# Heavy Cut Advice



## jas_racing (Jul 12, 2008)

Evening all,

As per my project thread on here I'm currently wet sanding and machine polishing my freshly re-painted Fiat Coupé but finding it tough going...I guess it's a good thing that the lacquer seems so 'hard' from a long term durability point of view but for now it seems like it'll take forever to get finished. Current process is lots of soapy water, sanding with 1500, 2000 then 3000 grit paper to remove orange peel and the odd inclusion in the lacquer, then polish with a yellow hex logic quantum pad on a DAS-6 using Menzerna Super-Heavy Cut 300.

I haven't got any further than this to refine as even after 5 sets of 6 passes on each area there's still a considerable amount of sanding marks remaining. I'm not sure the above would remove them all even after 10 sets!? If there were only odd marks I'd tackle them with another going over with the 3000 grit paper but in this case there's too many. I'm inclined to believe I need more cutting power but the Menz SHC 300 is the most aggressive I've got in my bag. I've tried Megs Ultimate Compound and Farcela G6 but neither cut as well as the Menz SHC 300.

Can anyone recommend another combo of pad and compound? Or something I'm missing? Or should I perhaps be tackling the job with a rotary machine instead of a DA??


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## Sawel (Aug 5, 2016)

Your compound should be aggressive enough. If it were me I'd get a Lake Country Thin Foam wool pad which can't be beaten for cut on a DA.


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## Steampunk (Aug 11, 2011)

Your compound is about as aggressive as it gets (Just below a matting compound like Scholl S0, really), and even on that pad is overkill for P3K. It really should be cutting out the defects, even on a rock-hard paint.

I'm guessing that the reason you're still seeing sanding marks is a mixture of a couple things:

(1) - The coarser grades aren't getting fully refined by the finer grades of paper, and you're not noticing until things are polished out... It's an easy thing to underestimate. Even with great paper, each subsequently finer step takes more passes to refine the previous one than you used before. Typically by a factor of at least 2.5x. 

(2) - Your sanding technique could possibly use scrutiny... Maybe a little too much pressure leaving deeper marks than should be there? Are you using a block? Keeping the surface flooded with enough water? Changing out frequently enough to avoid paper loading? Not all papers these days need soapy water, incidentally, and with the better ones it can actually get in the way of the paper cutting properly... Especially with the finer grits. 

(3) - The pad priming or pressure you are using isn't sufficient, or possibly your speed is excessive, and not fully letting the compound do its thing. 

(4) - If it's just an entry level DAS-6 we're talking about, the machine isn't doing you favors on such a hard job, and not working this combo as hard as it could be worked. If this is the case, stepping up the pad and the abrasive volume on it are both good things to try. The less machine power you have, the more aggressive than normal you sometimes have to make your pad/polish combos to compensate... Meguiar's #101, fully primed, water-spritzed, on a textile pad (CarPro Cool Hybrid would be a good option if you want to go maximum attack mode with M101...) would probably be the option I'd check out. However, I'd also agree with Sawel, that the LC 8mm PFW's would be a good possibility if you want to up the cut with your existing compound, now that CarPro's Cool Wool pads are very, very sadly discontinued...  Maybe CarPro Flash, or Scholl White Spider Sandwich pads if you want to stick with foam.

You'll know that your paint is rock-hard if SHC 300 is actually not leaving as much marring, and is generating more gloss than you'd expect... Otherwise, the issue is probably more the fact that your sanding defects might be extreme. In terms of aggression, SHC 300 should really should be able to cut out shallow P2K scratches on a Yellow Hex pad. So diagnostically I'd go through some of the options for why it isn't sufficient, before I tried to go more aggressive... If you have examined the possibilities with #1-3 already, your instinct is right, and skip to #4. 

Hope this helps...

- Steampunk


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## jas_racing (Jul 12, 2008)

Steampunk said:


> (1) - The coarser grades aren't getting fully refined by the finer grades of paper, and you're not noticing until things are polished out... It's an easy thing to underestimate. Even with great paper, each subsequently finer step takes more passes to refine the previous one than you used before. Typically by a factor of at least 2.5x.
> - Steampunk


Good point, I perhaps could be spending more time on the 2000 and 3000 grit stages. I'm not exactly rushing, the driver's door alone took me 4 hours to wet sand, but difficult to say in retrospect how much time I spent on each stage. At a guess I'd say I'm spending about the same in each so need to extend the 2000 and 3000 grit stages.



Steampunk said:


> (2) - Your sanding technique could possibly use scrutiny... Maybe a little too much pressure leaving deeper marks than should be there? Are you using a block? Keeping the surface flooded with enough water? Changing out frequently enough to avoid paper loading? Not all papers these days need soapy water, incidentally, and with the better ones it can actually get in the way of the paper cutting properly... Especially with the finer grits.- Steampunk


I don't apply much pressure and certainly keep the area flooded with water. I've tried with and without a block but the results seem the same. Paper is changed frequently, and is 'Klingspor' branded stuff I've used for some time.



