Subject: FAQ part 3 of 8

From: [email-masked] (Jim Kirkpatrick)
Date: 3 Oct 94 03:14:07 MDT

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 8.

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?

The questions being answered in part 2:

6.  What are good magazines to subscribe to?
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.

The questions being answered in part 3:

16. How do I drill round holes?
17. What's TIG and MIG?
18. MIG welding technique.
19. Which MIG welder should I buy?
20. Books on welding.
21. Soldering/brazing topics.

The questions being answered in part 4:

22. What are bolt grades?
23. What is XYZ made of?
24. How do I build a furnace or forge?
25. What is Damascus steel?
26. How do I repair/replace this old leather belt?

The questions being answered in part 5:

27. Can I use a drill press as a cheap vertical mill?
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?
34. What are the various tapers (Morse, JT, R8, etc.)?

The questions being answered in parts 7 and 8:

35. What is Electric Discharge Machining (EDM)?
99. Names and addresses of publishers and suppliers
    (OK, so I got tired of re-numbering it every time a new
    question was added!)

-------------------------------------------------------------------------------

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.

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 [email-masked]

      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), [email-masked] 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 [email-masked]
     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.