This is the FAQ for rec.crafts.metalworking. It is in several pieces to keep the overall size of each part below the limits imposed by some news systems. This is part 3 of 11. Generally, units below are United States dollars, degrees Fahrenheit, and all the other silly backwards units we Americans still use. Sorry. ------------------------------------------------------------------------------- 12. How do I wire up this strange motor? (with thanks to Bill Brown) The following describes how to deal with an AC/DC "universal" motor that has 4 unmarked wires coming out. Be sure you don't have some other motor, such as a 3-phase unit. Other motors are covered in an FAQ for the newsgroup rec.woodworking. The FAQ postings (six of them) for rec.woodworking are normally posted around the first of each month, and possibly also posted to the newsgroup news.answers. I can't say how long *your* news system will choose to keep these around! Look for "Frequently Asked Questions about Electric Motors." Also, the "Electrical Wiring FAQ" may be of interest. The universal motor is called that because it can run on AC or DC. Older units might have been designed this way because very early power distribution had not settled on AC or DC, or with 50 or 60 cycles. Thus, such a motor could be used universally, in all locations provided the voltage was within reason. This still may be a concern with some on-site jobs feeding power tools from DC sources such as portable welding rigs. Another nice thing about these motors is that they are easily reversible. They are also easily speed-controlled, such as in hand drills, whereas induction motors prefer to run at or near synchronous speed. The first task is to determine which two wires go to the armature, and which go to the field winding. If you can't tell by examining where the wires go (or the nameplate), get an ohmmeter and connect it to the wires until you find two that show some continuity. Rotate the shaft slowly by hand and note if the resistance changes as you turn it. If it does, you probably have the armature, and the fluctuations are due to the brushes making and breaking contact with the commutator. The other winding (field coil) should show a steady resistance. Presuming you want the ability to reverse the motor, find a switch that can handle the rated current, in the double-pole-double-throw configuration with a center-off position. The suggested hook-up is (as usual, a bad ASCII graphic): +-------------------+ 1 | | 2 ----------FIELD-------o<--O o A 0 white \ / R \ / M V X A O / \ T L black / \ U T ----------------------o<--O o E S | | +-------------------+ NOTE: no connection at "X"; Include a green-wire frame ground if at all possible Avoid reversing the motor while it is moving in the "other" direction as this could severely stress the switch and motor (particularly the brushes). Move the switch to the center (off) position, and continue on to the other direction after the motor has stopped. Please, always be careful when dealing with electricity. If you don't feel comfortable and safe doing such a hook-up, find someone who can do it for you, or at least who can check what you're doing. 13. How do I deal with mail-order suppliers? The following suggestions were offered by Stu Friedberg -- Get the catalogs and know what you want. There are often many sizes, models, and sources of an "X", so you need to know which particular X when you write and especially when you call to place an order. Even the smallest industrial supply houses deal in tens of thousands of items, which means even very knowledgeable order-takers can't always give you the information you need over the phone. Reserve queries about details for stuff that you couldn't figure out for yourself. Many of the order takers are very helpful and knowledgeable. At *SOME* sources the order takers can actually go look in the stock bins, take a micrometer to measure a shaft diameter, etc. I have had people at three different companies do something like this for me. However, some companies have computerized centralized order taking at a location completely separate from their stocking locations, so don't *assume* people can tell you anything that's not written in the catalog. I've had one company tell me to just order a set of change gears and return them if I couldn't use them. This wasn't crazy, the order taker simply had no relevant information available. Get the catalogs and shop around. Very often there are *big* differences in price between identical items, and even more often one source will have a unique or slightly different item at an excellent price compared to the "standard" item. There are lots of reasons for this. I have seen 2 to 1 price ratios on things like shim stock (from the same manufacturer) and "can't twist" clamps (from different manufactures but of equal quality). Occasionally, you will find 10 to 1 price ratios on things like boxes of hose clamps. Great deals if you look around. If you can, examine a tool