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So, I got a screw and things that look like rings (washers). One of them looks like incomplete ring (C-shaped), another is really a complete bigger ring.

The assembly instruction says I need to put both types of washers on the screw.

But on which side?

Should they be on the different sides like this:

enter image description here

Or should they be on the same side like this:

enter image description here

However, the instruction says this:

enter image description here

According to this, it looks like

head, C, O, material, nut

But several people answered my previous question that it's 

head, material, C, O, nut

I am confused at this point. Could you please explain?

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    I'm confused as to why you asked this question on here. You have an instruction manual which tells you the order, very clearly!
    – AndyT
    Feb 24, 2016 at 11:04

5 Answers 5

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The "rings" you mention are commonly called "washers".

It's hard to tell from the photo, but I believe the "incomplete ring" you mention is a "split" or "spring" lock washer:

enter image description here

If that's the case, then the are stacked as you have them in your second picture, the flat washer against the bracket, then the lock washer on top of that.

Note that this assumes that you don't have a nut that goes on the screw, if that's the case, then it's possible that the lock washer goes against the nut and the flat washer goes under the bolt head.

Based on the diagram you provided in the edit, it looks like the diagram wants you to put them in this order:

enter image description here

That looks like it's a wooden bedframe, so the flat washer is there to give a bigger surface for the bolt head when it screws down onto the soft wood.

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  • Thank you very much! I also edited the question to ask another question about the order of head, materials, and washers. Could you please explain if you know it? Thank you again!
    – user42459
    Feb 24, 2016 at 1:13
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"Picturing" that the screw goes into a deep thingy, I'm voting for the second shot & indeed the washers stack. The hole in the bracket looks pretty big & too big for the smaller washer, but I'm also imagining the screw head would go on the other side.

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  • Thank you very much! I also edited the question to ask another question about the order of head, materials, and washers. Could you please explain if you know it? Thank you again!
    – user42459
    Feb 24, 2016 at 1:36
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    Yep, your 2nd shot was all right...that was my 2nd guess. The instructions look good to me. You would slip the leg under the rail & drop your big washer then small washer onto the rail & finally drop your screw clean through to then twist your nut on. As long as you're using the item mostly for it's intended purpose I don't see any reason to change or reverse anything.
    – Iggy
    Feb 24, 2016 at 2:28
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Those are called washers. The 'c shaped one' is a split washer (we refer to it as a lock washer) and the complete one is just a regular washer (flat washer). They go on the thread end of the screw, inside of the material, so...

Screw head

(Hole in material)

Lock washer

Flat washer

Nut

The lock washer is used to basically press into the material to grip onto it. The flat washer is used to create an even distribution of pressure from the nut. Both also create a larger holding surface for the nut and bolt to connect everything.

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TYPICAL installation is screw, materials, flat washer, lock washer, nut.

But for some reason, the engineer requires the assembly be in the order of screw, lock washer, flat washer, materials, nut. And that is the sequence you should follow.

There are materials types and clearances, I presume, makes the engineer require this order.

Also, it looks like the nut is a nylon lock nut. Which precludes the need for a lock washer next to the nut.

When you install the nylon lock nut onto a bolt or threaded stud, the nylon insert wraps around the threads and locks the nut in place. This gives a nylon lock nut a distinct advantage over a lock washer when the bolt or threaded stud is subject to vibration, as the nylon lock nut is unaffected by vibration.

Ciao!

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What is the purpose of the washer? You don't show any nut in your picture, so what's the screw doing?

Washers may be used to make a hole smaller, and/or to modify the surface against which the head or nut rubs against.

The split ring is actually a very short spring. It provides pressure that you tighten against, rather than squeezing the material being bolted.

In this case, the little spring may need another stable surface on one end, because the hole in the thing is larger and it would not fit flush against the material, but might get the cut end fouled into the hole. So I suppose the solid washer goes on next to the surface being passed through, and the split washer after that.

Nut C O material Head

Or, the nut might not cover the bulk of the split washer well so the solid washer is used as a pusher:

Nut O C material Head

But, more generally, look at each component and how it relates to the basics. What does the split washer do, without the solid washer, against the other components? How does that change with the solid washer?

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