Bodywork Questions

[rustbucket49]

2. Any good wax a grease removing solvent with work. Talk to you local paint supplier for that one. Just don't use anything like laquer thinner of varsol. These will leave a film behind.

Uh oh, I've been using lacquer thinner - good thing I ain't done anything yet !!!

P.S. - those are some sweet rides you show on your last post !!! Unbelievable !!!!

 

[fatdog409]

i own my own shop aswell and have to agree with most posted ,allways try to do your bodywork over epoxy dp40 dp90 ect is a great product, production shops dont do this just because of time factors. i start sanding my filler with 80 and work towards 180 and then start with my high build, i also will high build twice, the first block with 220 finishing with 320 to get things nice and straight, then reprime and this will be sanded and preped for paint using 500- 800 . you need to do more metal finishing if you have enough filler on to start with 36 or 40 grit .and you must remember your finished results are only going to be as good as the products you use.

 

[bob w]

The experts that have provided information in this thread are much appreciated. I have learned a lot.
Thanks,
Bob

 

[rustbucket49]

I have this post over in Welding as well, but no responses, so I figured I'd try it under this thread as well since it is entitled "Bodywork QUestions".....

I am still working on my trunk lid that I've posted on my build site.... I got a 6" strip of flat steel welded in up on top and was very careful to skip around, cool the welds, etc. to avoid warpage. I was successful doing that...

So I go to grind the welds down (used a MIG), and used an 80 grit flap wheel on my 4.5" grinder. I jumped around grinding down the welds, cooled where I was grinding w/ a wet rag and really didn't notice any appreciable amount of heat build-up. However, the patch panel is no where near flat now. I can probably flattened it out w/ body filler, but is there another way to take out the waves and dips ?? I've heard about shrinking discs, but don't own one and don't know where to buy one... Not sure the correct method to straighten it back out.....

Also, what is the correct way to grind out welds to avoid this in the first place (assuming I stick w/ the MIG)??? I still have some more to finish up.

Any suggestions from you experts ??

 

[Sam_Fear]

Also, what is the correct way to grind out welds to avoid this in the first place (assuming I stick w/ the MIG)??? I still have some more to finish up.

I got a lot of MIG welds to clean up myself - same concern.

 

[madman]

The shrinking disk is one tool that will pay for itself the first time you use it. I bought one a few years back and I must say it's the best $40 I ever spent. It's super simple to use and gives fantastic results.

The first time I used it was on a 73 Pantera that had some extensive damage to the front fender top. It was so bad that there was well over 1/2" of bondo on it, in fact they built up the other fender with 1/2" of bondo just so it would match. Within an hour and a half the fender was almost perfectly straight. Plus it will take out oil canning in no time.

You can get them on e-bay here:
http://cgi.ebay.ca/Shrinking-Disc-F...ryZ63702QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I highly recommend this disk to anyone who does even the smallest autobody jobs.

 

[rustbucket49]

Madman, you've got me seeing a light, but I am hoping it's not another train!!! . Hope this is an "easy" fix....

So give me some details on how to work it... The pictures below shows where my problem is..... The red lines are low spots and the yellow are high spots. Green are where the contour is ok...... It is essentially the area between where I did the grinding on the welds. Hope this make sense.

So how would you work this?? These areas were fine before grinding...

And how do you avoid this in the future - I still need to grind the other side and around the main seam....

 

[madman]

To avoid warpage I suggest ditching the flap wheel and use a regular grinding disk. When it's almost flat switch to a 24 grit flexable disk. Don't press hard, just let the tool do it's job. Don't work one spot too long or you'll build up heat and don't quench it, just let it cool naturally.
The shrinking disk is very easy to use. You simply run it back and forth over the warped area and then quench it with water (squirt bottle works great) or compressed air. That's it! Sounds too good to be true but it is.
Don't forget to put a wee bit of bar soap on the disk or you'll make a horrible mess.

 

[rustbucket49]

To avoid warpage I suggest ditching the flap wheel and use a regular grinding disk. When it's almost flat switch to a 24 grit flexable disk. Don't press hard, just let the tool do it's job. Don't work one spot too long or you'll build up heat and don't quench it, just let it cool naturally.
The shrinking disk is very easy to use. You simply run it back and forth over the warped area and then quench it with water (squirt bottle works great) or compressed air. That's it! Sounds too good to be true but it is.
Don't forget to put a wee bit of bar soap on the disk or you'll make a horrible mess.

10-4 on the flap wheel. So the regular grinding disk - is that the hard stone disk ?? And the flexible disk - is that like a backer plate and a piece of the sandpaper?? Or is it an actual disk? Where do you get those?

What size shrinking disk to you use? The 9" or a 5"??? Will the shrinking disk take out the low spots as well as high spots??

 

[freakdude]

Alright, Im sanded it all down and put five coats of primerr over it . Now I got surface rust popping though. I guess I should have used a sealer???? Can I buy some kind of sealer in a spray paint can??? Any help would be appreciated>>

 

[madman]

You got it Rustbucket, the hard stone dealies. You can get the flexable ones at any auto body supply store, just tell them you want a 24 grit grinding disk, they'll know what you're talking about.
I'm using the 9" shrinking disk. It will take out high spots and low spots like magic. Have a peek at this video to see how easy it is.
http://www.youtube.com/watch?v=X8cruauERmI

 

[Sam_Fear]

I gotta say thanks too Madman - real helpful info.

 

[madman]

Glad to help!

 

[rustbucket49]

You guys ROCK !!!!! Thanks to those who have stepped up to the plate to help an inexperienced body worker dude. The info shared by all is invaluable for me. This thread will be a great reference for me for a while !!! I'm sure I'll have another dozen or so questions .....

P.S. - I ordered a shrinking disk today...

 

[rustbucket49]

Freakdude, if I'm not mistaken, high build primer WILL NOT prevent corrosion and rust. That is the purpose of epoxy or acid primer.

One of you experts are welcome to correct me if I'm wrong.

 

[kelseydum]

What is the life expectancy of a shrinking disc?

 

[madman]

High build primer will not hold out moisture, in fact it will retain moisture and wreak havoc if not top coated.

The shrinking disks are made of quite thick stainless steel and, unless dropped or abused, will last forever. Glad you picked one up Rustbucket, you will not be disappointed!

 

[kelseydum]

Cool, thanks Madman. I may have to get me one too.

 

[freakdude]

Someone told me to use a self etching primer and it will keep out the rust. Sound right??

 

[rustbucket49]

Someone told me to use a self etching primer and it will keep out the rust. Sound right??

My $0.02 again, but I believe there is a difference between an etching primer and an acid primer or epoxy primer. A regular etching primer may not give you the corrosion protection.

Again, this needs to be verified by one of the other guys.