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re Problem with Pencil Torch Flame

Discussion in 'Electronic Repair' started by W. Curtiss Priest, Apr 6, 2007.

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  1. ***
    W. Curtiss Priest, Director, CITS
    Center for Information, Technology & Society
    466 Pleasant St., Melrose, MA 02176
    Voice: 781-662-4044

    Chinese, Generic Pencil Torch Technical Note
    March 12, 2007

    Failure Mode:

    No flame
    No blue flame, torch flares, butane escapes very quickly

    Keywords: repairing torches, fixing torches, problem with
    pencil torch, unable to light pencil torch


    If you have found this note and have not tried to open the
    torch, you are probably in luck. If you have unscrewed
    the torch burner head, you most likely have lost the orifice.


    I had to purchase a second torch just to see what comprises
    the orifice. It turns out that this is a thin sliver of
    a disk and demanding for even good eye sight.

    Those who are used to standard BernzOmatic propane torches
    know that when the torch has low or no gas flow (no audible
    sound) and cannot be lit, that there is a brass orifice
    between the tube from the tank and the burner head. Further,
    the head has two flat spots, as the maker expects it to
    be disassembled when the orifice is clogged.

    Included in most kits is a sheath of fine steel wires. To
    clear a clogged orifice, one pushes a wire through the center
    drilled hole in the orifice. The diameter of the wire is
    9.5 mils, suggesting that the orifice is around 10 mils in
    diameter. Most importantly, the orifice is a largish object,
    about 1/4" long and a taper fits into the end of the tube and
    the face is rounded to create a seal with the head.

    Decades ago BernzOmatic made a pencil torch, model TX. It
    used an earlier style stubby propane canister. However,
    it can be adapted to use with a standard 14.5 oz. propane
    tank by using a valve fitting to the tank that has a ribbed
    hose connection, a short piece of high pressure polyethylene
    tubing (the kind used to bring water to ice machines), and
    adding a ribbed hose connection at the torch end -- I cut
    the top of the empty tank so I could solder the hose connection
    to that. I see that BernzOmatic makes a similar hose
    connected miniature torch, the ST-900.

    When the orifice on the TX clogs, the hole is only 2.5 mils
    in diameter and no common steel wire is easily available. The
    smallest such wire is a common part of a sewing kit -- it is
    the steel wire loop that is supplied to make threading
    needles easier. That wire is 5 mils in diameter. However,
    there is the alternative of using an ultrasonic cleaner and
    many people have one -- called a humidifier. The style that
    uses a tank placed on top of a white base uses a piezioelectric
    element to aggitate the water enough to create tiny droplets
    above the element. Those droplets are funnelled up and
    dispersed into the air. That element can easily be used as
    an ultrasonic cleaner.

    To clean an orifice, or anything small, like a small mechanical
    watch or jewelry, remove the tank, clear away the salts that
    deposit around the element and then use an appropriate solvent.
    As the unit depends on the liquid (water) to cool the element,
    these units always have a sensor for water level. If it is
    a unit that senses conductivity from a pin to the element, just
    take a clip, a short piece of wire and clip to the pin and place
    the wire into a little puddle of water over the element. If it
    is a float, use string to lift it. Whatever, do not let the
    element run dry.

    To clean an orifice, use water with a drop of detergent. First
    run the unit for a minute with just water/detergent to clear
    away anything soluble. Then rinse the area. Now place the
    orifice into the water/detergent puddle and turn the unit on
    for a minute. After rinsing and shaking the orifice, see if
    you now see a pin hole of light. If not, give it another

    As for the orifice on the Chinese pencil torch, the orifice
    is incredibly small. From the factory it is a steel disk
    that is 2.45 mm. in diameter and .05 mm. thick. And the
    pin hole is about the same size as on the BenzOmatic TX,
    about 2 mils in diameter.

    Repair if you have not lost or damaged the orifice:

    If you still have the orifice, clearing the hole is
    simple but exacting. Most of us have no experience dealing
    with a disk this small. It can be bearly handled with
    fingers. It defies tweezers, wanting to fly out when
    pinched, as it is slightly tapered at the edges.

