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  • Music wire

    Like many RC aircraft modellers I use music wire for landing gear and so on. For the first time however I had occasion to attempt to drill a 3/32 hole in a 1/4" piece of music wire. It is very tough stuff. The drill would not touch it. So I heated it white with the torch and cooled it as slowly as possible. Still no go. Does anybody know what this stuff is? Certainly not mild steel. How would you anneal it for drilling, then return it to correct temper?

  • #2
    It is easier to drill if you make a cross drilling setup (a v-block with a hole, the clamp has a drill bushing in it to guide the drill) Use a good 135* split point to drill it once you have everything clamped tight. You should not have any problem drilling it once it is "bound & gagged". If your drills can't hack it, use an endmill, or "slot drill". You shold not have any problems doing it this way. Are you using quality HSS bits or cheap imports (Nachi, Norseman/Nordic, titex are very good brands)?

    dave

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    • #3
      I believe that music wire is plain high carbon steel similar to drill rod. Seems like your annealing procedure should be OK, though you don't need to get it so hot, bright red, not quite orange should be enough. You could check with a magnet, I believe, when the steel no longer is attracted to a magnet it's hot enough. When you say you cooled it as slowly as possible, Did you cool it in the flame? The critical temperature range is from bright red to dull red (as I recall. I don't have my color chart handy.) With a thin section (1/4 " isn't all that thin) cooling in room air will probably quench it and leave it hard. Try this: Heat it to bright red, hold it there for one minute, then slowly withdraw the flame so that over the next two or three minutes it cools to well below glowing temperature, still in the flame. Turn the rod continuously to keep the temperature uniform. (Leave the room lights off so you can really see what the steel is doing.) Then let it air cool. Maybe that will do it, I'm kind of guessing here.

      Hardening would start the same way except that after you've brought it to temperature and "soaked" it, you quench it in water. That leaves it dead hard. Then you polish it up and re-heat to a lower temperature to reduce the hardness somewhat and return some toughness and ductility. You judge the temperature by the colors of the oxides that form since this is below thermal glow temperatures. How much depends the requirements of your application, more than I can get into here. But it seems to me that music wire would come in at least normalized condition. I kind of doubt that you can make it much softer than when you bought it.

      [This message has been edited by Randy (edited 02-12-2002).]

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      • #4
        I also suspect that you may be cooling the wire too fast (and thus re-hardening). I've had good luck annealing small pieces of steel by heating to bright red/orange and immediately plunging them into a coffee can ful of vermiculite (available at gardening supply stores). The vermiculite is a great insulator and will allow the work piece to cool only very slowly. Wait several hours and be careful when you try to get it out. A 3/8" ball bearing treated in this manner will still be too hot to handle after 1 hour in the vermiculite.

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        • #5
          You can also heat it on a heavy steel plate - the plate lets it cool slower as it retains lots of heat. The other ways work well too.

          You should be able to drill it without doing any of this with thr wire in its "out of the box" condition.

          dave

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          • #6
            At what RPM were you drilling? I would chuck the bit as short as possible, try to get a stub that will just make the cut. Then, on a slower than normal speed, feed the bit hard, till you think it going to break. Use a drop of a nice thick lube or pork fat, and that should do the trick.

            ------------------
            James Kilroy
            James Kilroy

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            • #7


              You Wrote:
              '"
              <font face="Verdana, Arial" size="2">Originally posted by dmcdonald:
              Like many RC aircraft modellers I use music wire for landing gear and so on. For the first time however I had occasion to attempt to drill a 3/32 hole in a 1/4" piece of music wire. It is very tough stuff. The drill would not touch it."
              STEVE- Unless you need the hole in line with the wire, try silver soldering/brazing or even soft soldering a tab on the wire and drill the tab. Any hole prevents the wire developing its full strength around the hole. 1/4 inch minus 3/32 leaves 5/32 for load carrying. Use 5/32 wire, gain some strength, lose some weight. the tab will also assist in preventing the wire rolling, slipping, acts as a washer to distribute the clamping forces. but that info (useful or not) dont answer your question. read on.

              "So I heated it white with the torch and cooled it as slowly as possible. Still no go."
              STEVE- My expereince with music wire (making springs mainly) is that, like many special metals, once heated to excess (what ever that means) the metal is ruined. You went well beyond the critical temprature when you went white hot. Find the critical temp as follows:
              get a good strong magnet. with your material, laid as you will have it when heating, and magnet practice several times finding where you can feel the magnet being pulled toward the material. Dont touch the magnet to the material. Now slowly heat the material (by slow i mean at a rate where the inside of the material is heated at about the same rate as the outside) along the area you wish to heat treat (anneal or harden). Beginning at a dull red, pass your magnet near the material. When you reach "critical temperature" the material will SUDDENLY become non magnetic. Keep the material at that temp so far as possible for a short while (long enough to insure the deeper parts are at critical temp also. To anneal, cool slowly. To harden (glass hard) quench in cold water. The hardened material will be brittle and will shatter if stressed. The softened material will bend and work like baling wire.


              " Does anybody know what this stuff is? Certainly not mild steel."

