I’m trying to install couplers & coupler boxes on a metal HO scale flat car. I have small screws that go through the center of the draft box, coupler and lid that I’ve used on plastic cars. How do I go about doing this on a metal one?
Thanks
Dale8chevyss,
I have never tapped out a coupler box hole in Metal…I just used a 2-56 screw, fine and coarse threads to make it’s own threads in castings. If You make sure to keep it perpindicular to the hole when starting, Has always worked for me. Or get 2-56 self tapping screw’s, will work in metal or plastic. Experiment! I have even done it on 1-72 screws.
If You want to go the drill/ tap route: Screw Tap drill Clear drill
1-72 53 47
2-56 50 42
Take Care! [:D]
Frank
For tapping metal, it helps if you have sone cutting oil. Just a few drops is needed; dip the end of the drill or tap into the oil. It may seem counter-intuitve to add a lubruicant when you are trying to cut a hole or threads in metal, but it does help. If you can find a very small amount at the hardware store, or better still a couple of ounces if you know someone who works at a machine shop.
If I understand your question correctly, you want to freely pass a screw through the coupler box and have it thread into a metal portion of the flat car underbody. No matter what method you use to drill/tap the hole, I suggest you detach what you are drilling into from the flat car body itself because drilling from underneath will surely damage the deck of the car even if you don’t break through. For example, if you use a 2-56 screw and matching drill & tap, you must separate the body of the car because the typical tap has an angled tip to get it started in the hole to tap. Practically speaking, this means you will have to go through the other side to properly cut your threads. You can get bottom-out taps that do not have the tappered nose, but these are harder to get and also more of a pain to use. If you cannot separate the top of the car from the underframe to do the work, you will have to decide if you can live with visible holes from the top.
BTW, the suggestion of using cutting oil is a good one. I prefer to use bees wax as lubricant. I just twist the drill into a cake of wax (can usually get at any hardware store) for trouble-free drilling without the flying oil.
Excuse my wordy response, but thought I’d spell it out some since you have not done this kind of work before.
Joel
If these parts were supplied together in the form of a kit, more than likely the screws self-tap correctly into the designated holes.
Since that’s not the case here, follow the guidelines for tapping and clearance drills for the screw you use in each case.
Yes, with flatcars there’s not much solid to mount into, depending on how thick the casting is. If the screw will be too long, no matter what, I typically use a brass screw and cut it flush. Some paint and weathering will conceal things in most cases. The other problem is that if you plan to tap it to match the screw, then you need a blind tap to tap into a hole that doesn’t go through. Do they even make them this small? I don’t know. But going on through with the hole facilitates tapping with a regular tap and it’s tapered end.
Is this a very old model with a metal body? I can tell you that some metal cars of the 1950s (and perhaps later) do not take well to drilling and tapping - they are zinc alloy castings and the zinc has turned brittle with age. I have had unhappy experiences trying to drill into such metal. When it gets bad enough it just crumbles but before it gets to that stage it is still OK so long as it is left alone. I ended up using Walthers Goo as I recall to attach the Kadee boxes to those cars.
If it is a brass car, or a more modern metal casting, the small holes at either side of the regular Kadee coupler box are rather small drills and a bit tricky to tap. It might also be better to drill all the way through and plug the hole than try to stop the drlll from breaking through. I have had some luck tapping such metal but it is a bit of a trick.
Dave Nelson
Hey, are you sure you need to drill and tap? Isn’t there a sort of cylinder in the box? If there is, try the Walthers catalog, as Kadee used to have blackened, self-tapping screws, but of course, I’m out of touch: haven’t had a new catalog from them un years. If you just have to drill and tap, it’s a really good idea to remove the underframe and coupler box to avoid damaging the deck, as the man said, use cutting oil–or even 3 in 1, in a pinch–and tap carefully. If nobody’s mentioned it, once it’s caught, turn forward 1/4 turn, and back a half turn or more to clear the chips. Even if it’s soft metal–and it probably is–clogged tap threads can strip the threads or even break the tap.
Deano
Oh heck, I misread your original post, Rambo: Senior Moment (I sometimes have SENIOR WEEKS!). I got into tapping holes when I was still a teenager being mentored by my older brother, using drills and taps for 00-90, 0-80, 1-72 (a lot of people ignore this size, but it came in handy almost immediately when an 0-80 screw hole stripped; I re-tapped it 1-72 without missing a beat), and 2-56. When I went into O scale, a few years later, I added 4-40, which is the norm for truck kingpin screws. I later went back to HO–and then back to O scale when my eyesight could no longer handle HO. I now have tap drills, clear drills, taps and threading dies for 1-48 (rarely used–no screws or nuts, but useful for drawbar pins on the loco end: 3-32"!), 6-32, 8-32, and 10-32, which is within .004" of 3/16. (O scale is BIG!) With care, nobody has to be afraid of tapping; as a teenager, I drilled out a hole for a handrail post, drilled into it, and soldered brass wire handrail posts. I have since drilled, tapped and countersunk for flathead brass screws so I could solder something in place on Zamak castings (tender bed). I’m happy to see scratchbuilding and kit-bashing are still alive in The Hobby! Happy railroadin’! Deano
I’ve got a tap for 2-56, and the appropriate drill bits, too. My first suggestion is to get a punch so that you can start the hole where you want. If you start with a punch, the bit will stay in the hole, but if you just try to drill first the bit will likely wander a bit and the hole will not be centered properly.
If you do accidentally drill through, cut the screw short so that it’s flush with the top of the car. Then you can paint and weather it and it will be hardly noticeable. I use thin wood sheathing pieces on top of my wood-topped flat cars anyway. I think it gives a better look than trying to weather a metal or plastic flat car anyway.
The tap drill for a 2-56 tap is .070 in diameter for soft metals and plastics. Harder metals, steel, stainless steel, Iron, use a .073 diameter. Use a light lubricant, such as 3 in 1, Marvels Mystery oil. No need to use oil on plastic. Use a tap handle. A 2-56 is very brittle and prone to breaking; so, be very careful!
Turn the tap in and once you know it has started, turn in two full turns and back the tap out 1/2 turn to clear chips. Make a couple more full turns and back 1/2 turn, repeat until depth of threads desired is obtained.
Having been a tool and die maker I never paid attention to drill numbers as I found them confusing; so, I always stuck to the actual dimension desired.