PC and the 5" PB

ai5u

ai5u

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Forgive me for being a noob on this (1st time equipment user). I just received my new PC from AGOL:). I've read the actual PC instruction/user manual and have found the special washer (that came in the plastic bag with the adjustment tool) that needs to go between the BP and the spindle, but I also noticed a very thin larger fiberglass type washer that was on the backplate spindle bolt? Does this need to be included with the installation of the BP? I'm guessing that this fiberglass backing washer helps reduce spinning wear and tear of the BP?

Thanks
 
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While I can't tell you the purpose of the fiberglass washer, I can tell you my original PC didn't come with one and in 7 years of use, I haven't seemed to have missed it. No BP "spinning wear and tear" that I have noticed.
 
Just went out and looked at mine. It has a larger white in color washer that is atatched to the backing plate then you put the smaller washer on top of that. Maybe your larger one came off the bp? Oh mine is only 1 1/2 mo. old.:detailer:
 
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All backing plates come with a washer. Use the one that came with your PC or the one on the backing plate, but use the washer.
 
What is the purpose of the washer?
The BP doesn't really need any additional spacing for wrench access.
The washer doesn't appear to be capable of doing much insulation from heat nor does it look like it would do anything for vibration.
I have not found anything in the manual that came with the machine and it seems like the washer came with the machine and the original foam pad. I have purchased 2 Hook & Loop backing plates and I don't think either one came with a washer.

Edited because of brain fade. I said pads when I meant backing plates.
 
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CharlesW said:
What is the purpose of the washer?
The BP doesn't really need any additional spacing for wrench access.
The washer doesn't appear to be capable of doing much insulation from heat nor does it look like it would do anything for vibration.
I have not found anything in the manual that came with the machine and it seems like the washer came with the machine and the original foam pad. I have purchased 2 Hook & Loop pads and I don't think either one came with a washer.
Click to expand...
Pads don't come with washers...backing plates do. Any screw or threaded bolt that is attached to a sleave should have a washer between them.
 
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Rsurfer said:
Pads don't come with washers...backing plates do. Any screw or threaded bolt that is attached to a sleave should have a washer between them.
Click to expand...
Whoops.......
Brain fade on my part. I should have said backing plates, not pads. (I did correct the error in my original post.)
I still don't see the purpose of the washer. Aren't lots of bolts and screws used without washers? Why does a backing plate need one?
 
CharlesW said:
Whoops.......
Brain fade on my part. I should have said backing plates, not pads. (I did correct the error in my original post.)
I still don't see the purpose of the washer. Aren't lots of bolts and screws used without washers? Why does a backing plate need one?
Click to expand...
When you bolt an object down, don't you normally put a washer between the bolt and the object you are securing? Same goes for a nut... if you were using a nut to secure an object, wouldn't you use a washer between the nut and the object you are securing? The washer keeps the object from damage from the bolt or nut. Same goes for a screw, you should use a washer for the same reasons stated above, unless you countersunk the hole.
 
Rsurfer said:
When you bolt an object down, don't you normally put a washer between the bolt and the object you are securing? Same goes for a nut... if you were using a nut to secure an object, wouldn't you use a washer between the nut and the object you are securing? The washer keeps the object from damage from the bolt or nut. Same goes for a screw, you should use a washer for the same reasons stated above, unless you countersunk the hole.
Click to expand...
I would have to go look, but I think many of the bolts and nuts on my vehicles, lawn mower, snow blower don't have washers. Definitely not fiber washers which is what came with the PC.
Granted, some do, but certainly not all of them.
 
Jason posted a link to the PC Manual for a couple of models in this thread.
http://www.autogeekonline.net/forum...updates/18898-porter-cable-7424xp-manual.html

The manual includes the following line on page 2 under "Changing the backup pad".

C. A spacer is supplied with the 7346SP and 7424XP to allow the backup pad to clear the eccentric
plate screws (F) Fig. 5. Mount the spacer on the shaft before attaching the backup pad.

That seems to answer my question as to the purpose of the washer/spacer.
FWIW, The manual that came with my PC in October of 2002 does not include that information.
Porter-Cable obviously feels the spacer is necessary, but I did use mine several times without it and had no problem.
I actually thought it was to go between the side handle and the machine and since I didn't use the side handle, it didn't get used. It was probably close to a year later that I read that it should be used between the BP and the machine. The reason given was to have room for the wrench. There was room for the wrench without it on mine, but I did use it there. Mostly because someone on the internet said to and I believe everything I read on the internet.
 
I think the spacer offer a couple of benefits,

It offers some squish to it and this probably helps to prevent loosening of the backing plate kind of like a nylon lock washer. (Just a guess). Not that it really matters because in all the years I've been using these polishers if you tighten the backing plate down like you normally would, I've never had one loosen and spin off.

It acts as a space between the free rotating spindle assemble and the backing plate itself. Some backing plates have rivets that protrude outward farther than a backing plate without rivets and it could be that a little more wiggle room insures there's clearance.

5inchbackingplateon5_5inchpadHT.jpg




It's possible it might provide a dampening effect so you don't have metal against metal or even act to reduce vibrations

Where's the in-house engineer when you need one?


:D
 
The vibration comment was interesting to me.
I replaced my fiber washer with thick rubber washers on a couple of BPs for just that reason. That and the fact I was able to get rubber washers that you had to screw on the threads and they stay in place when the BP is not in use.
I can't say that I see any difference in vibration.
PCs are noisy and vibrate, end of story. :)
 
I used the washer that came with the back plate and had no problems, just make sure the back plate clears the screws on the PC.
 
Cool!

Thanks guys!

I will use both the PC included washer and the BP included
thin wafer spacer.
 
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