I have never owned a spotweld cutter. To me they always seemed like a "gimmicky" took with limited real world value. I usually grind off the top layer, or just drill out the whole damn thing, but never using one, I wanted some opinions from folks who have.
what kind, I dont like the blair type thats like a mini hole saw. I always break them. But the regular drill bit type are nice. its like a flat drill bit the cuts the top panel away. I hope you didnt mean the whole tool that looks like a fancy drill. never used one but theyre expencive and dont look like they could go many places.
Agreed with Noland on the "mini hole saw" type -they break too easily. I recently had to separate the original frame structure from a mustang II front end - probably about 50 spot welds. I broke all 3 of the bits from a Snap On kit in about 5 welds. I went to a regular drill bit, did them all quick and didn't break a single bit.
Here's my take on the good and bad with the various methods of spot weld removal.... What you use will largely be determined by which panel you are saving, what access you have to either side, and how well you and the tool work in harmony. If you are facing the piece you wish to save, and the lower panel is essentially a throwaway, then simply use a drill bit the same size you would select for plug welds, and drill out the spot weld. When you place the new panel beneath and clamp it up, the hole you drilled in the top panel now serves as your plug weld hole. If you are saving the lower panel, and throwing away the top, you can use whatever works best for you. There are many ways to accomplish the same thing, but if you are not proficient in using one method, try another. I think each method has it's faults, so pick the one that best suits the area you are working. The holesaw type cutter typically cuts like any other holesaw does, and once the teeth start to cut a "channel", it is difficult to see how far along you are progressing. At the point the cutter reaches the second layer, which is where you would want to stop, if there were a bit of rust between the two panels and your cutter had enough speed, you would have a visual indicator in a wisp of "rust smoke" that is seen coming around the cutter. It is here that, even though some moderate speed is needed to produce this indicator, light pressure is also needed (better classified as "restraint") so that you don't go through too far and damage the second panel. In my case, I found myself going through too far, and would either need to repair the deep channel I just cut in the second layer, or would have to weld in a circle to repair the gaping hole I just left. Needless to say, I no longer use this method, and gave the cutter I did have to someone else that hopefully is having better luck with it than I did. Some of the cutters have a spring loaded center punch, much like a machinists roto-bore. Even with an intial center punch used in the middle of the spot weld, These cutters have the misfortune of slipping off center, and many people will simply drill a 1/8" diameter hole, either partially or all the way thru, to prevent the cutter from walking about. I'll stop here and offer a generalized thought. If you have difficulty filling an 1/8" hole in a piece of sheet metal with your welder, you will likely have problems with the pilot drill method, and perhaps should try one of the other methods. I think the Wivco cutters will work better than the hole saw type, in that they mimick an end mill, so the cutter is relatively flat on the bottom. This should give a less aggressive cut, a plus for people like me who may have a problem of leaning too hard on the cutter. The open flute design will also allow you to better see what is going on than the holesaw type, which obscures everything. It does use the pilot bit, so if that is not an issue (see above paragraph), then this is a good choice. The blair cutter is available in either the spring loaded version or the pilot bit version, I think these are likely a more aggresive cut than the wivco, especially since the cutting surface is extremely narrow, so it may be more likely to pose the cut through problems I described initially. The rounded burr grinder is also a good method which should somewhat limit the damage to the (throwaway) panel to just slightly larger than that of a spot weld cutter. The downside is that these also come with little tiny slivers of metal that are a pain when you get them in your skin, so it would be advantageous to address these with a vacuum cleaner/foxtail and dust pan on occasion to keep the issue at bay. A pair of work gloves come in handy as well. Keep some duct tape handy to pull out the slivers that sneak by. The last method I'll discuss is the one that I use because I don't play nice with the holesaw type. I use a 3" cutoff wheel with a 1/16" thick cutoff disc and use the tool to grind away the spot weld. I find for myself, it offers a less obstructed view of any of the methods listed, and with the proper speed (fast), will give you an indicator in the discoloration of the top layer (blue or darkened) usually before you have even broken into the second layer. Basically the metal is heating up and as it starts to get thin, it heats up more quickly and shows this via a color change. The color change back to bright silver will indicate you have reached the second layer, and act as a guide where to not grind anymore (the bright area) and where to grind, the blue/dark circle surround it. The disadvantages with this method, are the top panel is basically useless now; you will need good eye protection (moreso than the holesaw type cutters), and due to the grinding particulate, will need to use a respirator/mask to prevent you from hocking up black globs shortly afterward. I usually get a 3M or equivalent paint respirator, as the typical dust masks only serve to fog up your safety glasses, and as is evident upon the removal of the dust mask by the residue alongside the bridge of your nose, they don't work all that well. A paint style respirator exhales to the sides, away from your safety glasses, and typically conforms to your face much better. Grind pattern visible: Now as discussed at the beginning, had we wanted to save the flange and the rear panel was a throwaway, you could simply drill through the spot weld, and the resulting hole in the top panel would serve as a plug weld hole for re-attaching to the new rear panel. That should give a brief view of both the good and the bad with each method, I feel it's up to each individual to figure out which one works best for them and best for the situation at hand.
