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-   -   sandblast question (http://www.hotrodders.com/forum/sandblast-question-230577.html)

benchracer1 03-11-2013 11:41 AM

sandblast question
 
I have access to a 100 cfm compressor and own a clemco 60 resperator. i have several items to blast. Is it worth the money to rent a clemco or marco blast pot? I have a cheap hf blaster and am not sure if it would became a weak link in the blasting procees. With a 100 cfm compressor what would be a good nozzle size to blast with using 30 grit? And last of all roughly how many pounds of sand does it generally take to blast a mid sized car assuming no filler and 1 coat of paint.....Steve

MARTINSR 03-11-2013 12:02 PM

My advice is DO NOT sand blast the body panels. You can and likely will destroy one or all the panels. And we aren't talking about "Damn I have more work to do" kinda damage, we are talking "#^@& I HAVE TO BUY A NEW HOOD!" kinda damage.

Unlike the common myth that the sand blasting is causing heat to warp the panels (I too thought that for yeas. You are blowing air on the panel so it actually gets cooler, try it, I have, after sand blasting the metal is cooler.

The warpage is caused by "Mechanical compression" that being each of those pieces of sand is like a tiny hammer putting a little dent in the surface of the metal stretching it. The top surface of the metal gets larger than the lower layer and it warps.

Can you sand blast sheetmetal without warping it, yep you can. I don't see a need to see when it works and when it doesn't personally, I am going to find another way like chemical striping or sanding it off with an orbital sander which creates much less heat than a "grinder". But I wouldn't be sand blasting it.

Brian

benchracer1 03-11-2013 01:40 PM

I was looking at possible chemical stripping of the wide open areas like hood, door panels and such then using sand blasting on the areas like firewall, doorposts. I know stripper sux to get in seams. Do the professional blasting outfits have a techniqur to avoid panel distortion?

MARTINSR 03-11-2013 01:57 PM

I've even had pro's ruin panels. I don't know, I think it is more about what material you use, but sand is a no-no. There are a couple of guys on here that know a bunch about the subject let's see if they respond.

On the stripper,that I have done a ton of and have a few tips. The trick to stripper is you simply mask off what you don't want it on just as if you were painting it. Here at work we will strip the roof of a year old car leaving not a mark on the rest of it, simply my covering the car in plastic, exposing the roof by cutting it out and then adding some masking paper over the top around the top just for good measure. After it's stripped being very careful to peel the paper off as to not touch or drip it on the car and wham, done deal bare metal roof.

Seams and such you always want to cover with duct tape then after it's stripped you remove the duct tape and remove the paint and gunk in the seam with a surface conditioning disc .....

http://3mauto.com/media/catalog/prod...0440188229.jpg

Or a "clean and strip" disc.

http://www.lulusoso.com/upload/20120...strip_disc.jpg

They work WAY better than a wire wheel.

But this is the norm, to cover up what you don't want stripped. I have even done complete cars that were assembled (no chrome and handles and stuff though) where all the door, fender, hood, trunk seams were duct taped and any other holes like antenna and handles and locks. Then remove all the tape and sand off the remaining and wham, bare metal car.

One thing I can't stress enough, if you can't really jump on this car and knock it out in a day and sand it and get it into epoxy primer I HIGHLY recommend you do a panel at a time. It takes a little more time but you don't get overwhelmed. it is VERY easy to be overwhelmed by a bare metal car sitting there. And you just can't walk away until you feel like it. So doing one panel at a time getting it back into epoxy primer then moving onto the next is a recommendation.

Brian

Brian

OneMoreTime 03-11-2013 02:44 PM

The rule is sand where you can and blast where you must such as on flanges and door posts where sanding is difficult..i use the 2 inch rolocks and can get into some amazing tight spaces with those and if I need to blast I use vitrogrit in an 60/80 grit and run 40/50 psi and have not issues..blasting the whole car takes lots of media and makes more of a mess that I want to deal with..

Sam

benchracer1 03-11-2013 03:16 PM

what grit would you guys recomend for sanding with a da? I definitely dont like the mess involved with sand either. I definitely like the idea of sand where you can and blast where you must. Taping seams is a good reccomend. I dont mind combining blasting, sanding and chemical stripping. 1 size doesnt fit all. frames and such I will definitely blast

496CHEVY3100 03-11-2013 06:13 PM

Quote:

Originally Posted by benchracer1 (Post 1655812)
what grit would you guys recomend for sanding with a da? I definitely dont like the mess involved with sand either. I definitely like the idea of sand where you can and blast where you must. Taping seams is a good reccomend. I dont mind combining blasting, sanding and chemical stripping. 1 size doesnt fit all. frames and such I will definitely blast

Dont know if its rite or wrong but it what i was taught , if you use stripper we use aircraft stripper ,cover the panels you have stripper applied to and not working with plastic helps to keep from drying to soon ,dont get to far ahead cover one panel while working the next .as for sandpaper i use 180 to remone paint if you use finer grit 320/400 to strip paint it will cause heat that you dont need.

benchracer1 03-11-2013 06:18 PM

Would 120 be to aggresive?

