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 4 of 11. Generally, units below are United States dollars, degrees Fahrenheit, and all the other silly backwards units we Americans still use. Sorry. ------------------------------------------------------------------------------- 19. Which MIG welder should I buy? 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@ix.netcom.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. In late 1995 (10/1), Ernie Leimkuhler (ernieleim@aol.com) wrote: The best of all the baby migs are the Lincoln SP-125, Miller 130, and Hobart Handler 120. All 3 are gas MIGs that can also run flux-core (but why would you want to if you don't have to ?). I own a Handler 120 and have loved it for the last 3 years. I've welded stainless, aluminum and steel with it without a hitch, although the aluminum capability of all the baby migs is pretty limited. For regular steel I use a 75% argon / 25% CO2 mix, but if I need to do a bunch of stainless I swap my 75/25 bottle in for a bottle of Helium-tri-mix. This gives hotter, cleaner welds on stainless and as long as you own your tank it doesn't cost much to swap out for a specific job and then swap back. Eventually I suppose I'll buy another tank, but for now it doesn't seem worth it. Flux-core is only recomended where a sheilding gas is likely to get blown away, such as in-the-field repairs. It is considerably nastier and means a lot of cleanup. BTW instead of buying 10 lb. ($50 - $60) spools of stainless, I buy the little 1.1 lb ($6 - $7 )spools made for spooler guns. This saves a bit of money for small jobs, but if you are doing a lot of stainless, it is cheaper per pound to buy the 10 lb spools. Remeber to match you filler metal on stainless, other wise you can get some funky welds. 308L SS filler wire is used for 304 SS. 316L SS filler wire is used for 316 SS. (The "L" stands for elevated temperature stable). The Hobart, Lincoln , and Miller machines all run close to $500 for a package. I would stay away from the cheesier brands on principle allthough some members of this newsgroup have bought them and been quite satisfied. The problem is that the low end companies tend to have probems with warranty repairs and replacment parts, whereas the larger companies have certified repair stations all over the country. All these machines have similar max output amps and tend to max out on 1/4 inch plate steel. For thick sections just preheat to above 400 deg F. -- to which Jim Campbell (campbellj@fdtc.flo.TEC.SC.US) replied: The Chicago Electric systems also have a clever marketing scheme that uses non-standard wire diameters that may commit you to using their systems and materials only. That's probably why their machines are priced rock-bottom, especially through Harbour Freight. For those asking Mig theory questions, are you getting enough info in your operator's manual (When all else fails)? A good little book on Mig is ESAB's "Mig Welding Handbook" revised in 1994. Only $7.50 and evaluation copies FREE for students/educators/advisors to schools, or whatever. ESAB was once Union Carbide/Linde. They may sell a small Mig unit too, but I am not familiar with theirs. ESAB's snail mail is: PO Box 100545 Florence, SC 29501-0545 and voice is (803) 669-4411. (I do not work for them, but use their mechanized stuff). 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. ----------- According to Jim Campbell (campbellj@fdtc.flo.TEC.SC.US): For those asking Mig theory questions, are you getting enough info in your operator's manual (When all else fails)? A good little book on Mig is ESAB's "Mig Welding Handbook" revised in 1994. Only $7.50 and evaluation copies FREE for students/educators/advisors to schools, or whatever. ESAB was once Union Carbide/Linde. They may sell a small Mig unit too, but I am not familiar with theirs. ESAB's snail mail is: PO Box 100545 Florence, SC 29501-0545 and voice is (803) 669-4411. (I do not work for them, but use their mechanized stuff). 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%