Epoxy Putty vs Body Filler: Which One Should You Buy?

Epoxy putty vs body filler comes down to the shape of the repair. Epoxy putty is a kneaded stick that rebuilds, bonds and fills a gap, and it can be shaped, sanded and drilled once hardened, and some putties can also be tapped. Body filler is a spreadable compound that levels a dent so paint can go over a smooth surface. For a hole, a crack or a missing piece, putty fits; for a shallow dent that needs a smooth finish, filler fits.

Other tools worth a look

• J-B Weld 8237 PlasticWeld Plastic Repair Epoxy PuttyCheck price on Amazon
• J-B Weld Tan KwikWood Wood Repair Epoxy PuttyCheck price on Amazon
• J-B Weld 8258 KwikWood Wood Repair Epoxy Putty Stick-7 inchCheck price on Amazon
• Boncart High Strength AB Epoxy PuttyCheck price on Amazon
• J-B Weld WaterWeldCheck price on Amazon
• Epoxy PuttyCheck price on Amazon

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Below: how the compounds differ, what each one does well, and epoxy putties ranked for metal and plastic repairs.

Epoxy putty vs body filler: where the difference comes from

Putty starts as a stick with two parts that are kneaded together by hand. Once mixed, it can be molded and shaped by hand, then shaped again with tools after hardening. That makes it a rebuilding material: it can replace missing material, bond parts together, and fill holes and cracks in surfaces named across these listings, including metal, plastic and wood.

Filler starts as a spreadable compound that goes on over a dent in a thin layer. It is not made to rebuild a missing piece or to bond two parts together; its job is to leave a level surface that can be sanded smooth and painted. A repair that needs rebuilt material, a bond, or a filled hole belongs with putty, while a repair that needs a flat, paint-ready surface belongs with filler.

Gear that fits the job

Ranked first is the J-B Weld SteelStik, in a 2 oz – 2 Pack size. The listing states a tensile strength of 4000 PSI, a set time of 5 minutes, and hardening in 1 hour, with a hardened color of Dark Grey. It can withstand continuous temperatures up to 350F (176C) and intermittent temperatures of 450F (232C), and it is chemical resistant against petroleum, hydraulic fluids and other chemicals when fully hardened. The stated surfaces are iron and stainless steel, copper and brass, aluminum and bronze, fiberglass and plastic and PVC, and the listing states NSF certification and safety for contact with potable water. It can be molded, shaped, sanded, drilled and tapped, which makes it the quickest hardening putty in this group, and the metal-focused putty here.

Ranked second is the J-B Weld PlasticWeld, in a 2 oz size. The listing states a lap shear strength of 600 PSI, a set time of 25 minutes, and hardening in 3 hours, with a hardened color of Off-White. It can withstand continuous temperatures up to 250F (121C) and intermittent temperatures up to 300F (148C) when fully hardened, and it does not shrink. The stated uses are ABS, PVC and CPVC pipes and plastics, auto bumpers and trim, vinyl surfaces and siding, marine repairs and fiberglass parts, and plastic water tanks. It can be molded, shaped, sanded, drilled and cut, and it is NSF certified and safe for contact with potable water. For plastic repairs, it is the putty in this group made for that material, even though its lap shear figure is a different measure from the SteelStik tensile figure, so the two figures are not directly comparable.

Ranked third is the Boncart High Strength AB Epoxy Putty, in a 400g size, in White. The listing states a 1:1 ratio for cutting and kneading, a working window within 30 minutes, and full hardening after 24 hours. It withstands temperatures from -58F to 266F, and it is stated as resistant to corrosion, acids, oils, water and impact. The stated materials are metal, plastic, stone, wood, tile, ceramic, acrylic and glass, and the stated uses include pipes, sculptures, wood furniture, bathtubs, pools, concrete and faucets. After hardening, it can be sanded, drilled, tapped and painted. It ranks third because no strength figure in PSI is stated, and its hardening time is the longest in this group, while the listing also states to avoid using it underwater.

When filler wins, and when putty wins

Filler wins when the panel is intact and the surface is uneven. A dent that can be pushed back close to shape, then levelled with a thin spread of filler and sanded smooth, is a filler job. Putty wins when material is missing, when a crack needs filling, or when two surfaces need bonding. A hole in a pipe, a broken bracket, or a cracked housing needs a material that fills and bonds, not a thin levelling layer.

Material also decides the choice. SteelStik names metal surfaces, PlasticWeld names plastic compounds, and Boncart names a broad list from metal to tile and ceramic. Pick the putty whose stated surface list includes the material in hand, and check the set time and hardening time against the job, since SteelStik hardens in 1 hour, PlasticWeld in 3 hours, and Boncart in 24 hours. For a dent that will be painted, filler still has the edge on finish, and a sander made for filler work, such as the best DA sander for body filler, leaves the levelled surface ready for paint.

Follow each maker’s instructions for mixing, handling and hardening, and work in a ventilated space. Store any unused Boncart putty in a sealed plastic bag, as its listing states, so it stays usable for a later repair.

FAQ: garage tools

Can epoxy putty replace body filler on a car dent?

For a dent that needs rebuilding or bonding, putty can fill and bond, and the SteelStik listing states it can be molded, shaped, sanded, drilled and tapped. For a shallow dent that only needs levelling for paint, filler is the simpler choice, since putty is made to rebuild rather than to leave a thin, paint-ready layer.

Which putty fits metal, and which fits plastic?

SteelStik names iron and stainless steel, copper and brass, and aluminum and bronze, with a tensile strength of 4000 PSI. PlasticWeld is formulated for plastic compounds, including ABS, PVC and CPVC, auto bumpers and trim, and vinyl surfaces and siding. Boncart names metal, plastic, stone, wood, tile and ceramic, so it covers both, but it states no PSI figure.

How long before epoxy putty can be sanded?

Wait for full hardening, not just the set time. SteelStik sets in 5 minutes and hardens in 1 hour, PlasticWeld sets in 25 minutes and hardens in 3 hours, and Boncart must be applied within 30 minutes and hardens after 24 hours. Sanding before full hardening risks a soft, uneven surface.

Can hardened epoxy putty be drilled and tapped?

SteelStik can be molded, shaped, sanded, drilled and tapped, and Boncart can be sanded, drilled, tapped and painted after hardening. PlasticWeld can be molded, shaped, sanded, drilled and cut. Check the listing for the putty in hand, since the stated after-hardening work varies by product.

Does temperature matter for epoxy putty?

Yes, and the stated ranges differ. SteelStik withstands continuous temperatures up to 350F (176C) and intermittent temperatures of 450F (232C). PlasticWeld withstands continuous temperatures up to 250F (121C) and intermittent temperatures up to 300F (148C). Boncart withstands temperatures from -58F to 266F. Match the range to the part, since an exhaust or engine part runs hotter than a trim piece.

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