at a local store (where the prices may be higher) to see what the quality is like, before placing the order by mail or telephone. You can also learn a great deal by perusing the catalogs, both about tools in general, and about specific details of specific tools. There's seldom enough room in a catalog to print all the manufacturer's data, but different sources will select different stuff to print. I have many times used one company's catalog to select the precise thing I wanted, then bought it from another company because the price was better. Most suppliers ship quickly if they have a credit card authorization. If they don't ship within two working days on a routine basis, shop somewhere else in the future. One full working day is quite common. I have had only one bad incident in the 4 or 5 years I've been buying industrial stuff by telephone, and came through with no losses. A supply company (which entered bankruptcy proceedings just a little while ago, by the way) charged my credit card for the full amount of my order, didn't ship for a month, and was completely clueless as to when they would ship my order. That is intolerable, and protection against abuse like that is one good reason to use a credit card rather than sending a check. You don't need to sue to get your money back if the merchant doesn't come through. (If it's not obvious, I got my money back and started to throw out that company's catalogs as they arrived.) Some industrial suppliers don't do back orders because it slows things down. The stock pickers send what's in stock and mark out of stock items on the invoice. This may be a little different from retail mail order sources you've dealt with in the past. Contact them about what's in stock and when it's expected to be available. Be prepared to return an item. Having to return an item because it was misshipped, defective, or of unsatisfactory quality is *NOT* an indictment of the supplier. If you do enough shopping for industrial supplies, you will find that you have to do a partial return maybe 1 time in 5. Don't get mad; don't get upset. It's routine. Industrial supply and consumer retail have different expectations about quality control. When you return an item, follow instructions. Many, but not all, suppliers require you to contact them for a "return authorization" number, which you must write on the outside of the package. You should include a copy of the invoice in the package. This is *NOT* an opportunity for the supplier to screw you over. This is a routine matter, and most of them just ask you to note on the invoice what was wrong and if you want credit, a refund, an exchange for something else, or whatever. 14. How to sharpen knives, chisels, and other tools? This is actually a tricky subject, and beyond the scope of this FAQ. However, an excellent book on sharpening knives and similar tools is: The Razor Edge Book of Sharpening, by John Juranitch. 1985 by Warner Books, ISBN 0-446-38002-4, $12.50 This book can sometimes be found in the larger knife stores, such as frequently found in USA malls (e.g. Cutlery World). It is a bit biased in that John also sells sharpening equipment, but the techniques are fundamental and can be used with competitor's equipment such as Lansky's. Another source for the book is Knife World Books, (800) 828-7751 Ext 71. Sharpening drill bits has never seemed easy. If you have lots of money, Darex makes drill and mill sharpeners, and Glendo's Accu- Finish line addresses simpler cutting bits (and they even re-sell some Darex tools in conjunction with their grinders). Black and Decker reportedly make a decent drill sharpener (1/8" to 1/2") for around $250. Some of the magazines will print articles from time to time on sharpening, and/or building sharpening equipment. 15. The following text on safety was donated by Gary Preckshot: The forces involved in metalworking machinery are far higher than most people expect. You can either be struck by shrapnel or pulled into a machine by being caught by a moving part. There are several rules that reduce these hazards: a) Don't wear loose clothes, ties, unsecured braids, or jewelry. b) Turn off machines and *WAIT* for rundown before approaching the working area. You'll spend a lot more time in an ER than you'll ever save by jumping in right away. c) Don't snap chips using a shop towel. Use a brush or air. d) Don't mess with long chips curling off a turning. If you get build up, stop the machine and remove the chips wearing leather gloves and using pliers. e) Keep power transmission belts of any kind isolated and guarded. Flat leather belts are especially hazardous because they tend to be unguarded on crowned cone pulleys. If in doubt, add more clamps. If in doubt, chuck more deeply or use a collet. A turning that comes adrift can damage both the lathe and you. A workpiece that shifts can damage both the mill and you. Stuff gets hot when cut. Let it cool before picking it up. Metal cutting generally leaves a sharp burr. Break the