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Bolts and screws locking up? It’s not the quality of the parts but a common problem faced when using stainless steel fasteners.
The beneficial nature of using stainless steel is that it is corrosion resistant. This property is due to the fact that stainless steel, among other alloys, generate a protective oxide surface film. Though this may be beneficial, it can sometimes lead to problems with installation.
Thread Galling occurs during stainless steel fastener tightening and installation. When pressure builds between the contacting surfaces of the male and female threads, the protective oxides or coatings begin to shear, causing high points, or imperfections in the raw material. The result is that both pieces become locked together. The increase in friction causes the two parts to seize or “lock-up”. In serious cases, this difficult to understand problem is even referred to as “cold welding”, which illustrates the severity of the issue. Often, galling can cause damage to the thread of the fastener, but it can still be removed. In severe cases, the two materials completely weld together preventing loosening of the parts, and adding the difficult step of a forced removal and new parts to the process. The frustrating aspect of this is that both the nut and bolt can clear inspection individually, but fail to function effectively as a mechanical unit.
Reducing friction is the best solution to this problem. That is why we recommend lubrication, and MRO Solutions offers a lubrication that can lessen the threat of thread galling while also offering other benefits including corrosion and weather resistance. Galling can be a frustrating problem, but it can be prevented.
|MRO Product||Fel-Pro Loctite Part Number||Antiseize Technology Part Number||Neverseez Part Number||Jet-Lube Part Number|
|Solution 800 Low Friction Moly Antiseize||51048, 51049, 51145|| ||NBBT-8, NB-160, NSB-35B||28003, 28007, 28023|
|Solution 1000 Food Grade Antiseize||51168, 51170, 51171||31018, 4101||NSWT-14, NSW-160, NSW-8|| |
|Solution 2000 Premium Copper Antiseize||51144, 51147, 51005, 51006, 51007, 51008, 51009, 51010, 51011, 51146||11010, 11016, 11018, 11025, 11030, 11050||NS-40, NSBT4, NSBT-8, NS-160, NSBT-16, NS-168, NS-42B, NSA-16||10055, 1255, 10002, 1250, 10004, 10007, 10023, 1252, 10013, 10015, 10029|
|Solution 2500 Metal Free Antiseize||51605, 51606, 51607, 51608|| || || |
|Solution 2600 Premium Nickel Antiseize||51285, 51102, 51119, 51152||13008, 13016, 13018, 13030||NSBT-8N, NSN-165-N55, NSBT-16N, NSN-8||13602, 13604, 13607, 13623|
Seized, Stuck, Broken Bolts - All About Thread Galling | Fasteners 101
Seized, Stuck, Broken Bolts - All About Thread Galling Transcript
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Bob: Welcome back to Albany County Fasteners - Fasteners 101. I'm Bob and today we're going to talk about galling. Broken bolts, nuts seizing on bolts, etc. So, lets get started.
Galling is a term, mainly for stainless steel but it happens in aluminum and in many other metals. Typically, in stainless, you'll find this problem of galling or people saying that the nut or bolt is mis-manufactured or there's something wrong with the threads because they go to put the nut on and as you can see here here's a broken socket cap screw and the nut is still on there because the nut is jammed.
A customer actually sent this back to us due to the galling issue. Galling does happen for many reasons. I will go over one specific reason. That is that when you manufacture a screw or bolt, the bolt's threads are roll formed. They're cold roll formed, and the nut is cut formed. So, the nut, they actually go in and they have a tool that goes into the nut and thread cuts the threading. This (the bolt) goes into a jig in a machine and they roll form these threads.
So, you have two different types of threads. On the nut that is thread cut, under a microscope you can see that there are little fibers inside the nut. These (bolt threads) also have some fibers and high points because rolling is not perfect at the end of the day. So, when you put this, a regular finish nut, on you'll get some possible resistance as you screw it on and in this situation... here we go, it just started. So, what happens is the two different cut threads start to heat up as you're turning it on, and this is a regular finish nut.
If you go to use a nylon locking nut, a nylon (lock nut) has a nylon cap that's integrated into the nut. Okay? And that nylon creates substantial friction, which creates heat, and at the same time it accumulates the debris that's inside the threads in the high points. Then your nut will lock up and you won't be able to turn it all the way on.
