From: jimkirk@news.uwyo.edu (Jim Kirkpatrick) Newsgroups: rec.crafts.metalworking Subject: FAQ part 3 of 7 Date: 1 Sep 94 10:13:32 MDT Organization: University of Wyoming - Laramie, WY 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 7. Generally, units below are United States dollars, degrees Fahrenheit, and all the other silly backwards units we Americans still use. Sorry. The questions being answered in part 1: 0. Where is this FAQ kept, and where are archives of the newsgroup? 1. The original rec.crafts.metalworking charter. 2. The CLOCKS bitnet mailing list, and other related lists. 3. What are some good books and/or video tapes on metalworking? 4. Who makes good lathes/mills/etc? 5. Where do I buy a machine? 6. What are good magazines to subscribe to? The questions being answered in part 2: 7. Where might one take classes or get instruction? 8. Where can I get raw material for my projects? 9. Where can I get tools, drill bits, etc.? 10. What are some of the related professional/hobby associations? 11. How do I harden/temper metal? 12 How do I wire up this strange motor? 13. How do I deal with mail-order suppliers? 14. How to sharpen knives, chisels, and other tools? 15. Some safety reminders. 16. How do I drill round holes? 17. What's TIG and MIG? The questions being answered in part 3: 18. MIG welding technique. 19. Which MIG welder should I buy? 20. Books on welding. 21. Soldering/brazing topics. 22. What are bolt grades? 23. What is XYZ made of? The questions being answered in part 4: 24. How do I build a furnace or forge? 25. What is Damascus steel? 26. How do I repair/replace this old leather belt? 27. Can I use a drill press as a cheap vertical mill? The questions being answered in part 5: 28. What is involved in building a steam engine? 29. How do I anodize aluminum? 30. Rust! How do I deal with rust? The questions being answered in part 6: 31. Are there any machinery museums? 32. How do I cut metal? 33. What kind of oil should I use on my lathe/mill? The question being answered in part 7: 99. Names and addresses of publishers and suppliers (OK, so I got tired of re-numbering it every time a new question was added!) ------------------------------------------------------------------------------- 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@cup.portal.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 "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. 19. We frequently see "What should I buy" questions; one example is "What MIG welder should I buy?" There is no definite answer, and the prospective buyer should read the other entries in this FAQ regarding welding. What follows is an example of such a question and the answers received (June, 1993). We claim no responsibility for correctness or liability for your money! Keith King asked: I'm looking at the purchase of a MIG welder for auto body repair and other light welding jobs around the homestead and I don't have much background on this type of equipment. The models I'm looking at are the Lincoln SP-100 and the Miller 130. Both models are 110v portables. The Miller has a higher rating but I'm not sure if that's critical for my applications. The Lincoln has the advantage of having infinitely variable power output vs. stepped output for the Miller and the salesman said the gun on the Lincoln was a "Tweako?" whatever that means. Both units are similarly priced/warranted etc. Century has a bunch of lower priced, shorter warranty, cheaper looking, MIG welders. Does anyone have any experience/opinions on these welders or other MIGs to help me make a more informed purchase. Jim Narem answered/asked: I'm also interested in MIG welders for sheet metal and roll bar work. I've used the Italian made SIP 110V MIG unit. It works; it was worth $100 (purchased at some close-out sale) but not the $350 that places want retail. It's tough to get parts; even the tips have to be ordered. The wire feed mechanism sucks. I've seen some new Lincoln's on the market; both are wire feed welders with optional MIG kits as opposed to the SP-100 and SP-130 which are purpose build MIG units. Lincoln Weld-Pak 100, 88 amp, 18V @ 20% duty, 110V, $354 w/MIG kit. Lincoln Weld-Pak 125, 130 amp, 20v @ 30% duty, 220V, $556 w/MIG kit. (Prices are Connecticut Home Depot, tax bandit not included) The MIG kits are about $80 each, they have a gas flow regulator, solenoid and (I think) a different gun. Does anyone have any experience with these welders? They seem cost effective compared to the SP-100 and SP-130 but I'm nervous since Lincoln seems to be releasing some home/consumer grade equipment (like their new AC arc welder with the cheezy variable amperage control). There are also several Century MIG units commonly available at large home improvement shops (yup, WELD on that new addition). I've used their AC/DC arc welder and was impressed with its cost/performance. Has anyone used any of the Century MIGs? Ken Clarke answered: I took an evening welding class at a technical high school (10 weeks) and got to try various types of welding (stick, MIG, TIG, and oxy/acetylene. Also got some good tips on safety, and on how to by a