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Thread: Filler Primer for cast iron
04-20-2007, 06:28 PM #1
I'm restoring a lathe and need to paint a number of parts. Some require stripping of the old finish to do the job right. It is clear that a primer has been used that fills a lot of the roughness in the cast surface. The spray can primer that I am using doesn't fill this very well. Can folks here recommend a reasonably available high fill primer that would work for this. I definitely don't want or need bondo type of filling.
Thanks in advance,
04-20-2007, 06:32 PM #2
Well, thats what they probably used. Bondo or an early form of it. Hard to beat too.
04-20-2007, 06:44 PM #3
Stay away from any auto body fillers. Way too hard to sand. What you want to use is a Sherwin Williams Polane series of machine tool finishes. A product called Spray-Fil is used first to fill the casting. The filler sands very easy. Then you use a sealer after you sand the filler. (optional) Then you use one of their Polane 2 part polyurethane paints for the finish.
These are professional products and are readily available at a commercial Sherwin Williams store. They will mix any color or gloss you want for about $150/gallon, or pick from stock colors for about $60/gallon.
Being professional products, you must use proper handling and safety precautions with them.
If you look, you should be able to find PDF data sheets for the products online.
04-20-2007, 06:56 PM #4
If finished results are any measure, I would
suggest JB Weld, that is what Paula (over on
the SB forum) uses, and those things turn out
Probably not terribly sandable even in comparison
04-20-2007, 07:04 PM #5
One old time product that used to work VERY well but is hard to find now was "stove black" They have less effective products now like "stove polish" but if you can find the regular stove black it is GREAT!....Joe
04-20-2007, 07:04 PM #6
I used sandable auto body filler on mine and it worked nice. A good auto parts store will have a good selection of different fillers.
04-20-2007, 07:12 PM #7
JB Weld might work but it's far too expensive. It also won't sand and will barely grind.
I'd use one of the professional products mentioned above. Bondo is too soft and there's something about using it on machinery that I don't like.
Lots of the vises and cast items at H.F. use regular bondo and it will chip off eventually.
04-20-2007, 07:26 PM #8
Rick, we're busy restoring a SIP mp4b ( 1930s manuf) to show condition for a collector and have similar problems. Keep in touch with me and I'll send you pics. I wrote a while ago at quite some lenght about painting machinery but anyhow here is my (professional) opinion :
Try not to strip the previous finish. The castings are MUCH MUCH MUCH rougher than meets the eye. They resamble by no means car body pannels and this makes sanding a serious chore. The "putty" used years ago was a mix of linseed oil, fine sand, led oxide and talcum powder. You won't match it's adesion on a fresh casting. You'll need a very hard filler or the sanding will "sink" between higher CI regions. CI does not like body filler - it doesn't stick well. The best way to get a good look is to spot prime with an acid primer, fill with a good auto body filler ( STANDOX ) and paint with a good, honest enamel. This gives the kind of realistic look a machine tool should have.
04-20-2007, 07:47 PM #9What you want to use is a Sherwin Williams Polane series of machine tool finishes. A product called Spray-Fil is used first to fill the casting. The filler sands very easy.
I really, really wish I used the Polane Spray-Fil first on the cast iron castings -- it would have saved me a lot of work. The big problem is that it only comes in gallon containers (at least, thats what the local Sherwin-William shop told me).
I've got a Brown & Sharpe #5 (Universal Tool and Cutter Grinder) on the way, and I'm looking for a high-build primer to use this time. I'm seriously considering using the Dupont automotive high-build primer (which comes in quarts), and then painting with Polane on top of that.
04-20-2007, 07:58 PM #10
The trick with Bondo filler is to start work while it's still curing. Once it's mostly hard you use a rasp file to get the rough smoothing done, final sanding later is much easier.
Rick - Bondo also makes glazing compounds that might be more in line with what you want.
Be careful if you use Polane, it's one of the isocyanate catalyst paints. I'm not a professional painter so I stay away from products where the MSDS sheet says "Contains solvents that can cause permanent brain and nervous system damage".