    So, clear a table space and place a white fine cloth down.
    Now, if the disk falls, you'll see it. And the disk will
    not travel far if it tries to roll or skate.

    Removing the disk:

    1. hold the body of the torch in one hand and standard
    pliers in the other

    2. lightly grip the head with the pliers, not too tightly,
    not too lightly

    3. loosen the head

    4. holding the unit horizontally over the white cloth
    unscrew the threaded tube to the head

    5. the disk tends to stay inside the head, but, as you
    pull the two apart, look at the face of the threaded
    tube, you should see a fairly large hole ... if the
    disk is stuck over that, then brush it with your
    finger to get the disk onto the cloth

    6. when the disk is inside the head, you can try to
    rap the disk out by tapping the threaded end of
    the head against the cloth

    7. if the disk will not fall out or rap out, you need
    a pin that is less than .07" in diameter. A #52
    drill bit will do, or a largish sewing needle

    you press the pin into the center hole of the
    front of the burner head. You will feel it hit
    the disk, now slowly push the disk onto the cloth

    8. you might wish to verify if you can see the clog,
    but, be warned -- holding the disk up to a light
    is pesky and be sure not to raise the disk, say,
    more than a foot above the white cloth

    9. as the disk is so thin, the clog is easily removed
    using a fine sewing needle. Note, there are dozens
    of ways sewing needles are sized. Singer, for example,
    sizes them with the British gauge number. But, Dritz
    sizes them with a scale that runs about 3-10, where
    10 is the finest

    also ... important ... the sewing needle is much
    larger than this hole ... we are just using the
    sharp point on the tip of the needle. And, the
    size of the point does not always correspond to
    the size of the needle, but, in general, the finer
    needles have sharper points in the last 1 or 2 mils
    of their length

    So, a Singer sized needle to use is a #26 or #27

    And, a European sized needle to use is a #9 or #10

    If you have a Jo-Ann's Fabric store, get the Dritz
    "20 Quilting Betweens" number 56B-10. "Betweens
    are only shorter in length than "Sharps" -- and
    both have the same points. The Betweens are available
    in the smaller size because working on fine quilts,
    the person wants a shorter needle for dexterity

    10. with the needle on the cloth, just press the needle
    into the hole until it stops. Now flip the disk
    over and do that again. The clog should be cleared

    [Note: some people lick their fingers to work with
    small things, such as thumbing pages. But, do not.
    You don't want to introduce junk. Natural levels
    of body oils on the finger tip will typically provide
    enough stick to pick the disk up if you scoot the disk
    as you try to raise it.]

    11. to replace the disk do not attempt to either drop it
    into the hole in the head or use the threaded tube
    to place it into the head. If you drop the disk in,
    it will most likely not be flat and will be crushed.
    If you attempt to start screwing the threaded tube
    onto the head, with the disk balanced on the end
    of the tube, the disk can easily slip and get caught
    in the threads, and become pulverized

    12. to replace the disk, you want to balance the disk
    on the end of thin rod with a flat end that just
    fits into the threaded region. A number 40 drill
    bit will do, or, you can use a common round tooth
    pick -- Diamond "Elegant tooth picks." This
    dowel is 2.1 mm. (.0825"). One end is slightly
    rounded -- carefully grind or sand that end flat

    with the toothpick pointed up, with the disk centered,
    now just lower the threaded hole of the torch head
    down onto it ... the toothpick will go in about 1/4"

    you can now hold the head horizontally and look
    at a lamp through this hole ... you should see
    a tiny pin hole of light

    13. with the torch head pointed down, clear lose cement
    from the threaded tube and screw the tube in, hand
    tight. Now hold the body of the torch and with
    the pliers give the head a snug turn ... you are
    lightly crushing the copper onto the two brass
    surfaces ... now, the only opening will be the pin

    Some might ask, is this worth it? Well, if you have only
    one pencil torch and are in the middle of a project that
    requires that one torch, then surely this is worth the
    twenty minutes to do this. And, while the #10 Dritz is
    the ideal point, probably almost any of the smallest needles
    in a pack will do, say, even a #23 (Singer size).

