No-silbrazing downsizing of worn jet

Discussion in 'Fettlers Master Class' started by presscall, Mar 2, 2015.

  1. loco7stove

    loco7stove Subscriber

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    Hi John

    Makes sense as long as the needle is held tight & at 90 degrees to the thread brazing should be a cinch :-s [-o< :D :thumbup:

    Stu :D
     
  2. loco7stove

    loco7stove Subscriber

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    Sorry i meant parallel to the threads ](*,) :doh:

    Stu :D .
     
  3. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    I took delivery of a pack of fifty 25-gauge hypodermic needles today - more than enough to keep me downsizing jets for the rest of the year I'd imagine

    1425587263-36.JPG

    1425587273-37.JPG

    1425587285-38.JPG


    There's the crucial dimension - so the Wikipedia table was correct - 0.5mm outer diameter, 0.25mm inner. One-fiftieth of a millimetre oversized bore, especially since it's not likely to wear larger for quite some time compared to the original brass, isn't consequential on the combustion qualities of the jet stream - as the test firing will confirm

    1425587295-39.JPG


    Terry posted something about cheap jets on ebay and I'd bought some myself, possibly from the same source, I can't recall. The jet threads are good, but the jet orifices are a bit 'variable' shall we say. The twist drill impaling that jet is 0.4mm size and it's a loose fit. I'd not drilled out the jet incidentally, that's how it came out of the packet

    1425587304-40.JPG


    Whatever, a good subject to pop a jet liner in.

    Stu (Loco7stoves) kindly sent me a couple of aids to make this work a bit easier - this jet holder which has a tapped hole to take a jet ... handy to hold the jet when reaming out the hole with a 0.45mm drill

    1425587317-41.JPG


    1425587326-42.JPG


    ... and this jet holder/vice clamp in alloy angle, which takes a jet for the 'pressing in the insert in a vice' stage of the process

    1425587335-43.JPG


    In actual fact, I screwed in the jet to be worked on in the ally angle device for all stages of the job. Stu himself would admit the tool's not essential - as my prototype effort established - but it makes it a lot more convenient to do. Thanks Stu!

    On the left is a 0.23mm jet from my 1951-dated Primus 71. On the right the jet to be downsized. It's taller you'll notice ...

    1425587346-44.JPG


    That extra depth is accompanied by a correspondingly deep chamfer to the jet hole

    1425587356-45.JPG


    I decided to dispense with that extra height and the chamfer and machined off the excess with my Dremel cutting wheel

    1425587368-46.JPG


    Here I'm drilling out the 0.4mm (should be 0.32mm hole if the jet specification were right in the first place) hole with a 0.45mm drill

    1425587389-47.JPG


    The tip of one of the hypo needles (slight chamfer put on it with the cutting wheel) is jammed in the hole ...

    1425587397-48.JPG


    ... and cut off with the cutting wheel, leaving an amount protruding that I've measured will line the full length of the jet orifice when pressed home

    1425587405-49.JPG


    Pressed in, slightly above the surrounding surface due to the serrations in the vice jaw (I could have used a packing piece or lined the jaw, true)

    1425587429-51.JPG


    I'd a decision to make now. I've assumed chamfers are put on jet orifices to help guide a pricker wire in. With an abrasive tip in the Dremel I could restore a chamfer, but a fiddly job. I could have also left a chamfer on the jet and pressed the needle into the chamfer cavity using a very small steel ball during the pressing in the vice stage - also fiddly.

    Instead, I decided to machine the surface flat using the cutting wheel. To be honest, I've found that chamfers don't actually guide a pricker wire in all that well and it's a case of feeling for the hole with the pricker wire, aiming for the centre of the jet

    1425587438-52.JPG

    1425587447-53.JPG


    It works fine. Jet ready to install for test

    1425587461-54.JPG


    Installed in my Primus 71

    1425587471-55.JPG


    Just after priming, self-pressurising underway

    1425589432-56.JPG


    FLAME SHOTS IN A 'REPLY'
     
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  4. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Still getting up to speed

    1425589639-57.JPG


    Good and hot now. Good combustion and an even flame pattern. I'm happy with that

    1425589649-58.JPG


    Best to check it will simmer. It did

    1425589657-59.JPG


    Back up to maximum

    1425589668-60.JPG


    Needle stub put safely away for another jet insert, possibly two

    1425589677-IMGP1951-001.JPG

    1425589687-IMGP1952.JPG


    Incidentally, in that other post on this theme, but relating to lipstick burner tube repairs ... Anglo-American co-operation ... I see Wim has said,

    Yes it would, Wim. In the case of the 8R Russian clone, a 24-gauge hypodermic needle would be necessary to get the worn jet back to 0.32mm spec and the existing jet pricker wouldn't baulk at working in conjunction with the insert, since there's no insert projecting in the interior cavity of the jet if it's measured up right for the pressing in of the insert stage.

