How to find spot welds in rusted metal?

[Rymanrph]

I'm trying to drill out some spot welds to save a piece, but the metal is rusted and pitted and I can't see any of the spot welds. Anyone have an idea on how to identify them so I don't destroy this piece looking for them?

[Geonovast]

It would help if you told us which piece. Also, pictures say a thousand words :thumbsup:

[500 MJ]

Magnetize it somehow and do something with some iron filings?

 

'bout all I got.

[Rymanrph]

Its the center channel running down the driver side floor board. I'm trying to take it out to put in my new floor pan. Its still in decent shape, so I don't want to destroy it when I take it out.

[codybutz]

I saved mine by, using a wire wheel on a drill and running up and down the flanges of that channel. a couple passes revealed where the spot welds were. you could probably get away with just cutting the floorboard out with that channel attached and then just drill out the spot welds and you'd have to just butt weld the channel back together after you replaced the floorboard.

[Rymanrph]

I thought about doing that, but I'm glad I didn't. I was able to find several more last night and I was able to lift enough of that channel up to find that the floor pan was nonexistent under the channel. It just crumbled into the unibody rail. I still have a ways to go though.

[LEAD_NOT_FOLLOW]

Spot welds typically leave an "indentation" due to the nature of how a spot weld is done (clamping pressure). Typically the best way to find them is to run course sandpaper over welded flange areas a few times. This will remove rust and/or paint along the flanged areas but will leave traces of paint and/or rust within the low areas. These low areas are the spot welds. If your lazy or that is taking to long you can run a wire brush over the welded area a few times. This will yield similar results as using sandpaper. The rust and/or paint along the flanged areas will remain and traces of rust and/or paint will remain within the low areas, or spot weld areas.

[Rymanrph]

There hasn't been any paint left in a long time (gone long before I got it); its far beyond surface rust. I've used a wire brush to try and clean up the area, but its so pitted and uneven, you can't tell the difference between an indentation from a spot weld and where the metal has just rusted away.