    Now, what if you have lost or damaged the disk?

    If you have time and are not interested in a "construction
    project" -- then stop here and order another torch. In
    that I sense that these torches are sold in the millions,
    perhaps a local hardware store or hobby shop has one, within
    driving distance (however, I do sense that small retail
    hobby shops are dying out ... several that I called had

    However, if you enjoy projects, as a hobby, then it is
    a fairly easy matter to make a disk, or many disks :)

    To make a disk we fabricate a custom punch for copper
    and we use the above Dritz needle to create the 2 mil.
    diameter hole.

    Copper flashing is commonly available. Also often the
    interior of PC monitors are lined with a copper sheet
    for RF interference protection. The following instructions
    are for 3 mil. copper. If the copper is thicker or thinner,
    you will have to adjust the piercing force (below) as

    Fabricating the punch:

    I pondered how to make this tiny disk and I realized that
    the only practical way to make a "perfect" round disk
    of this size is with a punch. If you are a hobbiest,
    then you may have already acquired a punch set for cloth,
    rubber, or soft metals ... mine is called a "Maxi Punch
    Set" and has a handle and six punches ranging in size
    from 8 mm. down to 4.8 mm. But, of course, not 2.45

    And, to punch copper, we can make a punch with soft
    steel. It turns out that an 8-32 steel screw is a
    usable size, so we machine one that is 1" long.

    You need, at least, a drill (preferably a drill press),
    a number drill set, and a rotary grinder (preferably a
    Dremel-like with a cutoff wheel). We will drill a hole
    down the center of the screw and then taper the screw
    from the outside with the cutoff wheel at an angle, thus
    creating the cutting edge.


    1. cut the head of the screw off with a hack saw
    or cutoff wheel

    2. to accurately centerpunch one end of the screw, place
    the screw in the drill, and, with it turning, take
    the rotary tool with a carbide cutter -- such as
    a chishel tooth and holding the bit in the plane
    of the screw, remove the threads on the part of
    the screw protruding from the chuck

    as soon as you see no threads, you are done, and
    it does not matter if you were perfectly parallel --
    we are just clearing the threads to see the end.
    Do not remove material further, we need the remaining
    wall size

    3. carefully locate the center and centerpunch

    4. with a #45 drill, place the screw in a machinest
    vise (there are "V"s to hold round objects straight)
    and drill in about 1/4"

    5. we want to finish with a #41 drill, but, because that
    size drill bit gets close to the outer diameter of
    this trimmed screw

    at this point I never trust that the final drill
    will be centered if I see that the current hole is
    not perfectly centered

    my way of assuring centricity is to eye the hole
    and with a carbide chishel bit of a size smaller
    than the current hole (or any burr or diamond
    coated bit) I carefully remove material on the
    inside wall that is "too far in." You are "walking
    the hole out." And, as you do, you are also getting
    it closer to .096" diameter -- the size of the hole
    a #41 drill cuts.

    now drill the end with the #41. If you break through
    the wall, you must start over

    6. tapering the outside is fairly quick and easy. You
    again turn the screw with the threaded end in the
    chuck. As you turn, you angle the cutoff wheel at
    about 45 degrees to the end of the screw/punch

    if the result is a punch with a ragged end, just
    square the end off by pressing it against the side
    of a spinning cutoff wheel, and then angle the end

    7. to permit removing a punched disk we need to create
    a hole to the other end of the punch. Take a #50
    drill, place the punch in the bench vise, and drill
    from the punch end through to the other end. As
    this is nearly an inch long hole, be sure to raise
    the bit every few seconds so that the cut metal is
    released and the bit does not bind

    When done, the punch can be held with vise grips as described

    Fabricating the torch orifice:

    One is making a very small disk which is difficult to handle
    because it is also thin. Work in a contained clear area
    with bright light.