MARTINSR 03-11-2013 06:26 PM

Quote:

Originally Posted by 496CHEVY3100 (Post 1655881)
Dont know if its rite or wrong but it what i was taught , if you use stripper we use aircraft stripper ,cover the panels you have stripper applied to and not working with plastic helps to keep from drying to soon ,dont get to far ahead cover one panel while working the next .as for sandpaper i use 180 to remone paint if you use finer grit 320/400 to strip paint it will cause heat that you dont need.


Very good point, details details. :D

You can cover it with plastic after you apply it but if you do one other thing you don't much need to. That would be you don't "Brush" it like you do paint, back and forth. You pour some out then "spread" it out ONE WAY, with the brush. Don't back stroke, spread it out one way. The reason being the gases escape when you back stroke it and open the surface again. This makes a HUGE difference in how the stripper works. And this isn't out of my head, it says so in the instructions.

Another thing is you run some very coarse paper like 36 or 40 over it well to scratch the surface so the stripper can jump right in and do it's job.

Very good point to bring up there Dave! :thumbup:

Brian

496CHEVY3100 03-11-2013 08:45 PM

Quote:

Originally Posted by MARTINSR (Post 1655892)
Very good point, details details. :D

You can cover it with plastic after you apply it but if you do one other thing you don't much need to. That would be you don't "Brush" it like you do paint, back and forth. You pour some out then "spread" it out ONE WAY, with the brush. Don't back stroke, spread it out one way. The reason being the gases escape when you back stroke it and open the surface again. This makes a HUGE difference in how the stripper works. And this isn't out of my head, it says so in the instructions.

Another thing is you run some very coarse paper like 36 or 40 over it well to scratch the surface so the stripper can jump right in and do it's job.

Very good point to bring up there Dave! :thumbup:

Brian

Brian i tried a PM dont think it went thru.it is 10.44 here what time is it there probably to late to call.

timothale 03-11-2013 08:52 PM

paint removal
 
There is a lot of info here on hotrodders in the Wiki Section. , My willys had about 6 coats of paint and I scraped the top layers off, a lot of chips, no gooey mess until I got down to the bottom layer and used stripper. I also use my 3500 Psi pressure washer, to remove the stripper-paint that doesn't come off easy with a scraper. It will remove a lot of paint just slower, I also have a wet blaster from northern tool for heaver metal parts, frames ,axles, etc. water and sand, NO dust, just a wet mess, I had my nash roadster blasted by a guy the restorations guys use. He knows what he is doing and doesn't warp panels but cannot get out all the pits in sheet metal.

zmaxmotorsports 03-12-2013 12:04 AM

Ive had decent luck stripping sheetmetal with a soda blaster,takes a while but its much easier on the metal:)

496CHEVY3100 03-12-2013 06:23 AM

check with your pait supplier BEFORE using soda blaster NO paint company i know of will warranty wheir paint if you use soda it leaves film that effects paint .You can use a Dustless Blaster that uses water and recycled glass ,check on web. Your state might be different but i dont think so,You can strip an entire car under an hour.

Chevymon 03-12-2013 08:25 AM

Quote:

Originally Posted by MARTINSR (Post 1655892)
Very good point, details details. :D

You can cover it with plastic after you apply it but if you do one other thing you don't much need to. That would be you don't "Brush" it like you do paint, back and forth. You pour some out then "spread" it out ONE WAY, with the brush. Don't back stroke, spread it out one way. The reason being the gases escape when you back stroke it and open the surface again. This makes a HUGE difference in how the stripper works. And this isn't out of my head, it says so in the instructions.

Another thing is you run some very coarse paper like 36 or 40 over it well to scratch the surface so the stripper can jump right in and do it's job.

Very good point to bring up there Dave! :thumbup:

Brian

Brian, there is a very good explanation of how the stripper works and some tips on using it in this link
Acetone • How to Paint Your Own Car, Auto Body Discussion Forum & Videos • AutoBody101.com

http://www.wmbarr.com/ProductFiles/A...%2025%2009.pdf

MARTINSR 03-12-2013 08:33 AM

Quote:

Originally Posted by Chevymon (Post 1656060)
Brian, there is a very good explanation of how the stripper works and some tips on using it in this link
Acetone • How to Paint Your Own Car, Auto Body Discussion Forum & Videos • AutoBody101.com

http://www.wmbarr.com/ProductFiles/A...%2025%2009.pdf

Very good stuff there, I love how understanding the product at a chemical level helps you use it better, I sure learned this lesson with paints! But yes, and what he said about letting it dry is a no-no, very good basic info that REALLY changes things. I was blown away when I first started brushing only one way spreading it out and not back stroking, just that changes EVERYTHING in how that stripper works.

Brian


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