The Best Cheap Paint Depth Gauge And Why You Shouldn’t Trust It

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How to use a paint depth gauge

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I spent quite a while searching for the best cheap paint depth gauge after many years of not using one at all. Like many things in the detailing industry, these gauges can be a polarizing topic. Some people believe they need to buy an expensive one and trust it fully. Others think they can go by feel and rely solely on their experience to tell them how much paint is on a car.

Although I’ve never burned through a clear coat myself throughout my years of paint correction, I believe you can never be too careful. I chose to buy the Extech CG204 after doing some research on these cheap paint depth gauges as a way to add to the investigation before I begin polishing a car. I find this one does a great job of giving me the info I need.

Why did it take me so long to finally buy one? To be honest, I just didn’t trust the readings. I still don’t 100%, and neither should you. I view these gauges as simply a piece of the puzzle. A puzzle that I put together to learn the history of a paint job before I even consider touching it with a polisher.

You can never know too much about a vehicle’s history before you polish its paint. Has it been polished or repainted previously? Is there filler beneath the surface? Are all the panels equal in terms of thickness?

Being naive to what can happen if you over-work a section of thin paint can and will send you to the body shop with your tail between your legs. It’s better to avoid the cost (and embarrassment) entirely by erring on the side of caution.

How to use a paint depth gauge

Paint depth gauges: cheap vs. expensive

It’s not uncommon to spend over a thousand dollars on a paint depth gauge. Are they more accurate or do they last longer than the cheap ones? I can’t say for sure. I don’t put enough weight behind them to justify buying an expensive one to find out.

I’ve seen plenty of cases where even the expensive gauges have been proven to be inaccurate. One example that comes to mind is a video Matt from Obsessed Garage did with Jason Kilmer and Andy Ward of KXK Dynamics. (If you’re serious about paint correction and haven’t seen it, make sure to check out the video series).

In the video, they were using a DeFelsko gauge to show how much paint is removed by wet sanding. They hit an area of a hood aggressively with 1500 grit, then refined it further up to 3000 or 5000.

The shocking result was that the paint had magically grown according to the gauge even after aggressive sanding. There is no way that this is possible. They all agreed that this somewhat of a blooper moment in the video meant that you can never trust even a high-end gauge 100%.

So it seems as though even the expensive gauges aren’t flawless. That doesn’t mean that we should go too far in the other direction and buy a $30 paint depth gauge though. Something that cheap just doesn’t give you much peace of mind. The super cheap ones lack in features and longevity.

What’s the solution then?

That’s where the mid-range paint depth gauges like the Extech CG204 come in. They’re more expensive than the really cheap ones but MUCH cheaper than the expensive ones. Will it last as long? I guess time will tell.

What made me decide on the Extech unit? Oddly enough, it was another Obsessed Garage video. This one was featuring the Rupes training center – more specifically, a class taught by Jason Rose and Dylan Von Kleist.

In it, Jason mentions his gauge of choice. You guessed it, the CG204. He explained that he’s been back and forth on the subject. He started with the cheap ones, then moved up to the expensive ones. For whatever reason, he has now come full circle and is back to using these cheap ones.

If you aren’t familiar with Jason Rose, he’s an OG in the detailing world. He was instrumental in the development of many hugely popular products from Meguiar’s and is now in charge of training people at the Rupes USA facility. He’s an expert in the industry and if this gauge is good enough for him, it’s good enough for me (and you too).

Cheap paint thickness gauge

The best cheap paint depth gauge: Extech CG204 

This gauge has some decent features for the price. It’ll switch between reading ferrous and non-ferrous metals automatically without you having to change any settings. You can choose your preferred unit of measurement, either microns or mils (I use microns).

You can also set high/low alarms as well as a min/max/average reading at the bottom. The menu is very straight forward and easy to use. Nothing fancy here, just what you need to get the job done.

The CG204 comes with a few accessories. Extech includes a nice carrying case to keep it safe in your tool kit as well as a series of samples for calibration, USB cable and software, and even a pair of AAA batteries to get you started.

How to use a paint depth gauge

There are some things this gauge doesn’t do. It will only give you readings on metal surfaces (steel and aluminum). In order to get measurements on other substrates like plastic, carbon fiber, and fiberglass, you’ll have to step up to a much higher price point.

It also won’t read separate layers of the painted surface. Some expensive gauges will divide the readings up in layers showing any filler, primer, base coat, and clear coat measurements. The CG204 gives you one reading – the total thickness of everything on top of the metal. It’s up to you to decide how much of that might be clear coat.

Another thing I’ve noticed while using this gauge is that it doesn’t always hold its calibration when you turn it on/off. I tend to at least reset the zero calibration every time I use it, just to be safe. This is a minor annoyance but if you give me the choice between this and spending an extra $800+, I’ll take the annoyance. Setting the zero calibration is quick and easy to do.

You can pick up the Extech CG204 online for a couple hundred bucks and have plenty of info to work with for detailing.

How to use a paint depth gauge

In detailing, paint depth gauges are used to determine how much (if any) paint can be safely removed during a paint correction. Any time you polish your vehicle, you’re leveling the paint by removing some of it – that’s how scratches are fixed.

