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Our second class of the year was our first Advanced Class of the year. Got that?
As per usual, we started with classroom instruction, then moved out to the training garage for plenty of hands on time with both hand sanding and DA sanding, plus rotary polishing to restore gloss.
The first step, hand sanding, used 1000, 2000 and 3000 grit Unigrit papers.
We used a cross pattern for sanding, meaning the 1000 grit was done in up and down strokes, 2000 grit was done at a roughly 45 degree angle to the left and 3000 grit was done at roughly 45 degrees to the right. In the image below you can see the edges of the sanding marks in various directions, as well as the lack of gloss in the more aggressive grit area (ie, the reflection of the fluorescent lights cuts out at the edge of the 3000 grit sanding marks, obliterated by the previous 2000 grit marks below it). Yes, that means we actually gained gloss as part of our sanding process.
We then moved on to DA sanding. Here we're showing how DA sanding with a foam interface pad and a foam finishing disc will allow you to safely cross even tight panel contours without just cutting through the paint on the higher spot.
Contrary to the above, with the foam interface pad removed you have a firm, flat backing for the abrasive disc and you will be overly aggressive on those tight body contours. If you are damp sanding as part of a defect removal program, you should always have that foam interface pad in place - it will save your bacon and give you much more control.
This is a common mistake with new users - tilting the sander so that the abrasive disc is not in full contact with the paint. If you do this when DA polishing it's not that big of a deal since all you do is reduce your cut. But with a sanding or finishing disc, you end up making an uneven sanding pattern in the finish, and that's not good at all. But it's easy to spot, even from the perspective of the user: just look at that narrow path being left by the DA sander.
Here the sander is totally flat against the paint, so the path it creates is just as wide as the diameter of the sanding disc.
Once you're sanded to your satisfaction, it's time to remove the sanding marks. We do that with a rotary buffer, a wool pad and M105. Here we're showing the proper technique for picking up a bead of compound.
The rotary buffer has plenty of power, a huge jump over that of a traditional DA, but it's still not hard to control..... as long as you don't fight it!
And there's no need to generate a lot of heat, either. Use it correctly and the rotary is a fantastic tool, removing defects very quickly.
Now that looks great!
Use it wrong, however, and things can heat up very quickly. Here, a foam cutting pad is used to demonstrate the very fast escalation of heat that is possible if you aren't careful. Yes, that's 189F, and it only took a few seconds to get there, and all it took was a bit too much pressure.
Another potential issue is rotary swirls. The shot below shows what happens when you run a pad up on edge at speed, and move it quickly over the paint. Compare this to the similar image above and the difference is clear. But we used the same pad, same tool, and same compound - only the technique was changed.
Here's a demo of edge polishing. The pad will turn in a clockwise motion, so we have it tilted to lift the (from operator's perspective) 9 o'clock edge off the panel so that it doesn't ride up onto the edge. That means the 3 o'clock position of the pad is simply rolling off the edge and not interacting with it. This makes it easier to control the buffer, and prevents burning the very thin paint on the edge.
Once our compounding is done and all sanding marks are removed, we move onto finish polishing, using M205 and a black foam pad.
And that's how black paint should look!
OK guys, have at it!
Look at the concentration on Danny's face!
This is Gary's hand sanding pattern after refining with 3000 grit. This is textbook for how your sanding marks should look when done, just before compounding. And a sanding mark this uniform and predictable is going to be a breeze to buff out, and that means introducing almost no heat at all to the surface. Nicely done!
Two of the three stations getting a work over.
This is what we strive for!!
As per usual, we started with classroom instruction, then moved out to the training garage for plenty of hands on time with both hand sanding and DA sanding, plus rotary polishing to restore gloss.
The first step, hand sanding, used 1000, 2000 and 3000 grit Unigrit papers.
We used a cross pattern for sanding, meaning the 1000 grit was done in up and down strokes, 2000 grit was done at a roughly 45 degree angle to the left and 3000 grit was done at roughly 45 degrees to the right. In the image below you can see the edges of the sanding marks in various directions, as well as the lack of gloss in the more aggressive grit area (ie, the reflection of the fluorescent lights cuts out at the edge of the 3000 grit sanding marks, obliterated by the previous 2000 grit marks below it). Yes, that means we actually gained gloss as part of our sanding process.
We then moved on to DA sanding. Here we're showing how DA sanding with a foam interface pad and a foam finishing disc will allow you to safely cross even tight panel contours without just cutting through the paint on the higher spot.
Contrary to the above, with the foam interface pad removed you have a firm, flat backing for the abrasive disc and you will be overly aggressive on those tight body contours. If you are damp sanding as part of a defect removal program, you should always have that foam interface pad in place - it will save your bacon and give you much more control.
This is a common mistake with new users - tilting the sander so that the abrasive disc is not in full contact with the paint. If you do this when DA polishing it's not that big of a deal since all you do is reduce your cut. But with a sanding or finishing disc, you end up making an uneven sanding pattern in the finish, and that's not good at all. But it's easy to spot, even from the perspective of the user: just look at that narrow path being left by the DA sander.
Here the sander is totally flat against the paint, so the path it creates is just as wide as the diameter of the sanding disc.
Once you're sanded to your satisfaction, it's time to remove the sanding marks. We do that with a rotary buffer, a wool pad and M105. Here we're showing the proper technique for picking up a bead of compound.
The rotary buffer has plenty of power, a huge jump over that of a traditional DA, but it's still not hard to control..... as long as you don't fight it!
And there's no need to generate a lot of heat, either. Use it correctly and the rotary is a fantastic tool, removing defects very quickly.
Now that looks great!
Use it wrong, however, and things can heat up very quickly. Here, a foam cutting pad is used to demonstrate the very fast escalation of heat that is possible if you aren't careful. Yes, that's 189F, and it only took a few seconds to get there, and all it took was a bit too much pressure.
Another potential issue is rotary swirls. The shot below shows what happens when you run a pad up on edge at speed, and move it quickly over the paint. Compare this to the similar image above and the difference is clear. But we used the same pad, same tool, and same compound - only the technique was changed.
Here's a demo of edge polishing. The pad will turn in a clockwise motion, so we have it tilted to lift the (from operator's perspective) 9 o'clock edge off the panel so that it doesn't ride up onto the edge. That means the 3 o'clock position of the pad is simply rolling off the edge and not interacting with it. This makes it easier to control the buffer, and prevents burning the very thin paint on the edge.
Once our compounding is done and all sanding marks are removed, we move onto finish polishing, using M205 and a black foam pad.
And that's how black paint should look!
OK guys, have at it!
Look at the concentration on Danny's face!
This is Gary's hand sanding pattern after refining with 3000 grit. This is textbook for how your sanding marks should look when done, just before compounding. And a sanding mark this uniform and predictable is going to be a breeze to buff out, and that means introducing almost no heat at all to the surface. Nicely done!
Two of the three stations getting a work over.
This is what we strive for!!
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