Electronic Paint Thickness Gauge

[BobbyG]

I understand the basic principal behind electronic paint thickness gauges but do have a few questions.



How accurate are they in real life usage?
How does it measure only one layer of paint?
What happens if the surface was repainted and could have several coats?
Do they work with fiberglass, carbon fiber, sheet molded compounds?

[jlb85]

I understand the basic principal behind electronic paint thickness gauges but do have a few questions.



How accurate are they in real life usage?
How does it measure only one layer of paint?
What happens if the surface was repainted and could have several coats?
Do they work with fiberglass, carbon fiber, sheet molded compounds?


By the questions I would say you need to look into them more.

Accuracy: very, much more than you need it to be, and much beyond what a human is able to repeat. Not an issue, all guages are decent and well beyond the detailer's scope of use.

Layers of paint: who said they measure only one layer? There are 3 models that measure from only ferrite containing alloys (steels and of course iron), another that measures alloys of all metals (aluminum panels for example), and the top model that measures on any surface. The first two are based on measuring the magnetic force and determining how thick of a non-conductuve coating is covering the substrate. In our case this coating is paint. The last type measures sonic resonance (ultrasound) instead of magnetic forces, thus its ability to measure on non-conductive substrates.

Thus if the panel has been repainted a paint thickness guage will measure how thick the resulting coating of paint is regardless of how many coats it has.

Prices vary. From around $75 for a Harbor Freight cheapo to the $2700 Defasko 200 advanced (the most advanced ultrasound guage that does individual layers or type of coating, ie base, clear, to some degree primer).

[agpatel]

* How accurate are they in real life usage?


For the deflsko one AG has
http://lib.store.yahoo.net/lib/autogeek/defelsko-specs.jpg

It will b e plus or minus .1 mil plus 3%. This tolerance will go up and down depending on the PTG you get.


* How does it measure only one layer of paint?

All metal ones only measure total paint thickness, meaning from the bare metal to the top of the clear. Only ones made for plastics using sonar will do individual layers.


* What happens if the surface was repainted and could have several coats?

Then it will show the total thickness (on metal panels), of all layers of paint/primer/rust coating.

* Do they work with fiberglass, carbon fiber, sheet molded compounds?

Very few do, and ones that do are over $1-2k and use ultrasound.

[ExoticAutoDetai]

Ptg-6000 and ptg-200 what you need to measure over anything.

Exotic Auto Detail via tapatalk

[C. Charles Hahn]

From around $75 for a Harbor Freight cheapo

$75? I paid $6 for my HF coating gauge.

Funny part is I found that the Cen-Tech model they sell is being sold under another brand elsewhere for $200+

Im the MAN

Regardless, I hardly use it unless I've got a huge amount of sanding to do.

[SATMAN40]

If you want one, make sure it does fiberglass, if you want to wet sand a corvettes...

[C. Charles Hahn]

If you want one, make sure it does fiberglass, if you want to wet sand a corvettes...

Be prepared to shell out big bucks for that (as in nearly $2k)

[oldmodman]

I am still very glad that I bought the Harbor Freight "cheapo", even though I got it before it was discontinued and paid full price. Which was less than 60$ Unfortunately, it is now discontinued and there is no new model at Harbor Freight.

And I do agree that it may not give you an absolutely accurate measure of thickness. However, it will give you a "close enough" measurement. At least close enough to know when the surface you may be considering working on is already thin. Plus it will give you a very accurate measurement of how much build you may be removing in the course of your work.

But here is my test of it from years ago.


http://www.autogeekonline.net/forum/auto-detailing-101/13340-paint-thickness-gauge-cheapo-harbor-freight-first-test-results.html

[jlb85]

I am still very glad that I bought the Harbor Freight "cheapo", even though I got it before it was discontinued and paid full price. Which was less than 60$ Unfortunately, it is now discontinued and there is no new model at Harbor Freight.

And I do agree that it may not give you an absolutely accurate measure of thickness. However, it will give you a "close enough" measurement. At least close enough to know when the surface you may be considering working on is already thin. Plus it will give you a very accurate measurement of how much build you may be removing in the course of your work.

