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Thread: Tack welding / spot welding...

  1. #1
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    Tack welding / spot welding...

    Hi all,
    I've signed up here to hopefully get an opinion or three. First off, while I have welded in my life, I haven't gone near welding in decades so I'm really out of touch with all the current tricks and treats that seem to be currently available. And...I was never really very good at it to be honest.

    That said, I'm designing some expansion chambers for a friend's Rotax 503 powered hovercraft. It's really all just pure amusement and while I can roll up all the cones and tubes to suit the design, I'm not going to wreck things by trying to relearn the little bit of welding savvy I once had.

    Problem is, I'd really like to tack everything. There's going to be a lot of fitting in place and I'd like it to be really top-notch when it comes to fit and finish. So I'm looking for an easy, simple, idiot-proof method to be able to tack or spot weld things together, and make sure it's strong enough to be able to be transported to a proficient welder to do all the seams. This may not be 'a trip down the street' - more like across the country, so perhaps you understand my concern that the tacks / spots are sturdy enough.

    What might anyone suggest would be an inexpensive method to achieve what I would like? All the seams are to be butt welds. All the metal: CRS ASTM-A366 20 gauge (0.036") with the exception of the actual flanges to connect to the cylinder heads - those however could almost remained tacked as the sheet is to be set through the flanges and flared over.

    Sure would appreciate some assistance with this. Thanks very much everyone.

    Gord

  2. #2
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    Re: Tack welding / spot welding...

    Gord - welcome to the forums.

    Can you tack on bands? You mention that your parts are going to be butt welded. I assume they are going to be TIG welded eventually.

    If you tack the butt weld joints you might disturb the joints more than what would be best for the finish welding process.

    If you can tack weld bands across the joints your welds won't be disturbing the material in the final joint.

    If the parts are subject to much vibration and stress while being transported to where the finish welding will be done I would be very careful with the parts. Are you transporting? Or are you packing up and shipping via a conventional carrier like UPS, DHL, etc? If shipping - multiply the concern of disturbing the parts by 10.

    If you are wanting to get a welding process for your own use I highly recommend starting with stick welding. It is very versatile. The entry fee is quite affordable and you don't have to worry about shielding gas (a complexity you don't need right off the bat). I would go a bit further on stick welding and say that I think all welders need an oldschool transformer tombstone welder - preferably one that does AC and DC. They are quite robust and if you have other machines that end up going down for what ever reason you will always have the tombstone to stick metal together with. Been there, wish I had one at the time - now I do.

    If you are going to weld many alloys (aluminum, various stainless steels, what have you), and thinner metals, then TIG welding is where you will want to end up. I wouldn't recommend it off the bat unless you are dead set on it and willing to accept the learning curve. Though, TIG machines will stick weld also. So you would have both processes. Just know if any alloys containing magnesium, aluminum, etc are in your future you can not weld them with DC TIG - you need AC. Adding AC to a TIG machine usually significantly increases the price. For aluminums you need a lot of current, also. Much more than steel. So you have a double-header there - AC adding to the cost and the higher current/duty cycle required adding to the cost.

    So if you want to start on the lower priced end of the spectrum - stick is really hard to beat. Find you an old tombstone (miller dialarc, lincoln idealarc, for example). The older ones were made with heavier transformers - thick copper. Newer ones (maybe 80's newer) aren't made as robust as the old stuff. There are things you can do with stick that you can only do with stick, also. Hardfacing and cast iron welding come to mind. There are also cutting electrodes (use in place of an oxy/acetylene torch or plasma cutter - expensive way to cut, but will work if you don't have the other options and something has to get cut apart). Yeah, the welds aren't as clean and you have to deal with slag. When you consider the versatility and the entry fee to get going with it - you can't beat it, though.

  3. #3
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    Re: Tack welding / spot welding...

    Are you using tubing, I'm assuming from your description. Mig with .025 wire would be my recommendation based on experience. Tig would be ideal but more experience and an almost perfect fitup is required on that gauge metal. Make your tacks small and hot and if possible in an area that's fairly easy to access for thinning out with a grinder.

