Worn jet, hypodermic needle insert

Discussion in 'Fettling Forum' started by presscall, Aug 1, 2020.

  1. presscall

    presscall United Kingdom Subscriber

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    The original jet for THIS Hipoloito had worn oversized such that a 0.23mm stove jet pricker could easily be inserted.

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    For some time now I’ve been using a technique to repair stove jets that involves silbrazing a short length of hypodermic needle in the worn jet orifice.

    Needles come in a series of progressively finer gauges, defined by the Birmingham Wire Gauge. It’s possible to select a needle size with the desired internal diameter/bore, or a very close aproximation. For the majority of stove jets I use 24 gauge (0.32mm jet) or 26 gauge (0.23mm jet).

    For the Hipolito I needed a needle much finer, 31G (0.133mm), but didn’t have a batch in stock.

    I recently bought this assortment of blunt hypodermic needles, not used for injections but for laboratory use dispensing tiny amounts of fluids.

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    A Chinese source, the colour coding didn’t correlate with the Wire Chart and I’d to select a couple that seemed possible, with not too sloppy a fit on a Petromax 150cp jet needle.

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    The finer of the two, the purple one, didn’t offer an easy enough clearance on the Petromax jet needle.

    The white one was better.

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    There were several needles of that gauge in the assortment and I ground flats on the tip of one to enable it to drill its own clearance hole in the Hipolito jet ...

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    ... which it did by gently rotating it between finger and thumb while applying very slight pressure.

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    I inserted just the tip of the hypodermic needle I’d not ground flats on into the Hipolito jet and silbrazed it in position.

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    Flux washed off by dunking the jet in boiling water for a couple of minutes, excess needle on the outside of the jet trimmed off, face of jet levelled off, jet polished.

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    Stainless steel liner just visible (and tip of Petromax jet needle, trying it for clearance).

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    John
     
    Last edited: Aug 1, 2020
  2. Norman

    Norman United States Subscriber

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    Well done John as always.

    Are you grinding a slight tapper on the tip protruding on the inside of the jet/nipple so the pricker does not get stuck and bend and if so what type of grinding tool are you using.

    I've thought about doing the same thing you are doing but none of my tapered Dremel grinding tips will fit inside the jet.

    Cheers,
    Norman
     
  3. Tony Press

    Tony Press Australia Subscriber

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    Nice job, John.

    I’ve done that a few times for stoves (following your example at CCS) but haven’t needed to do it on a lamp yet.

    Cheers

    Tony
     
  4. presscall

    presscall United Kingdom Subscriber

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    It’s critical not to have it protruding Norman.

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    The Hipolito jet nipple doesn’t have the internal taper profile of the Petromax and lacking the original Hipolito pricker needle, that’s where I’m heading next, to create a comparible needle. Though I’ve not seen an example of the Hipo needle I expect it’s the fit of the body of it in the jet bore that guides the needle into the jet orifice in the absence of an internal taper. There’d need to be a lengthwise slot in the needle body to allow the passage of fuel vapour.

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    Meanwhile, the Petromax jet and vapouriser serve.

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  5. MYN

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    That was a neat technique and a brilliant idea. The brazing work could be a little tricky there for a tiny part.
     
  6. ROBBO55

    ROBBO55 Subscriber

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    @presscall

    Nice work so far John :thumbup:. I'm following this post with interest as I have a Petromax 900 "Baby" with an enlarged jet and an unusual size thread.

    I believe you are right but I believe the body of the pricker is triangular in shape (same as petromax) and that guides the needle into the jet and allows fuel to pass.
     
  7. presscall

    presscall United Kingdom Subscriber

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  8. isfuzzy

    isfuzzy Subscriber

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    That now steel orifice should last a hell lot longer from just brass or bronze jets :shock:
     
  9. presscall

    presscall United Kingdom Subscriber

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    @isfuzzy
    That’s been the case with stove jets.

    In THIS post on the CCS site I reported having used a microscope to take photos of the stainless steel insert, such as this one.

