Porter Cable 7424XP Dual-Action Car Polisher Guide

Dual-action Car Polisher User's Guide

This how-to guide covers the Porter Cable 7424 and 7424XP, Meguiar’s Professional Dual Action Polisher, and Griot’s Garage 6″ Random Orbit Polisher. A buyer’s guide for these same polishers is available at Car Polisher Buyer’s Guide.

The purpose of this guide is to offer information and instructions for the safe operation of a dual-action car polisher. This type of polisher is very safe. Even if you have never polished a car by machine, you will be able to use a Porter Cable, Meguiar’s or Griot’s Garage car polisher to achieve excellent results. All you need to do is learn some basics.

Dual Action Car Polisher Overview

A dual-action (DA) car polisher operates by orbiting the polishing pad around a center spindle. Some DA polishers are forced drive, while others, including the Porter Cable 7424, allow the tool head (pad) to free spin on its own axis. A counterweight on the opposite side of the center spindle helps to reduce vibration.

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

The polisher’s tool head action, often called random orbit or orbital, prevents holograms (symmetrical buffing marks), paint burns and other forms of paint damage often associated auto buffers. If you use a DA polisher with proper care, the orbital mechanism virtually eliminates the possibility of paint damage.

The huge benefit of a dual-action polisher is that it closely mimics how you would baby your car’s paint working by hand, only the polish can make up to 6,800 circles every minute. Try doing that by hand!

I have seen some people defining the Porter Cable 7424’s polishing action as “jiggling”, but this is not accurate. The head of a dual-action car polisher freely rotates on a bearing and orbits around the centerline drive shaft. Pad rotation on the polisher is a free-wheeling action caused by the 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
The orbiting head action, combined with a high-speed motor offers the same gentle polishing action as your hand, only at super high speed.

If you have previously owned a random-orbit car polisher that made a lot of racket, but did little or nothing for your car’s paint, you will appreciate the 7424 XP as a professional tool. Most consumer car polishers don’t have enough power, have a very small orbit (often less than 1/4 inch), and have limited accessories. The Porter Cable 7424 was the first machine to shatter these limitations and became the industry standard.

The rotation of the foam polishing pad by centrifugal force is beneficial to the final outcome of your polishing work. While working, you will always be striking a delicate balance between down force required to work the polish and pad rotation necessary to get the finish to run clear and buff out.

Porter Cable 7424XP Features & Safety

The Porter Cable 7424XP has a powerful 4.5 Amp, 500 Watt motor. The motor on the 7424XP is 20% more powerful than the original 7424, making it significantly more capable when it comes to removing paint defects.

The Handle

Griot's Garage Polisher Handle
“D” Style Polisher Handle

Both Porter Cable 7424 models include a reversible side handle. The side handle makes the machine very 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, but individuals with large hands may find it just as easy 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 polisher both use a D handle that allows you to grip the polisher on-center. Many people feel this makes for more comfortable, smoother polishing.

The Speed Control

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

The Porter Cable 7424XP functions at 2,500 to 6,800 operations per minutes (OPM). The original 7424 is slightly slower, with a top speed of 6,000 OPM.

To control the speed, you rotate a thumbwheel speed dial. 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) to distinguish the difference between orbits and center shaft revolutions. At 6,800 OPM, this machine is really moving!

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 to avoid eye injury from flying debris.
  • Always switch the machine off and unplug the machine from the power source before changing accessories. Switching on the machine while changing accessories may cause an injury.
  • Never operate the Ultimate Detailing Machine unless the cleaning or polishing accessory is pressed against the surface to be cleaned, polished or buffed. This means that you both start and stop the machine while the tool it is resting flat on the surface of the car.

Porter Cable 7424 XP Dual-Action Car Polisher

Buffing Pads & Backing Plates

It’s possible to use a range of backing plates and pads with the Porter Cable 7424XP and other dual-action car polishers. Velcro backing plates are available in sizes ranging from 3 to 6 inches.

For proper and safe operation, the backing plate and pad combination must be balanced to the installed counterweight. The purpose of the counterweight is to dampen harmonic distortions (vibration) caused by the pad whipping around in its tight orbit. If the counterweight was not in place, you would not be able to hang on to the machine for more than a few minutes before your hand went numb.

Sonus offers a variety of pads and pad sizes for different applications.

