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  • Stainless exhaust fabrication/welding

    I'm about to get involved in two stainless street rod exhaust projects and I wanted to ask some questions. I'm not certain of the thickness of the tubing but I'd say 18 gauge or something close. My first question is what do most pro's cut there tubing with ? I want to get my cuts very precise because I don't plan on any grinding of the welds and to get perfect welds you need perfect fit-up. I'm curious how a Evolution Rage compound mitre saw would do on thin stainless. Second question is what size tungsten and filler wire do most people use for this type of work ? I typically use 3/32" tungsten for most of my work but I've got 1/16" and .040 tungsten if it would work better. As for filler I have 1/16" 308 ss and 347 ss. Also have .035" in both grades as well. What would be the better choice for 304 ss as far as type of filler ? Thanks and please make suggestions if you've got real experiance doing this type of work. Btw I just bought a Burns Stainless collector for a Harley 2 into 1 exhaust project and would love for my work to come out close to the quality of theres. It[collector] has very nice small beads and excellent finish.Thanks again.
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  • #2
    I don't do manifold fab, but my customers do the fab and I weld. They use many methods of cutting, like bandsaw, coldsaw, hacksaw and such. What they all tend to do is grind into a precision fit and then I tack for another fitup. I like to use a thin sharp tungsten like 1/16.

    If you use 304 tube, I don't see why 308 filler would not work. The big issue is that with the thin wall will sugar on the inside. To prevent contamination migrating into the material, I always gas purge it. The high heat of the exhaust gasses will certainly fatigue and embrittle the HAZ from the inside in a short time. Regular steel is somewhat forgiving in that manner, but need corrosion prevention from moisture.

    I would save your 347 for another project that needs the high heat compatability.
    Nothing welded, Nothing gained

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    • #3
      I used to hand cut my tubing on a band saw than final fit with a flap disk. Always wanna purge the inside of your tubing while welding to prevent sugaring the inside as mentioned. I've used burns stainless collectors in the past, they are a very nice piece, great finish and craftsmanship from them. 1/16 tungsten with 1/16 filler 308 will work fine on 304, and I liked to run a nice big gas cup with a gas lens to keep the welds from oxidizing on the outside.
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      • #4
        I hear you all on the purge , I do x-ray boiler tube welding for a living. I'm pretty well rounded on the welding end just curious what size tungsten most use and wire size. Looks like I will be sharpening up some 1/16" tungsten. I've got 1/16" wire and plenty of .035 308 wire so I should be covered. I've got a portaband I can use and I'm curious as to how my 10" compound mitre saw would work on this stuff. It's a Craftsman 10" thats made for wood but this is what I use on all my aluminum and never had any trouble what so ever. This may be the time to break down and buy that Evolution cold mitre saw I've been wanting if the Craftsman wont handle it.I've also thought of making a collar that would fit over the tubing so I could use a flapper wheel on a small grinder to make sure all the ends are perfectly square. I'm surprised no one mentioned a bull d1ck to get the ends to match each other perfectly.
        Dynasty 200DX "Blue Lightning"
        Bernard 3500ss water-cooler
        Rockwell vertical mill
        Beverly Shear B-3
        Beverly Shear JR
        Home-made English wheel
        Milwaukee Porta-band
        " Sawz-all
        Tennsmith 36" stomp shear
        Fixer upper 1968 Redface Lincoln sa200
        Powcon 300st

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        • #5
          Ive cut aluminum with my wood miter saw, with the normal wood blade. But i defiantly wouldn't cut stainless with it. I assume you have a metal cutting blade for yours? even so, i think id stick with the porta-band, or buy the evolution saw with the stainless specific blade.

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          • #6
            I use a stationary belt sander to sqaure off all my tubing cuts for welding. The latest project I've done was a bunch of 304 ss floats, 2" dia, 0.016" thick, fusion (autogenous) welded, using 8 amps on my 300 Dynasty. The weld isn't as consistant and pretty as I'd like it to be, but I had a hard time just seeing what I was doing with a shade 9 and @ 8 amps. I used a 1/16 tungesten, but if I had a choice I would have gone smaller.
            Attached Files
            Last edited by JonnyTIG; 09-27-2010, 02:06 AM.
            Jonny

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            • #7
              Showdog -

              Thin wall ss tubing is best cut with a friction bandsaw...... Which is nothing more than a bandsaw with the blade turned backwards and the speed set to max.