Steampunk said:


> (3) - The pad priming or pressure you are using isn't sufficient, or possibly your speed is excessive, and not fully letting the compound do its thing.- Steampunk


I've varied the amount of pad priming but it doesn't seem to make much difference, and pressure is merely the weight of the DAS-6 on horizontal panels and light hand pressure on vertical ones. The speed is set to 5 out of 6 and seems to work the polish well, so I don't think the speed is excessive.



Steampunk said:


> (4) - If it's just an entry level DAS-6 we're talking about, the machine isn't doing you favors on such a hard job, and not working this combo as hard as it could be worked. If this is the case, stepping up the pad and the abrasive volume on it are both good things to try. The less machine power you have, the more aggressive than normal you sometimes have to make your pad/polish combos to compensate... Meguiar's #101, fully primed, water-spritzed, on a textile pad (CarPro Cool Hybrid would be a good option if you want to go maximum attack mode with M101...) would probably be the option I'd check out. However, I'd also agree with Sawel, that the LC 8mm PFW's would be a good possibility if you want to up the cut with your existing compound, now that CarPro's Cool Wool pads are very, very sadly discontinued...  Maybe CarPro Flash, or Scholl White Spider Sandwich pads if you want to stick with foam.- Steampunk


Yes it's an entry-level DAS-6 but has worked well on every other job I've done until now in the last 3 or 4 years, but perhaps because it's not been put to the test on hard paint thus far.

Anyone know where I can buy the LC 8mm PFW pads in the UK?



Steampunk said:


> You'll know that your paint is rock-hard if SHC 300 is actually not leaving as much marring, and is generating more gloss than you'd expect... Otherwise, the issue is probably more the fact that your sanding defects might be extreme. In terms of aggression, SHC 300 should really should be able to cut out shallow P2K scratches on a Yellow Hex pad. So diagnostically I'd go through some of the options for why it isn't sufficient, before I tried to go more aggressive... If you have examined the possibilities with #1-3 already, your instinct is right, and skip to #4. - Steampunk


No the SHC 300 barely leaves any marring at all, and does leave much more gloss than I would expect, almost to a 'finished' level.



Steampunk said:


> Hope this helps...
> 
> - Steampunk


It does help massively, thank you :thumb:


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## Steampunk (Aug 11, 2011)

Okay, I think I understand what's going on...

You gave me three reasons why your sanding scratches are abnormally deep:

(1) - The coarse scratches are very likely insufficiently refined.

(2) - If you sanded areas without a block, trust me, this will give you deeper patches of scratches and a less consistent result. You need a good rubber block, like Mirka or Meguiar's.

(3) - Klingspor paper... I've used quite a few brands of SiC wet/dry paper, and this was by far the worst. Loaded fast (No wonder you're using soap, though this is also part of why you're struggling to refine with the coarser scratches, as finer grits in particular tend to hydroplane more with soap or other lubrication added to the water.), the scratches were deeper and less consistent then their grits would suggest, wore out fast, didn't cut fast, etc... I'd definitely look into switching sandpaper brands... I would recommend Mirka Waterproof, Meguiar's Unigrit, or Starcke Matador in ascending order of quality.

You also gave me a few reasons why your compound isn't cutting as much as it can:

(1) - You're not using enough pressure. Try adding 5-10lbs of pressure, so that the BP speed slows down to about 1-3 rotations a second (Put a mark or piece of masking tape on the backing plate to see.), but keep it spinning at all times.

(2) - Slow everything down; add more pressure to slow down the RPM's and get the abrasive to bite, bring your OPM's down a notch to the 4-5 range unless you're in a spot that you need 6 to keep the BP rotating (It's like offroading; keep some power in reserve.)... It sounds counter-intuitive, but more speed doesn't mean more correction... Think launching a car at too high of an RPM; this doesn't get the power to the road any better.

(3) - Your paint is _definitely_ granite hard. Upgrading your pad is probably going to be part of the equation in finding a solution. I think CYC has the thin LC PFW's, but honestly, CarPro Flash or Scholl White Spider pads are just a shade under PFW in terms of cut. If you're comfortable with foam, stick with foam.

Hope this helps...

- Steampunk


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## [email protected] (Apr 2, 2007)

I believe its your sanding technique first off as has been mentioned, are you sanding in one direction or is it criss corss? You need to be going in a east west direction. You should be using fairy liquid (other brands of washing up liquid are available) in your water as well and change your paper often. The 1500 grit paper should be removing just about all the peaks of the orange peel. Lastly the 2000 grit paper should be removing the 1500 grit sanding marks and so on, so your polishing stage should not need serious effort to remove the sanding marks.

A couple of pictures might help.


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## jas_racing (Jul 12, 2008)

Steampunk said:


> Okay, I think I understand what's going on...
> 
> You gave me three reasons why your sanding scratches are abnormally deep:
> 
> ...