MIG welder. The instructor spoke of the "big three" in the welding business (Miller, Lincoln, and Hobart). He was a confirmed "Miller" man, but we used Lincoln (and Airco) welders in the tech. school. I now think that it makes sense to buy whatever you decide to buy at your favorite welding supply store. The guys there have lots of good advice and if you go with one of the big three, you will not have any problem getting parts and consumables for your welder. I looked around for a while and compared the 110v portable welders by Lincoln and Miller and Hobart. My favorite welding supply house was having a "package deal" that included the Hobart Handler 120. Included in the package was the welder, a 2 lb. spool of .024 wire, a Jackson welders mask with the 4x5 face plate (get a number 10 shade), a *good* pair of welders gloves, a 55 cu. ft. tank of shielding gas (C25 which is 25 percent CO2 and 75 percent Argon), a dual-gauge regulator and connecting hose. This was about 1.5 years ago and I believe I paid $625 for the package. The Hobart has been great. It works fine on auto body panels and I have also done work on exhaust systems, mailbox posts, minibike mufflers, lawnmower parts, and am finishing up a trailer axle for a friend this weekend. So, I guess I'm advocating the Hobart, but if you can get a good deal on the Miller or the Lincoln, those would probably be fine, too. A few of the features on the Hobart that I liked were: 1. A "purge" feature, that allows you to set the flow rate on the shielding gas without spooling out wire. 2. The wire feed mechanism that lets you set the tension on the drive wheel but also lets you change wire spools without moving the setting. 3. The ergonomics of the unit, the way the wire spool goes in, the way the lid hinges down (not up like the others). 4. Five year warranty on power diodes and SCRs, three years on major components and one year on parts and labor. I would stay away from the Century welder. I don't think it has the quality of the "big three". I think you would have trouble getting parts, probably would have to order them. All parts for the big three can be had at local welding supply houses, in-stock. Also, the "Tweeko" comment is referring to the gun end of the welder. I hear that it's supposed to be a very common industry-standard type of part. Parts for the Tweeko handle/gun should be available at any welding supply house. Jim Swonger answered: "Tweako" is actually Tweco, a manufacturer of MIG and TIG handpieces and such. What this means is that parts are pretty readily available; they're everywhere. For sheet metal welding you'll run nowhere near the maximum heat setting on any machine. On my 160 I'm down on "2" for heat. The higher current machines of some of the cheaper brands need to be looked at carefully; some of them have -very- low duty cycles, leading me to believe that the critical parts are not much, if any, better than the cheaper models. The "purge" feature is good to have; however if you do not find a machine with it you can add it pretty simply. An auxiliary control switch for the solenoid valve is all it takes, in parallel with the relay that runs off the gun trigger. For serious sheet metal work spot and stitch modes are very nice amenities, allowing you to tack up a large piece with spaced short beads, minimizing distortion and allowing a fast, even hand motion. You can get by without it, but if it comes free or cheap... Quite a while later (26-Sep-1993), mrehmus@cup.portal.com wrote -- I've owned a Century 90 amp MIG welder for 4 or 5 years now. Never a problem with the unit and I've put three large reels of 0.024" wire through it. The one time I thought I had a problem the people at Century were very helpful. Century may not be one of the "big three" but they have been around for a very long time (mainly they make many of the professional battery chargers sold in this country, so I'm told). ------------ Other comments that have come up from various sources, especially Ken Clarke: Arc welders are often rated for a particular duty cycle, such as 30%. This means you can weld for about 3 minutes at full power, then you have to let the welder cool off for 7 minutes. The cheap units are typically low duty cycle, where the professional units have a high duty cycle. Also, units are often rated at a certain lower amperage where they can safely be operated at a higher percentage; for example, a 200 amp unit might be rated at 50 amps @ 100%, 100 amps at @ 60%, and 200 amps at 30%. Look for some sort of automatic cutoff to protect your investment in case you get carried away. DC systems are nicer than AC systems, especially if you can reverse polarity. AC systems splatter a bit more. DC doesn't as much, and makes a nicer weld as a result. Reversing polarity apparently can direct heat away from, or to, the workpiece; directing it away from a sheet metal weld can reduce warpage. Inverter models run off DC, or rectified line current. Their portability is the main selling point, for field welding where 220V isn't available. For the home or small shop, they are probably overkill. Large spools of wire, or other welding