Author Topic: Athearn Truck Screws  (Read 383 times)

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ljudice

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Athearn Truck Screws
« on: April 13, 2019, 11:46:12 PM »
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Anyone know the size of Athearn truck screws that could be used in a hardware store?

I need a bunch and they want an astronomical sum + $10 shipping for them at Athearn...

thx

Maletrain

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Re: Athearn Truck Screws
« Reply #1 on: April 14, 2019, 12:03:17 PM »
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Looking at one of mine (from a 3-bay hopper) under a 10x loupe, those do not seem to be machine screws.  Their threads look more like sheet metal screws, having raised threads, with space between them, on a round shaft rather than V-shaped threads cut into a shaft. Not surprising, since they are intended to be screwed into a hole drilled in plastic without tapping that hole, first.

The threads on mine measure 0.069" outside diameter, which fits into a #1 machine screw clearance hole, but the thread pitch is more like 48 tpi, which is much coarser than a 1-64 or 1-72 machine screw.  Looking at charts for screw sizes, I found that #0 = 0.060" and #1 =  0.073", so the Athearn screws might be metric versions, rather than British. That 0.069" is about 1.75 mm, so I looked here https://www.metricscrews.us/index.php?main_page=index&cPath=342_347&zenid=l2d3pumo1ikl0ngthh3sloq6f6  for metric "M1.7 tapping screws".  Some of those threads look really similar, but none of the screws in that site have the same head type as the Athearn screws.  (I don't remember the name for a screw head that has a washer-like ring included in the head, but a truss head would probably work just as well.)

I don't know what they are, but at least I have told you some things that they are not. 

I also would be interested in anybody can find the proper specs for these screws.  I seriously doubt that Athearn has had special screws made for them to use only in N scale models, so there must be a bulk source for them, somewhere.  But, I doubt you are going to find them in an average hardware store.
« Last Edit: April 14, 2019, 12:15:40 PM by Maletrain »

Mark5

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Re: Athearn Truck Screws
« Reply #2 on: April 14, 2019, 12:20:14 PM »
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mmagliaro

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Re: Athearn Truck Screws
« Reply #3 on: April 14, 2019, 11:30:16 PM »
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How many is "a bunch"?  If you have to tap 100 holes, I guess I could see hunting around for a match on the original screw.
Otherwise, do you have a 1-72 tap?   I would be inclined to just tap the hole with a 1-72 machine thread so you can use an easy-to-find screw size.    I don't know how many times over the years I have just retapped a truck screw hole to be a standard size I already had, rather than try to match what was there.

Maletrain

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Re: Athearn Truck Screws
« Reply #4 on: April 15, 2019, 12:20:49 PM »
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Looking at the treads of the Athearn sheet metal screws, I suspect they would hold better than a tapped hole with a machine screw.  The threads are just bigger.  As long as you are careful to put the screws back into the same threads as they originally cut into the sides of the hole, they should last a long time.  (You do that by inserting the screw into the hole and gently twisting it counterclockwise until you feel the threads drop slightly into place, then turning the screw clockwise to tighten it.)  You also need to be careful how you reinstall machine screw in plastic, because these small size screws have very small thread depths, so it is easy to bugger the hole if you just start twisting them.

One thing I have done is to drill-out a bugger hole in a plastic bolster and fill it with JB Weld, which is a lot harder than styrene plastic, but can be tapped.  Just be sure to drill the new hole perpendicular to the desired horizontal surface and tap it straight, or you could end-up with a car that tilts to one side when placed on the track.  A drill press helps for drilling the hole and holding the tap handle.

ljudice

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Re: Athearn Truck Screws
« Reply #5 on: April 15, 2019, 12:37:00 PM »
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I really appreciate all the ideas here!   

I'm beginning to wonder if I  should invest more time finding the 20 screws I lost - or just pay Athearn!

This is for a bunch of Coalporters, which I have already spent a load of time on the coupler shank length / ride height issues...

Doug G.

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Re: Athearn Truck Screws
« Reply #6 on: April 15, 2019, 12:37:27 PM »
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If they are going into plastic, they would not be a machine screw requiring a tapped hole. They make their own threads.

Doug
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