Can You Hammer Weld MIG Welds?

Hammer welding, also known as forge welding, is a centuries-old technique that involves heating two pieces of metal to a high temperature and then hammering them together to create a bond. The question arises whether this process can be applied to MIG (Metal Inert Gas) welds, a modern welding method that uses an electric arc to melt and fuse the metal.

Considerations for Hammer Welding MIG Welds

Weld Quality and Penetration

According to discussions on Reddit, it is possible to forge or hammer over a MIG-welded joint, but certain conditions must be met. The weld must have full penetration and be free of undercut or overlap. The weld should be strong enough to withstand the hammering and heating process without cracking or breaking.

Weld Homogeneity

It’s important to note that forge welds create a homogenous joint that is visually and mechanically indistinguishable from the surrounding metal. In contrast, MIG welds may have some residual reinforcement or proud metal that can cause issues when hammering.

Hammer Welding Sheet Metal with MIG Welds

A YouTube video demonstrates the process of hammer welding sheet metal using a TIG or MIG welder. The presenter explains that hammer welding can be used to create a smooth surface and improve the overall appearance of the welded joint. However, it’s crucial to understand that hammer welding requires practice and skill, and may not be suitable for all applications.

Preparing MIG Welds for Hammer Welding

can you hammer weld mig weldsImage source: Mig weld example

Grinding the Weld

According to a forum post on The H.A.M.B., hammer welding should only be done on welds that have been ground down to near parent metal thickness. This is because hammering on a weld that has too much reinforcement or proud metal can cause issues in the long run.

Timing of Hammering

There is no appreciable advantage to hammering a weld while it is still hot, as it will not affect the strength or quality of the weld. The weld should be allowed to cool before the hammering process begins.

Techniques for Hammer Welding MIG Welds

Heating the Weld

To prepare the weld for hammering, the area around the weld must be heated to a high temperature, typically around 1200-1500°F (650-815°C). This can be achieved using a propane or oxy-acetylene torch.

Hammering Technique

The hammering process should be done with a heavy, rounded-face hammer, such as a blacksmith’s sledgehammer. The weld should be struck with a series of overlapping blows, gradually working the metal to create a smooth, homogenous surface.

Maintaining Weld Integrity

It’s crucial to ensure that the hammering process does not compromise the integrity of the weld. The weld should remain free of cracks, undercuts, or other defects that could weaken the joint.


In summary, while it is possible to hammer weld a MIG weld, it requires careful preparation and execution. The weld must be of high quality, with full penetration and no undercut or overlap. The weld should be ground down to near parent metal thickness before hammering, and the process should be carried out with skill and precision to maintain the integrity of the joint. With the right techniques and attention to detail, hammer welding can be a useful tool for improving the appearance and smoothness of MIG-welded joints.

Reddit Discussion on Forging Over a MIG Weld
YouTube Video on Hammer Welding Sheet Metal
YouTube Video on Hammer Welding Technique
The H.A.M.B. Forum Thread on Hammer Welding Thread on Hammer Welding