What Type Of Washer To Reduce Friction Between Moving Meatal Parts - Router Forums
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post #1 of 15 (permalink) Old 09-08-2017, 07:33 AM Thread Starter
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Default What Type Of Washer To Reduce Friction Between Moving Meatal Parts

I'm fixing the metal arm on pull down attic stairs. The rivet that attaches the metal arm to the fixed metal frame plate has worn out. This allows the arm to go out of alignment and the spring to pop out of its travel path. I've drilled out the rivet and will use a lag screw to attach the arm to the plate and penetrate the wood frame and attic floor joist. The lag screw will hold the metal arm to the metal frame plate but the arm has to be able to pivot. I'm planning on sandwiching the metal arm between 2 washers....one washer between the arm and the lag screw head and the other between the arm and the metal frame plate.
What type of washers to use? Plastic? Nylon? Fiber?

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post #2 of 15 (permalink) Old 09-08-2017, 08:50 AM
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White or black nylon washers work great. They hold up better than the softer plastic ones do. Black nylon (delrin) is supposedly self lubricating.
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post #3 of 15 (permalink) Old 09-08-2017, 09:25 AM
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post #4 of 15 (permalink) Old 09-08-2017, 09:46 AM Thread Starter
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White or black nylon washers work great. They hold up better than the softer plastic ones do. Black nylon (delrin) is supposedly self lubricating.
Thank You!!!
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post #5 of 15 (permalink) Old 09-08-2017, 09:46 AM
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Jim; if they're lag bolts, there's no mechanical advantage to cranking them down tightly.
Leaving a couple of thou clearance alone will greatly reduce the friction. The wear on the arm-holes, and bolt shanks where they contact, might be a concern?
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post #6 of 15 (permalink) Old 09-08-2017, 09:59 AM Thread Starter
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Jim; if they're lag bolts, there's no mechanical advantage to cranking them down tightly.
Leaving a couple of thou clearance alone will greatly reduce the friction. The wear on the arm-holes, and bolt shanks where they contact, might be a concern?
I'll be using a 3/8" lag screw......#8 if they have it. I'm not sure of the gauge of the arm or mounting plate metal but they are not thin or flimsy. The manufacturer connects them with a rivet. I've contacted the manufacturer and this type of wear is not an uncommon problem. I've seen some on-line blogs and a lot of folks seem to have encountered the same problem. One blogger was going to use a hex bolt and nylock nut to make the connection....not a bad idea but the bolt head would not be accessable if the nut ever loosened....so I decided to go with a lag screw. I could buy an entire arm assembly from the manufacturer but I figured I'd try this quick and less expensive fix first. This is for attic pulldown stairs which get very little use.
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post #7 of 15 (permalink) Old 09-08-2017, 11:03 AM
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Depends on often you use the stairway. Mine has been in the ceiling for a bit over 20 years and not worn out yet. I am, though.
If the stairway has worn out the original hardware already, go with metal washers and lightly coat them with Vaseline. The plastic will wear out.
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post #8 of 15 (permalink) Old 09-08-2017, 12:57 PM
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Using 2 or 3 metal washers works better than just one.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #9 of 15 (permalink) Old 09-08-2017, 01:09 PM
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the lag is softer than the original rivet... it won't last either..

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post #10 of 15 (permalink) Old 09-08-2017, 01:19 PM Thread Starter
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the lag is softer than the original rivet... it won't last either..
If it doesn't I can always buy the entire arm assembly from the manufacturer.
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