DAS pads are larger in diameter and will cover a large area faster. The recessed area on the back protects your car from accidentally damage with the backing plate. The DAS Orange Pad is ideal for removing light oxidation and fine swirl marks. When used with a fine polish, such as Sonus SFX-3 Final Finish or Sonus Paintwork Cleanser, the DAS Green pad helps improve overall gloss. The DAS Blue pad applies liquid waxes and sealants quickly and evenly.

SFX pads are smaller and have greater foam density for intensive polishing applications. When used with SFX-1 Restore Polish, the SFX-1 pad will remove fine scratches, heavy swirl marks and other paint defects. Use the SFX-2 Pad with Sonus SFX-2 Swirl Remover Polish to polish away fine swirl marks, holograms and cobweb effect. Follow with the SFX-3 Pad and Sonus SFX-3 Final Finish for the ultimate gloss finish. The SFX-3 Pad is also the right choice for machine application of all liquid sealants and waxes.

The effective pad contact diameter for the Porter Cable 7424 is 4 to 7 inches. Pads must be matched to an appropriate polish to achieve the desired results. Don’t try to use a fine hand polish with a cutting pad to remove heavy oxidation or swirl marks. It simply won’t work.

I discourage the use of coarse “cutting” pads by inexperienced users due to the real potential of removing too much paint material or creating severe hazing in the paint.

Selecting the Right Car Polish

Most of the major polish manufacturers make a selection of abrasive papers, compounds, cleaners, polishes and glazes to meet varying polishing requirements.

Here’s a quick definition of polishing abrasives:

Abrasive paper or pad – An ultra-fine grade of sandpaper (1500 to 3000 grit) that can be used effectively to level a paint finish and remove imperfections. I mention sandpaper here 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 the 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, as 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.

Each of these levels of polish can be used with a Porter Cable 7424 or Ultimate Detailing Machine, however, only a professional or very experienced user should undertake using an electric polisher with abrasive papers or pads. Always follow the manufacturer’s directions.

Do not use a polish that is not specified by the manufacture (or a qualified source) for use with a dual-action machine.

Maintaining & Improving Paint Gloss

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. When you polish bad paint (paint with scratches, heavy oxidation, swirl marks, stains, water spots, etc.), you remove the bad paint to reveal a fresh finish. Obviously you can only do so much polishing before you wear out (thin or completely remove) the paint, so only polish as much as necessary to maintain healthy paint.

Buffing pad and polish makers create products with different levels of aggressiveness to make your polishing tasks faster and easier. You can use an aggressive pad and polish combination to quickly remove paint defects or severe oxidation, but it won’t reveal the full gloss potential of your paint finish. Just like polishing a jewel, you must use several grades of polish to bring out the final radiance.

If your paint is new or like new, it is 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, and work the polish in with a light touch until most of the polish residue is gone. Remove the remaining polish residue with a quality buffing towel. Fine polishes won’t take a lot of heat before they cake up and clog your pad, so don’t apply pressure to the machine. Allow the pad and polish to do the work.

Some polishes respond well to a microfiber buffing bonnet, while others do not. If you’re using a polish that is not buffing out clear, try doing the final buff out with a microfiber bonnet over a clean pad.

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

Step 1: Select Correct Pad & Center on Backing Plate

Select a the most appropriate foam polish pad for the job. Here I’m using the Ultimate Detailing Machine DAS Polishing Pad, which is perfect for light polishing an cleaning.

Step 2: Apply Polish to Pad

Select a good pre-wax cleaner. I’m using Ultima Paint Prep Plus, which is a fine polish, paint cleaner and swirl remover in one. This product goes on amazingly smooth and leaves an amazing shine.

Step 3: Distribute Polish on Work Area

Distribute the polish over the work area. If you don’t, 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 the 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

As you work the polish, the film will get lighter until only a slight haze remains. At this point you can stop and inspect your work. You can 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.

Step 7b

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

Step 8

The polishing pads will leave dry dust on the surface. Use a detailing spray and a soft buffing towel to wipe away the 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, but 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

After polishing and waxing, your final paint finish should be smooth, glossy and wet looking.

Removing Common Paint Defects

If you allow the paint finish to degrade from oxidation, water spotting, acid rain damage and other environmental hazards, you will need to remove the damaged paint to restore the finish. 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.

The Porter Cable 7424 is an effective tool for removing most paint defects, including surface scratches, swirl marks, sanding marks, water spots, chemical etching, oxidation, scuffs and paint transfer. All of these problems are addressed in essentially the same way.

