Trepanning NRV washers.

Discussion in 'Fettlers Master Class' started by kerophile, Jun 16, 2008.

  1. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    12,223
    Location:
    Far North of Scotland
    One problem when using a punch to produce NRV washers is that the product can have a "dumbell" shape (having a waist, with the centre of the washer being of smaller diameter than the faces). This occurs because the punch compresses the nitrile rubber sheet before it starts cutting. Once cut, the rubber springs back and the characterisitic dumbell shape is the result.

    You can buy Nitrile cord of the correct diameter, but I had already come up with another fix:

    One of my favourite pens of all time is this ball-point pen made in Japan by Zebra Pens:


    DSCN0124_edited-4.jpg

    The refills for this pen come in packs of two, and also contain replacement springs:

    DSCN0125_edited-6.jpg

    When you get the old refill out, it seems a pity to throw it away:

    DSCN0126_edited-4.jpg

    The thin steel tube containing the plastic ink cartridge is about 5.3mm outer diameter and approx. 5mm internal diameter. It is easily extracted. The spring, suitably shortened can repair a NRV if you are stuck.

    You now sharpen the cutting edge of the thin-walled tube, using a file and abrasive paper, whilst the tube is rotating in the drill:

    DSCN0128_edited-4.jpg

    This thin-walled steel tubing with a sharpened end makes a trepanning tool. I put this tube in an electric drill, moisten the cutting edge with some WD 40 fluid, and can cut new NRVwashers

    DSCN0129_edited-4.jpg

    You are now ready to cut NRV washers, rather than punch them in the traditional way This is just for example, I generally use 3 mm thick nitrle sheet for making NRV washers.:

    DSCN0132_edited-3.jpg

    DSCN0170_edited.jpg

    Necessity is the Mother of Invention they say.

    Best Regards,
    Kerophile
     
  2. Henry

    Offline
    Joined:
    Aug 17, 2004
    Messages:
    2,941
    brilliant :D
     
  3. jlgatton

    Offline
    Joined:
    Mar 2, 2008
    Messages:
    103
    Excellent :D :D :D

    I just so happens the Zebra is the pen I carry so I always have used refills with springs, it just never occurred to me.

    Way to go,

    Jerry
     
  4. shagratork

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

    Offline
    Joined:
    Aug 9, 2005
    Messages:
    9,641
    Location:
    Durham, N.E. England
    Another example of great lateral thinking, George! :D
     
  5. Spiritburner

    Spiritburner Admin SotM Winner Subscriber

    Offline
    Joined:
    Jul 23, 2004
    Messages:
    10,647
    Location:
    N.E. England
    I've just bought a few meters of the nitrile cord (still waiting for it) so should be alright for many a year of nrv washer supply. However I will look at things with a more lateral view in future - I'm sure there are other items that could be called upon to make other washers. I just got a bench drill at the car-boot so I'm keen to start using it for odd jobs - the more stove related the better!
     
  6. hobowonkanobe

    Offline
    Joined:
    Aug 18, 2004
    Messages:
    1,835
    Had your coffee and cherios, yeah? Wow! That is briliant.
     
  7. spudz

    Offline
    Joined:
    Aug 31, 2005
    Messages:
    2,578
    :D :D :D :D :D :D :D :D

    Hat's off !

    =D> =D> =D> =D> =D> =D> =D> =D>
     
  8. parramethtrol

    parramethtrol Subscriber

    Offline
    Joined:
    Apr 18, 2008
    Messages:
    2,727
    nice one kerophile another one to remember,all i have to do now is find one of those pens,the kids will soon use up the ink for me
     
  9. sefaudi

    Offline
    Joined:
    Oct 19, 2004
    Messages:
    620
    Hey George, you showed another invention.

    I remember previously somebody else also suggested to connect hollow punch to a drill.

    Could there be additional usage if we keep nitrile material a little into deep freezer before cutting it?
     
  10. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    12,223
    Location:
    Far North of Scotland
    Hi Sefa, If my memory is working properly; I believe that most rubbers have the peculiar property of stretching more when they get cold.
    It is counter-intuitive , but is linked to the degree of cross-linking between the polymer chains, and its temperature dependence.

    Here is the Link:
    http://www.physlink.com/Education/AskExperts/ae573.cfm

    Best Regards,
    George.
     
    Last edited by a moderator: Jul 1, 2015
  11. David Shouksmith

    David Shouksmith Subscriber

    Offline
    Joined:
    Jul 28, 2004
    Messages:
    6,925
    Interesting answer from that website, George, but I must take the author to task on one small point:-

    I was teaching entropy in Biology in 1972 and I suspect it had been on the syllabus for a good number of years prior to that. Anyway, I got me a set of those drill 'punches' linked-to above which will save me faffing about with ball-pen refills. Great idea, though!
     