supplies, may corrode before they get used up in a hobby environment. Dry storage is important to preserve them. 20. Books on welding. Courtesy of kenm@daffy.cac.washington.edu Here's a source of good and inexpensive welding books. A catalog is available from: Lincoln Arc Welding Foundation PO Box 17035 Cleveland, OH 44117 They list a couple of dozen titles. Here are nutshell reviews of the ones I've seen: Metals and How to Weld Them, 400 pg, $5.00 A great book on the metallurgy of welding. It's not a how-to-weld book, but instead answered the Why? type questions I've had for years. Principles of Industrial Welding, 384 pg, $6.50 Your run-of-the-mill textbook. Design of Weldments, 464 pg, $7.00 A text on the design of welded machinery etc. There is a different book on welded structures. Well worth it it you are designing your own projects. New Lessons in Arc Welding, 528 pg, $5.00 Hard to describe - kind of a lab manual for a welding tips. Certainly worth the $5. Arc Welded Projects Vol 2, 272 pg, $5.00 Arc Welded Projects Vol 3, 170 pg, $4.50 Full of short (couple of page) descriptions of all kinds of rather ambitious projects - a tractor snowblower, log splitter, chariot, sailboat, woodstove, .... These are good books at any price, and great books at these prices. 21. Soldering/brazing topics. There sometimes seems a fine line between soldering (several types, at that), brazing, and welding. Here we try to shed some light on soldering and brazing. The following was contributed by Tim Kirby around 3/3/93 when the newsgroup was discussing the "true meaning" of silver soldering and the distinction between hard and soft solder. : Can anyone remember the "official" difference between : Hard & Soft solders ? While browsing for something else entirely, I found my copy of 'Model Locomotive and Marine Boilers' [Argus Press, 1988, ISBN 0-85242-923-1] by Martin Evans (well known in the Model Engineering field, at least in the UK) from which I have gratuitously (and without prejudice) stolen the following extract for your contemplation. As an aside, this is a useful book for those interested in designing and building boilers. Chapter 3, page 55: Silver Soldering and Brazing Soldering and brazing are processes which involve the joining of metals by the addition of molten filler metal of substantially different composition, at temperatures well below their melting point. An important difference between silver-soldering and brazing or welding is that the brazing alloy or filler material must be drawn by capillary forces right through the mating joint surfaces, and not merely deposited at the edges. Soft Solders are generally accepted as including the alloys of low melting point up to about 400 deg. C. They are usually based on Tin or Lead with small additions of antimony and sometimes silver. Hard solders, or silver-solders, are those alloys suitable for soldering which have melting points from 400 deg. C. up to about 800 deg. C. (see BSI 1845/1964) [for those who don't understand that reference, BSI is the British Standards Institute, similar in function to (for example) ANSI. BSI 1845 probably details this stuff in excruciating detail ;-) ... Tim.] Brazing alloys are alloys suitable for brazing (sic) which have melting points from about 800 deg. C. up to about 1000 deg. C. It should however be understood that there is no definite line of demarcation between silver-solders and brazing alloys. The former always contain a proportion of silver, while the brazing alloys generally contain copper, zinc and sometimes tin. Brazing alloys containing copper and phosphorus are also available but these are not recommended for boiler work. 22. What are bolt grades? We frequently see questions regarding bolt grades, so here's a partial list. Please note that just because a bolt is grade 2 does not mean it will break easily. Grading only refers to the minimum strength, not the maximum. Thus, if a machine uses a soft bolt as a safety shear pin, and you happen to replace it with a grade 2 bolt that was actually manufactured to grade 8 specs (but was marked down because too many of the bolts in the lot failed, so the whole lot was marked down) you could create some serious problems. Replace safety-related items with proper stuff! Also beware of improperly-marked forgeries. If your application is critical, test some samples or get certified hardware (not that readers of rec.crafts.metalworking are likely to be building interstate bridges or spacecraft, but it's worth saying). A note on "strength" which is actually a complex subject. First, note that there is a maximum "dry" tightening torque, and that part of this torque goes to overcoming friction. Thus, a lubricated bolt should be tightened to a lesser torque, as much as 1/2 the dry torque. Note too that bolts are rated as to their minimum tensile strength (presumably before breaking) and also their "proof" load, which is I believe the maximum load they can be subjected to as proof of their being grade "n", but this load is higher than the maximum suggested operating load. Thus, like automobile mileage figures, use these numbers for comparison