Getting a reading of the overall thickness of the painted surface with a depth gauge helps to remove some of the guesswork in knowing how much material can safely be removed.

The actual measurement itself isn’t that important to me. What I’m looking for are trends and comparisons on different areas of the car.

Usually, you can get an idea of what is considered “thin” for that specific paint by taking a reading in a door jam. To save costs, manufacturers spray just enough paint in there to make them the right color, and glossy. If you’re getting readings elsewhere on the car that match the door jams, that’s cause for some major concern.

How to use a paint depth gauge

Another way that I use these gauges is to point out anything that isn’t normal. For example, if the whole car is measuring around 230 microns and you have one fender that’s 500, that would indicate that the fender has been repainted at a body shop. Typically, aftermarket paint jobs at a body shop are much thicker than OEM ones. In this case, I’d be checking for differences in texture, tape lines, and signs of overspray that would confirm that the panel has been repainted.

In that same example, if a panel measures much lower at say 200 microns, that would indicate that it has been heavily compounded or sanded in that area. Perhaps a deep scratch has been removed or there was some other kind of damage that’s been polished out. Either way, that’s cause for concern and should be treated very carefully. The last guy might not have left you much clear coat, but it’ll be YOU that gets blamed for burning through!

Check out this video for more on how I use a paint depth gauge, and why I don’t trust the actual number itself:

Situational awareness, and how it applies to detailing:

Any time you put a machine polisher on your paint, you risk causing damage to it. That’s why it’s important to educate yourself first, and manage your expectations when it comes to achieving perfection.

Knowing when to draw the line and quit while you’re ahead is the name of the game. Things can go badly if you push too far or you aren’t paying attention. A paint depth gauge won’t guarantee any safety.

An important thing that police officers are taught during their training is situational awareness. Knowing their surroundings at all times. It plays a big role in making sure they go home to see their families every night.

I believe that although it’s not a matter of life and death in our case, situational awareness is important when it comes to paint correction too. If you focus on one thing and one thing only, something else might come along and create a new problem.

How to use a paint depth gauge

For example, picture a police officer arresting someone at a house party. Our natural instinct would be to focus on getting the cuffs on him. A police officer is paying attention to much more than just his handcuffs in that scenario. They’re watching the crowd of angry family members that might try to intervene. They’re also making sure they aren’t in the path of a vehicle if it loses control while driving past. Don’t forget that barking dog on the thin leash.

They’re constantly watching over their shoulders, all while they focus on the task at hand – getting the cuffs on the person who’s the main threat at the time.

Pay attention!

In the detailing world, we have our own version of situational awareness. We can’t focus on just one factor while we polish a car. In the previous example, the reading on our paint depth gauge might be the guy we’re trying to handcuff. But what if that reading is inaccurate?

Are we ignoring other signs of thin paint, like differences in texture or burnt edges? What about the other threats that we aren’t thinking about? The drunk driver behind us, the barking dog; or in our case, paint that’s getting too hot, contamination in our pad, or thick filler under the paint that’s prone to cracking?

If you’ve followed along with my detailing videos on Youtube (you are subscribed, right?!) you’ll see me constantly checking things while I polish. When I’m working an area hard, I’ll take my hand off the polisher and feel the paint to see if it’s getting hot. If it’s too hot to hold my hand on it, it’s way too hot for safe polishing.

I also tend to look through the polish behind my machine rather than ahead at where I’m going. If something is wrong, I want to see it right away – not after finishing 3 or 4 passes and wiping the product off. By then it might be too late.

I’m making sure that I don’t contaminate my pad by hitting a piece of rubber trim, a tire, or simply a dirtier section of the vehicle I’m working on. I do all of this while I polish. Some people might not even notice me do it. But these are all things that are just as important to focus on as the reading on the paint depth gauge.

My point is that we need to consider ALL of these factors when polishing a car, not just the thickness measurement. Using a paint depth gauge is important, but so are all of these other factors. The reading is just a piece of the puzzle – and ignoring the other puzzle pieces can absolutely lead to trouble.

What is the paint thickness on cars?

You’d be shocked at just how thin the paint is on modern vehicles. It’s very common for the thickness of the clear coat to be around 25 microns or HALF of an average sheet of copy paper.

This is why paint correction should be taken very seriously. I explain more in this post:

How thick is a “mil” of paint, and other paint thickness measurement units:

This is often confused because many people that use the metric system use “mill” as a short form for millimeters. When it comes to paint depth gauges, a mil is actually a thousandth of an inch (0.001″).

The other common measurement for paint thickness is microns. 25.4 microns equals a mil. 1 micron is 1/1000th of a millimeter. It’s up to you to decide which unit of measurement you’re more comfortable with. Either way you slice it, OEM paint is very thin.

Conclusion

The bottom line is that you can never be too careful when polishing your paint. A reading from a paint depth gauge is a really helpful piece of information when investigating the history of a paint job, but you need to keep an eye out for other signs of thin paint too.

Trust your gut, and if something doesn’t feel right or you feel like you’ve been polishing for too long, stop! Remember, you can always continue to polish more but you can’t polish paint back onto the surface. Keep that in the back of your mind the next time you’re chasing perfection while removing a scratch.

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