              Its mostly high carbon steel in music wire.
              "How would you anneal it for drilling, then return it to correct temper?
              </font>
              "
              STEVE - The method described above will anneal. Drill in the soft state.
              returning to correct temper is hard and time consuming.
              My method is:
              1. know your original wire. Determine how hard your wire is before heat treating. polish the wire, try a file to nick the wire (noting the pressure exerted), or grind a flat noting how the sparks appear, try to bend the wire with some tool where you can duplicate the forces involved.
              2. Anneal the needed wire plus at least six inches. Drill and otherwise work it.
              3. heat the entire wire to the critical temperature and quench in non detergent motor oil- used oil is ok. shove the wire into the oil quickly, end first (laying the wire into the oil flat will surely cause it curl due to sides being at different temperatures). Now you have a hard brittle wire, unsoftened it will shatter like glass, softened a little it will make cutting tools, even softer knives. you problem is to "get it to the hardness you want". You determined that hardness when
              you filed/ground the untreated piece. Now take your excess piece, polish it bright and clean. keep your fingers off it!!!
              heat ONE end ofthe polished wire and you will (at about 430 degrees f) see colors show up. very pale yellow is about 430 F, straw is 450, deep straw is470, etc. the colors at 20 degree intervals are pale yellow $30, pale straw yellow, deep straw yellow, yellowish brown, brown yellow,bron purple, purple,blue, dark blue, light blue (640 degrees). If you heat your wire at one end the colors will "travel" down the wire as the wire gets hotter and hotter. Too much heat and the colors travel fast and the bands are close together- useless. heated slowly the bands are distinct and broad. for control purposes, remove all heat when the yellow band nears the end. THis leaves the end brittle and the heated end (at light blue) soft. The colors remain when the iron is cooled.
              Take the colored wire and test is with you file or grinder and find where the colors most closely conform to you original wire.

              prepare a box of (as one poster suggested vermeculite is good) insulating material with low specific heat. lay your wire in a sheet of clean iron, heat the sheet evenly until the colors start to show on your wire. when the color yo uwant shows, remove heat, cover both the wire and iron sheet with more insulation and let it cool.

              When you insist on checking to see if it cool nuff, just touch the iron plate. Leavethe wire covered till its all cool.

              If you worry about stresses (and you should) simply heat the wire to about 400 degrees in wifes oven, hold for couple hours andturn off. The wire is probably "normalized " for your purposes.

              The best article and colors, how and why they are formed I have found is is HSM may june 1989. I use this article for teaching. The article is well worth reading.
              Steve

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              • #8
                Try a carbide drill or end mill.

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                • #9
                  jkilroy:
                  MMMmmmm! pork fat! Aren't pigs just delicious - and they make good cutting lube too!

                  Dave

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                  • #10
                    I just looked up piano wire in Machinery's handbook. It is high tensile steel. To make matters worse, the action of drawing the rod through the dies work hardens the wire. It ends up after drawing at 300,000 to 340,000 psi ultimate strenth. It is basicly the same as plow-steel wire, that's the wire steel rope is made from. I doubt that you can anneal it. It is too small at 1/4" to hold the heat long enough. Proper annealing requires very slow cooling. We used to use Zonolite insulation and leave it there all night. Of course those were bigger items. Why do you have to use piano wire?
                    Hope there is something there that helps!
                    Jim

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                    • #11
                      No doubt on the pork fat, or lard, making a great cutting lube. Based on a tip I saw on another board I picked up a gallon container of real commercial lard. The stuff is great, it leaves no stains, cleans up easy, and smells like bacon when it gets hot. How in the world can you beat that?

                      ------------------
                      James Kilroy
                      James Kilroy

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                      • #12
                        Thanks all for the suggestions. I now have a neat hole in the end of my music wire. I cooled the end slowly over night in insulation, that seems to have been the key. I also clamped it firmly and used only a short bit of my new Westward drill protruding from the chuck. All worked fine. However, without the annealing, there was no way at all (6 broken bits to proove this, I am highly unimpressed with titanium drills).

                        The music wire has two uses for me. I string cable for a living and make long tools to poke through walls in order to pull back the cable. The center conductor is 3/32 inch, thus the need for the hole. These tools are lifesavers. The toughness of the music wire lets me hammer the tool into the drill hole if need be.

                        The other use is for RC models. I am getting into scale building, and for realism, mounting lugs are best used with a hole in the wire strut. This will be easier now that I have tamed the demon. Lots to learn about metal yet!

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                        • #13
                          The "Titanium" you refer to is TiN (Titanium Nitride) It is just a coating - it improves the performance of good tools but cannot turn a turd into a butterfly. It has been said before in these journals that TiN coated drill bits are (usually) a sign of a crappy drill bit. Most import drills are pretty bad. TiN is used on larger expensive drills (usually with coolant holes) but in most cases should raise a warning flag in your wallet.

                          Dave

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                          • #14
                            I am sure you are aware, but there are commercially available pullers. Also long (4 foot) drill bits with pull eyes in the web, drills that turn corners, and lots of other cool items for installers such as yourself.

                            In case you don't know about them, I can post a company that handles that stuff.

                            Comment


                            • #15
                              My suspicions about titanium are confirmed. What about the so called Cobalt drills? Muchos expensive. Seems to me that a good set of HSS drills and a sharpener set up that works is the best way to go.

                              Speaking of sharpening, I have looked at the standard shapening guides that sit beside your grinder wheel. But I wonder what happens to the temper of the drill after sharpening. Do you re-harden in oil after sharpening?

                              I know about the specialty tools and own a few. Music wire is cheaper. I have all kinds of custom tools that I make for the occasion. Might as well, I like to work metal!

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