Putting Auto Body Putty in Place

Auto body putty is not a fix-all for every sheet metal restoration challenge that comes down the pike – particularly for filling in deep dents, nicks, or gouges. That's because any vibration can cause the body putty to crack or pop off metal. Especially on tractors, which vibrate a lot more than cars, making them poor candidates for the wholesale use of putty – a common practice in auto repair.

"You're always better off pounding out deep dents or replacing heavily pitted parts with new metal," says veteran restorer Jeff Gravert of Central City, Nebraska.

A $70 to $150 investment will buy you a good set of auto body tools. For example, Eastwood Company sells a seven-piece set of professional-grade hammers and dollies for $99.99 (800/343-9353 or visit eastwoodco.com).

Body putty, however, when applied in thin layers, can be a godsend when filling small imperfections and pits or hiding a patch job. Naturally, the key to any successful putty job is preparation. Putty, like paint, adheres better and stays intact when applied to bare metal. So make sure you completely remove all oil, grime, solvent, rust, and paint from the surface.

Before using auto putty be sure to use a Scotch-Brite pad to scuff the surface of primed metal to give the putty something to adhere to. Next, use compressed air to blow off the area to be filled. The key to making a permanent putty replacement is to avoid deep application thickness. Instead, keep the amount of putty applied as thin as possible to avoid future cracking and popping.

In the good old days, your choice of body putty was limited to plastic fillers. Not anymore. Evercoat (evercoat.com), a source for professional auto body supplies, has 15 different filler products.

Offerings range from a lightweight resin filler called Rage Xtreme (guaranteed to be pinhole-free) to Metal-2-Metal. The latter incorporates fine aluminum particles, and Evercoat says it's the "nearest thing to lead."

Another Evercoat innovation, Fiber Tech, is formulated with Kevlar, which gives it superior strength.

What's the best filler?

When in doubt as to which putty to use, the best bet is to start with a basic Bondo-like product, taking care to apply it properly and in layers. Remember to sand between layers and remove all dust before applying the next coat.

Don't be completely put off by alternatives, though. Evercoat's Metal-2-Metal virtually eliminates corrosion under patch areas, making it ideal for use on surfaces exposed to water (from radiators) or fluids (like fuel). The metal-filled putty sands out nicely.

Another filler product worth taking a look at is a liquid-thin glazing putty that fills in all pinholes and microscopic seams.

Buy a spreader set of tools

If you're a serious restorer, you'll want to buy a spreader set of tools consisting of different types of flexible spatula-like trowels. Some sets come with a plastic mixing board, but covering cardboard with aluminum foil works just as well and is cheaper. When you're done, just toss the foil.