View Full Version : Filling pits in sheetmetal?

11-16-2004, 09:53 PM
I am starting my Fairbanks engine rebuild and restoration.The sheetmetal parts(there are two http://bbs.homeshopmachinist.net//biggrin.gif)have some pitting.
So far I have sandblasted and primed with red primer,but still need to fill the pits.What is the best way to do this?Glazing compound,many coats of primer and sanding?

11-16-2004, 10:11 PM
There is a paint called high-build primer-filer-surfacer.......it is used on cars.,
I recently used the easy sand varity two pack on my surface grinder......but there is a big but .......I have a feeling that this stuff has made my machine less resilient to knocks and scrapes.......i dont think I would use it on a machine again because it's just too soft.
Now your at the stage your at, I sugest you paint over the pits untill they apear no more .....then flat the paint down and give the whole lot another finishing coat.
You could use other products like car body filer (bondo) I supose ......but on a machine that gets knocked about , I'm not sure how it would fair up.
Next time I will build up the surface with ordinary primer...many coats ......this stuff is hard and resilient.
hope this helps...
all the best...mark

11-16-2004, 10:14 PM
Depends upon how deep and wide and how hot the parts will get.

Will a skim coat of Bondo (or clone product) do it or a filler primer?

Don't make fun of Bondo in this case. This can be a perfect use for this.

11-16-2004, 10:23 PM
No heat on either part,the most visable is the crankthrow guard.It mostly has small pits that 5 or six coats of regular primer would probibly fill.However there are also quite a few deeeper pits that are probibly on the order of .015" or better deep.
The local automotive paint supply has polyester glazing compound that is supposedly made for the purpose,but I have never used it.

[This message has been edited by wierdscience (edited 11-16-2004).]

11-16-2004, 10:30 PM
Glazing compound is what you want to use. Squeegee on thin coats with plastic squeegee or putty knife, allow to dry thoroughly and sand it smooth. It can be wet sanded.

What Fairbanks are you restoring?

11-16-2004, 10:42 PM
Fairbanks-Morse 7-1/2hp "Z" style B.
Luckily I have all the parts and the only one broken is the governor bracket.

I also need to find the paint codes for the unit.It has the blackish green body color with the greenish grey secondary on the wheel spokes and gear covers.I haven't been able to find any eleswhere on the web.

[This message has been edited by wierdscience (edited 11-16-2004).]

11-16-2004, 10:54 PM
Yes glazing putty. Plastic filler will be to thick in consistency and the "filler" will be too large. Some have glass beads or stranded filler that just wont get into the pits. JRouche

11-16-2004, 11:48 PM
Polyester putty - the kind that you use cream hardner with not the old laquer type. also primer is good -two part high solids again with a hardner , If needed you can brush on this will cut down on overspray and fill deeper pitts a little more sanding though.stay away from the lacquer primer it just skrinks to much Ed Bannister

11-17-2004, 12:03 AM
bondo is great stuff if you prep the surface (rough sand and wipe with acetone)and it will take a pounding.

foundry patterns get bondo and the squeese and jolt, vibe does not knock it loose, it takes a meat head with a 40" square flask bashing into it to hurt it.

I would fly in a plane made of bondo, no sweat.

edbannister "Polyester putty - the kind that you use cream hardner "

yes thats the good stuff im talking about..i just call it bondo. http://bbs.homeshopmachinist.net//smile.gif

11-17-2004, 01:08 AM
If they are small diameter (as well as shallow), you can probably get away with the glazing compound just fine. It sure is easy to deal with, but I don’t like the stuff much as it is awfully soft and shrinks a lot, no better than high build primer. I would probably go with a minimal amount of bondo myself.

11-17-2004, 02:21 AM
<font face="Verdana, Arial" size="2">I would fly in a plane made of bondo, no sweat.</font>

Uh, I wouldn't go quite that far but it will certainly do the job here.

11-17-2004, 04:07 AM
Or...if you wanted to get real serious...lead the holes in. This won't chip out like bondo. Lot more work to put on though. I've never put it on a heavy casting so am not sure how it'd work. I have used it on lighter stuff and it works great. the best is a proper body file for lead but you can get by with regular files and a card. Sand the lead as anything else.
Edit: Sorry...just reread the part that said..."Sheetmetal"...duh. Lead would work fine there!

[This message has been edited by torker (edited 11-17-2004).]

Michael Az
11-17-2004, 10:30 AM
I also use polyester filler for this purpose, works great, much finer material than bondo for those small pits.

11-17-2004, 01:52 PM
Lots of copper plating. Plate/Polish... Plate/ Polish until filled. Then a nice chrome or nickle plating. It'll be the shinest Fairbanks engine around. http://bbs.homeshopmachinist.net//smile.gif http://bbs.homeshopmachinist.net//smile.gif


11-17-2004, 04:30 PM
I believe the color you are looking for is 1967 chevy truck green. This is what is recommended as a cross match for my FM dishpan. Do you have the S/N for the engine? I may be able to look it up.


11-17-2004, 06:44 PM
I have used J-B Weld for that type of thing

11-17-2004, 09:07 PM
Geez...It seems we have a winner! Tinker2...that's a really good idea...never thought of it before. I like lead for auto stuff...it's easy to shape but it's not a real healthy thing to use.

11-18-2004, 02:51 PM
If none of those methods work, and you have oxy/acetylene, lay a thin coat of brass over the pitting. Clean it up well to start and use a "000" tip, it will give you a small enough flame to do the job and will not warp it.......with some care. Permanent fix, one I use on my old trucks, like on those impossible patches at the bottom of window wells.

11-18-2004, 03:06 PM
Chester...did you see on the Hotrod show...even Boyd Coddingtons guys use that one.

11-18-2004, 05:04 PM
That is a really old one, first saw it done when I hung around an Edmonton body shop in the mid fifties.

No I haven't seen Coddington use that one or much else. They seem to be "Bondo" freaks, quite a disapointment as I always associated that name with quality work. That '57 Chebbie they built recently was a real cheese wagon. Dream Car Garage seems to deliver what I would
expect from a first class shop.

Lynn Standish
11-18-2004, 05:23 PM
One thing I might mention with regard to glazing compounds, priming, painting, etc.

When you prime this thing, and then sand the primer, you'll probably get some spots where you sand through the primer to metal or the compound or whatever. Then you'll re-prime and sand lightly to avoid going to bare metal in places.

That's where the problem comes in. You need to let the final coat of primer dry for 2 - 3 days before final sanding. Otherwise you will put your finish on, only to discover later that the primer kept shrinking as the solvents in it continued to evaporate and you will have noticeable high spots in your finish where you didn't sand through the first coat of primer, giving you two coats in that spot.