    Last edited by a moderator: Jul 1, 2015
  12. fyldefox

    fyldefox R.I.P.

    Offline
    Joined:
    May 30, 2005
    Messages:
    3,103
    This is a great piece of lateral thinking George, although I do find that hand operated leather punches also do a fine job for NRV rubbers.
     
  13. Doc Mark

    Doc Mark Subscriber

    Offline
    Joined:
    Dec 12, 2004
    Messages:
    17,738
    Hey, Kerophile,

    Very nice bit of "McGuyverism" (sp?)!! I'd like to make one of those ball point pen punches, "just because", but like a few others, have had very good luck punching out my NRV gaskets with a plain-jane set of punches from Harbor Freight. I very probably won't change what's been working so well, but it would be fun to mess with Kerophile's Patented Pen Punch, when time presents!! :D :D Very nice, George!! Take care, and God Bless!

    Every Good Wish,
    Doc
     
  14. oops56

    Offline
    Joined:
    Oct 23, 2005
    Messages:
    1,824
    Yep i just got 4 refills now how do i get the ink out oh man i can see a mess coming up.
     
  15. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    12,223
    Location:
    Far North of Scotland
    Hi Robert. The beauty of the Zebra refills I recommended is that the ink never touches the steel tubing. The plastic tubing holds the ink.

    Of course if you use the pen until the ink is all used up...there wouldn't be a problem even if the ink was held in the steel tube ....Doh.

    Best Regards,
    George.
     
  16. Spiritburner

    Spiritburner Admin SotM Winner Subscriber

    Offline
    Joined:
    Jul 23, 2004
    Messages:
    10,647
    Location:
    N.E. England
    Thanks for the link - if they'd gone up to 3/4" I may have gone for them. Anyway, as a result of George's idea & seeing the drill punches I had a go at something similar. I have a small punch set with a small handle (mandrel?) & various screw in punches. I found a punch perfect for the nrv, screwed it to the tool & clamped it in the chuck of the bench drill. It wasn't too good at first so I sharpened it & then ran a load off in no time.
     
    Last edited by a moderator: Jul 1, 2015
  17. parramethtrol

    parramethtrol Subscriber

    Offline
    Joined:
    Apr 18, 2008
    Messages:
    2,727
    nice one Ross
    any chance you could tell me the size punch's that are used on fuel cap gaskets (opti ) and also the inner safety valve washer as i have just bought a set of Maun punches but i'm unsure if it contains all the sizes i'm likely to need the set i have got contains these
    5,6,8,10,12.5,16,20,25 and 32mm
    143443752_o-640.jpg

    i think i'm going to need a 19mm or 3/4" for the lid i have another set in my sights but there will be a bit of duplication on some sizes

    both sets have got the centring pin so i should be able to punch fairly accurate washers,i would have liked the set with the ability to cut washers in one pop but they are really expensive (70 quid)

    i now have these size cutters
    5mm 6mm 8mm 10mm 11mm 12.5mm 13mm 16mm 19mm 20mm 22mm 25mm 28mm 32mm 35mm
    will this cover everything ?

    this the other set i have bought


    5MM 6MM 8MM 10MM 11MM 13MM 16MM 19MM 22MM 25MM 28MM 32MM 35MM
    �28 including delivery
    punch.jpg
     
    Last edited by a moderator: Jul 1, 2015
  18. bolexguy

    bolexguy Subscriber

    Offline
    Joined:
    Oct 17, 2008
    Messages:
    397
    sometimes i'm amazed at how simple the things around in everyday settings are just raw materials waiting to happen

    excellent thanks !
     
  19. HappyCamper

    Offline
    Joined:
    Apr 29, 2010
    Messages:
    1
    Thank you very much for posting this information. As a result I was able to make my own NRV tool and Washer. I have two Optimus 111T (I believe) and now one is operational thanks to the great information here.

    I used bicycle inner tube to make my washer. Is this going to last. The inner tube is from a bicycle that is less than 5 years old and seems to be of a different materiel than old school inner tubes. So far no blow by thru the NRV. I ended up inverting the NRV spring and pip and inserting my newly made washer. This works so far. This has eliminated the pip hanging up in the hole on the side of the NRV Cylinder. I managed to repair one stove but severely damaged the NRV on the other so I am looking for parts if anybody can help.

    Thanks again.
     
  20. BernieDawg Banned

    Offline
    Joined:
    Feb 23, 2008
    Messages:
    1,656
    Try this eBay link for a fellow who is selling used NRV's at the mo.
    Link

    When the link above expires, try searching for "davedja", the seller, at eBay.

    Best,
    Gary
     
    Last edited by a moderator: Jul 1, 2015