04-20-2007, 09:30 PM #11I would suggest JB Weld, that is what Paula (over on the SB forum) uses, and those things turn out pretty nice...
04-20-2007, 10:09 PM #12
Paula, thanks for that! "Feather-Fill" is made by EverCoat -- the same people that make the super high-quality polyester body fillers.
It's sprayable, comes in quarts, and is pretty inexpensive ($24/quart) at AircraftSpruce:
04-20-2007, 10:38 PM #13
Be careful if you are just trying to fill small imperfections. After painting the repairs may stick out like a sore thumb unless you do a lot of filling and sanding to get the entire surface flat as opposed to just painting the stock cast surface.
04-20-2007, 10:38 PM #14
I'll add my two cents worth for Sherwin Williams Spray Fil. I bought a gallon just yesterday for $53 and they added some color so it nearly matches the finish coat, which will be Polane B.
Spray fill can be coated very thickly by continuing to add coats as it flashes over. I routinely got it 40 mils thick where desired.
The folk where I get it - Columbia, SC - are very customer friendly. Last year they topped of a half used gallon of Spray Fil and added color for just the cost of the added product. I'm confident they would sell it in quarts if I wanted it. They tell me that there is so little call for stock colors most of their industrial coatings that they sell the custom mixed colors for the same price as stock colors.
SteveF is right about the hazards of catalyzed urethanes. I'm not a professional painter either but I use a simple hood with a supply of fresh air from a separate hose. I don't even get a whif of the fumes. They are very inexpensive.
Here are a couple photos of my last project using Spray Fil under Polane B. The original finish was removed to bare casting in many places. UM 1 UM 2
04-21-2007, 12:12 AM #15
When I ordered my Polane HS Plus, they colored it for free, but dang, you got a great price on that Spray Fil! It was close to $100/gallon in Austin.
04-21-2007, 01:38 AM #16
Here is a link to a prior discussion on the fillers used to smooth out casting imperfections on older machines. This was not a discussion on primer type fillers, but the ones used before bondo came on the scene.
04-21-2007, 01:16 PM #17
Does anyone know if the commercial Sherwin Williams products are available in California? All I have ever seen are stores selling water base house paint.
04-21-2007, 05:06 PM #18
Bill, I'm pretty sure there are Sherwin-Williams Industrial stores in California, because there are Polane blends that are made specifically for the stricter California VOC requirements.
It's confusing trying to find a Sherwin-Williams Industrial store -- Sherwin-Williams Industrial & Marine Coatings is a completely separate subsidiary of Sherwin-Williams, with a completely different product line. To make matters worse, the Sherwin-Williams consumer stores sell "Industrial Enamel", which is good, but not nearly as durable as the two-part epoxies like Polane.
I can never find the number of the SW Industrial store in Austin, so I just open the Yellow Pages, call a random Sherwin-Williams store, and ask if they sell Polane. If they don't, they'll immediately tell you "You need to call the industrial store at xxx-yyyy."
The other way to tell if it's a Sherwin-Williams Industrial store: when you go inside, it has plain floors and concrete walls, and a bunch of professional painters waiting for large quantities of paint.
If the Sherwin-Williams store has nice floors and paint chip displays, and Soccer Moms looking through color samples, you're in a retail store [img]smile.gif[/img]
04-21-2007, 11:23 PM #19
Look into 2K Kwik prime by Transtar. Two part filler primer that is very good. Builds/fills excellent. Sands easily. Very good adhesion to bare metals, primer of choice in my rebuild shop.If available use a gravity feed gun w/1.7 tip, max fluid feed and have at it. Stay on the faster side of reducer speed to reduce runs. Just finished a cast iron unit that had complex shapes, very difficult to sand. You can spray 2K and watch it "flow" around the surface, smoothly.
Approx $25 qt.
04-21-2007, 11:54 PM #20
The other thing that works is have them pour off the gallon into four qu's That way you can get four differnt color. Ya they may clip you for for qut cans but for some projects it is cheaper