edges with a file or a de-burring tool before you release the work for general handling. Don't let kids, wives, husbands, girlfriends, or boyfriends close to metalworking operations without training or close supervision. Chips are extremely sharp. Long, curled chips from lathe turnings are especially dangerous because kids, wives, husbands, girlfriends, or boyfriends see only how pretty they are. You can get a very deep cut by handling such chips with your hands. Have a system for removing and storing chips. Use it regularly. Use eye protection - ALWAYS. Beware of fascination. Metal cutting tools flash and glint as they spin. An unwary person may reach toward the pretty, shiny tool. This is no joke. It happens. Then you take a trip to the local ER. Don't watch welding without adequate dark glass filters. You can get a tan in 2 minutes and a burn in five on any exposed skin close to arc welding. It doesn't hurt for about 3 hours, but then it hurts for days. Cover up. Don't play with air. Not only can it inject chips (by blowing them) into your body, but it can inject oily air as well. Sometimes right through the skin. Air is no joke. In general, no horseplay in the shop. Banish anybody who can't understand this simple rule. This is one place where absolute dictatorship is better than democracy. Take your time. You'll save on rework time, machine repair, and medical costs. 16. How do I drill round holes? In May 1993 the following question was posted. This brought a lot of useful suggestions for a problem often seen ... Subject: I can't drill round holes I am trying to drill 1/4" holes in 3/32" mild steel with a H/S twist bit in a 12" Delta bench press. The holes are not round. They tend towards the triangular. The piece I am drilling has a 1 1/4" square cross section. The distortion is worst in the exit hole through the bottom of the member. What is going on? Is there anything I can do to correct the problem? Morgan Hall gave the following shot as to how a simple twist drill manages to create a non-circular hole: Hint -- look at the rotor and housing of a Mazda rotary engine You can model the working end of a drill bit as a single straight line of finite length. If you fix one end and try to rotate it, the opposite end of the line sweeps out an arc. (the drill flexes) After about 1/3 revolution, the stuck end breaks free and sweeps out another arc while the formerly free end sticks. With alternate ends sticking, then breaking free, the arcs will form a kind of polygon with arcs of radius equal to the drill's diameter. After the first cuts, the "corners" of the polygon tend to stop the sweeping cut for each drill flute. The most common I've seen is the triangular hole, but other polygons are definitely possible. I suspect that this occurrence is related to some sort of resonance in the drilling setup. The suggestions that followed may be useful to anyone trying to drill holes. Some of them may qualify as 'obvious' but they're still worth bearing in mind... * Ensure the drill is sharp. * Make sure the work is firmly clamped * Don't try and run the bit too fast for the drill size and work material. * Don't force the feed rate; as with *any* cutting process, let the cutter do the cutting. * Keep as much of the drill in the chuck as possible. The more flexibility there is in the drill, the more likely you are to have problems. * When drilling thin material, it is often useful to provide some form of backing clamped to the work. This has the added advantage of keeping the burrs to a minimum. * The drill tip may need to be ground to a different angle, depending on the material being worked. * An undersize pilot hole is often a good idea. If you are drilling using a mark made with a centre punch and the tip of the drill is larger than the mark, you are unlikely to get accurate placement. * Don't forget to use a cutting lubricant * The quality of the hole is only going to be as good as the machine you are using will allow. If the drill spindle is sloppy, there may be nothing you can do about it. As a final comment, if you really want a round, accurately sized hole, you are unlikely to get it with a twist drill. Drill undersize and use a reamer if it's important. Another alternative to very finely finished holes is to force a hard polished sphere through a slightly undersized hole. See the vendor list, under "Spheric". 