used.

              Think it Through Before You Do!


              • #8
                What you've shown is that there is a huge variation in impact drivers. You'd have to pry mine from my cold dead fingers. My best friend has built some pretty amazing things in his job all with an impact, and he literally says "It has changed my life" so much that it became a running joke at his company. Both of us build everything with high-quality impact drivers and bits.

                This entire system was built with a few impact drivers and Tek screws, no drills, no hand drivers...

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                • #9
                  I think the problem with stainless steel screws, the ones that break the heads off, has to do with the way they are manufactured. A quote from some of my old notes, donít remember where it was copied from....It is a common misconception that stainless steel is stronger than regular steel. In fact, due to their low carbon content, many stainless steel alloys cannot be hardened through heat treatment. Therefore, when compared to regular steel, the stainless alloys used in bolts are slightly stronger than an un-hardened (grade 2) steel but significantly weaker than hardened steel fasteners. Unless great care is taken, stainless fasteners are susceptible to seizing up during installation, a phenomenon known as galling..... end of quote..... that said, The manufacturing of bolts and screws is usually done by simply rolling a particular size rod with dies to press in the threads or screw flutes, then the head is stamped or mashed into shape. The junction of the head of the screw/bolt to the threads is a point of great stress to the metal and is prone to break when over torqued. Thatís why the heads snap off! Thatís what torque specs are all about.
                  From my experience a higher grade stainless bolt that appears to be plated does not have a problem with seizing or galling, and is what is normally included with automotive and marine add on kits. Try installing common 316 stainless fasteners with an impact and there wonít be and removing them, if you are lucky enough to get the bolt threaded on far enough to seat. Thatís probably the reason a lot of stainless fasteners are plated, to protect us from ourselves.


                  • #10
                    I've installed a lot of plain 316 stuff with an impact. SLOWLY! I also made the mistake of grabbing my air gun while installing some in a swim platform, and it welded itself in half a second. The hardware on my Jeep is Ace Hardware/Home Depot type stuff, for guards I made myself. Again, it's about the method, not the tool.


                    • #11
                      Usually when I am using screws in situation where it might split, I drill a holes first. This has become almost second nature to me. Just this past week, I had a drill with 1/8" bit and then my impact driver. Drill holes place screws. Do it right even if it is overbuild. At least it will last.
                      Hank Lee

                      Experience is what you get when you don't get what you wanted!


                      • #12
                        One thing that I havenít seen mentioned is lubricating the screw. I have a block of paraffin wax that I use on my jointer table that I scrape the threads with. Find you a screw pilot hole chart on line and use the correct drill for a pilot hole, usually recommends a tapered drill, lubricate your screw and you will see better results. Just for laughs google ď stainless steel screw heads break offĒ, make a pot of coffee and prepare for a lot of reading. You are not the only one who has this problem.