Detailing World  

Go Back   Detailing World > Technical > Machine Polishing
DW Home Forum Home Merchandise Store Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Machine Polishing Need help with Machine polishing

Reply
 
Thread Tools Display Modes
Old 08-12-2016, 07:56 PM   #1
jahk86
Unwashed Member
 
Join Date: Nov 2016
Posts: 23
Thanks: 0
Thanked 2 Times in 1 Post
Machine Polishing/Compounding PTG

Say I want to machine polish a bonnet using a DAS PRO PLUS with 15mm throw, what is the general rule of thumb on returning to this area again. How many times can you give an area the paint correction treatment before you have removed too much clear coat.

I know this is a broad question which leads me onto my next question.

I've read the only way to truly know is to use a PTG, which one is good for someone who does not want to break the bank but needs something in their tool kit as a beginner, and also in terms of the readings when is it too low to even think about reaching for the compound?

Looking for a general rule of thumb for when you don't have a PTG, and a recommendation for a good entry level PTG and some info on what the readings mean?
jahk86 is offline   Reply With Quote
Old 08-12-2016, 08:48 PM   #2
gaswizards
Washmitt Meister
 
gaswizards's Avatar
 
Join Date: Oct 2016
Location: Ballymena
Posts: 134
Thanks: 289
Thanked 49 Times in 48 Posts
Garage
Hope this helps ( this is part of the da detailing guide on here):

HOW MUCH PAINT?
Most machine polishes use mechanical abrasives to remove the paint defects. This means that as you are polishing, you are eroding away a certain amount of paint, the exact amount depending on how harsh an abrasive you are using.

If possible, before starting to use the machine polisher, it is a good idea to check the thickness of the paintwork on the car. This can be done by using a Paint Thickness Gauge (PTG):



Most PTGs will measure to total thickness of paint on a panel. Paint generally consists of either two or three distinct layers: Base Coat; Colour Coat; Clear Coat (on most cars). It is the thickness of the top layer of paint which is of interest – going through this layer (strike through) will result in a respray being needed! So it is necessary to interpret the readings you see on the gauge and a certain amount of guess work will be required. Very generally speaking:

200 MICRONS +
This level of thickness can be expected on older cars that have been hand painted – the Ferrari F355 for example. It is also indicative of the possibility of the car having been painted at some point in its life. This is something important to note as non-OEM paint can respond very differently to factory paint in terms of hardness and polish behaviour – so if any regions appear quite thick, make a mental note of this for when you come to machine polishing them.

An example of just how thick paint can be is seen in the picture below where a reading of over 1000um was taken – that is paint that is 1mm thick!



BETWEEN 100 AND 200 MICRONS
This is normal paint thickness. Reading in this range point to standard paint (generally speaking) and shows a healthy thickness that should present no problems when it comes to machine polishing.

BETWEEN 80 AND 100 MICRONS
For most cars with clear coats, readings in this range point to quite thin paint. Many newer cars give thinner paint readings, but reading in this region should raise caution. Think twice about using more aggressive polishes on thinner paints as significant amounts can be removed, resulting in strike through and the need for a respray. Paint of this level can still be machine polished – but greater care should be exercised in polish and pad choice.

LESS THAN 80 MICRONS
Now we are in the realm of very thin paint, especially if a clear coat is present. Care should be taken when choosing a polish for these thinner paints. A big consideration should be a filler heavy polish which can achieve correction by filling the marring rather than removing any further paint. Thin paint can be a result of aggressive machine polishing in the car’s past life.

LAYER THICKNESSES?
As said at the start of this section, it is the thickness of the top layer of paint which is of most interest for assessing the suitability of using machine polishes. But with a reading of only the total thickness, how can you know the thickness of this top layer? The answer is that, unless you buy a PTG that can measure the individual layers (expensive!), you cannot know to high accuracy – but you can give an educated guess.
50-25-25: Very generally speaking, on most cars the clear coat makes up 50% of the total thickness. This is a general approximation, and only a first very rough estimate.
Inside of door: Measure in here. This will give you the thickness with much less clear coat sprayed and you can assume this to be the thickness with no clear coat to a pretty good approximation. The difference between readings inside the door and on the exterior paintwork gives the thickness of the clearcoat.
gaswizards is offline   Reply With Quote
Old 08-12-2016, 10:02 PM   #3
jahk86
Unwashed Member
 
Join Date: Nov 2016
Posts: 23
Thanks: 0
Thanked 2 Times in 1 Post
Do you have a recommended PTG, there are many out there?
jahk86 is offline   Reply With Quote
Old 08-12-2016, 10:12 PM   #4
lowejackson
Distinguished Detailer
 
lowejackson's Avatar
 
Join Date: Feb 2006
Posts: 8,879
Thanks: 606
Thanked 2,886 Times in 2,467 Posts
Polishing without a PTG is guessing but this needs to be put into context. I would guess the vast majority of people do not have a PTG and the forum is not full of pictures of damaged paint. If you know the history of your car, the odds decrease in hitting a problem.

