Coupler mounting advice

[bigdawgks]

Hello. Usually the task of body mounting a Micro Trains coupler is easy - drill a #62 hole and tap for 00-90 screws. However, I have encountered a pair of cars that have proved problematic. It seems they have hard metal weights installed right on top of the floor where the coupler mounting holes need to go and these have proved too hard to cut through with my pin vise. There's no use trying to get my tap through without clearance so I need to figure out a different way (preferably nothing permanent like glue) to mount them. I'm looking for any tips on what to do. For example, is it possible to find self-tapping screws that will fit through a coupler box and are short enough to only thread into the plastic floor?

And if you say why not remove the weights, well - the car body is sealed shut with them inside. I don't see a way to remove them without risking damage to the car.

[peteski]

Yes, drilling thought a steel plate using a pin vise is not something I would attempt either. Any chance you could find a friend with small drill press to drill the hole through the plastic and the metal weight?

A brass 00-90 screw will create its own threads (tap) into styrene.  But if the plastic is fairly thin, this setup might not have a lot of strength. You can also trim those brass screws to any length. I do that quite often.  The problem is that trimming the screw distorts the thread.  See https://www.therailwire.net/forum/index.php?topic=41502.0 . You can also take small 1/16" or 1/32" thick brass plate, drill and tap a hole in it and use that instead of the nut used in the above thread.  it is easier to hold the plate than just a screw with a nut while trimming it.

[nkalanaga]

If you need a shim to get the right height, it's easy.  Screw the coupler to the shim, glue the shim to the car.

If it was me, I'd probably try drilling through the plate with some type of power drill.  Even if you need to drill a larger hole, and fill it with a plastic rod, that might be easier than trying to glue to a MT coupler.

[bigdawgks]

I had tried using a power drill but it was not successful. The setup was not rigid enough and the drill was still barely cutting into the metal. I had to stop because the wobble was starting to enlarge the hole too much. Definitely seems like a drill press with proper metal cutting bit would be needed to cleanly punch through.

I do have some short brass 00-90 screws, I can try getting them to self-tap into the plastic but yea my concern is whether there's enough material.

[Narlie]

I had tried using a power drill but it was not successful. The setup was not rigid enough and the drill was still barely cutting into the metal. I had to stop because the wobble was starting to enlarge the hole too much. Definitely seems like a drill press with proper metal cutting bit would be needed to cleanly punch through.

I do have some short brass 00-90 screws, I can try getting them to self-tap into the plastic but yea my concern is whether there's enough material.

Did you succeed with mounting these couplers? Have not tried it myself but would an adhesive solution such as epoxy work?

[bigdawgks]

I have shelved the effort for now. I haven't yet decided on how to move forward. It's my intention to avoid gluing the coupler boxes by all means, but I'm thinking now about cutting out the underbody above the box and gluing in a replacement piece with pre-tapped hole for mounting screws. That has its own challenges but these cars are a bit low on my list of priorities so I'm not yet ready to commit a lot of attention to them.

[jagged ben]

What models are these?  Are you talking about a metal floor or a plastic floor with a metal weight above?   If the first one, I find it pretty easy to drill through metal with a jewelers twist drill.  Or, perhaps a Dremel, especially in a drill press setup.   Might work for the weight inside too.

Curious what model is sealed up so you can't open it.

[bigdawgks]

These are Red Caboose X29 boxcars. Like intermountain AAR cars, the floor appears to be molded together with the body as one piece. The only access inside must be from the roof, but it looks pretty well glued on. I don't really want to attempt prying them off because it could risk visible damage. I've drilled through the floor no problem, but that's where I encountered a metal plate all along it on the inside. I tried drilling through these too but after a while I didn't see any chips coming out and it wasn't getting any deeper. It's possible I dulled my bits attempting to punch through it, but I've no idea how close I was as I cannot identify how thick the plate is.

[nkalanaga]

Cutting a chunk out of the floor should work.  I've installed a lot of couplers on old MDC boxcars by screwing the coupler to a piece of styrene, then gluing that to the metal floor.  Those need a shim anyway, so it had to be done.  Your idea is basically the same thing, with a little extra cutting.

[Maletrain]

If you haven't give up on drilling through the floor metal weight, I suggest that you buy the appropriate sized cobalt steel bit.  Note that "Kobalt" is a brand name that does NOT guarantee the bit is made of cobalt steel.  The real cobalt steel bits will retain their sharpness much better when drilling metals that are not "soft", such as mild steel.

But, cutting a chunk out of the underlying plastic can work too.  The best method for YOU really depends on what tools you already have.  With a drill press and a good bit, I have no problems drilling through metal weights.