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 have 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, you switch to a polishing pad and a gloss enhancing polish (often called a “swirl remover polish”) to remove the hazing or light dulling caused by the compound. This step will remove the remaining 10% of the imperfection, and reveal smooth, healthy paint.

Be very careful compounding and polishing on heavily oxidized paint until you know how much healthy paint is remaining. You could find yourself removing too much paint, creating thin spots or worse. If you over-buff an area of paint, you will completely 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. Don’t get discouraged, this is not uncommon. Slow progress is better than rapid progress when it comes to paint polishing.

If you have a small area with deep damage that the Porter Cable 7424 cannot remove, you have a couple of choices: you can polish by hand using a heavy rubbing compound, you can wet sand with 1500 to 2000 grit paper, you can switch to a rotary buffer and a cutting polish, or you can live with the improvement you made.

Sometimes the secret to repairing a defect is knowing what pad to use. In this picture a Sonus Spot Pad is being used to remove a scratch from a spoiler. A 4″ spot pad is the perfect solution for polishing tight areas or localizing a repair area.

Polishing Secrets Revealed

Machine polishing is messy. No matter how skilled you become, the machine will always sling off polish. 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. This little step will save you a lot of clean up work.

Polishing can be quite detrimental to trim. If you need to polish close to trim, I recommend masking it with painter’s masking tape. If you run your polisher against black plastic trim, 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 reduce your clean up work and save you a lot of heartache from mistakes. Be safe; take the time to mask off your trim.

Use masking tape to mask off trim around windows and areas where polishing would harm the finish. It only takes a few minutes to do an entire car. In the end it will save you a lot of time and grief.

Many people mistakenly believe that polish should be used sparingly. Doing so puts more of the workload on the pad and causes the polish to dry out before you achieve any work. Use polish liberally. Apply enough polish to work an area for one to two minutes before the polish hazes and begins to buff out.

Polish safely by keeping the pad flat on the surface you’re buffing and the cord off of the paint. I like wrapping the cord around my wrist once and draping the rest over my shoulder. You’ll have to find a solution that works for you.

Polish with the pad flat on the surface. If you 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. Tilting your Porter Cable 7424 will 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.

I like to 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. Don’t drench the pad.

When your pad becomes caked with polish, use a small nylon or horsehair detailing brush to gently remove the polish. This must be done with the polisher switched off. I like the horsehair brushes the best, as they don’t seem to rough-up the pads as much.

A dual-action polisher and a rotary buffer work polishes very differently. Using a rotary buffer to compound a car, you would run the buffer at a speed range from 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. So, you have to turn the speed up on the Porter Cable 7424 to remove defects.

Pad & Polisher Maintenance

The Ultimate Detailing Machine and Porter Cable 7424 polishers are low maintenance tools. Both manufacturers recommend yearly lubrication by a qualified repair center. If you use the machine professionally, I would follow the manufacturer’s recommendation. For the typical enthusiast, sending the machine in for lubrication every two or three years should be sufficient. If you feel comfortable doing the job yourself, all you need is red lithium grease and a screwdriver.

There are varying opinions on pad cleaning techniques. Not long ago, the pad manufacturers themselves would tell you not to wash the pads, as the water and detergent would de-laminate the Velcro from the foam. For the most part, this seems to be resolved.

If you are a professional detailer, washing pads after each use would be very time consuming. The best solution for the professional is to keep pads brushed clean and store them in large Zip-lock baggies. Mark the back of each pad with a marker to indicate which product is on the pad. When the pad becomes too dirty to use, wash it.

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 and fill it with water. Soak the dirty pad for up to 30 minutes. 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. Rinse the pads in the bucket of fresh water, squeeze, and set aside to air dry. Do not machine dry.

Soak your pads in a bucket of water and add a pad cleaning solution. Sonus Der Wunder Wasche is designed specifically for cleaning microfiber towels and foam buffing pads. It’s a low foaming detergent that’s easy to rinse. Allow pads to soak for up to an hour.

Practice Makes Perfect

While the Ultimate Detailing Machine and Porter Cable 7424 are easy car polishers to master, practicing on an older car with an imperfect finish is the best way to learn. You should experiment with a variety of polish and pad combinations until you learn how to achieve the best results.

There is 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 the final results. Don’t get frustrated if your initial experience is not perfect, as the smallest change (a different pad, polish or speed) can make a huge difference.

A dual-action car polisher makes polishing easy and allows anyone to create a stunning finish or restore a badly worn finish. All it takes is a little practice and the right selection of pads and polishes.

Be sure to check out the famous Perfect Shine article!