The Ultimate Porter Cable 7424XP Dual-Action Car Polisher Guide (Updated For Summer 2020)

Dual-action Car Polisher User's Guide

This must-read how-to guide provides detailed information about 2 leading consumer car polishers:

The Porter Cable 7424, but especially the 7424XP model.

Please Note: A separate buyer’s guide (which includes machines by competitors) is available at Car Polisher Buyer’s Guide.

Dual Action Car Polisher Overview

First, let’s quickly go over how these wonderful tools actually work.

A dual-action (DA) car polisher operates by simply orbiting a polishing pad around a center spindle.

That’s the basic functionality.

To clarify, some DA polishers are forced drive. Others, including the Porter Cable 7424, allow the tool head (pad) to free spin on its own axis.

Note: There is a counterweight (on the opposite side of the center spindle) that helps to reduce vibration.

Here’s where the true value of these machines lie…

Dual-action polisher eccentric mechanism
Most dual-action polishers use an offset spindle that freely orbits around the center shaft. A counterbalance weight virtually eliminates vibrations.

A polisher’s tool head action, often called random orbit or orbital, prevents holograms (symmetrical buffing marks), paint burns and other forms of paint damage.

That’s one reason why they’re so great!

Use a DA polisher with care and the orbital mechanism virtually eliminates a possibility of paint damage.

Basically, dual-action polishers mimic how you’d baby your car’s paint by hand.

Only the polisher can make up to 6,800 circles every minute.

Folks, try doing that by hand!

Right now, I want to clear up a misconception.

Defining a Porter Cable 7424’s polishing action as “jiggling” is wrong.

It’s simply not accurate.

The head freely rotates on a bearing. It orbits around the center-line drive shaft.

Polisher pad rotation is a free-wheeling action. It’s caused by centrifugal force of the backing plate and spindle caused by the orbiting head.

This “dual-action” is where the Porter Cable 7424 car polisher gets its “DA” nickname.

Dual-action polisher oscillation patern
Orbiting head action, combined with a high-speed motor, offers gentle polishing action at super high speed.

Have you ever owned a car polisher that made a lot of noise, but did little else?

Take it from me…

You will appreciate the 7424 XP as a professional tool.

Here’s the deal:

Most cheap car polishers don’t have enough power. They often have a very small orbit (often less than 1/4 inch), and with limited accessories.

The Porter Cable 7424 was the first machine to shatter these limitations. It became the industry standard.

Porter Cable 7424XP Availability & Features

Amazon sells the 7424XP for a very competitive price.

For just a few dollar more you can get it with digital pressure gauge which is pretty cool.

Plenty of Power

The 7424XP has a particularly strong 4.5 Amp, 500 Watt motor.

It’s actually 20% more powerful than the original 7424. This makes it more capable for removing paint defects.

Hence the nickname, “The Ultimate Detailing Machine!”

The Handle

Griot's Garage Polisher Handle
A look at the “D” style polisher handle.

Both of these Porter Cable models include a reversible side handle.

The feature makes it easy to hold and control, even when working on vertical surfaces.

[Use of the side handle is a personal preference. It adds a bit of safety.]

Those with large hands may find it easier to grip the machine by the head end (with one hand and the rear with the other.)

Meguiar’s and Griot’s Garage 6″ Random Orbit polishers both use what’s called a D handle (see image).

The Speed Control

Porter Cable 7424XP ergonomics
The Porter Cable 7424XP has a reversible side handle and a top-side speed control.

The Porter Cable 7424XP functions at 2,500 to 6,800 operations per minutes (OPM).

Again, that’s impressive!

The original 7424 is slightly slower, with a top speed of 6,000 OPM.

How to control the speed?

You simply rotate a thumbwheel speed dial. Easy!

The speed dial is on the top-rear of the Porter Cable 7424XP, and on the rear of the original 7424 polisher (Meguiar’s and Griot’s Garage polisher are also on the rear).

The OPM measurement is used instead of revolutions per minute (RPM). You see, this distinguishes the difference between orbits and center shaft revolutions.

Remember: Safety First, Always!

Warning:  Failure to follow safety precautions may result in bodily harm or damage to your vehicle.

  • Wear safety glasses when operating this tool. Avoid eye injury from flying debris.
  • Always switch the machine off and unplug it from the power source BEFORE changing accessories. Switching on the machine while changing accessories may cause an injury.
  • Never operate unless the cleaning or polishing accessory is pressed against the surface to be cleaned, polished or buffed. This means you both start and stop the machine while it is resting flat on the surface of the car.
Porter Cable 7424 XP Dual-Action Car Polisher - Proper Use
This is the proper position for engaging and disengaging a polisher.