Of course, none of this matters if you hit primer whilst you are polishing......
lowejackson is offline   Reply With Quote
Old 08-12-2016, 10:14 PM   #5
DrEskimo
OCD Sufferer (Obsessive Car Detailer)
 
DrEskimo's Avatar
 
Join Date: Jan 2016
Posts: 1,503
Thanks: 446
Thanked 725 Times in 549 Posts
The idea of all of this detailing melark is that you carry out a safe wash routine that results in little to no damage. Coupled with a decent coating for protection, there should be no reason to have to carry out a paint correction on a semi-regular basis.

I would borrow one if you can, make sure the paint is all good if the car has an unknown history (great for telling you if any panels have been repainted), carry out the correction and then hopefully never have to correct again.
DrEskimo is online now   Reply With Quote
Old 10-12-2016, 09:05 PM   #6
jahk86
Unwashed Member
 
Join Date: Nov 2016
Posts: 23
Thanks: 0
Thanked 2 Times in 1 Post
I think what I mean is, I don't have a full history on my car of each and every time its been machine polished. I have no idea other than as part of the approved BMW purchase they machine compounded it as part of the prep.

I have since hand polished a few areas.

Now I have a DAS6 PRO PLUS, I would like to do a full panel to really remove some of the imperfections I couldn't achieve by hand.

I don't want to tape off the bonnet, start a quarter and immediately burn through the clear coat, because unbeknown to me it has been done by the previous owner....?

So, do I take a risk and do a full paint correction then retain this through proper cleaning techniques, OR do I buy a PTG and check before I start machine polishing?
jahk86 is offline   Reply With Quote
Old 10-12-2016, 09:44 PM   #7
Kickasskev
PC Perfectionist
 
Kickasskev's Avatar
 
Join Date: Sep 2012
Location: Sunderland - Seaham
Posts: 424
Thanks: 237
Thanked 85 Times in 73 Posts
I use the painted area on a door shut as a guide, for example

If the door shut has 60 microns I would know that going beyond the 60 on a panel would be very risky, if the panel was 100 micron I know that I would roughly have 40 microns to play with, the reason being the door shut usually has the thinnest amount of clear coat, this is the guide I use and it hasn't failed me yet, but always check in case the panel you are polishing has been previously painted, if so this guide would be no good and you should really take caution.
Kickasskev is offline   Reply With Quote
Old 10-12-2016, 09:51 PM   #8
Kickasskev
PC Perfectionist
 
Kickasskev's Avatar
 
Join Date: Sep 2012
Location: Sunderland - Seaham
Posts: 424
Thanks: 237
Thanked 85 Times in 73 Posts
Chance of burning through with a DA are very slim to zero, I quite often have to revert back to my machine polisher because I cant remove all scratches with the DA as they are so gentle
Kickasskev is offline   Reply With Quote
Old 10-12-2016, 10:49 PM   #9
suspal
Distinguished Detailer
 
suspal's Avatar
 
Join Date: Dec 2011
Posts: 8,221
Thanks: 1,151
Thanked 3,809 Times in 3,094 Posts
I've seen people strike through with a DA,it depends on the state of the paint and common sense,although a DA is a safer bet as the way it spins and relative slower speeds than a rotary,lets say pad,polish/compound and technique plus a ptg are king.
suspal is offline   Reply With Quote
Old 11-12-2016, 11:15 AM   #10
diggy87
Sponge Jockey
 
Join Date: Jun 2015
Posts: 48
Thanks: 3
Thanked 10 Times in 8 Posts
I'm toying with the idea of a PTG myself and keep looking at this one -

http://www.wish.com/c/57bd72c8a44a141c6fdd93ef
diggy87 is offline   Reply With Quote
Reply

Tags
ptg machine polishing


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 10:40 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
DTO Garage vBulletin Plugins by Drive Thru Online, Inc.

vB.Sponsors
Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
DTO Garage vBulletin Plugins by Drive Thru Online, Inc.

vB.Sponsors