    1. small bench vise with a 3/8 inch brass nut, with a side
    face, facing upwards
    2. 2 small vise grips
    3. one shortened #10 Dritz sewing needle
    4. one home made copper punch
    5. one postal scale (or, ideally, a slide spring scale)
    6. one block of wood
    7. a number 52 drill bit
    8. a number 40 drill bit
    9. a flat punch -- around 1/4" diameter


    3 mil copper (for other thicknesses you'll have to adjust
    the force on the piercing needle)


    As one will put the orifice into a copper disk, the scale
    will push on the end of the needle with a selected force. As
    the #10 needle is only .0180" in diameter, it is easily bent.

    One of the vise grips should be a pair with either a smooth
    or serrated jaw at its end, say, 3/8" of jaw width. The
    sewing needle is shortened such that its point comes out one
    end of the jaws about 1/16" and does not come out the other
    end. (Now, pressure on the side of the vise grip will press
    the needle into the copper foil.)

    With practise, it takes about four minutes to punch and
    prepare the copper disk. It takes about one minute to
    press the hole.


    1. With the punch in a "needle nosed" vise grip, pointing
    out the front of the pliers, place the copper sheet
    over the wood block, press the punch, and rotate about
    half a turn left and right with constant pressure

    Too little pressure, you will not press through to the

    2. Press the copper disk out, using a #52 drill through the
    far end of the punch onto the brass nut. Surround the area
    with your fingers, as when the disk pops, it can fly. (you
    can always punch another one :)

    3. The disk will have an edge curl. This must be removed.
    Take the end of a flat punch (or almost anything with
    a flat end) and press down on the disk, evenly. Look
    and assure yourself that you flattened the disk evenly.
    Press with a slight circular action -- this will assure
    contact with all edges.

    3. Take a black permanent marker and roll it on the disk to
    mark that side. Roll off of the disk, as, just lifting
    will take the disk with the pen.

    4. Eyeball the center of the disk (not critical). Place the
    point of the Dritz #10 needle/vise grip in the center and
    hold those pliers so that the needle is straight up.

    5. A number 7 Petersen Vise Grip weights 160 grams. With
    your scale you need to add somewhere around 1200-1500

    This is sufficient force to drive the point of the needle
    through the disk and into the brass. But, it pushes only
    the needle end which is about 2 mils diameter and not
    the entire needle which is 18 mils in diameter.

    You should be able to pick up the disk by just raising
    the vise grips. You should see the point end of the
    needle, just coming out the other side of the disk.

    6. Inserting the disk is touchy. It cannot just be dropped
    into the torch end of the unit because it will not lie
    flat and screwing in the torch body will crush the disk.

    So, you need to do a balancing act. And do this close
    to the table so when the disk falls, you can easily
    recover it. Note: the disk is light enough that the
    oils on your finger tip is enough to pick it up from
    a flat surface. Do not lick your finger -- that would
    leave material that could clog the orifice. You will
    find that pressing your finger on the disk, with a slight
    sideward swiping action will pick it up reliably.

    One places the disk on the flat end of a #40 drill bit
    with the black side facing the bit. Why? You have not
    drilled a hole, you have pierced one. So, there is a
    tiny copper coller around the hole on the side the
    needle came out. If you point that towards the butane
    source, it will more easily clog, so we point it away.

    You have the disk/bit in one hand and the torch head
    in the other, you carefully line the end of the bit
    up with the screw threaded hole in the torch head
    and push it in (about 3/8"). You should be able to
    hold the torch head towards a light (keep the head
    horizontal to keep the disk in) and see a tiny, tiny
    pin hole of light.

    If you see no pin hole, start over and press the needle
    with another 200 grams of force.