I use the coveted sacrificial sardine can technique where the key implements of destruction include, but are not limited to, a screwdriver, cutoff wheel, and needle nose pliers. Did I mention I can NEVER find all those little bastards?
i find that, for jobs where the outer panel must be saved and re-used, the holesaw style that i have are invaluable. some of the holes went all the way through both panels, but i'm no expert bodyman, just a shadetree redneck. i even used a couple of those holes to put a drift through to line the panels back up fo welding. my vote: use 'em, if you're comfortable with them. BTW: i bought two of them, expecting to bust one nearly immediately.... i still have two of them, after doing the cowl on my '62 Falcon.
I recently used one to remove the brackets that the trans crossmember bolts into on my Chevy II. I wasn't re-using the floor pan I cut them off of, but I was using the brackets. They worked well for me, the brackets came off nice and clean.
Timely thread as I'm getting ready to drill out a serious bunch of spot welds in the next few weeks. I bought some spot weld cutters but haven't tried them yet.
I have used the holesaw stlye cutters and have had success, use a little oil and don't turn them too fast. I found the rotary broach cutters like above and I like them much better, they last a lot longer and are less likely to break. They are much more expensive though
As MP&C said it depends on the panel you want to save and access.I have always found the ones that look like a flat drill bit with a little spike in the middle to work well and are the most dependable i have used these working on new and old cars working full time as a panel beater and never had a problem.The other types can cost alot more and don't seem to last as long.What ever way you go make shure to have a thin cold chisel (i like to sharpen mine at the tip and down one side)and a hammer this is used get between the panels after they have been drilled and cut any excess weld because sometimes you don't always get the full spotweld with any of the methods mentioned.
Always use the burr pit on a air tool, and in any case, throwin upper, throwin lower, thorwin both or throwin any, it works perfect. I HATE drills, as they always get stuck and twist your wrists bad. mine does it all the time. I also used a plasma cutter once, and worked rather good.
Just regrind a regular twist drill so that the business end is flatter, but leaving a tiny point to pick up your centrepunch mark. Holesaw type is a waste of money....
These. But it's a love-hate relationship. If you're working on removing thinner metal from thicker metal a cutting torch can be amazing. Once you get it going it just skims right along. This is, of course, if you don't want the thinner metal.
I use this type. Cheap, fast, & good. They tend to stop cutting when a small bur develops on the flute if the bit. It takes less than a minute to get it cutting again with nothing more than a few passes of a chainsaw file. Resharpened one cuts better than new one. It doesn't care how thick the metal is, won't screw up either piece, and have never broke one. sometimes I wish its diameter was a tad bigger. LOVE IT.
I was the parts and material manager of a large two dealership body shop with twelve bodymen. They each had their own idea for what to use to cut spot welds. They expected me to stock them all but we did finally settle on the Blair 11094 with center guide and a supply of short double ended 1/8" drill bits. Once everyone got used to using them they were the most cost effective of all that we tried.
I've had success with the solid style ones like in the picture above. The hole saw type ones I found the key is to turn the speed of your drill way down - don't have at it with your air drill at a million rpm's. Think of a holesaw on a drill press - low & slow. I'm with MP&C - whenever possibile, I grind thru the spotweld with a cutoff disk, then I use a sharp chisel on an air hammer to finish splitting the panels.
I haved used em all. The cutters with the 1/8" center bit adds extra steps with having to weld the hole up and finish it. Plus i always broke one of my spot-eze flutes or the centering bit. My favorite is the solid two flute type with a centering point made by Wurth. Use them all day in a production setting with many diameters. Keeping my drill speed in check i can make those last a long time and even hit the edges with a sharpening stone to extend life. But once the point is gone they are pretty much done. But i have ground off the point and then use that to clean the spot of the exsisting holes onto the panel being welded. Keeps you from haveing to clean all the metal of the area your welding and narrow it to just that plug weld. Plus keeps the ecoat/primer on and protected.
I purchased a Blair Rotobrouch Spot Weld cutter with a drill tip pilot and have great success breaking over 100 welds on my pickup project. The only trouble a had from time to time was the tip skateing if the weld was on a roll or curve in the sheet metal. When this happened I made drilled a small pilot hole first.
The Jalopy Journal
