View Full Version : The Importance of the Backing Plate Washer

Michael Stoops
Jan 9th, 2013, 01:47 PM
The Importance of the Backing Plate Washer (https://meguiarsonline.com/forums/showthread.php?57529-The-Importance-of-the-Backing-Plate-Washer)

Anyone who owns a DA buffer has seen the little washer that slips over the threaded stud on the backing plate, but you may not think it's all that important. Well, it's actually critical to the operation of the tool, and here's a perfect example why. But first, just to clarify the part in question, here are a couple of pictures:

The black washer on this W67DA backing plate is the part we're focusing on here.

This is a W68DA backing plate (ships with the G110v2) and it also should have the same washer in place.

Same W68DA plate but with the washer pulled up a bit just to get a closer look at. Seems like a pretty innocent little part, doesn't it?

Well, a customer contacted our Customer Care Center saying that he couldn't remove his backing plate from his G110v2 and thought something in the tool might have broken. The pad would also stop rotating with even light pressure, no matter the tool speed. The tool arrived with backing plate attached (not one of our backing plates, as it turns out, but it still illustrates the problem) and, sure enough, we couldn't get it to come off either. With the wrench holding the spindle nut in place the plate would just turn. It also had a pretty big wobble showing when turning it; so much so that you could just wiggle the thing around as if it were a plate sitting on a ball. Close inspection showed that the spindle was definitely not moving when held by the wrench, so we wondered if maybe the threads inside it were stripped. But wouldn't that mean we could basically just pull the backing plate off?

And then it hit - the threaded stud on the backing plate is basically one end of a rivet, or it's welded in, depending on the construction of the plate. Like we said, this isn't one of our backing plates so we didn't know exactly how it was manufactured. We then thought maybe the stud was broken inside the backing plate. So out comes the Swiss Army Knife and we started cutting through the face of the backing plate. And that's when it got interesting!

With the center of the backing plate cut out we could see the head of the stud was broken away from the inner metal disc of the backing plate, and the plate would just spin around it. A pair of vice grips gave us a hold on the head of the stud and, with the wrench on the spindle nut, we could unthread it from the tool.

This is the side of the plate you're all familiar with, showing how it broke. With the soft foam body and hook material on the face of the plate holding it all together, everything was just loose inside the plate and therefore it couldn't be removed from the tool. And since it was loose inside the backing plate, pressure placed down on the pad would cause the pad to stop spinning while the broken stud would spin inside the backing plate.

And that wobble we mentioned a bit earlier? Look what it caused to the tool itself! As that wobble got worse it caused those three small rivets you see in the shot above to contact the tool, gouging it quite noticeably. This constant impacting of plate to tool is what most likely caused the ultimate failure of the threaded stud. We found that we could still thread a new backing plate into the spindle nut and everything ran fine (with the washer installed of course!) and we could then remove the backing plate just as you always do. No stripped threads here. The tool itself, other than some cosmetic damage you can see below, is perfectly fine.

So, don't omit the washer when mounting ANY backing plate to your DA. There are enough similarities between all the various popular DA buffers on the market that we'll go so far as to say regardless of the plate or the tool, don't skip the washer!!!

Moral of the story: Little things mean a lot.

davey g-force
Jan 9th, 2013, 02:30 PM
Wise words indeed. Thanks for the heads up Michael.

Jan 9th, 2013, 07:11 PM
Pretty sure you can get similar size washers at the hardware store but you can get a 5 pack from AGhttp://www.autogeek.net/backing-plate-compression-washer.html

Jan 9th, 2013, 08:26 PM
You know, I have to admit, when I got my DA last October, unpacked it, and started to put the backing plate on the polisher, I noticed the washer and wondered should I leave it on the stud or was it meant to be removed before putting the backing plate on the polisher.:confused:

Well, I left it on, figuring it must be there for a reason, I didn't tighten it on very tight at the moment, and then I got on the 'Net and searched the forum for some type of definitive answer. Found the answer.

Just blind dumb luck I left the washer on. Lucked out that time. :o

I need to check the instruction book again to see if I missed it back then.:dunno

Mar 6th, 2013, 11:27 PM
I was at the hardware store and saw some metal washers for 7 cents each....is it ok to use metal in place of the supplied plastic ones?

Mar 7th, 2013, 05:09 AM
I was at the hardware store and saw some metal washers for 7 cents each....is it ok to use metal in place of the supplied plastic ones?

Not really. The washer is there for two reasons, one to insure the BP doesn't kiss the housing and the other so the BP won't 'freeze' to the spindle. Hence the need for a 'fiber washer.'

As long as you're at the hardware store, waltz on over to the plumbing department, you should be able to find one there. Lot of plumbing fixtures have fiber washer(s).


Michael Stoops
Mar 7th, 2013, 08:51 AM
Great tip, Bill!

Mar 7th, 2013, 11:13 AM
Thanks Bill, I have more than enough of the fiber washers on the dozen or so BP's i have on hand...but I just wanted a handful of these spares :)