17. What's TIG and MIG? TIG - Tungsten Inert Gas A small torch with a tungsten electrode is used to make the arc inside an envelope of an inert gas, usually argon or some argon mixture. A filler rod is manually introduced to complete the weld. The resulting weld is very pretty and usually requires no further finish. It is used mostly for welding sheets of mild steel, stainless steel or aluminum. The better machines have a foot control and a high frequency arc starter. Any sizable stick welder can be retro-fitted to do TIG welding, but without the foot control. MIG - Metal Inert Gas MIG and wire feed are the same thing. In this process, a consumable wire electrode is fed from a spool to the torch where the weld occurs inside an envelop of pure carbon dioxide, pure argon or a mixture of both. The weld continues as long as the operator has the trigger depressed and there is something to weld. This process is very fast, easy to learn and results in fairly good looking (better with argon) and strong welds. Most production welding of mild steel is now done with MIG welding. There is no slag to chip, but there is a slight thin coating of a glassy material that probably should be wire brushed off before painting. MIG welding can be used for thin or thick materials and is commonly used on mild steel, stainless and aluminum. Some common features of MIG machines are spot welding and stitch welding of sheet metal. There is a special wire called flux core that can be used in a MIG welder without the shielding gas. This process leaves a slag coating that must be chipped off. For most people on this group there isn't much use for flux core, as it was developed to reduce cost for large- scale welding where the cost of Argon starts piling up. There are fairly cheap 120 volt MIG welders that will only weld thin sheet metal. A more practical 240 volt machine that will weld up to about .25 inch is about $1500-$2000 new, $800-$1200 used. The machine I have will do MIG welding and stick welding, but most are MIG only. A machine that will weld .25 inch in a single pass will still weld thicker materials with multiple passes. 18. MIG welding technique. (The following was submitted by James Swonger on May 4, 1993) The quality of a MIG weld is controlled by gas flow, the qualities of that gas, the "heat" and feed rate settings. While getting a quality weld is less dependent on "touch" than gas or arc welding, it does depend on the right combination of the settable machine parameters. There are three modes of material transfer in a wire feed machine. One is "blob mode", where the wire sticks, then melts locally, then breaks. This occurs at the lower end of the heat/wire feed range. I say heat/feed rate as a ratio, because this pretty much determines which deposition mode you will see. Blob mode welds are the lowest penetration and lowest transferre heat, because there's almost no real arc action, just mostly resistive heating of the wire and contact point. The second mode as you move up the range is a soft arc with the metal being pushed through it. You'll recognize this mode when it happens; there's no more "wire push", the sound changes from a random snapping to a more uniform sizzle and everything just gets smooth. This is what I consider the ideal mode. The arc is stable but most of its energy is transferred into melting the fed wire and a localized area of the workpiece. In this mode I see about 1/4" of heat affected zone around the weld (automotive sheet metal thickness), and by proper setting I can get perfect penetration which I define to be some backside protrusion but no sag or burn-through. The handpiece ("gun") in this mode may have a buzzing feel to it but none of the bucking you get in blob mode. The third mode is when heat is much higher than the wire feed rate needs. This mode is akin to traditional arc welding, except with a fed wire. The arc energy now is biased more into the workpiece, with attendant heating and penetration. The wire still adds filler but there is more tendency to undercut, eat back and blow through especially on thin pieces. In this high heat/feed mode the buzzing/sizzling sound is replaced by a more purely electrical arc sound (whispering/crackling). This mode is desirable when welding pieces much thicker than the wire, especially when you haven't taken the bother of grinding proper chamfers and need to get penetration. Gas flow provides an important cooling effect. This is one reason why flux cored wire is harder to use on sheet metal; there's no place for the weld heat to go except the workpiece. Argon, A75 and CO2 have different welding characteristics. Argon will make the weld "sit up" higher, CO2 gives the most penetration and A75 is in the middle somewhere. Only Argon is suitable for aluminum; A75 is sort of marginal for stainless (leaves some carbon) but pretty ideal for general mild steel use. An adjustable regulator provides more latitude in balancing arc heat/feed and cooling. A high flow of gas can reduce warpage while allowing faster material transfer. I have a cheap preset flow regulator which is a compromise setting, compromise price type deal. To minimize panel warpage you must apply some technique as well. The MIG machine does not eliminate the need for skill; it just lets you apply your attention to more important things and lets you slide on some of the basics. Warping results from too much differential heating and expansion in the workpiece. By understanding the material and equipment you can keep this from being a problem. Duty cycle is one simple way of further reducing overall heat input. By welding