    The various hypo needle gauge sizes would provide insert material to get any jet back to specification. It's just a case of choosing the right size of drill to ream out the hole to get an interference fit with the needle insert.

    John
     
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  5. loco7stove

    loco7stove Subscriber

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    Great addition to your post John 8) :clap: :clap: :clap: :thumbup: , & glad to help :D :thumbup:

    I suppose this should work on the jets of a Opti 111 & 22 stove using the correct sized needle when they get worn out :-k whch would save a good bit on replacements 8) :thumbup:

    Stu :thumbup:
     
  6. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Cheers Stu.

    Optimus 111/22 jets? 8R and Russian clones too come to think of it ...

    What I said about needing a fillet of silbraze on the thin metal tip of a lipsick burner tube requiring one of these inserts applies for the Optimus jets I'd say.

    I've just measured a 111 jet and the conical tip of the cavity inside accommodating the jet cleaner needle when raised goes up to barely a millimetre of the outer face of the jet.

    Unlike the 'regular' replaceable jets I've been using this technique on with about 3 millimetres of metal to grip the insert, that's not enough to secure the insert by interference fit, especially since there's the not-infrequent movement of the cleaning needle within the insert.

    I'll be ordering some 24-gauge needles (0.311mm bore) to bring oversized 0.32mm jets back to specification and will try out the technique - with silbraze filler - on a 111 jet. I'd best make sure too that the pricker wire of a 111 will still pass through the slightly undersized jet insert - 9 thousandths-of-a-millimetre undersized. Hopefully it will.

    John
     
  7. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi, I have been following this topic with great interest.
    A good idea and impressive implementation.
    With reference to Optimus 111 jets and cleaning needles, i have found that the cleaning wires are less than 0.3mm diameter:

    https://classiccampstoves.com/threads/27081

    As you have noted, the thickness of material which the aperture extends through is quite small, and there is a conical lead which quides the rising cleaning needle to the aperture.
    If the hypodermic implant extends too far into the jet it will prevent the centering action of cone on the rising needle.

    Just a thought.

    Best Regards,
    Kerophile.
     
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  8. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Good to know about the 111 needle size, thanks George.

    Good point about the possible snagging of the pricker on any projection of the insert into the pricker rack cavity. I've been avoiding having any needle insert stick out at the back of the jet in order not to leave the insert too long and restrict gas flow, but that gives added incentive not to do so with a 111 jet of course.

    That point I've made about in impact of length of insert on gas flow is something I want to test in practice by intentionally leaving an insert too long. Possibly it won't make a lot of difference?

    I'll probably overcome the issue of an insert in a 111 jet snagging the jet pricker wire by pushing in the insert from the thread end of the jet, using a jet pricker in the cavity to push it home in the vice.

    That way, I can put the chamfer on the other end of the needle and can ensure the 'inside' end is smoothly finished with no chamfer to snag.

    John
     
  9. Admin

    Admin Courtesy of Iani

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    Picture 1 : Internals of a 111B jet
    The top to the bottom of the orifice is 1.67mm approx

    It will be interesting to see how you do the 111 jets. The diamond cutter disc that you have been using will be too coarse. Perhaps using a very fine diamond polisher of some sort

    There is a source on the net selling 111B jets at the moment. They are not original parts, I have tried them on 111B's, 111 Paraffin roarer burners, Op 8R's, and Svea 123R's, just be cautious when trying to fit them, as they are a very tight fit - they are not suitable for the above stoves

    Picture 2 : A regular jet



    1425642814-IMG_7339_opt.jpg 1425642840-IMG_7340_opt.jpg
     
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  10. shagratork

    shagratork United Kingdom Moderator, R.I.P. Subscriber

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    Moved to the Fettlers Master Class where it belongs.
     
  11. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Thanks Trevor.

    Outstanding contribution that, Ian, thank you.

    Photos are great. Point taken (no pun intended) about the finish put on the insert to prevent snagging of the the cleaning jet.

    In it's favour, I've noticed that the stainless doesn't throw up burrs, though it does leave sharp edges of course and the inner edge of the jet rack side of the insert would benefit from honing.

    John
     
  12. Hazet

    Hazet Subscriber

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    I like this idea, thanks for the write up.
    I've found boxes of 100 25G x 1.5" (and 1") needles on ebay for less than $10 shipped, so that would be more than a lifetime's supply for me.
    I've also found the exact drill set pictured above on ebay for $8.10 w/free shipping.
    This seems to be a very cost effective repair! My 71 should be happy.
    Where can replacement jets be purchased so I can make/modify them (ebay seller name or link)?

    Also, as dogface mentioned in the lipstick repair thread, you can get precision tubing elsewhere.
    Look in the "Precision Miniature Stainless Steel Tubing" section here:
    http://www.mcmaster.com/#standard-stainless-steel-tubing/=w6y084
     
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  13. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    I looked at that McMaster source and it's micro-inches stock only. Conversion to metric of the sizes suggests an over/ and an under/- sized option approximating to 0.23mm, which is ok.

