why don,t you own a spot welder?

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
I got asked a question on a different site, that went something like this
" Grumpy I see you answer several threads on welding and noticed you have and ARC, MIG, TIG and oxy-acetylene torch welder, but no spot welder?
care to tell us why?
when many automotive panels are factory spot welded"


https://www.yardstore.com/

well first it may help to point out what SPOT WELDING IS AND HOW ITS DONE,
now I'm certainly not an expert welder, but I have managed to constantly improve my skills and acquire ever improved tools over 4 decades so through trial and error alone Ive learned some skills and through mentors help other skills, and I'm certainly not suggesting theres not a place in a good repair shop for a decent quality spot welder, its just that I don,t do enough body panel restoration to warrant owning one and that a good TIG welder can do almost anything I need done, in that type of repair.

spot welding is electrical resistance welding thats done by momentarily compressing two thin completely clean bare metal panels (USUALLY STEEL) and usually using a fixture or clamps to hold the panels together in a JIG or fixture to insure the proper alignment in relation to each other or with two panels having index pins so they will be precisely aligned, the area to be welded is small, generally about 5/16" in diameter, this area is clamped firmly from both sides and a high amp current is run through briefly turning the area between the contacts to a molten state that cools as a single solid mass fusing the two panels together , its fast, cheap and requires very little skill once its been correctly set up, as long as its a constantly duplicated procedure.
on issue I have is that the panels being spot welded tend to be slightly bent as they are clamped and welded leaving a series of small voids between the weld points in the seam that will tend to collect moisture if its not filled and sealed from both sides, the factory tends to dip cars in rust sealants after welding and before painting but later repair work can not take advantage of this proceedure.
yes being a tool junky I have to resist the urge to buy every tool I see, but in some cases a bit of logic prevails and I see little or no need for a rather limited and redundant tool, thats easily superseded and easily out classed with a good MIG OR TIG WELDER
this makes it great for production , where semi skilled labor can be taught to run the equipment about as fast as a staple gun, the panels can be stitched together, and with practice this produces a decent bond provided the spot welds are close together so the panels are solidly held and can't flex.
http://www.harborfreight.com/welding/spot-welders.html

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your problem with spot welding on a completed car is that you generally don,t have easy multi angle access from all sides on panels, you generally don,t have 100% clean new metal surfaces,
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spot welding generally leaves a stitch weld the gaps between welds are filled with a rust and moisture barrier paint.
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to repair these older panels the spot welds are drilled out
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and a new panels placed where the old damaged panel was previously, then the new panels drilled using the old existing spot weld drill holes in the matching remaining panel, CLECOS are used to hold it in place, the two panels are now MIG OR TIG PLUG WELDED
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as theres now an OPEN SMALL hole where there used to be two panels to compress and spot weld making the spot welder useless, and you can,t just spot weld a 1/2" to either side as you now generally have one or both panels painted,but even if clean and free of rust access is generally limited compared to the original production line


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use the replacement panel as a pattern , leave enough metal to use cleco pins
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READ THESE THREADS
http://garage.grumpysperformance.com/index.php?threads/welding-in-new-floor-pan.10735/#post-46871

http://garage.grumpysperformance.com/index.php?threads/want-to-buy-a-mig-for-sheet-metal.10601/

http://garage.grumpysperformance.co...-fire-extinguisher-handy.81/page-2#post-42551

http://garage.grumpysperformance.co...-t-do-stupid-stuff-get-decent-equipment.1669/

http://garage.grumpysperformance.com/index.php?threads/welding-sheet-metal-repairs.4232/

http://garage.grumpysperformance.com/index.php?threads/welding-auto-sheet-metal.4604/

http://www.eastwood.com/welders/spot-weld-cutters.html

http://garage.grumpysperformance.co...y-hand-held-1-2-chuck-drill.11823/#post-56021

http://garage.grumpysperformance.com/index.php?threads/most-versital-shop-welder.1594/


welding-lectures-1-3-15-638.jpg

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a mig or tig welder allows the full edge of both panels to be welded or plug welds to be used to replace older drilled out spot welds making the mig or tig welders far more versatile, but it does take more skill, to use them, and you generally need to weld only an inch or so in one area then move to a different more remote area to weld, then skip around, so no one area gets hot enough to heat warp as the areas are welded, by skipping around then back in a stitch skip stitch skip pattern you avoid panel warp-age.
it may help to remember the difference between MIG and TIG
MIG welding mandates the addition of wire every time you weld,
TIG welding isolates both processes allows heat and fill rod to be added, or with held in totally independent amounts, thus with TIG you can re-heat a weld to smooth and blend a welded area without adding metal

welding-joints.jpg
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http://www.northerntool.com/shop/tools/ ... _200383234
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Auto trivia guestion, "which automobile manufacturer (the top 4 in the US) from the mid-60s through to the mid 80s used spot welding in product production (either robotically or manually) the most?
 