  4. #4
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    Re: Tack welding / spot welding...

    Morning FlyFishn, M.J.D., thanks and thanks for the welcome as well!

    The banding idea is clever though I'm not sure if you mean just little perpendicular bridges across the seams or somehow around the circumference? You see, while it will be all 'rolled from sheet' tubing, very, very little of it would be straight, and then with the cones, the diameters increasing, straightening out for a bit, then decreasing, ending up with what's known as 'the stinger' (a 1" OD tube) at the outlet. That's the only piece that would actually be seamless 'store bought' tube.

    The tacking issue is exactly as you've guessed: probably shipping by a commercial transport company which is indeed my fear. Even with all sorts of pictures and indexing marks, the fitting really has to be as designed with virtually no room for error. TIG for the final welding indeed, and I'm not at all a TIG savvy welder.

    I did catch a YouTube vid of a fellow doing clever tacks with a TIG unit and that was impressive, looked relatively easy (ha) however he was using substantially thicker material for his demonstration and he had all the equipment ($).

    My prior experience was with classic Miller and Lincoln stick welders and some oxy-acetylene. I still have access to the oxy but I don't think that's an ideal choice at all. From what I saw in that vid, the fellow cranked up the current and gave the seams a very short 'blast' and it did seem very successful.

    I would consider buying "something" be it old or new - I could go to 220 volt max but it would be an extra hassle where I am, and if I could find something that might do it off of 110 volt...bonus. I really don't do welding now is the big issue, and any amount I spend on equipment is in theory kind of lost. It truly is a one-off sort of thing - I just need to absolutely assure that what gets designed comes back as designed. Oh, all the seams will be as close to perfect as humanly possible. This is where I'll be spending the time and effort, as it's the volume, cone diameters and angles and such that must be razor accurate to get the most out of the expansion chamber.

    Also on YouTube, I saw a 'one sided spot welder'. I don't know the price but I thought something like that couldn't be too costly (might be wrong) and was thinking if that would give the short / sharp 'zap' adequate to hold the joints in place. There's virtually no way I could get in to the tubing and cones with a two-sided spot welder and I don't even know if the whole theory is valid as spot welding sure seems to be used 99.9% of the time on overlaps. <sigh>

    Thanks again for the suggestions and recommendations thus far. They certainly do have me thinking.

    Gord

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    Re: Tack welding / spot welding...

    Get the seams of the cones touching with little to no gaps. Then tack with a 110 volt house current mig welder. Use C25 for the gas and .023/025" er70s-6 wire. Try to just put the smallest spot on the seam with the lowest current. When tacked take to a tig shop for additional tacks and blend off the mig tacks. Then weld up complete.

    If your seams are touching and you have an oxy-acet welder you could do what I learned in the 70's as a teenager trying to get a job at a fab shop in Canoga Park, Torque Engineering. They made expansion chambers for dirt bikes. Basically you get a neutral flame, lay the tip on it's side against the seam, and then rock the side of the neutral flame cone gently onto the seam enough to join it with side of cone. Makes a nice little tack. Repeat as required. The welds were just a rocking motion back and for with the side of the neutral flame cone and looked like a really clean tig weld. If you can tack this way the tig shop could weld it out.
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    Weld like a "WELDOR", not a wel-"DERR"
    MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.

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    Re: Tack welding / spot welding...

    Thanks kindly, Shovelon! That's an interesting method and as I do have the oxy-acetylene here (and some scraps to play with), I could do some trials and see if I could manage it.

    Really appreciated - thanks again!

    Gord

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  8. #7
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    Re: Tack welding / spot welding...

    As to the band question - I meant short strips tack welded across the joint only, not wrapped around the whole part. The idea would be that the tack welds for the bands would be back away from the joint = they won't interfere with the welding of the joint like @M J D mentioned with blending the tig welds over the feathered (ground back) tack welds in the joint. A good welder can get through the tacks - that is common practice. However, if you aren't well prepared for the fab you're doing it would be less risky tacking on the meat of the part and not the very edge of the part = hence the bands. Provided you don't blow a hole in the part with too much heat on the tack, you can cut them back and grind the finish smooth when you remove the bands.