only. I suggest reading the below-listed references before building any life-critical contraption. And remember that tensile strength is not the same as shearing strength. And note that there have been many scandals over the years involving manufacturers or distributors who certify hardware as high grade, incorrectly. John M. Peterson kindly typed this in on July 20, 1993, and I have added a few strength figures (jk): Taken from Machinery's Handbook 23 , page 1286. Torque: see Pocket Ref, by Thomas Glover, page 250. Strength: Standard Handbook for Mechanical Engineers, 7th ed., page 8-35. This also has a table of safe loads, as well as tensile and shearing strengths. ----------------------------------------------------------------------------- ASTM and SAE Grade Markings for Steel Bolts and Screws ----------------------------------------------------------------------------- Grade Marking Spec. Material ----------------------------------------------------------------------------- SAE - Grade 1 Low or Medium Carbon Steel No ASTM - A 307 Low Carbon Steel Mark SAE - Grade 2 Low or Medium Carbon Steel ----------------------------------------------------------------------------- -- -- SAE - Grade 3 Medium Carbon Steel ----------------------------------------------------------------------------- | SAE - Grade 5 Medium Carbon Steel Quenched and Tempered ASTM - A 409 / \ Min Tensile Strength: 105,000 to 120,000 psi Proof load: 74,000 to 85,000 psi ----------------------------------------------------------------------------- | SAE - Grade 5.2 Low Carbon Martensite Steel \ / Quenched and Tempered ----------------------------------------------------------------------------- | -- -- SAE - Grade 6 Medium Carbon Steel | Tempered ----------------------------------------------------------------------------- | ASTM - A 325 Medium Carbon Steel Type 1 Quenched and Tempered A 325 Radial dashes optional / \ ----------------------------------------------------------------------------- | ASTM - A 325 Low Carbon Martensite Steel \ / Type 2 Quenched and Tempered A 325 ----------------------------------------------------------------------------- ASTM - A 325 Atmospheric Corrosion (Weathering) Type 3 Steel, Quenched and Tempered A 325 ----- ----------------------------------------------------------------------------- ASTM - A 354 Alloy Steel, Grade BC Quenched and Tempered BC ----------------------------------------------------------------------------- | SAE - Grade 7 Medium Carbon Alloy Steel Quenched and Tempered, -- -- Roll Threaded After Heat / \ Treatment Min Tensile Strength: 133,000 psi Proof load: 105,000 psi ----------------------------------------------------------------------------- | SAE - Grade 8 Medium Carbon Alloy Steel \ / Quenched and Tempered ASTM - A 354 Alloy Steel, / \ Grade BD Quenched and Tempered | Min Tensile Strength: 150,000 psi Proof load: 120,000 psi ----------------------------------------------------------------------------- \/ SAE - Grade 8.2 Low Carbon Martensite Steel \ / Quenched and Tempered \ / ----------------------------------------------------------------------------- ASTM - A 490 Alloy Steel, Type 1 Quenched and Tempered A 490 ----------------------------------------------------------------------------- ASTM - A 490 Atmospheric Corrosion (Weathering) Type 3 Steel, Quenched and Tempered A 490 ----- 23. What is XYZ made of? Metals 1. What is Brass made of? Brass is a combination of copper and zinc, in approximately the ratio of 2/3 to 1/3, respectively. Sometimes lead (about 3%) is added to improve machinability. 2. What is Bronze made of? Bronze is usually made of copper and tin. However bronze describes any bronze colored alloy even if it doesn't have any tin. Various bronze alloys include silicon, manganese or phosphorus. Mostly bronze is used for bearings. 3. Steels Steel is a refined iron where the impurities carbon, silicon, sulphur and phosphorus are removed and then the iron is combined with carbon and/or chromium and/or nickel. Various other metals may be added to create a nearly infinite variety of steel and steel alloys. A few common steels are discussed below. a. What is CRS? Cold Rolled Steel. b. What is HRS? Hot Rolled Steel. c. What is HSS? High Speed Steel. d. What is stainless steel? Stainless steel is low in carbon but has about 20% chromium. Stainless has a beautiful finish but it is very hard to machine. Both CRS and HRS are mild steels. Mild steels have a low carbon (<.3%) content and therefore can't be hardened. CRS is formed (into bars, rods or angles ...) "cold" and therefore has internal stresses inside. Because of these stresses, an intricate part, like a one piece crankshaft, or a heat treated part may distort. CRS has a smooth surface, which requires no additional finishing. The steel stock found in the hardware store or home improvement center is usually CRS. HRS is formed hot so it does not have any internal stresses but it has a rough black scale surface. HRS is a little cheaper, but CRS is easier to find. HRS is used for welding, so a welding shop with steel stock would be a good source for HRS. HSS is a carbon steel (0.3%