Superb, top-notch advice again thank you  I've ordered a Mirka rubber sanding block and some of their 1500, 2000 and 3000 grit paper. Noted on the polishing advice, will put everything you suggest into practice :thumb:

CYC seem to be out of stock of the 5" thin LC PFW pads; are these the Scholl and CarPro products you refer to?

https://www.cleanyourcar.co.uk/scholl-concepts-spider-pad-140mm

https://www.elitecarcare.co.uk/product/carpro-flash-pad-heavy-cut-160mm/


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## MidlandsCarCare (Feb 18, 2006)

Amazing advice above. As stated 3000 grade should be quite easy to remove if the prior steps and this have been executed correctly. 

Do you have the budget to invest in a ‘better’ polisher too? This will also speed things up a bit for you. 

Fair play for diving in the deep end and having a go yourself


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## Steampunk (Aug 11, 2011)

jas_racing said:


> Superb, top-notch advice again thank you  I've ordered a Mirka rubber sanding block and some of their 1500, 2000 and 3000 grit paper. Noted on the polishing advice, will put everything you suggest into practice :thumb:
> 
> CYC seem to be out of stock of the 5" thin LC PFW pads; are these the Scholl and CarPro products you refer to?
> 
> ...


Yes, those are the ones, though with a 5" BP I'd suggest the 130mm version of the Flash pad... Honestly, either the Flash or the Spider will serve you well give how hard your paint is, though I do find that on softer finishes the Spider has the finishing edge.

One question: Where did you find 3K Mirka Waterproof paper? To the best of my knowledge, this line only goes up to P2500? 

Glad to be of help...

- Steampunk


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## jas_racing (Jul 12, 2008)

MidlandsCarCare said:


> Do you have the budget to invest in a 'better' polisher too?


Sadly not while I'm unemployed


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## jas_racing (Jul 12, 2008)

Steampunk said:


> One question: Where did you find 3K Mirka Waterproof paper?


I didn't - the package arrived in the post today and the 3000 grit is 'Matador' branded


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## jas_racing (Jul 12, 2008)

Update on this...following Steampunk's advice I swapped to using Mirka 1500 & 2000 grit and Starcke 3000 grit paper, all on a Mirka rubber block and with a much more thorough going over at the 2000 and 3000 grit stages. The result is far far less deeper scratches and my stocks of Klingspor paper has gone in the bin!

For the DA polishing I opted for the CarPro Flash pad but could only source one so if that wears out I'll try a Scholl Concepts White Spider pad instead. Working with Menz FG300 gives formidable cutting power! Still needs 2 sets of 6 passes but that's a dramatic improvement on previous. The only downside is the pad gets clogged fairly quickly and needs cleaning regularly but that's a small price to pay. By comparison my yellow Hex Logic pads seem really soft now 

There are still odd deeper scratches after polishing but as there's only 1 or 2 per area I've just been going back at them with 3000 grit then polishing again.

The bonnet and one rear quarter are done and look fantastic, but the rest is still to go at...I've been adding up my time from the beginning of the wet sanding with the Klingspor stuff and I'm up to 60 hours now :doublesho

Thanks again to Steampunk :thumb:


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## Steampunk (Aug 11, 2011)

jas_racing said:


> Update on this...following Steampunk's advice I swapped to using Mirka 1500 & 2000 grit and Starcke 3000 grit paper, all on a Mirka rubber block and with a much more thorough going over at the 2000 and 3000 grit stages. The result is far far less deeper scratches and my stocks of Klingspor paper has gone in the bin!
> 
> For the DA polishing I opted for the CarPro Flash pad but could only source one so if that wears out I'll try a Scholl Concepts White Spider pad instead. Working with Menz FG300 gives formidable cutting power! Still needs 2 sets of 6 passes but that's a dramatic improvement on previous. The only downside is the pad gets clogged fairly quickly and needs cleaning regularly but that's a small price to pay. By comparison my yellow Hex Logic pads seem really soft now
> 
> ...


I'm thrilled that these new products and tweaks helped... 

It's amazing the difference that quality sandpaper makes, isn't it?

Shrinking your polishing area to concentrate your cutting power at this point in time is really the only thing left to try to get the scratches cut-out in 1-set. Don't be afraid to go as small as 12X12 inches, with languorously slow arm-movement... One inch every two seconds.

Wetsanding by hand is quite time consuming, but very much worth it... Quite enjoyable, too, if you can just put in some music or an audiobook while you're working, and zen-out.

Next time you try this: DA damp-sanding.  Just wait 'till you try P6000 sanding discs... :buffer:

- Steampunk


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## Titanium Htail (Mar 24, 2012)

In respect that it gets the job done where time constraints are not an issue, the final results are what count. If it were a paid job then the length of the process would be important. Good luck it is all learning trial error plus some great advice from the guys..

John Tht.


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