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MG TD TF 1500 - Machine paint sanding

We started wet sanding the paint on TD 4139 today.

We wanted to try some of the new ultrafine sanding discs that 3M produces in their Trizac line.

3M has good video's that go over the process.

The pads come in various grits, from 600 to 5000.

These are hook and loop disks that you attach to your air operated sander. You run the sander at a medium speed. You also need a foam interface pad for your sander. This allowed the paper to smooth more evenly without putting too much pressure on the paint surface.

We started with 800 grit. Some of the video's say to start with 1500, others say 6 to 8 hundred depending on the amount of orange peel in the paint.

You wet the disk and lightly wet the panel. Enough water (with a few drops of dish soap) to lubricate the surface, but not enough that you cause hydroplaning. I use a spray bottle so that the water stays clean, and periodically add a bit more water while sanding.

You sand in back and forth and up and down lines, overlapping each line as you move. You should frequently stop and spray the sanding pad off to assure you do not get any particles on the disk that may cause larger scratches.

As with hand sanding or machine compounding, tape off or avoid edges to prevent burn through.

I stop frequently to check the surface. You should have a smooth finish that is without orange peel.

After washing and blowing off the panel (I also wipe it down with a tack cloth), you switch to 1500 and go over the panel again, repeating the frequent pad washing. You use almost no pressure on the sander.

Wash the panel and blow it off again and then go to 3000 grit.

This will leave a very smooth and just minimally dull panel.

You now switch to doing compounding using a buffer with a cutting wool pad.

After this, switch to ultra-fine compound and a polishing foam pad.

I was very happy with the results. The use of the sander will make this process go a lot quicker and I believe will give a more uniform surface leveling (Not to mention, a lot easier on my arms and shoulders that hand sanding causes). There was not enough light to get a good picture, but I will take some tomorrow.

The 3M Trizak pads run about $2.90 apiece, but 3M says you should only need a few as they have a triangular abrasive that lasts a long time.

If possible, I recommend doing the sanding in as controlled an environment as possible to avoid dust particles that can cause scratches. If you see pigtail scratches in the paint, this is a sign you had some contamination on the disk.

The compounding should remove these, but it is easier if you can avoid them.
Bruce Cunha

I have been using the 3M system for the last ten years. It work great with a lot less hand work. They have recently started making the 5000 grit Trizac. I always start with the 1200 grit Finishing film discs. I have a 3' DA and a 3" buffer to do the small areas.

Gary
gl krukoski

Bruce: Thanks for great report. It will be very helpful to others.

One thing you might want to mention in this thread is the type of paint you used and what the manufacture stated about cure time after painting before you did your sanding/polishing.
Christopher Couper

The paint used was TCP Global single stage acrylic urethane. Cure time is not stated on the can or in the literature from TCP, but web sites say 24 hours should be good. We waited about a week.

Today I started on the rear valance. It came out nice, but I still have small swirl marks. I am using 3M perfect-it 1 and 3 cutting compound on course and fine foam buffing pads with the polisher at a lower speed.

Here is what the back of the fuel tank came out






Bruce Cunha

Here is a tank I did off of a 1932 MG J2. Black is one of the hardest colors to get the final swirl marks out. The paint was Sherwin Williams Base Coat- Clear Coat auto paint.
The four step buffing process was used after the power sanding was completed.
Wool pad, 3M extra cut compound.
Then straight cut 3M compound with foam pad.
3M Swirl remover compound with a very soft foam pad.
Final compound was 3M Final Glaze using an egg carton foam pod on a DA sander. This final step removes the haze from the paint.

Gary





gl krukoski

Thanks Gary. This is a learning process for me.
Bruce Cunha

Bruce,
Thanks for this detailed thread. As Christopher said, it will be invaluable for us who have not tackled the paint yet.
Jim
JV Smith TD17744

We had good weather today, so I worked on the color sanding.

On the panels that have swirl marks, I resanded them with 1500 and 3000 on a sanding block. I then finished this with #1 3M compound and then #3 3M compound on two separate wool pads. Much better results. No swirl marks and a great deep shine

So my plan is to still used the orbital sander to smooth the surface imperfections, but I will hand sand to get rid of the swirl marks.

Gary. I know I should be able to do this with just the machine sanding, but for now, I will use both.

I have not found anyone around me that can give me hands-on instructions to figure out what I am doing wrong.


Bruce Cunha

I stripped and painted wife's favorite TD, and spent a great deal of time polishing it to a nice shine.

She read somewhere deglosser will improve the finish of paint, so she went over the new paint to give it a nice flat finish!
JIM N

I came across these after just completing the cut and polish on my Jag MK2. Took ages. Next time I am trying these babies.

https://www.aliexpress.com/item/4000602468117.html?spm=a2g0s.9042311.0.0.22c04c4dkkbEBE


Worth a punt given the price.

Cheers.


Dave
D Moore

Dave. Those look interesting. I think I will order a set. I have a lot of parts to still do. Worth a try.
Bruce Cunha

Making slow, but steady progress on the color sanding. I am unsure exactly if it is the paint or what, but the issues I was having with scratches was continuing.

It is like the paint is still too soft. I checked the formula and we were mixing the correct amount of hardener to the volume of paint.

A body shop friend recommended that after doing the 1500 and 3000 sanding, to let the paint set for a few more days to allow the open paint to dry out even more before polishing

This is helping, but it also slows down the process.

Today, I started the tedious job of hand sanding the louvers. Oh, Joy is this fun.


Bruce Cunha

This thread was discussed between 21/01/2021 and 17/02/2021

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