The Use of Buffing Pads

Let’s touch on versatility for a moment.

You can use a range of backing plates and pads with the Porter Cable 7424XP. This is true for other dual-action car polishers as well.

Velcro backing plates are typically available in sizes ranging from 3 to 6 inches.

For safe operation:

Ensure the backing plate and pad combination are balanced to the installed counterweight.

This dampens harmonic distortions (vibration) caused by the pad whipping around in its tight orbit.

Let me be clear:

IF the counterweight isn’t in place, you won’t be able to hang on to the machine for more than a few minutes. Your hand will go numb!

Backing Plates to the Rescue!

Larger-sized pads obviously cover a bigger area. This makes most polishing jobs easier and faster.

Don’t worry!

The recessed area on the back helps protect your car from accidental damage.

It’s called a backing plate. A generous foam layer that protects the paint surface.

Recommended Pads & Correct Applications

Pads are color-coded (which I love).

An Orange Correcting pad is considered ideal for removing light oxidation, fine swirl marks and scratches.

What about for just improving a shine?

When used with a fine polish, such as Sonus SFX-3 Final Finish, a high quality Green foam pad will greatly improve overall gloss.

Finally, a Blue light finishing pad works well to apply liquid waxes and sealants quickly and evenly.

A Word About Sizing

Generally, the most effective pad contact diameter for the Porter Cable 7424 is 4 to 7 inches.

Further, pads should be matched to an appropriate polish for desired results.

As an example, don’t use a fine hand polish with a cutting pad to remove heavy oxidation or swirl marks.

It simply won’t work!

Caution: I discourage the use of coarse “cutting” pads by inexperienced users. It’s easy to remove too much paint material or create severe hazing.

Selecting the Right Car Polish

Most manufacturers produce abrasive papers, compounds, cleaners, polishes and glazes to meet a wide variety of polishing requirements.

For Reference: Glance over this list of quick definitions of polishing abrasives:

Abrasive paper or pad – An ultra-fine grade of sandpaper (1500 to 3000 grit) that can be used to level a paint finish and remove imperfections. I mention sandpaper because it is an abrasive, like all polishes, and it has its place in the polishing process.

Compound – A compound, often called a rubbing compound or a paint cleaning compound, is a cutting polish designed to remove heavy oxidation, some common forms of paint damage and defects and the scratches created by fine sandpaper. Use compounds with a foam cutting pad. Always start with the least aggressive pad and compound possible.

Polish – A specially formulated blend of components designed to remove minor scratches, surface imperfections, water spots, acid rain spots, light oxidation and swirl marks created by compounding with a machine. Use a foam polishing pad or a fine cutting pad.

Glaze – A very fine polish. Some glazes are safe to use on fresh paint. They do not seal or contain silicones. A glaze does not have enough cutting power (if any) to remove imperfections, but will increase surface gloss. Use a fine foam polishing pad or a finishing pad.

Pre-wax cleaner – A fine polish containing chemical cleaners to help remove minor surface contamination and dirt not handled by normal washing or claying. Use a fine foam polishing pad or a finishing pad.

You’ll be happy to know that each of these levels of polish can be used with a Porter Cable.

That said, only a professional or very experienced user should use an electric polisher with abrasive papers or pads.

Follow the manufacturer’s directions.

You may wish to play it safe by avoiding use of a polish that isn’t specified by the manufacture (or a qualified source) with your dual-action machine.

Maintaining & Improving Paint Gloss

The reality is this:

It is polishing, not waxing, that offers the most improvement in the overall appearance of paint.

If you wax over bad paint, it’s still bad paint.

There is a catch though…

When you polish bad paint (with scratches, heavy oxidation, swirl marks, stains, water spots, etc.), you remove the bad paint to reveal a fresh finish.

You can only do so much polishing before wearing out (thin or completely remove) the paint.

I can’t stress this enough:

Only polish as much as necessary. Do it when it makes sense.

Buffing Best Practices

Buffing pad and polish makers offer products with different levels of aggressiveness to make your polishing tasks faster and easier.

But, it’s not that simple…

You can use an aggressive pad and polish combination to quickly remove paint defects or severe oxidation.

Nevertheless, it won’t reveal the full gloss potential of your paint finish.

You see, just like polishing a jewel, you must use several grades of polish to bring out the final radiance.

For New Car Finishes

With new paint, it’s really not necessary to use heavy abrasives.

You can use very mild pre-wax cleaners and glazes to maintain the factory finish or create a finish that glows like a gem.

To do so, use a fine polish and a foam polishing pad. Work the polish in with a light touch until most of the polish residue is gone.

Simply remove the remaining polish residue with a quality buffing towel.

The truth is fine polishes can’t take much heat before they cake up and clog your pad.