              Burns does it this way too.

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              • #8
                When welding 18 gauge s/s for exhaust I generally use .040" ceriated tungsten, gas lens w/ #7 nozzle and .035" 304s filler. I try for a fusion weld but have the rod ready to introduce in spots if necessary. I will step up to 1/16" tungsten and possibly 1/16" filler if welding to either a flange or coupler but try to stay with the larger nozzle.

                As far as cutting I just use an abrasive wheel in my chopsaw and clean up/bevel with a small 3" roloc disc then wire brush it prior to tacking/welding. Like others have already mentioned backpurging is a must with thin s/s tubing. Mike.

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                • #9
                  Exhaust tubing typically 16 or 18 gauge. I use mostly 3" (which is unnecessary for 99% of the dual exhaust out there). I try to use 4" radius bends but have on occasion used 5" or even 6".

                  I have cut with abrasive saw with acceptable results - either a 14" cutoff or a 12" abrasive blade put into a Dewalt miter saw (note: the metal gets hot enough to melt the 'insert' on the miter saw). If you are going abrasive, cut very very slow. Abrasive saws tend to melt their way through making for a very uneven cut.

                  Band saw, with a miter gauge is my favorite way to cut. I have a large Delta sander (6" wide belt + 12" disk) to touch it up - also using miter gauge. If you use a portable band saw, you can cut long segments. See the tables made by:
                  http://www.swagoffroad.com/

                  Note: even mandrel bent tubing is not perfectly round - a bit oval. So if you are cutting bends in the middle of the bend you will be trying to line up ovals... not too bad with quality mandrel bent tubing, but if you are going to polish it will show. You can either buy the tubing bent exactly as you require or two options that I use are: 1) Lilse tools or Snap on used to make a wedge that used an air hammer/chisel to round out the exhaust. Stainless does have spring back so it will never be perfect. Of course 18 gauge is a lot easier in this respect.

                  I do have a cold cut saw now but have limited use on it so far (actually mostly aluminum) but assuming you can clamp exhaust pipe that should be a good alternative. Clamping 3: pipe should be doable, 4"... not so sure.

                  For fitup, I use sharpies to make witness-lines and hold everything together with masking tape. Masking tape is pretty good and cleans off easily.

                  Tungsten .040 and .035 308L filler (the less carbon the better). A high frequency pulse (400Hz) is suppose to concentrate the heat. Miller's web site has an article about pulse on stainless I think it was a refrigerator manufacturer. Hasn't helped me much.

                  As for purge, if you fitup is good, and you can weld without filler, you can get away without back purge. Essentially you don't get full penetration (its an exhaust pipe - not structural steel). This is actually not so easy to achieve. Stainless can move quite a bit, so you need 4 good tacks, examine the gap and make a decision if you can do it without filler. Solar Flux on the back side doesn't hurt.
                  *** If you find your self ever needing filler, or dwelling at a spot trying to move the puddle, your done - purge is necessary to prevent boogers.

                  If you fusion weld, and want to polish it later, a second pass with filler can be used to build up the weld joint. The second pass can be done without back purging. The issue this time is simply the size of the weld puddle. If you can keep the weld puddle to less than 2x metal thickness, you should be OK.

                  Without purging, corrosion resistance will be compromised for sure, but from my experience it seems to be a surface issue and not a full penetrating rust. Also, from my experience, 4 tack welds is enough to hold exhaust pipes in place - which means full circumference welds - even if slightly compromised via corrosion, will hold just fine.

                  Just a note: Borla a maker of aftermarket stainless exhaust - with their "Million Mile warranty" is MIG welded and follow up with chemical passivation (I believe Walter Abrassives makes a tool for this - think $1800).

                  As for finishing the stainless. The cheapest way seems to be Makita 7" polisher (as opposed to a grinder) + accessories from either Fein or Walter.
                  http://www.fein.de/corp/us/en/fein/p...po_wsg_acc.htm Fein's list prices on their belt polishing seems to be the best considering you get 10 belts vs. Walter's 3.

                  Note - both the Walter and Fein solutions are for low speed tools, not for 10,000 rpm grinder.

                  Metabo makes a similar tool. The Walter solution bolts to the standard 5/8-11 chuck, the Metabo and Fein require a 4" adapter to use their belt sanding/polishing. Metabo wants like $250 for the adapater (I don't know exactly, I passed out after seeing the 2...) Fein more like $80.

