Small Dia Threaded Rod – Pt 2

I was curious as to the actual size of a 1:48 scale 1-1/4″ Acme threaded valve stem .. 5 tpi .. would be. In the drawing the major diameter of 1-1/4″ is reduced to 0.026″/0.661mm. The various dimensions are shown .. all of which are below the minimum detail that FUD can be printed at. The red square shows that minimum size .. 0.1mm

Im not necessairly saying that I have to print in FUD .. but that was the first thing that came to mind.

Using that minimum 0.1mm for FUD I drew out the best that I could possibly hope for if I printed this in FUD. The therads per inch end up around 2.5 .. twice as coarse as the scale version but I think would look fine if the printing was possible.
Is this possible? Not sure but I kind of doubt it .. at least for printing in FUD. The minor diameter of 0.461mm is below the 0.6mm minimum for a ‘wire’ when printing FUD. It *might* slide by .. but would be ‘iffy’.

What I was looking for was some basic dimensions that I could work toward. I would like to go another route and create some rollers with the thread on them. I could possibly use them to roll the threads onto a length of small dia solder. Not too crazy .. that’s how bolts and screws are mass-produced .. the threads are rolled into a metal rod with dies. The problem is .. what to use. The example above is using FUD .. but that is too soft, brittle, weak to act as a die .. even for solder (at least, I believe so). There is Stainless Steel at Shapeways but the minimum detail is way too big for this – 1.0mm .. ten times that of fud.

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About etraxx

Retired from the Army in 2006. Served during Vietnam - 1969-1972 as as 72B - Communications Center Specialist (Teletype Operator). Got out .. and went back in 1987 as a 19K - Armor Vehicle Crewman - (M1/M1A1 tanker) getting out in Korea in 1999. Went into the Reserves .. got mobilized in 2001 .. stayed active until my retirement with 20 years in 2006.


Small Dia Threaded Rod – Pt 2 — 3 Comments

  1. Ed,

    As with most of your posts, I’ve been following along on the “Small Dia Threaded Rod” — so far, all BOTH of them! 😀

    I got a few questions and comments I’d like to throw out there…

    $50 a foot for small threaded rod is pricey — but how much rod would you use for the valves? As in, you’d have LOTS left over for other projects. Or maybe you could cut the rod into inch-long lengths and sell it to other modelers for $5 an inch… just a thought.

    Regarding using files to cut “threads” in a piece of solder — is there a possibility that jewelers’ files could be used? They wouldn’t cut very deep, but should have a lot more teeth per inch.

    What is FUD an acronym for? (Yes, I’m too lazy to look it up right now…) 😉

    And I know that a “true” scale rod would be very difficult to achieve. Would you be able to get something small enough to represent the rod you’re trying to show, look decent, but not be exactly in scale? Maybe one of those small threaded rods with half the threads per inch — at half the cost? Just thinkin’ out loud here…

    Anyway — I enjoy your projects and posts — keep up the good work!

    Tom Stockton

    • Tom,
      Appreciate the follow. I kinda tossed the thread out for responses. The thing is .. it’s not so much the price (it IS but not everything) as it is that .. I just need to simulate thread. I was thinking that possibly .. I could wind some small dia copper wire .. say .004″ around a .015″ rod. It would probably look very much like a threaded rod unless you look closely at it with that terrible lens of a camera. I have one of those battery operated screw-drivers that I modified with a chuck. If I could figure a way to secure both ends of the wire like a second chuck .. I could probably wind a wire around it. Something worth looking at.

      Sorry. FUD is Frosted Ultra Detail. That’s the highest resolution material that Shapeways will print a 3d object it. It will give a minim detail of .1mm

  2. I came back to this thread today after someone viewed it – to be honest I had forgotten about it.

    Thread rolling machines make most bolts, rods and such. It is actually stronger then cutting threads since the rolling process is really forging the threads

    That got me to thinking that the answer might be simply to roll the threads on this little shaft. It doesn’t even have to have a pitch .. the thing being so small. Three disks grooved for the threads could roll a piece of plastic rod easily enough. If these disks had actual threads cut into them you could thread the rod .. if you could figure out how to align everything so they would fit into the threaded rod correctly.

    As small as this rod would be though .. again simply impressing the length with a simulated thread would work. You could fix two of the dies in place so they acted like a saddle where the rod would rest .. and then have a third on a movable shaft to press into the rod and force the threads into it. You could probably get away with gearing just one shaft.

    Have to think about this .. might be fun to do.

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