Don’t apply pressure to the machine. Bad idea!

Allow the pad and polish to do the work.

Some polishes respond well to a microfiber buffing bonnet. Others do not.

Tip: Do a final buff out with a good microfiber bonnet over a clean pad if your polish isn’t buffing out clear.

How To Use A Polisher (Step-by-Step)

Here’s how I utilize my dual-action polishers to keep my paint looking new:

Step 1: Select Correct Pad & Center on Backing Plate

Select the right tool for the job. It depends on your intent. (Here I’m using a Green polishing pad).

Step 2: Apply Polish to Pad

Select a good pre-wax cleaner. I’m using Ultima Paint Prep Plus (a fine polish, paint cleaner and swirl remover in one).

It goes on amazingly smooth and leaves an impressive shine.

Step 3: Distribute Polish on Work Area

Apply the polish over your target area. Otherwise, the polish will sling off of the pad. You can dab it, as I have done here, or smear it.

Step 4: Start Polish at Low Speed

Start the polisher at a low speed (2 or so on the dial). Get the polish loaded into the pad before increasing speed.

Step 5: Increase Speed and Work-in Polish

Step 5

Work that polish into the paint. Keep the polisher flat, and apply just enough pressure to keep the pad in full contact.

Use slow, smooth back-and-forth and up-and-down sweeping motions.

Step 6: Polish Until Film is Nearly Gone

Step 6

You’ll notice something as you work the polish…

The film gets lighter until only a slight haze remains. At this point you can stop and inspect your work.

Remove the remaining polish haze with a buffing towel or switch to a finishing pad.

Step 7: Switch to a Finishing Pad or Bonnet

Step 7

You can use a finishing pad or a bonnet to remove the final polish residue. Some people prefer doing this step by hand. Your choice.

Step 7b

Step 8: Remove Dust with a Detailing Spray & Buffing Towel

Step 8

Polishing pads will leave dry dust on the surface. It’s normal.

Use a detailing spray and a soft buffing towel to wipe away polish dust before waxing.

Step 9: Switch to a Finishing Pad for Waxing

Step 9

After polishing, use a finishing pad to apply your favorite wax.

Liquid waxes are easy.

You can also pop most waxes out of their can, as I do here with a can of P21S Carnauba Wax.

Work the wax in well (use a low speed). Then, use a clean buffing bonnet to buff out the final finish.

Step 10: Cleanup Cracks & Crevices

Step 10

After waxing, use horsehair detailing brushes to remove polish and wax residue from all cracks and crevices.

Step 10b

Step 11: Inspect Final Finish

Step 11

You’ll be smiling after polishing and waxing. Your final paint finish should be smooth, glossy and wet looking.

Removing Common Paint Defects

What’s the fix when a paint finish degrades from oxidation, water spotting, acid rain damage and other environmental hazards?

The damaged paint needs to be removed in order to restore the finish.

There’s no other way!

Even if you meticulously care for your car, sooner or later we all get paint defects.

Polishing removes a very thin layer of damaged paint to reveal fresh paint and a restored finish.

Enter the Porter Cable

It’s a spectacularly effective tool for removing most paint defects.

We’re talking surface scratches, swirl marks, sanding marks, water spots, chemical etching, oxidation, scuffs and paint transfer.

All these problems are addressed in essentially the same way.

Lessons Based on Experience

You start by using a cutting pad in conjunction with a fine rubbing compound to remove just enough paint material to cut away the imperfection.

I’ve always found that removing about 90% of the imperfection in this step is plenty.

Leave a bit for the final buff out, or you’ll remove more paint than necessary.

After compounding, switch to a polishing pad and a gloss enhancing polish (often called a “swirl remover polish”).

This will remove the hazing or light dulling caused by the compound. This step handles the remaining 10% of the imperfection (and reveals smooth, healthy paint).

Be very careful compounding and polishing on heavily oxidized paint. That is until you know how much healthy paint is remaining!

You don’t want to remove too much paint, creating thin spots or worse.

If you over-buff an area of paint, you will wear away the clear-coat or color. The only repair for this mistake is to have the panel repainted.

You may find that you have to polish an area several times, and with a couple different polishes to get results.

Yes, it’s frustrating.

Yet slow progress is better than rapid progress when it comes to paint polishing.

Do you have a small area with deep damage that the Porter Cable 7424 cannot remove?

You have a couple of choices:

  1. You can polish by hand using a heavy rubbing compound
  2. You can wet sand with 1500 to 2000 grit paper
  3. You can switch to a rotary buffer and a cutting polish, or…
  4. You can live with it (don’t do this)

Often times the secret to repairing a defect is knowing what pad to use.