                  In case you haven't done the work before - hang your mufflers and exhaust tips first - then, with the suspension mocked up, connect the dots. Rule of thumb is 1" spacing all around. You can get away with less, but why push it? Things, flex, suspension moves, rubber bushings give etc. I like putting a slip joint over the rear axle so I can take the exhaust back out with out having to drop the rear axle. A local shop expands the pipe for me. To seal the slip joint I use exhaust bands - also in 304 stainless - available at better autopart stores or truck part stores.

                  Last but not least, if you find a good turbo style stainless muffler, let me know. Right now Borla, magnaflow, and Corsa seem to be the only ones making 304 stainless and they are essentially big glass packs. Gebler Headers, in Greenbelt Maryland, makes a spiral header and he only works in stainless. This is similar to the Moroso design. Corsa seems to sell only complete kits.
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                  • #10
                    Get a hose clamp from any auto parts store you can use this to hold the tubing for tacking drill a hole big enough to put a tack on the tubing that way you won't have to use tape or fumble around trying to tack it. As for square cuts you can use a tubing cutter, I've used this takes more time but the cut is straight make sure to clean the cut as it will leave a lip on the inside of the tubing

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                    • #11
                      Originally posted by Showdog75 View Post
                      I'm about to get involved in two stainless street rod exhaust projects and I wanted to ask some questions. I'm not certain of the thickness of the tubing but I'd say 18 gauge or something close. My first question is what do most pro's cut there tubing with ? I want to get my cuts very precise because I don't plan on any grinding of the welds and to get perfect welds you need perfect fit-up. I'm curious how a Evolution Rage compound mitre saw would do on thin stainless. Second question is what size tungsten and filler wire do most people use for this type of work ? I typically use 3/32" tungsten for most of my work but I've got 1/16" and .040 tungsten if it would work better. As for filler I have 1/16" 308 ss and 347 ss. Also have .035" in both grades as well. What would be the better choice for 304 ss as far as type of filler ? Thanks and please make suggestions if you've got real experiance doing this type of work. Btw I just bought a Burns Stainless collector for a Harley 2 into 1 exhaust project and would love for my work to come out close to the quality of theres. It[collector] has very nice small beads and excellent finish.Thanks again.
                      We used a 14" abrasive saw (chop saw or Target stationary saw) or Fischer cold saw to cut dairy tube, all our work was tig 100% penetration and purged, fitup was critical to us as well.

                      Some brands of the abrasive wheels work better than others as far as burs left on the tube etc.
                      mike sr

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                      • #12
                        I heard from the a guy working at the LWS that some abrassive wheels are indeed better.

                        I typically use a wheel I bought at Home Depot - I guess "Dewalt brand" or similar. When cutting 16 gauge 304, you can watch the material glow/spark as the saw comes down. The more pressure I put, the more heat goes into the stainless and the wider the kerf gets. The variation in Kerf width is my biggest issue.

                        So I try to adjust my force by watching the kerf, which is never perfect. So I end up cutting a bit long (at least 1/16") and sanding back to the line.

                        Am I doing something wrong or using the wrong abrasive wheel? Its kinda academic right now because I have access to a band saw now.

                        To the idea using hose clamps. I'm going to try it. I will say using tape actually allows me to bang things around a bit. If the hose clamps were a bit wider, I think they would work better. I suspect that something will break apart and I will curse your name
                        Con Fuse!
                        Miller Dynasty 350
                        Millermatic 350P
                        -Spoolmatic 30A

                        Hypertherm PowerMax 1000G3
                        Miller Multimatic 200 - awesome portable MIG (and stick and TIG)
                        Miller Maxstar 200DX - portable TIG and stick

                        Comment


                        • #13
                          If it says "long lasting" on the blade you dont want it, they tend to glaze over and push up a large bur.

                          The best wheel I had was a "severit with everett" but they were expensive and smelled really bad when cutting, but there was no burr and I could shave 1/32 off the end of the tube with them and they didnt flex. They were good for fitting odd angles such as headers etc.

                          I used vice grip clamps with the pad on each side and welded a small angle on each one to center the tube and hold it in position, these worked well for me.

                          2sfn x 8" 3m Wheels worked well for removing tarnish
                          5ACRS x 6" matched the finish on the tubing better but if run overspeed they will come apart.
                          mike sr

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