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USA 4-40 thread.


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Can any body tell me what thread the Dubro 4-40 threaded items correspond to please? I want to use the Dubro n/o 302 4-40 steel rod ends, what thread type  can I use. Is there a similar that can be engaged, aim is not to keep ondoing it so a close type  that might even be helped with thread ock or glue,is there asimple answer, I doubt it.

Thanks in advance.

Bas

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I would reckon, if you buy a 4-40 die, you could cut a 4-40 thread onto 3 mm rod, as long as the steel is not too hard.

Or, you might get away with just cutting a 4-40 thread, straight onto a 3mm thread. But a caveat here, test the result is fit for purpose

 

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If the rod is even slightly undersize then the clevis etc might slip under load.

Note that threaded rods supplied for RC are usually rolled threads which means the rod is undersize and the threading action increases the actual size.  So you probably cannot cut a thread on the other end etc.

Tracy Tools are a good place to buy taps and dies  - a 4-40 die is 3 pounds

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Or possibly some epoxy. Then, if they need shifting, a warming from a gas flame will undo.

The problem with mixed threads, how much do you trust them.
I have a memory, BA pilot, windscreen blew out, plane landed, and a female crew member was holding him in by ankles. Mixed metric and imperial threads. 

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35 minutes ago, Don Fry said:

......

I have a memory, BA pilot, windscreen blew out, plane landed, and a female crew member was holding him in by ankles. Mixed metric and imperial threads. 

It was actually a male crew member who grabbed his legs.

Story with photo of all involved at the pilot's bedside afterwards HERE.

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Wherever possible I take US threaded components and throw them as hard as possible into the dustbin and replace them with metric.  I have one Great Planes ARTF Super Stearman which has some US threaded components built into the wings for the interplane struts and I'm forced to use US components but otherwise, see my first sentence.  The chances of apparently correctly fitting threads failing is too great.

 

Geoff

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41 minutes ago, Gary Manuel said:

It was actually a male crew member who grabbed his legs.

Story with photo of all involved at the pilot's bedside afterwards HERE.

Gary, you are right. I am a born romantic, and remembered lusts cloud memories. 
Still involves idiots confusing metric and American threads.

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40 minutes ago, Geoff S said:

Wherever possible I take US threaded components and throw them as hard as possible into the dustbin and replace them with metric.  I have one Great Planes ARTF Super Stearman which has some US threaded components built into the wings for the interplane struts and I'm forced to use US components but otherwise, see my first sentence.  The chances of apparently correctly fitting threads failing is too great.

 

Geoff

I go with Geoff on that, I try to ensure all my rods, quick links, nuts & bolts are Metric although I have bought second hand models with 'merican sized fixings its always a pain when something has to be taken apart or repaired. I picked up a 1/3 scale Bucker Jungmeister about 8/9 years ago and it had BA fittings throughout. Fortunately it came with a beautifully made set of box spanners covering 6BA to 0BA plus a couple of open ended spanners as well.

I still have the spanners but a sold the model on a while ago.

Edited by FlyinBrian
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1 minute ago, FlyinBrian said:

I go with Geoff on that, I try to ensure all my rods, quick links, nuts & bolts are Metric although I have bought second hand models with 'merican sized fixings its alsways a pin when something has to be taken apart or repaired. I picked up a 1/3 scale Bucker Jungmeister about 8/9 years ago and it had BA fittings throughout. Fortunately it came with a beautifully made set of box spanners covering 6BA to 0BA plus a couple of open ended spanners as well. I still have the spanners but a sold the model on a while ago.

 

I admit in my early days, coming from an electrical background, I used a lot of BA threaded nut and bolts - mostly 2, 4 and 6.  But, IIRC BA is actually a metric thread.  BA was used a lot for clocks and watches.  My grandfather's watchmaking bench had containers of BA bolts as tiny as 20BA (and perhaps smaller).  I remember seeing him working as a child (we all lived at the shop) when he must have been well into his 80s during the war when I was 4 or 5 years old.

I have lots of BA spanners still.

 

Geoff

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Geoff, I could not contest what you say, I recall 6 (a bit tight) and 8 BA being used to bolt my Mills .75 and DC Merlin engines into planes back in the 60s then everything seemed to go metric almost overnight. Maybe due to the preponderance of German kits and German & Japanese engines on the market at the time.

 

BTW Model Fixings has almost any thread type of nuts and bolts from about 1mm dia upwards which is handy if you get stuck.

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Have you tried using Google?

Plenty of 4-40 threaded rods around, and not expensive at all!

 

Mixing threads in flying machine is a great no-no for most people - there is enough risk without that...

Personally, I prefer the American 4-40 and 2-56 fasteners simply for the quality. There is plenty around the model shops.

 

Steve.

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13 hours ago, Geoff S said:

Wherever possible I take US threaded components and throw them as hard as possible into the dustbin and replace them with metric.  I have one Great Planes ARTF Super Stearman which has some US threaded components built into the wings for the interplane struts and I'm forced to use US components but otherwise, see my first sentence.  The chances of apparently correctly fitting threads failing is too great.

 

Geoff

I find the hassle of changing out US threaded components for metric more of a hassle than living with them, particularly as some of the US stuff (e.g. Dubro) is of good quality. It's easy enough to check the fits. Threads that are too small are obviously too sloppy often to the point that clevises can be pulled off, whereas ones that are incompatible, and tight, jam up to the point of crossing the threads.

 

I keep drawers of metric and US threads, but only check threads with a new model, or when I am transferring gear from crashed models. 

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