grinding weld on 304 exhaust tubing

[enen]

Hi all
I'm welding up a custom exhaust system. I'd like to grind the welds smooth.
I've used a 1/4 die grinder but it takes too long.
I've used a larger angle grinder with a flap disc but often take out too much material of the tube.
What works for you on makeing butts welds look seamless?
thanks, as always

[NOHOME]

Sadly, the answer is "Patience"

For most of my welds, I use the side of a 1/16" cutt-off wheel.

The problem with exhaust is that unless it is off the car, access is not easy and you need a variety of methods.

If off the car:

Get a wood dowel about 2" diameter. Drill a 3/8 hole in the middle. run a 3/8" rod down the hole.

You are going to put one end of the rod in your drill. On the other end. you need a bearing or wheel that will spin on the rod. You are going to hold this in order to create tension on the belt.

Buy a belt for a belt sander. Turn it inside out so the abrasive is facing in.

slide the belt over the pipe until it is over the weld. put the wood dowel in the inside of the sanding loop.

Holding the drill and the bearing, ( or wheel or whatever) you should be able to have a reverse belt sander to work on the weld. Takes a little practice to balance the belt on the dowel while maintaining pressure, but it does work.

Disclaimer:

Not responsible for damage caused by your learning curve or the bearings in your drill.

[cweed]

I do a lot of SS work and I use an electric die grinder with stone grinding tips first, then go back and flip it out unles I want the project polished. Either way it still takes time. The small sanding cones that screw on to a 1/4" arebor work realy well too.

[bobadame]

2" diameter Rolock discs in a 90 degree air motor work well for this kind of work. If you want dress the weld well enough so that the piece can be buffed, The final step before sanding and polishing is to draw file the area with a clean, sharp single cut file.

[James(Western Canada)]

BOB: What brand/type of file are you using to file STAINLESS STEEL??

Thanks!
James

Originally Posted by bobadame

2" diameter Rolock discs in a 90 degree air motor work well for this kind of work. If you want dress the weld well enough so that the piece can be buffed, The final step before sanding and polishing is to draw file the area with a clean, sharp single cut file.

[bobadame]

Originally Posted by James(Western Canada)

BOB: What brand/type of file are you using to file STAINLESS STEEL??

Thanks!
James

Nichols Mill Bastard.

[Rasper]

One of the keys to filing stainless welds is to anneal them. I gas weld a good bit of 304 stainless sheet metal in my sculpture work. I found the ****ed welds were harder than my files. So now I anneal them by heating to 1900F, (bright yellowish orange), and quenching in water. Softens it right up. Files beautifully.

R

[Peter Miles]

Originally Posted by Rasper

One of the keys to filing stainless welds is to anneal them. I gas weld a good bit of 304 stainless sheet metal in my sculpture work. I found the ****ed welds were harder than my files. So now I anneal them by heating to 1900F, (bright yellowish orange), and quenching in water. Softens it right up. Files beautifully.

R

Does that level of heating leave any color pattern in the metal?

[bobadame]

I used to work for a company that made food service equipment. We would TIG weld seams then grind and polish them to make the piece look seamless. We did this almost every day. This was 20 years ago but I don't remember that the process required annealing of the welded area. We used 308 filler rod and straight argon and as little heat as possible to keep the bead as small as possible. It's important to clean both sides of the metal of any oil or other crud. I would just wipe it with a rag. That seemed to be clean enough. To keep the inside of the pipe from oxydizing you might want to flow a little argon through it. Argon is denser than air so run the argon through a plug in the bottom of the pipe.

[Rasper]

Does that level of heating leave any color pattern in the metal?

Definitely turns the surface of the metal several dark colors, but it sands right off. I polish this stuff to a mirror finish. I used 308 rod the first time I welded 304 stainless. Welds nicely but it is a different color than 304 sheet metal. I had a pinkish line running through my polished sculpture piece. I had to junk it and cut up some 304 on a shear for welding rods.

We would TIG weld seams then grind and polish them to make the piece look seamless. We did this almost every day. This was 20 years ago but I don't remember that the process required annealing of the welded area.

I figured that the problem of hard welds may be peculiar to gas welding. I use a slightly reducing flame, not much, but a little, but it must add enough carbon to the mix to make the bead hard.

Richard