    7. Clear the threaded end of the torch body of lose cement

    8. Screw the thread into the torch head until it stops

    9. Take regular pliers. Hold the torch body in one hand,
    apply the pliers to the torch head, lightly. Too hard,
    you'll score the head. Too soft, you'll skate. Now
    just give the head a snug turn. This compresses the
    disk/washer around its edges so that the orifice is now
    the only passage for the butane into the head

    If you have a microscope you can view your result. Use
    a 30x magnification. To determine the size of your hole,
    place the disk with the black side down. Now take the
    needle threading wire (measure its thickness with a caliper
    or micrometer; they tend to be 5 mils) and place the wire
    next to the hole. You should see a hole that has a diameter
    about half that of the wire -- i.e., the pierced hole is
    about 2.0 mils.

    This size -- 2.0 mils. -- is about as large as the hole
    should be. The flame size will be somewhat greater than
    the original.

    One interesting side-effect of being able to make these orifices
    is that you now have the ability to make the torch cooler or
    hotter. The smaller the hole, of course, the smaller and thus
    cooler the flame. (This can also be done by adjusting the gas
    flow from the body, but, this behaves differently, and requires
    fussing. If you are, say, a jeweler, you can tame the flame
    to a known setting. If you have two torches, you can set
    one for a small flame and another for a larger flame.


    W. Curtiss Priest, Director, CITS
    Center for Information, Technology & Society
    466 Pleasant St., Melrose, MA 02176
  2. Way overlong; booorrring; mildly informative if you can stand it; well
    written; waste of time as typical of cross-posting trollish pedants.

    Bob (opinions are us) Swinney

  3. JR North

    JR North Guest

    Speaking of WAAAAY overlong, you really didn't need to quote the whole
    fucking text to point that
    Dweller in the cellar

    Home Page:
    If you're not the lead dog, the view never changes
    Doubt yourself, and the real world will eat you alive
    The world doesn't revolve around you, it revolves around me
    No skeletons in the closet; just decomposing corpses
  4. North sez:

    "> Speaking of WAAAAY overlong, you really didn't need to quote the whole
    Are you the watchdog here? Read what you want, let the rest hang out.

    Bob (BS filter off) Swinney
  5. Gunner

    Gunner Guest

    Least it wasnt in Chinglish..kinda sorta.

    Fred Thompson and Condi Rice in '08!!!
  6. Gunner sez: "> Least it wasnt in Chinglish..kinda sorta.
    Watch it Gunner ! You might invoke the ire of the Bandwidth Police. They
    are very sensitive to reposting stuff, don't you know ?

    Bob Swinney
  7. Gunner

    Gunner Guest

    Ooops! My bad!



    A human being should be able to change a diaper, plan an invasion,
    butcher a hog, conn a ship, design a building, write a sonnet,
    balance accounts, build a wall, set a bone, comfort the dying,
    take orders, give orders, cooperate, act alone, solve equations,
    analyze a new problem, pitch manure, program a computer,
    cook a tasty meal, fight efficiently, die gallantly.
    Specialization is for insects. Lazarus Long
  8. Then I was making pinhole cameras in skool, I had nothing but trouble
    using sewing needles to make the pinhole in aluminium or brass foil. I
    read an old book that suggested using tiny cactus needles. I tried it
    and found that it makes a much smaller and cleaner hole (when viewed
    with a microscope). The needles have almost no bending strength but
    are very strong inline with the point (as long as the needle isn't
    bent). Building a tool to hold the cactus needle was tricky, but I
    was impatient and just used tweezers.

    Way off topic but interesting... pinhole eyeglasses:

    Pinhole FAQ:
  9. Dear Mr. Liebermann,

    I see that some folk simply have no patience to learn the fine art of
    engineering and redesign. Really too bad. They might get a life.

    As for using a cactus needle, this is truly interesting. I wonder if
    needles are as small as 2 mil, or how their point is shaped? With
    vise grips, gripping such things has become very predictable. One
    feather the tightness on the cactus needle to the point it would not
    slide, but
    not so hard to crush it, to breaking.

    Truly, the hole created with a sewing needle looks like a bullet
    through -- the copper is flared, thus the reason I put that "noise"
    away from the butane source. A cactus needle, of course, is barbed,
    I presume it acts like a miniature rasp!

    I'll try it some time.


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