Noobie here...Porter Cable 7424XP wobble

J

jdonnell

New member
Hey guys, I was using my PC and about 1/2 way through I noticed the backing plate appeared to stop rotating with only little pressure applied. My PC was set at 3.5 and I indexed the 5.5 inch backing plate, and indeed, it doesn't rotate with minimal pressure. Also, when viewing from the side the backing plate appears to wobble out of plane. I tried removing the backing pad (it has no markings) and reinstalling, but same result. I'm not sure if it is a PC or backing plate issue????? I only used these a couple times. Thanks.....
 
Rotation

Believe it or not these backing plates rotate better under more pressure than less and also at a higher speed setting like 5.

When I'm applying sealants or wax my speed setting is 3 and just the weight of the machine really and I see very little if any plate rotation.

Wobble

Unless your machine has a bent shaft, most of the wobble comes from the backing plate. The threaded steel stud is over molded with the rubber compound and if it's not perfectly perpendicular with the lad face you'll see a slight wobble...

Washer

Are you using the washer / spacer supplied with these plates? This is very important as it affects the operation of the machine..
 
Thanks for the quick reply. There is a very thin spacer between the backing plate and PC. So it is intact.

Originally I thought it was the backing plate, but since rotation stalled I thought it was the PC. I did what you referred to in increasing the speed to see what it does, and it dose rotate but very SLOWLY. Is that normal then?
 
Yes.

A dual action polisher rotates very slowly when compared to a rotary machine. There may be some information here somewhere but I'd guess the backing plate on a dual action polisher rotates somewhere in the vicinity of 30 to 40 rpm's....
 
Hmmmm...I'm thinking mine is like 10 rpm at high speed w/pressure. I think I'll go ahead and get a higher quality backing plate along with one that takes smaller pads. Any recommendations?
 
These are the pads and backing plate I use on my Porter Cable 7424...



Yellow Low Profile Cutting 5.5 inch Foam Pad - Use this pad to apply compounds or polishes to remove severe oxidation, swirls, and scratches. It is the most aggressive and should only be used on oxidized and older finishes. Always follow this pad with an orange or white pad and a fine polish to refine the paint until it is smooth.

Orange Low Profile Light Cutting 5.5 inch Foam Pad - Firm, high density foam for scratch and defect removal. Use this pad with polishes and swirl removers. It’s an all around pad that will work on most light to moderate imperfections.

White Low Profile Polishing 5.5 inch Foam Pad - Less dense foam formula for the application of waxes, micro-fine polishes and sealants. This pad has very light cutting power so its perfect for pre-wax cleaners.

Gray Low Profile Finishing 5.5 inch Foam Pad - Composition is firm enough to withstand added pressure during final finishing to remove buffer swirls. It has no cut and will apply thin, even coats of waxes, sealants, and glazes.

Blue Low Profile Finessing 5.5 inch Foam Pad – Flat pad has soft composition for applying glaze, finishing polish, sealants, and liquid waxes. Flat pad provides full contact with paint surface to minimize the pressure applied by the user.

The Flex 3401 is an amazing polisher and because of it's forced rotation you never have to concern yourself again....
 
I do use the LC pads which I think are 6 inch. Being a noob and not to create damage, I'm using white pads for polishing and red pad for sealant application. I currently use Blackfire (love that sealant!!).

I can still buy the smaller backing plate for the PC, right? Are the threaded studs universal?

Ronkh, I read great reviews for the FLEX, but I understood it to be for professionals that know what they are doing. I bought the PC for damage control. Maybe one day I'll progress, but I think detailing is more of a craft verses something everyone can do.
 
jdonnell said:
I do use the LC pads which I think are 6 inch. Being a noob and not to create damage, I'm using white pads for polishing and red pad for sealant application. I currently use Blackfire (love that sealant!!).

I can still buy the smaller backing plate for the PC, right? Are the threaded studs universal?

Ronkh, I read great reviews for the FLEX, but I understood it to be for professionals that know what they are doing. I bought the PC for damage control. Maybe one day I'll progress, but I think detailing is more of a craft verses something everyone can do.
Click to expand...

FLEX XC 3401 VRG HD Orbital Polisher

The FLEX XC 3401 HD Orbital Polisher is a true forced-rotation dual action polisher! What that means is this polisher not only orbits but it also rotates too, at the same time. This dual action gives the Flex XC3401 HD superior paint correction ability. The FLEX XC3401 HD quickly removes swirls, scratches, oxidation and other paint defects that can’t be removed by other dual action polishers.
 
Once you go flex, your pc will collect dust...................

Or you can do what I did, and get the smaller backing plate for your pc and use it for tight areas
 
But in't the PC foolproof compared to FLEX?

Thank goodness for the cold front coming through FL, because I've spent all day on this forum. It's addictive. Great info!
 
Sounds like I need to further research a new toy. Never really happy with the PC anyway - no fault of it, just awkward side handle.

68F. I think its high 50s to low 60s here which is cold for us FL folks.
 
jdonnell said:
Sounds like I need to further research a new toy. Never really happy with the PC anyway - no fault of it, just awkward side handle.

68F. I think its high 50s to low 60s here which is cold for us FL folks.
Click to expand...

Hello Jdonnell,

How old is your machine? Have you tried the stock PC Backing Plate, the one that comes with the machine, and has the permanently attached white pad?