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  10. Darryl Durdin

    Darryl Durdin Australia Subscriber

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    great reading, above my skill set, thank you for sharing
     
  11. isfuzzy

    isfuzzy Subscriber

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    What i hate the most.. Pmax jet life.. Worn so fast :rage:
     
  12. JonD

    JonD Subscriber

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    I think once you have done this modification the jet will last almost forever.

    Afterwards the pricker wire and the jet have about the same hardness when before the soft brass stood very little chance against steel pricker wire.

    I haven't tried this on a lamp or a stove yet but @presscall is the master. I will try it one day but as yet I have no deserving customer for the technique.

    My H502 is a bit over bright, I was thinking about a 350CP conversion. But then what will sear my eyeballs when it's capabilities are required? Must buy another...
     
  13. isfuzzy

    isfuzzy Subscriber

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    @presscall Did you use a pencil torch for the silbrazing?

    @JonD I cannot imagine doing this on a Coleman tip :shock:
     
  14. Tive

    Tive Sweden Subscriber

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    Cool !!
     
  15. JonD

    JonD Subscriber

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    @isfuzzy - putting out the challenges!! :)
     
  16. presscall

    presscall United Kingdom Subscriber

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    No, I used this, a MAPP gas blowtorch.

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  17. isfuzzy

    isfuzzy Subscriber

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    @presscall :shock: Bernzomatic seems like poking a 3mm hole with an elephant gun... i managed to obliterate a piece of sheet brass while brazing once :lol:

    @JonD I was tempted to do so for the 0.008 coleman tip to use for kerosene... The severity of the tip's tiny-ness and shaky hands, i'm not sure im up to the challenge.

    I saw this 2020 Iron Type Tilley Vaparisor Iron Jet . However, the generator body has to be steel somehow.

    Tilley Vaparisor Iron Jet _ eBay.jpg
     
  18. Reese Williams

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    I think it would be doable on a Coleman jet with a pencil torch because they are so small. However, Coleman generators with jet are so readily available at reasonable prices I'd be hard put to justify the exercise, unless just to prove it can be done. I've used John's technique to save a Borde stove and it works a treat. Thanks again John for showing us the way.
     
  19. isfuzzy

    isfuzzy Subscriber

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    @Reese Williams Actually i am facing the need to get separate jets to fit on a R55 generator. R55 can be cleaned out and rebuilt, but different jets aren't readily available unlike Pmax jets. Running kero on the R55 with the issued jet runs too rich. I did swap to a smaller jet from another generator which is older and has a smaller orifice, works well. But at the end of the day, i need to get around to have a bunch of spare jets :-({|=
     
  20. Reese Williams

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    @isfuzzy I'm going from memory here but I think some folks use a 200a jet on kero conversions. Look over on the CCF and do a search on kero conversions, should be a fair bit of info.
     
  21. MYN

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    @isfuzzy
    Not all Coleman jets/tips could be easily repaired using the hypodermic needles and brazing. Not only they are generally smaller than the Petromax-type jets but quite a fair number of these have a recess where the orifice is. Brazing metal would fill up the recessed area around the orifice instead.
    That significantly increases the required level of skill and trouble.
     
  22. isfuzzy

    isfuzzy Subscriber

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    Not to mention the dexterity to mount it on the lathe for final touch ups. On a 2 inch 4-jaw chuck :shock:
    I guess peening is an easier approach for the colemans??
     
  23. MYN

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    Lathe and machine work on a small piece can be pretty tough. I've had a couple of Coleman 237 gas tips(jets) being made in a machine shop here. Milling out the tiny square sides from brass stock, turning out the rounded section on a huge, general purpose lathe, tapping the threads with a 4-48UNF die and worst of all, drillig a 0.008"(~0.2mm) orifice on the same lathe...
    Thank goodness, it wasn't the Milspec or the Petromax 900 jet that had to be made.
     
  24. isfuzzy

    isfuzzy Subscriber

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    I don't think i am game enough for the 0.13mm hole drilling nor is my lathe capable of that.. Would need some watchmakers' for those tiny jets i reckon :-k
     
  25. MYN

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    I think those could be drilled using a good quality miniature or micro lathe so long as the speeds are variable and the chucks runs true and don't wobble. Those tiny drill bits are not common here and are quite expensive too.
     

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