More Polishing Secrets Revealed

Machine polishing is messy.

No matter how skilled you become, the machine will always sling off polish.

Hey, it happens.

Want to avoid a huge clean up job?

I recommend using an old bed sheet to cover areas of your car that you don’t want splattered with polish.

Take it from me…

This little step will save you a lot of clean up work.

Protect Your Trim

Polishing can be quite detrimental to trim.

If you need to polish close to trim, I recommend masking it with painter’s masking tape.

I’m serious! With rubber seals or brushed aluminum trim, you run the risk of ruining the original matte finish.

Masking around window trim, door handles, windshield washer nozzles, antenna masts, door guards and other trim will save you a lot of heartache from mistakes.

Be safe; take the time to mask off your trim.

It only takes a few minutes to do an entire car. In the end it will save you a lot of time and grief.

Polish: Don’t Be Stingy

Many people mistakenly believe that polish should be used sparingly.

BUT doing so puts more of the workload on the pad and causes the polish to dry out before you achieve results.

My friends, use polish liberally!

Apply enough to work an area for one to two minutes before the polish hazes and begins to buff out.

Polishing Techniques

Polish safely by keeping the pad flat on the surface you’re buffing AND the cord off of the paint.

In fact, I like wrapping the cord around my wrist once and draping the rest over my shoulder.

Back to positioning…

Never tilt the polisher! You risk excessive heat build-up, pad destruction, and potential damage to trim.

Unlike a rotary buffer, which is capable of applying energy to the edge of the buffing pad by tilting the buffer a few degrees, a dual-action polisher is not able to effectively focus polishing action.

Warning: Tilting your Porter Cable 7424 may quickly destroy foam pads (it causes the backing plate to cut into the pad) and may build-up enough heat with a rubbing compound and cutting pad to burn paint.

Tilting is a no-no!

Here’s what you SHOULD DO:

Prime a fresh, clean pad with a shot or two of detailing spray (Doing so makes the initial buffing a little smoother).

Use just a light mist.

When the pad cakes up with polish, use a premium horsehair brush to gently remove it. Do this with the polisher switched off.

The reason I like horsehair brushes is they don’t rough-up pads as much.

Rotary vs. Dual Action

Briefly, let’s compare rotary to DA machines.

To be clear, a dual-action polisher and a rotary buffer work polishes very differently.

A rotary buffer/polisher typically runs at a speed in the range of 500 to 800 RPM.

The size of the pad, the torque of the motor, and a little pad pressure generate the right amount of heat to cut, break down the polish and bring up paint gloss.

With a dual-action polisher, pad speed generates the energy necessary to get results from the polish.


You simply have to turn the speed up on the Porter Cable to rectify your paint defects.

Pad & Polisher Maintenance

Porter Cable polishers are relatively low maintenance. Yearly lubrication is recommend.

If you use the machine professionally, follow the manufacturer’s recommendation.

What about for the average Joe enthusiast?

Sending the machine in for lubrication every 2 or 3 years is sufficient. All you need is red lithium grease and a screwdriver if you do it yourself.

There are varying opinions on pad cleaning techniques.

Not long ago, pad manufacturers would tell you not to wash pads. They claimed water and detergent would de-laminate the Velcro from the foam.

For the most part, this seems to be resolved.

Washing pads after each use is very time consuming for a professional detailer. Professionals usually keep pads (brushed clean) stored in Zip-lock baggies.

For regular folks, when the pad becomes too dirty to use, just wash it.

Wait! Do not wash pads in the washing machine. They must be hand-washed.

To do so, simply add an ounce of dish washing detergent to a 5 gallon bucket. Fill it with water. Soak the dirty pad for up to 30 minutes.

Never machine dry.

After soaking, massage the pads to work out the caked in polish. Then, squeeze out the soapy water. Empty and refill the bucket with fresh water.

Finally, rinse the pads in the bucket of fresh water, squeeze, and set aside to air dry.

Practice Makes Perfect

The 7424XP is a pretty easy polisher to master. I highly recommended it.

Still, practicing on an older car (with an imperfect finish) is the best way to learn.

Experiment with a variety of polish and pad combinations until you learn how to achieve awesome results.

In my experience, there’s no silver bullet combination of pads and polish.

How you use the machine, your climate, paint hardness, paint color and other issues will all factor into final results.

Don’t be frustrated if your initial experience is not perfect. The smallest change (a different pad, polish or speed) can make a HUGE difference.

Bottom Line:

A dual-action car polisher makes polishing easy. It allows anyone to create a stunning finish or restore a badly worn paint job.

All it takes is a polisher, a little practice and the right selection of pads and polishes.

Be sure to check out the famous Perfect Shine article!