Perhaps try this one, to see what results you get then as far as this wobble is concerned?

Just because the other Plate is an LC, which I'm assuming it is, don't assume it cannot be defective. When I got my new PC7424XP about 6-7 weeks ago from AG, the 5" LC Backing Plate was defective, really poorly formed threads on it, it would not thread onto the machine, and had no luck trying to access a 5/16"-24 Die in this town.

A simple call to the AG Folks, and they sent me out a new one. The concensus by all the folks here, state the PC Machine works to its optimum capacity with a 5" Backing Plate, and 5.5" Pads maximum size. That larger than this, the PC Machine will then appear underpowered, and have difficulty properly working.

The thinner the Pad, seems to be another key with the PC Machine. I've gotten just the regular LC 5.5" Flat Pads, which are 7/8" thick.

I don't think there's anything inheritly bad about the PC7424XP, and it should work quite fine, provided it is combined with the right Pads, and Plates.

Also, the Handle may be removed, and replaced with Cap Screws of the proper size. Some have said the newest PC Machines are using a metric M8 screw size, rather than american standard thread-screw size. Best to check this before inserting any improper screw-thread size.

Mike Phillips has authored a thread here about the removal of the stick handle, and replacing with screws/washers, as without the stick handle installed, the plastic front cover of the machine can slide off.

No doubt the Flex DA Machine is a beauty, is without a doubt superior, as it should be for about 3 times the cost. Which direction you choose to go is ultimately up to you?

Hope this helps. Mark
 
Thanks Mark D for the detailed write-up. I did decide to order just a replacement backing plate first to see if that is indeed the issue. The original backing plate came as part of a kit and it did not include the stock one you are referring to, so no I haven't tried that one.

I thought about removing the handle and never even considered the front cover sliding off - that's good info. The handle is a pain but it does help when I set the polisher done to wipe polish off. I place the PC upside down (pad up) which the handle seems to help prevent it from rolling and contacting the garage.
 
jdonnell said:
Thanks Mark D for the detailed write-up. I did decide to order just a replacement backing plate first to see if that is indeed the issue. The original backing plate came as part of a kit and it did not include the stock one you are referring to, so no I haven't tried that one.

I thought about removing the handle and never even considered the front cover sliding off - that's good info. The handle is a pain but it does help when I set the polisher done to wipe polish off. I place the PC upside down (pad up) which the handle seems to help prevent it from rolling and contacting the garage.
Click to expand...

Not sure where you ordered your PC 7424XP from, but I was under the impression that the cheapo black plastic backing plate with the permanently attached white foam pad was standard issue with this machine, as well as the backing plate wrench?

Can anyone else confirm this?

As well, my Counterweight was already attached to the machine, and that's it, no other spare counterweight included.

When I ordered my PC machine from AutoGeek, I bought the Machine by itself, then bought the 2 LC Backing Plates (5" and 3.5") and an assortment of 4", and 5.5" LC Pads. IMO, there was not one package that seemed to fill my personal wants-needs. Mark
 
I think I purchased everything from Proper Auto Care in Tampa (i think). It was a few years ago before they decided to shut down.

I've only used the PC a couple times but now I have three cars to do. I ordered a couple more backing plates and hope that the problem will go away. If not, I'll explore other options.

Anyway, the kit I refer to did not come with that smaller white pad. It came with the counterweight installed, wrench, yellow no name 5.5 in. backing plate, BFWD stuff, LC pads and microfiber towels. I was quite pleased being a newbie.
 
jdonnell said:
I think I purchased everything from Proper Auto Care in Tampa (i think). It was a few years ago before they decided to shut down.

I've only used the PC a couple times but now I have three cars to do. I ordered a couple more backing plates and hope that the problem will go away. If not, I'll explore other options.

Anyway, the kit I refer to did not come with that smaller white pad. It came with the counterweight installed, wrench, yellow no name 5.5 in. backing plate, BFWD stuff, LC pads and microfiber towels. I was quite pleased being a newbie.
Click to expand...

Bobby G, who's got more experience than I with the PC 7424XP probably hit on another important key with the PC7424XP, two things he noted-made mention of, 1., the larger pads, and 2., the PC does not work effectively at lower speeds like 3.5 to get consistent rotation like a Flex, and do any meaningful paint correction.

Through all the articles I have combed through in the past 2-1/2 or so months here, folks here seem to say, and basically all agree, a wax-sealant applications at 3.5, OK, that it doesn't require rotation to lay down, or remove a wax-sealant, (if you choose to use the PC in such a manner) but for paint correction, there's only going to be two speeds, 5, or 6 that will work properly. BTW, there is no in-between 5-1/2 speed with the PC7424XP, it is either 5, or 6, they did not index the speed adjustment wheel in betwen those two speeds I've found.

Bobby, and many many others all seem to agree, the sweet spot with the PC7424 is a Lake County 5" backing plate, and 5.5" pads, nothing larger. Another good option, like I myself have, is the 3.5" Lake County Backing Plate, and 4" LC CCS Pads for working smaller areas.

Mike Phillips has repeatedly made note of liking flat pads over other convoluted, dimpled, or other types of pads for basic paint correction.

Again, hope this helps, my post here is basically a re-hash-repeat of what those in the know here have learned-shared, and am just again passing this info onto you. Mark
 
Also make sure you have the correct counter weight on it. Or if not, that will make a lot of wobble
 
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