But here is my test of it from years ago.


http://www.autogeekonline.net/forum/auto-detailing-101/13340-paint-thickness-gauge-cheapo-harbor-freight-first-test-results.html

I think I read that thread before buying mine! Thanks! A good read indeed, and I agree with your conclusions and how you were using the tool :xyxthumbs:

[jlb85]

* How accurate are they in real life usage?


For the deflsko one AG has
http://lib.store.yahoo.net/lib/autogeek/defelsko-specs.jpg

It will b e plus or minus .1 mil plus 3%. This tolerance will go up and down depending on the PTG you get.


* How does it measure only one layer of paint?

All metal ones only measure total paint thickness, meaning from the bare metal to the top of the clear. Only ones made for plastics using sonar will do individual layers.


* What happens if the surface was repainted and could have several coats?

Then it will show the total thickness (on metal panels), of all layers of paint/primer/rust coating.

* Do they work with fiberglass, carbon fiber, sheet molded compounds?

Very few do, and ones that do are over $1-2k and use ultrasound.


Good reply! The precision is even better than I remembered it. :xyxthumbs:

[BobbyG]

Thanks for the replies!

I think a paint thickness gauge does have it's place and I understand it's intended purpose but one question still keeps me scratching my head.

In general most finishes today are color-coat / clear-coat. Paint thicknesses today are scary thin and if anyone goes too far then it's time to head to the paint shop, which is very expensive.

Most is not all of our work is performed on the top coat or clear-coat. Knowing the thickness of the clear-coat is critically important in determining whether or not wet sanding or heavy compounding can be performed to effectivle remove a defect that has not broken through to the color-coat or deeper.

If these paint thickness gauges can only tell the total thickness of the paint film then what's the sense of spending what could be a large sum of money on them if the can't discern between layers?

[agpatel]

You can guess the rage of the clear thickness from the base thickness, you clear can be anywhere from 30-40% of the total thickness of the paint. You can also take paint reading from door jamb seams, trunks seems as those areas will have thinner coats of clear and paint and you can kind of guess the clear thickness. Also send a red flag up if you hit a spot that is really high you know it is repainted and go slow there.

You can spend the high money and get one that can show clear layer but it is not needed as with a little math, picking the right spots, and sense of how cars are painted you can tell when you are getting too low to polish a car.

Like anything it is just another tool to provide the detailer with more information to help them decide what the best plan of attack is.

[Tom Weed]

about 3-4 years ago I was searching for one, I found an ETG 2 on Ebay that a gentlemen was was a paint rep for DuPont was retiring and selling his. I got a pretty good deal on it, I think I paid 300 bucks for it. It measures steel/metal and aluminum.

Anyways, I've learned to what standard typical measurements are, generally on Fords/GM's later model vehicles, an average would be 4-6 mils, if it gets much below 4, I tend to really take caution when buffing in those areas. I take a measurements on a car I am not familiar with to see if it has any danger areas. I also like to use the gauge as a reference, checking and area before, during and after to see how much paint I am removing as well, but the problem can be, if you don't measure the exact location you checked before you started buffing then your reading will not be accurate due to the paint thickness being a little different from place to place.

I'm glad I got mine, gives me a little piece of mind on doing paint corrections.

Tom

[mxfly]

Just wondering if anyone has used this budget unit and what they think of it.

DIGITAL PAINT COATING THICKNESS GAUGE NEW 2010 MODEL! - eBay (item 270587423682 end time Jan-26-11 23:10:40 PST) (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=270587423682&viewitem=&sspagename=STRK%3AMEWAX%3AIT)

[jlb85]

Just like agpatel and Tom state, knowing some information is better than not knowing it, as long as the user understands the tools limitations. Even with a PTG tracking progress you can go through paint! Edges, corners, low spots and even worse high spots in the sheet metal can be passed over when inspecting or measuring and become more of a risk if readings show good paint health. So again, both sides have their advantages.

But a PTG without detailing forums would not be such a powerfully tool! As mentioned above, general guidelines on paint thickness on specific cars can be found relatively easily by searching here or on other forums. With this info and the PTG it is easy make a much better map to follow.