    Good stuff, but about eight-to-ten times the price of the needles and the plastic connector for a syringe that the needles are bonded to makes them easier to handle at the stage of pushing the needle part-way into the jet to grip it prior to cutting off a length to be inserted.

    John
     
  14. Trojandog

    Trojandog United Kingdom Subscriber

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    Hi John.

    Great post. One of the most useful on CCS. Even I might manage to do it! :lol:

    I notice from charts on the internet that the outer diameter of a 24G needle is .56 or .57mm (depending on which chart you use). I'd be interested to know if they will still work with a .45mm drill or whether the drill size will need to be increased.

    Regards,
    Terry
     
  15. loco7stove

    loco7stove Subscriber

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  16. Hazet

    Hazet Subscriber

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    John,
    I agree with the pricing difference you mention between needles and short lengths of tubing. I was just keeping that information linked for future reference in case of a "special needs" jet repair, or if a super cheap alternative (like a hypodermic needle) were not available for a specific size. The wiki link is good, but there are many other sizes of tubing available for custom applications or experimentation.

    I'd still like to know where to get new jets to do this modification to.
     
  17. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Of course, Hazet, regarding the tubing.

    I'm familiar with UK ebay sources for cheap 0.32mm jets but haven't explored USA ones.

    Having said that, THIS SUPPLIER ships worldwide and for the same price as the jets themselves for postage to USA I see (which sounds about right for a small, lightweight parcel). I should add, I've no commercial arrangement with that seller! I just happened to do an ebay search at random when you asked.

    Hi Terry! Stu's answered that point you raised about drill size for the 24-gauge needles.

    I was thinking 0.5mm was about right too.

    If the hole to press the needle into is too tight the needle, though hard metal and pretty resistant to bending like tubing is, will bend or snap off even so - I know because I tried pressing a 25-gauge insert into a jet drilled with a 0.4mm hole before I hit on 0.45mm as the right size.

    John
     
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  18. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    I've not yet taken delivery of the 24-gauge needles but this sorry specimen of a 111 jet was worthy of trying out the technique discussed to silbraze a needle insert in

    1425749458-61.JPG


    It came to me mangled like that when already in a stove, so I replaced it at the time.

    Not a lot of use putting a 25-guage needle insert in since there'd be no clearance for the pricker rack needle. It occurred to me that I happened to have a syringe I've used as an oiler and checking the needle installed in that I saw it was blue-coded, so a 22-gauge needle. Bore of the needle is oversized for the Optimus jet at 0.414mm, but it would serve as a prototype.

    Here I've drilled a pilot hole to take the needle, choosing a drill that made it a fit that I could push in by hand but that would stay in place when silbrazing

    1425749467-62.JPG


    I've trimmed the needle mount off here

    1425749479-63.JPG


    Stu's jet holder provided a useful anvil and using this dental pick ...

    1425749501-65.JPG


    I pushed the needle in so that the inner tip was flush with the base of the conical jet cavity

    1425749519-66.JPG

    1425749529-67.JPG


    There's no way a pricker rack needle would avoid snagging on that rough rim of the insert so I knew I'd have to do something about that when the insert was silbrazed in place and secure enough to work on

    1425749538-68.JPG


    I missed getting a photo of the jet/needle just after silbrazing but here I've trimmed the projecting bit of needle off. I also flowed more silbraze metal onto the jet than needed to secure the insert so that I could cut a couple of flats into the silbraze overflow to take a spanner

    1425749546-69.JPG

    1425749565-70.JPG

    1425749578-72.JPG

    1425749588-73.JPG


    I now needed to work on blending in the insert in the jet cavity to avoid the pricker rack needle snagging on it

    This abrasive tip for the Dremel proved handy ...

    1425749598-74.JPG


    ... blending in the insert with the conical surround. I used a pricker rack to test that there would be no snagging when installed in the stove

    1425749607-75.JPG


    Valve closed

    1425749617-76.JPG


    Cleaning needle raised, tip just visible

    1425749626-77.JPG


    Bearing in mind I'd used the 'wrong' needle gauge insert and the one installed has a bore of 0.414mm when 0.32mm would be right, it didn't produce a bad flame when throttled down.

    1425749634-78.JPG


    Opened up it got too rich. The flame pattern was even however and the jet pricker worked smoothly so I'd count the experiment as a success.

    John
     
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  19. loco7stove

    loco7stove Subscriber

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    Hi John

    Excellent job prepping that battered jet 8) :thumbup: , :-k so am i right in thinking a 23 gauge needle would work just fine :?:

    Stu :D :thumbup:
     
  20. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    23-gauge with 0.337mm bore as opposed to 24-gauge at 0.311mm?

    Optional I expect Stu, although I favour 24-gauge to rule out any prospect of running too rich.

    It'd be good to try both and see if there's any difference detectable on 111 paraffin, 111B gasoline and 8R/123R.

    I can see another ebay order on the way - my browser's started throwing up pop-up banners for medical supplies now!

    John