in short, spaced beads you can join panels without overheating any large areas. First the piece should be "tacked" every few inches, with bead lengths of 1/2" or so. Make several passes after that, filling in the gaps bit by bit and not working any one region for long. The workpiece's thermal spreading will cool the small HAZ (*) pretty quickly if the total heat deposited remains small. A spot cools much more rapidly than a line. The edge of a thin metal piece presents a special case, a "boundary condition" which behaves differently than the bulk. With half the heat dissipation ability of the bulk, the edge will tend to burn back, distort and so on. This can be addressed by reducing heat (although this may force you into running blob mode), by different choice of metal overlap configuration and by carefully running the arc. A true butt joint in thin material is difficult to make. A -perfect- butting is hard to do on formed sheet metal, and any gaps will tend to enlarge in the welding process. For this reason a lapped weld is often preferred. A panel can be flanged to let the two pieces overlap but keep the final surface flush. The flange provides a backup as well in case of erosion of the edge on the top piece. =========\\W++++++++++++ \\==== A second sort of joint is a butted-V which protects the edges as the weld hits the sidewalls without necessarily reaching the bottom of the groove. --------\WW+++++++++ \+ Places like Eastwood sell specialty tools for making both types of flanges on sheet metal. Of course, you need to be careful not to cause deformation from the flanging process itself. I have made my own flanging tool for the first form out of an extra pair of Channel-Loks with extra jaw material brazed in and ground to shape. The Eastwood tool is Vise-Grip based and looks like it's a bit better as far as force required to make the flange due to the compound action. I think a pair of beat up sheet metal shears might be a better basis for making a new one. (*) HAZ = Heat Affected Zone; the area where you see thermally-induced material changes in the workpiece. This is basically the extent of any visible surface discoloration when using the MIG, although if you run the gas after stopping the arc you may not even be able to see anything because oxygen is excluded. If you remove the gas and arc together you will get the normal thin oxidation layer like you see when grinding or heating to temper. The outside of the blue oxide region is the periphery of the HAZ, although the material effects there are probably negligible. -------------------------------------------------------------------------- The following was submitted by mrehmus@ix.netcom.com Use of MIG for body work. A bad idea fostered on us amateurs by our ignorance. If you look at the available wire for MIG, you don't find anything much softer than S60 or higher wire. In general, the higher the yield strength of metal, the harder it is to work. (Try forming tool-steel as a test). The weld bead left by a MIG is very hard relative to the body sheet metal and is almost impossible to work. It also cracks very easily even if one trys to anneal the metal in the weld. In restoring a 1967 Mercury Cougar I finally had to teach myself hammer welding using a welding torch. The results were much better!! 1. The seam is the same thickness as the parent sheet metal. 2. The seam is as soft or softer than the parent sheet metal. 3. The seam and the surrounding sheet metal are easily worked to remove any defects caused by the welding process. Should anyone want to equal the hammer welding process but with an electric source of heat, TIG is the only way to go. The filler metal selection is much, much wider and the TIG can be run way down to 10 amps or so which would probably let you weld aluminum foil if you wished. Oh yea, in the professional welder's world, the common opinion is that a TIG weld is superior to MIG. So why do the professional body shops like the MIG? It is necessary for the welding of high-strength steel that is commonly used in the structural parts of the modern automobile. Not, I repeat, NOT for the external sheet metal. The external sheet metal (the part we can see) is still mild steel because of the expense and difficulty of making sheet metal forming dies that would last and give good results with high-strength steel. Remember that body shops replace whole panels, they rarely "patch" a panel. The high-quality restoration shops use TIG or (usually) a torch and hammer welding. GOOD video tapes to know about: "Learning MIG Welding" by SIP (one source is J.C. Whitney, their # 12VL7580P, $26.99; their phone number is (312) 431-6102) "Hammerwelding Techniques" by Car Guy Videotapes "Patch Panel Installation" by Car Guy Videotapes I have watched these tapes many times, always learning more at every session. The tape on MIG welding uses a good visual filter technique to show every type of weld puddle. After viewing the tape, my MIG welding has been much better.