    As to welders and wanting to run 120v as opposed to 240v - you can certainly do that. I ran a flux core machine since the mid-late 90's on 120v. It is a light duty transformer machine. You can do it, however you need to have good power. The best way to ensure you have good power is to use heavy gauge wire/extension cord (if you have to use one at all) and to ONLY have the welder running. If your garage circuit, for example, is running lights, fans, etc and you try to weld off the same circuit you're probably going to have some challenges. I beat my head against a wall on a large fab project a couple years ago for that very reason. I ended up running 12 gauge wire to another circuit where the welder could be the only device sucking power from it. It improved my welding 100%. And I smoked the welder (went over the duty cycle, but that's another story).

    The inverter machines these days normally are dual voltage - for the conventional size ones (under 200-250a or so). You will have a current limit for running from 120v so even if you have a 40a circuit available for 120v the welder won't go past its limit for 120v.

    If you want to run on 120v then your best bet is going to be an inverter machine. If you are going that route then I would recommend looking at a nice TIG machine. The main reason is you can run stick with them also. You'll have everything in one box that will run on 120v also.

    Some options that come to mind are:
    PrimeWeld Tig225x
    AHP - any of the AlphaTig's
    Everlast PowerTig 185DV, 200DV, 210EXT, 255EXT
    HTP Invertig 221 (they have a 240 only and a dual voltage 120/240, be careful)

    *List includes machines that do AC and DC, not just DC. For alloys you need AC (to TIG weld, stick you can get electrodes that run on DC) so a DC machine would probably be too limiting if youre not wanting to invest in them and have multiple machines.

    If you are only doing light hobby welding (maybe some structural like angle, plate, tubing up to 1/8" or possibly 3/16" steel but concentrating on lighter/thinner alloys) you can save some money and get by with a lighter duty machine - maybe 200 amps @ 35% duty cycle on the top end, with a higher duty cycle at lower welding amps (where you may normally find yourself welding). If that isn't the case and you want to weld some thicker stuff then you're going to need the amps = beefier machine.

    The HTP in the list above has a pretty heavy following. It is a favorite on the forums and one of the ones I am considering, but for the specs (220 amps tops @ 20%) it is on the light side of where I'd want to be. Next up for them is their 313 model - at twice, or more, the price - not cheap.

    The PrimeWeld unit is under $1000 and has a pretty heavy following around the forum here and elsewhere. Look them up online. If you don't need the amps or duty cycle and are content with the analog dials it is a pretty good buy.

    There are the big names also - Lincoln, Miller, and Esab. You can throw Fronius up there also - they aren't as well-known, I don't think, but they are sure priced in the same arena. There are other European brands out there also, but pricey.

  9. #8
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    Re: Tack welding / spot welding...

    If you’re comfortable with mig, tack up using mig. I would do some practice tacks on same materials and joints you’ll be fabricating. Then do a test on completed tacks. Push, pull, twist , hammer , whatever it takes for you to be confident for shipping.
    I would contact the welding shop and tell them what you’re doing and see if they have a procedure. With mig weld tacks, you can melt the tacks tig welding without adding any filler metal . Finish weld should be as if all tig welded.


    Sent from my iPhone using Tapatalk

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    Re: Tack welding / spot welding...

    I wouldn't use any flux core on tacks for something to be tig welder. Those previously mentioned tacks are called " bridge tacks" and would be a complete PITA on what your doing.

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  12. #10
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    Re: Tack welding / spot welding...

