Thoughts on spot sprayers

[mcguijo]

Being too cheap to haul my TR tub to the nearest bead blasting shop (about 150 miles away), I decided to leave with the local body shop to have him block the tub and prep for painting. Not being completely satisfied with his job, I'm going to have to go back and do some metal prep work of my own. I've seen "spot blasters" advertised on Eastwood and other. I can see the benefit of using this spot blaster on hard to reach areas. However, what are folks thoughts about using them on flat areas of panels? Or what are your thoughts of spot blasters in general? Am I better off using a wire wheel (or the like)?

 

[Dave Russell]

The body shop must have done a terrible job if you are thinking of spot blasting. Spot blasting or anything similar usually leaves you with no place to stop. Careful or you will be starting completely over. Also likely to find some low spots that need to be removed or filled. Do you have any idea of how much blocking, priming, blocking, is required if you do this? If so, proceed.
D

 

[JamesWilson]

I've got a spot blaster. It came with a number of nozzles suitable for inside and outside corners and a small 3/8" spot and larger 3/4" spot. It works well at clearing those size areas very neatly, and they can then have the edges sanded to allow painting as with other bodywork fixes.

If you're looking to do large flat areas these are not the best choice. I found that the cannister holds enough for small areas but needs refilling too often and gets pretty heavy too for long jobs. Then some type of bucket or feed system is more useful.

The process is also very dirty unless you're using the spot blasters with a grit recovery attachment. Otherwise the media gets everywhere and can be a lot of trouble to clean up, particularly if you're going to paint (or put the insides of your engine back together!) in the vicinity.

I used a blast cabinet for my small parts and sent the big stuff out and kept the spot blaster for the odd "touch-up" on a few areas that I wasn't satisifed with.

I suspect you may be better off with a wire wheel or one of the composition wheels for removing old paint and rust. The spot blaster can run off a reasonably sized compressor, but if you're intending to do a large area you'll need more capacity and pressure probably. I had a 3 HP, 14 CFM system that coped very well for spots (and everything else for which I needed a compressor) but was a little gutless for the big stuff. Running two of them in parallel feeding the one gun did the job. A drill and wire wheel can be effective and far cheaper and cleaner.

Trying to spot blast a square foot area 3/4" spot by 3/4" spot would take forever and be tiresome so the wheel would be faster and more effective.

 

[mcguijo]

I'm very picky. I don't like to see old paint (shapes) under the primer. The guy also did not spend that much time in the front end (primed over some rust, some grease, etc.).

 

[Dave Russell]

You are not being picky. What you describe is down right terrible. No wonder you are starting over, at least in spots. Make sure that the primer you use is compatible with the top coat.
Hope it comes out well,
D

 

[Bugeye58]

Spot blasters are exactly that. They are intended to be used on small spots of rust that may be popping through the paint.
I would rank them as being among the typical "used car lot" type of tools, although they do have their place if there is just a minor glitch in an otherwise good panel.
Just an opinion from someone who has been at this for awhile.
Jeff

 

[mcguijo]

OK spot sprayer may not do what I need it to do. I have access to a 50 lbs siphon blaster, which I can set up on the back forty. I have a good deal of experience with small parts in a cabinet but am a newbie to large flat panels (such as those fender parts found on a TR3). Any suggestions (such a media that I should use) and pitfalls I should look out for?

 

[JamesWilson]

Is it paint or rust that you need to remove?

If its just paint then chemical strippers can do the job effectively. These would be particularly good for big flat panels, not so good for little nooks, crannies or seams that may be hard to clean out later.

If any of the panels have undercoating you be well advised to remove that before any blasting too, either with chemicals or scrappers.

Blasting would be better for rust.

 

[mcguijo]

I have used aircraft stripper in the past. I agree that chemical works pretty well, but is very difficult to get out cracks, crevices, keep off skin, etc. I'm thinking about using some sort of media like beads, glass, etc. to strip off some rust and spots of old paint. I just want to know what sort of media would be ideal and what pressure I should shoot it at to avoid any warping of panels. Or perhaps I should hit the panels with aircraft stripper first and then hit the crevices with blasting media.

 

[JamesWilson]

I've not done any panels with a blaster- only small parts, inner body areas and suspension components.

I have stripped the larger panels using chemicals and they work well and can be scrapped and wiped away easily enough, the spot blaster can then be used for small rust spots if any are found and the whole then cleaned and primed.

My experience isn't extensive enough to suggest what would be best for the larger area panels. If you have an old, unuseable panel to experiment on that might be best.

 

[mcguijo]

Although feeling somewhat unfaithful. . the following car forum has some interesting discussion regarding spot sprayers, various sanding medias, etc. Hot Rod Forum