By moving this up-and-down I get points where it starts to stop and jam up. To prevent this type of situation, you would have to use an anti-seize product. We have several of them here. We have four different types to use. When you're dealing with stainless you should always use an anti-seize product to lubricate the threads so you don't run into this problem. I'm going to demonstrate that for you. I'm also going to demonstrate, hopefully, this will jam up for me and seize, so I'll show you how that situation happens. We're going to move on to the demonstration of that.
So, I'm going to try and get this nylon lock nut to gall up on this flat socket head screw. This nylon lock nut has a nylon insert. It's not recommended that you use an impact wrench or a drill to put these on because the more friction you create will create more galling, more heat and you'll have immediate stoppage. So, I'm gonna put this in. Let's see what happens. See if I'm successful.
I'm doing this a little fast to see if it creates enough heat for it to seize up on me, which it's starting to right now. As you keep turning it's going to get tighter and tighter and that's galling happening right here. That's it. No more. I can back it off but it's just going to keep jamming further. I'm trying to back it off and now it's jamming in the opposite direction. So, this is exactly what they call galling; seizing of the two threads mating together. It’s sometimes referred to as cold fusion.
This goes to show you how far I got down. Not that far. This is a continual problem with stainless steel. If you use an impact wrench or a drill and put a socket into it and try to drive it on, they're just going to snap. The bolt is just going to snap off. I can feel the heat There you go, that's galling.
So now I'm going to show you using a new bolt with a new nut, with some anti-seize on, how easy this lock nut is going to go on. Okay? I have here some anti-seize solution. This particular one is an MRO product that we sell. Very happy with this. We get great results. This one is a marine grade anti-seize 2400 degrees. This will go up to 2400 degrees. It's a great product. This is one of our largest selling products, multi-use, I'm gonna apply some of this.
You can see, in here, it has a stick with some of the material on there. I'm going to apply this on a new bolt. You don't have to put that much on there. I'm just going to put a little bit. I'm going to screw it on here, put the nut on, look how easy that's going already and just put it in the vise and I'll show you how awesome this is to put in. That's all you need right there. Some anti-seize and you go all the way up. Not only that, you can also... remove it.
So, as you can see it's going on just fine. At the same time this won't vibrate off when you use the anti-seize; it just creates a barrier between the two metals, so you don't get that buildup of fibers in the threads. And here I am, I have to put some pressure on to get this off, but I can get it off if I have to and that's what locking nuts are made for because you don't want them to come off easy, you have to put some work in it but it's not going to be like this. Where it's seized on there. The only way I'm going to get this off (the seized bolt from earlier) is by over-tightening or over-loosening and it's just gonna bust.
This is a serrated flange lock nut and I'm going to put this one on. It has the anti-seize I put on there already. As you can see, I can hand tighten this up. So far, no problems. Now I'm taking it off and it's all hand. I get a little stoppage every once in a while, but overall no issue. There it is.
The purpose of anti-seize is to add corrosion resistance and prevent metal-to-metal contact which causes galling and seizing. They are lubricants for easy installation. Marine-grade. This is the solution 2400 marine-grade anti-seize. Goes up to 2,400 degrees.
MRO Anti-seize 2400 is used in extreme corrosion-resistant from water, salt water and humidity. Most popular recommendation for all applications. For use on stainless and/or in marine environments and water treatment plants.
The next solution I have is the solution 2000 copper anti-seize. This is used for copper/high temperature. Withstands up to 2,000 degrees. Extends fastener life. For use with nuts and bolts, pumps and valves, farm equipment, steam traps and fittings.
The next anti-seize I have is solution 1000 food-grade anti-seize. It's a soft white paste. Safe for food contact, water-resistant, temperature-resistant up to one thousand degrees and this is basically used in food processing equipment.
My last one is the solution 2500 metal-free anti-seize lubricant. This is a metal free grease-graphite blend. Metal-free is temperature resistant up to 2,500 (degrees). For use in applications, where it prohibits metal or copper, special alloy metals such as stainless steel, seals, packing, sleeves, etc.
There you go. Today I taught you about galling and seizing of bolts. I also taught you about anti-seize products; different types for different applications.
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