    Quote Originally Posted by FlyFishn View Post
    The HTP in the list above has a pretty heavy following. It is a favorite on the forums and one of the ones I am considering, but for the specs (220 amps tops @ 20%) it is on the light side of where I'd want to be. Next up for them is their 313 model - at twice, or more, the price - not cheap.
    .
    I have to admit you got my curiosity to get the best of me. No direct evidence, but I just drove my 221 to activate the thermal protection at full power. Twice. Display shows 218A (not sure why, maybe just production tolerances). First time took 4.5 minutes. Took about 5 or 6 minutes to "cool down". Immediately went full throttle again. 2nd time took 3.5 min. About to go back and do it about 3 or 4 more times to see just where it does level-out.
    1st on WeldingWeb to have a scrolling sig!

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    Re: Tack welding / spot welding...

    1st on WeldingWeb to have a scrolling sig!

    HTP Invertig 400
    HTP Invertig 221
    HTP ProPulse 300
    HTP ProPulse 200 x2
    HTP ProPulse 220MTS
    HTP Inverarc 200TLP
    HTP Microcut 875SC

  15. #12
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    Re: Tack welding / spot welding...

    i did body work for 35 years in dealers. a variable 110v welder would be perfect sounds like. insurance (I-CAR) testing used variable 110v for their testing. my sp125 lincoln was one like used in the testing. welds to 3/16 thick with good penetration. pretty much maxed out. c25/75 gas. co2 little better penetration. the 110 lincolns worked better for the body panels than the 200 and 250 amp machines. also as shovelon said on the wire and gas.
    lincoln 125sp
    monkey wards 250 ac/dc
    miller 211 w/spool gun
    ahp 200 sx tig
    lotos ltp5000d
    of course duramax diesel

  16. #13
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    Re: Tack welding / spot welding...

    I didn't read every ones comments but for tacking rolled cones and butt seams on thin material you have only two choices in my mind. Oxy/acetylene or Tig. You must have control of the deposition of material and the heat to make strong small tacks that can be welded over again.

    I was tig welding expansion chambers by the hundreds for a few years I was building them. Machining up all the parts. The bodies were stamping and you tigged the seams and sections together. Just too time consuming and doesn't pay what engine work and most other work I do pays.

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  18. #14
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    Re: Tack welding / spot welding...

    Quote Originally Posted by shovelon View Post
    Get the seams of the cones touching with little to no gaps. Then tack with a 110 volt house current mig welder. Use C25 for the gas and .023/025" er70s-6 wire. Try to just put the smallest spot on the seam with the lowest current. When tacked take to a tig shop for additional tacks and blend off the mig tacks. Then weld up complete.

    If your seams are touching and you have an oxy-acet welder you could do what I learned in the 70's as a teenager trying to get a job at a fab shop in Canoga Park, Torque Engineering. They made expansion chambers for dirt bikes. Basically you get a neutral flame, lay the tip on it's side against the seam, and then rock the side of the neutral flame cone gently onto the seam enough to join it with side of cone. Makes a nice little tack. Repeat as required. The welds were just a rocking motion back and for with the side of the neutral flame cone and looked like a really clean tig weld. If you can tack this way the tig shop could weld it out.
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    sounds like u been doing this a while. i was riding dirt bikes about 60 mi s.e. of there in the late 70s early 80's as a kid. i think (to my best memeory) i had a pipe called "T&M, but i never knew what initials stood for. it was on a 4 stroke though. maybe it was TE, or T&E, but the M seems to sticking in my head right now. anyway, u got me thinkin on this Torque Engineering

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    Re: Tack welding / spot welding...

    Quote Originally Posted by 123weld View Post
    sounds like u been doing this a while. i was riding dirt bikes about 60 mi s.e. of there in the late 70s early 80's as a kid. i think (to my best memeory) i had a pipe called "T&M, but i never knew what initials stood for. it was on a 4 stroke though. maybe it was TE, or T&E, but the M seems to sticking in my head right now. anyway, u got me thinkin on this Torque Engineering
    I only remember Torque pipes doing expansion chambers. The early thumper mods were done by some Japanese tuners is all I can remember. But then there were a bunch of tuners in SoCal.
    Weld like a "WELDOR", not a wel-"DERR"
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