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11-07-2009, 06:44 PM #1
Machine tool paint prep related- "thin" bondo ?
Say you have a machine panel where some of the paint is worn off but the rest of the paint is good, no "paint cancer" issues....so you want to blend in the paint to the bare metal, in preparation for primer and repainting the entire panel.
For this sort of thing Bondo is too thick but I vaguely recall a thin "glaze" for this situation...but as I recall the problem is the glaze doesn't use a hardener and therefore takes too long to dry. Any alternatives ?
11-07-2009, 06:51 PM #2
Spot putty dries faster, IIRC. Glaze is for filling scratches from sanding and should be mostly removed upon application. Either should be applied in thin coats.
11-07-2009, 06:52 PM #3
The glaze comes in a toothpaste tube in various colors. The colors represent different drying times, some dry very quickly.
11-07-2009, 07:01 PM #4
I've thinned Bondo with polyester resin....the kind of stuff you'd use with fiber glass. Mix to the desired consistency and use the regular Bondo hardener to kick it.
11-07-2009, 07:13 PM #5
The toothpaste tube packaged products, "spot putty," are lacquer based and can raise havoc with unknown undercoats. They take lots of time to dry and they shrink while doing it. They don't bond to metal worth spit.
Evercoat makes several polyester resin based glazing formulations available at any auto paint store that are intended for what you want to accomplish. My choice is "Easy Sand" but some prefer "Metal Glaze." Both will do exactly what you want to do, they're designed for the job.
Evercoat's website has plenty of info on them.
11-08-2009, 07:49 AM #6
They also make "high build" primers, that are sorta like sprayed on bondo. If there's a paint jobber around you, that sells to the commercial body shops, drop in one morning with a box of donuts, they will be glad to help. May even provide some 'samples' for such a small project.
11-08-2009, 09:15 AM #7
Over here high build primer is AKA primer filler and available in aerosol cans at just about any high street car spares outlet.
11-08-2009, 10:18 AM #8
11-08-2009, 10:48 AM #9
I recommend Bondo brand No. 907 "Glazing and Spotting Putty". It comes ready to use in a toothpaste tube, spreads easily and dries in about 30 minutes. You can then sand it, add more as needed, or paint. It's sort of like thick paint in a tube. (This is what kpotter uses at his shop and he has painted hundreds of machine tools.) No issues with enamel paints, but lacquer thinner will attack it.
You can get the Bondo 907 at most auto supply places like AutoZone and I've also seen it at Ace Hardware.
I've also used Dave's Evercoat Easy Sand and it's a very nice product, but it's a 2-part product and each batch has a fairly short working time--maybe 5 minutes. I wind up throwing away about as much as I apply and spend a lot of time cleaning up between batches. And if you make a mistake and under-catalyze it you have a real mess on your hands. It's not cheap and I don't think you can buy a small quantity (I have a 24oz tube here and I think it was over $50.)
It would be nice if someone had a 1-part high-fill primer in an aerosol can. Does anyone know of one?
11-08-2009, 11:14 AM #10
Just picking out the first website that I can find with this product: http://www.sjdiscounttools.com/sem42003.html
My local auto part sells it and I've been using it for years.
Even with glazing putty if it's real deep, this stuff helps achieve a great finish with a sanding block.
11-08-2009, 11:58 AM #11
high-fill primer in an aerosol can
11-08-2009, 12:38 PM #12
Dynatron Ultralite is a two part process filler
about $12 a gallon
DuPont Corlar high build primer.
$56 for 1 gallon of activator, $56 for 1 gallon of base.
in light gray or white.
In your description a fill with a high build primer is the correct
way to go. Then feather the edges with a sanding block with
11-08-2009, 01:12 PM #13
I have refinished a lot of machinery and have had very good luck with the Bondo glazing and spot putty. I have used it for filling paint chips after sanding and spraying some primer on the bare spot. It is very easy to sand too much off so after smoothing it lightly I will spray some more high fill primer on and use more spot putty if needed. Or keep building layers of primer untill it is filled and smooth. I have also found it helpful to use a sort of make shift stencil (cardboard with a hole cut in it) to keep the primer only where I need it.
11-08-2009, 02:13 PM #14
11-08-2009, 02:18 PM #15
I have been using two pack high build primer. For spot filling, I apply it with a cheap school-grade artist's paint brush and cure it quickly under a 1.3kW electric patio heater. That way, I can lay up enough layers to fill the crater in one session without it running out of the hole I'm filling.
I'm not convinced that it's as hard as it needs to be, but time will tell on that score.
11-08-2009, 02:33 PM #16
any good body filler will feather out just fine, even on shallow/small spots. get your filler at an auto body supply shop, dont get anything with bondo on the can, it's crap. i usually keep a can of evercoat z grip on hand, it's cheap at about $25 a gallon, and whatever extra it costs, it saves you the headaches later on. It sands well, has minimal air bubbles, and feathers out really nice. I actually dont even need to use a glaze with it at all. I used it on my lathe restoration and it's holding up great. I've also used it on several cars, and even a rubber bumper as a temporary fix, but 3 years later, still no cracks so i havent replaced it.
11-08-2009, 03:23 PM #17
The toughest filler you can use is -All metal-.
Not sure if it fits your application or not, but you can feather it out....so FYI for this project of future ref.
I've feathered it out very thin and it's tough as ....well...aluminum. Prolly because its poly resin and alum. powder, instead of talc like most all other filler / glaze compounds. Hit it with a hammer after its hard, won't chip....which can be handy for a high use area on a machine or control that gets handled or bumped.
11-08-2009, 04:21 PM #18
I just finished painting my 30' planer mill. It took twelve plus gallons of paint to do the job. It took lots of filling and I used USC's Icing product. A local truck body manufacturer uses it, that is how I found it. I haven't done any body work in 20 years and I couldn't believe how well this stuff worked.
11-08-2009, 06:09 PM #19
"Worn off" doesn't imply chipped paint. No chips = no fillers. A high build primer should do everything you need. Block sanding should provide all the leveling you need.
For panel repair I wouldn't get into 2 component primers or paints. A sandable enamel primer should be adequate for the base. Using a hardener additive in the topcoat helps with the chemical "drying" of enamels, and is worthwhile IMO. But using full blown 2K urethanes and such for topcoating isn't worth the cost or the time and aggravation associated with cleanup when painting some part or few parts of a piece of machinery.
DaveE907 covered all the bad points of lacquer based spot putties and glazes. I've painted cars, trucks, and machinery off and on for 40+ years, and if I happen to think of a good quality associated with these products, I'll let you know
Added: Evercoat and USC both make excellent products. Bondo is more into mass marketing to the spray bomb class of bodyman. Southern Polyurethanes http://www.southernpolyurethanes.com/homepage-old.htm has excellent automotive quality epoxy and urethane primers and urethane clears at prices in the neighborhood of half what the big names charge. Prices are on the website. Barry, the owner, participates in several auto painting forums as a valuable source of information and not as a shill for his products.
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