Certain tools for certain jobs. I've probably got 40-50 hammers. Sure I could use a body hammer to drive a nail in wood or a roofers hammer to bang a dent in sheet metal but the right hammer produces a better job with less chance of damage or personal injury. same with welders. A resistance welder can produce a nice bond on sheet metal. There are many cases where a spot welder can produce a more "factory correct" looking and performing weld for restoration work and an almost perfect looking reproduction of factory welds on modern cars for collision work. Both while saving a lot of time. No need to try and drill holes for every weld in a new body panel just certain key ones that may be better plug welded. Can also save hours grinding off plug welds for tail panel and quarter panel replacements.

My current favorite. Not mine as I wouldn't use it often enough to justify a $7,000.00 machine but it sure is nice to use when I need one.

 
I'm posting this info because I was asked too, by a friend who rarely visits the web site but who recently asked me for help in removing a spot welded fender, he had spent well over an hour trying to drill out a few spot welds but his issue was he could not keep the spot weld drill centered on the spot weld, and as a result he was damaging sheet metal around the weld but not freeing the panel, thus when he pried the two sheet metal surfaces he bent the good panel he intended to retain, as part of the spot weld remained.
when I pointed out that your very unlikely to keep the spot weld drill centered on the existing welded area UNLESS you first center punch the weld so the drill stays centered he was amazed that he had failed to realize that fact.
I also pointed out that most spot weld drills are expendable and considered a consumable like sand paper that you use until they get dull then discard, he also admitted that made sense.
and yes you can buy cheap disposable bits and punches but like most things price and quality tend to go hand in hand to some extent and a punch or bit that costs 1/4 the price of some professional grade tool will seldome be of similar quality

http://shop.blairequipment.com/ProductDetails.asp?ProductCode=13224&gclid=CLuAvvbYgdUCFQSTfgod8OYFuQ


http://garage.grumpysperformance.com/index.php?threads/welding-sheet-metal-repairs.4232/


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http://www.homedepot.com/p/General-Tools-Heavy-Duty-Automatic-Center-Punch-78/301345941?cm_mmc=Shopping|THD|G|0|G-VF-PLA-D27E-Electrical|&gclid=CJWvtenVgdUCFRaewAodMTQC_w&gclsrc=aw.ds
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much cheaper but not the same quality
https://www.harborfreight.com/3-8-eighth-inch-double-sided-rotary-spot-weld-cutter-95343.html

https://www.harborfreight.com/spring-loaded-center-punch-621.html
 
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http://www.tooltopia.com/blair-1109...tid=BLR11096&gclid=CIPCjb3TgdUCFQkMaQodQ1AIPg

http://www.mechanicalcaveman.com/4-best-spot-weld-cutter-review/

https://garage.eastwood.com/eastwood-chatter/5-easy-ways-to-remove-spot-welds/

https://www.blairequipment.com/spotweld-cutters
learning to correctly TIG weld with a decent TIG welder will open your eyes,
too huge field of options, and a myriad of potential and until then un-dreamed of ideas
owning a decent MIG and TIG welder and a heavy duty drill press or better yet a MILL and lathe ,
leaves you open to the potential to build a huge assortment of custom, & unique and in most case's,
project's with a great deal more performance potential than your limited too buying components off the shelf.

 
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Strictly Attitude
posted this info

a new toy to help out progress on the other side and the trunk filler panel.
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My harbor freight $12.99 air hammer stopped working properly (lost it's strength at first thought it was the chisel being dull but sharpened and still was weak) when I was working on the inner and outer wheel wells no fun need to replace should have saved receipt and grabbed a new one. Live and learn I will either pick up some shears, a nibbler, or a high speed air saw. Maybe a new hammer seems reviews on some other air hammers are not good either. Snap-on or Mac are not worth the extra coin as no truck is showing up at my house weekly to pay for that convenience. But still will get my ratchets from
 
I only use a spot welder to install the bolt rails on an AK47 rifle. Most other type spot welders cannot reach places other than at production time of manufacture or they are just to damn expensive.
 
I saw this question posted and was about to answer it but this guy beat me too it and he did a damn good job

why do they spot weld car bodies, and not use a continuous seam weld?
does it really cost more? it sure seems like a full seam weld would not be all that much more expensive.

As a retired welding engineer, I can tell you that resistance welding ("spot welding") is far cheaper than, say, MIG (GMAW) welding:
Precision positioning is not critical with spot welding. No filler metal is required (cost consideration). No shielding gas is required (cost consideration). Because these two systems are not needed in spot welding, machine maintenance is much, much reduced and downtime is all but eliminated (cost consideration).
Spot welding, properly done and on a well-designed weld joint, is quite sufficient in strength....and it's FAST. Much faster than any other comparable joining process.

Lots of economic reasons why spot welding is the preferred method of joining sheet and light gauge metal products the world over.
 
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