Marking steel fittings.

Discussion in 'Workshop Tips and Secrets / Tools' started by Tench745, Mar 4, 2019.

  1. Mar 4, 2019 #1

    Tench745

    Tench745

    Tench745

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    I asked about this over on Facebook and on the EAA forums, but got very few responses. It seems to me this might be the place for opinions and experience.
    I have made up nearly all the fittings for the wings on my Corben Jr Ace (Baby Ace model E).

    I am looking specifically at ways of marking the spar fittings and strut fittings for painting. I was wondering about using a number stamp and lightly punching in a part number. I feel like I saw a picture of a homebuilt with numbers stamped in some part, but wondered about the risk of this causing stress-risers or something. Is this a viable option or no?

    Wiring stamped aluminum tags to the parts before painting was suggested and I will go that route if there are no better suggestions, but I would like to permanently mark the pieces if possible. The fittings SHOULD be interchangeable, but theory and practice don't always align.


    TLDR Summary:

    Can I safely stamp part numbers into my strut fittings? (1" wide .090 4130)
    Is there another/better way to identify parts through painting?
    How does everyone here mark their fittings from creation through installation?


    Thanks all!
     
  2. Mar 4, 2019 #2

    BBerson

    BBerson

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    Factories don't mark small parts but keep them in separate labeled parts bins.
     
  3. Mar 4, 2019 #3

    Pops

    Pops

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    Small cardboard tag wired through a bolt hole with small wire.
     
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  4. Mar 4, 2019 #4

    cvairwerks

    cvairwerks

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    At work, all of our castings, forgings and certain machined parts get marked by either stamping or vibro-engraving along with ink jetted part numbers. Beyond that, everything else gets either an ink jetted part number or hand printed number once it's been primed. It gets an updated set of numbers after finish paint.
     
  5. Mar 4, 2019 #5

    wsimpso1

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    Where you have several parts all made to the same drawing, you should clamp them together for drilling, hold them together with split pins while finishing their shapes, and otherwise make them the same. Where these parts have holes that mate up with other parts, they too should be drilled and shapes finished together when possible. This results in parts that will require a minimum of fuss to reassemble even if they do not stay sorted. That being said, some parts will just not be interchangeable and I have an ID scheme that seems to be working...

    On fiberglass parts, you can apply stick-on letters or arrows on the mold or the class B surface. These emboss the part gently to indicate position, type, orientations, etc. On a class B surface. If you put the Class A surface, it will get filled and faired over before paint, so you might need tags... Usually, my Class A surfaces get closely fitted and so it is easy to find its mating part after paint.

    On metal parts, if I have left and right versions of each but they are otherwise distinguishable from other parts, I will put a small tack weld or punch mark on the ones for the right hand side.

    If I have more than two, I will number them with small weld dots or punch marks. If I have two or more sets of parts but the parts are otherwise distinguishable, I will number each set together. For instance I have four rudder pedals, brake pedals, and hinge pin/locks. They very definitely are not interchangeable. One dot on one set, two dots on the second set, etc.

    For large enough parts I use number stamps or engraver to ID FS or BL of where they go and a dot to indicate left side or right side. When you are doing this, it helps to know where the stresses are low, and put the ID there.

    If the parts are small or highly stressed or you can not tell where the stresses might be high - if you are building someone else's design you will not know - then you gotta go with part tags on most.

    I hope that this helps.

    Billski
     
  6. Mar 4, 2019 #6

    Tench745

    Tench745

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    Thank you, that was a particularly experience-filled response. I did clamp and work my fittings together, so theoretically they are identical. Still, I chose a specific fitting for each location to match-drill holes in my spars, so the port spar attach holes are drilled to match the two straps I chose for that location. Would the starboard straps work on the port side? maybe, but I know the one set will definitely fit, hence intent of the question.
    Wired tags seem easy enough. I will likely re-label once they have paint anyway.

    Thank you all for your responses. More are always welcome.
     
  7. Mar 5, 2019 #7

    akwrencher

    akwrencher

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    What about a label maker? They are only about 20 to 30 bucks. Useful for all sorts of things.
     
  8. Mar 5, 2019 #8

    Victor Bravo

    Victor Bravo

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    They're asking about keeping the parts identified during the time between bare steel and primer. Once the primer is on you can mark them with labels, but to be honest it is awfully difficult to keep a label on a bare steel part and still get the primer onto the steel under the label :)

    One potential idea is to use wooden dowels that are a snug fit in the diameter of the bolt hole. You can mark and tag the dowel and put the part through the priming process. Once you have it all primed, mark thep art itself (on the dry primer) and then you can go back and apply primer inside the hole with a small brush. The other end of the dowels can be stuck into a block of foam, or a piece of wood with holes in it, so the parts are held up in the air for spraying.
     
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  9. Mar 5, 2019 #9

    gtae07

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    Depending on the primer you use, you can mark with a sharpie and still see the sharpie (faintly) after priming. Then re-trace.

    That’s what I do with all my aluminum parts, anyway.
     
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  10. Mar 5, 2019 #10

    wsimpso1

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    This works for internal parts. DO NOT DO THIS with CLASS A surfaces - many permanent inks will walk up through some primers and paints and become visible on the outside. Ink in places that you do not want to see later should be removed from raw parts with solvent before any primer or paint hits it. Maybe someone will be able to tell us which combinations WILL NOT print permanent marker ink through...

    Billski
     
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  11. Mar 5, 2019 #11

    Pops

    Pops

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    What's so hard about wiring a small cardboard tag to a bolt or rivet hole on the part . If that is to hard, maybe building an airplane is not for you.
     
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  12. Mar 5, 2019 #12

    Little Scrapper

    Little Scrapper

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    The question was answered on the Facebook group. You need to consider you're overthinking this because that's also an option. This airplane has been successfully built since the 1920's.
     
  13. Mar 5, 2019 #13

    Victor Bravo

    Victor Bravo

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    Occam's Razor, aviation style :)
     
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