Roundhouse Machine Screw Hole Help
#1
Im hoping someone can help me out here, i just got 14 Roundhouse 5-bay Rapid Discharge Hoppers lettered for CSDU and CSDPU, and they all have metal weight frames that "lock" into the under body of the cars. This is where the holes are drilled out on both sides for mounting the trucks and the coupler covers on, only there not nearly deep enough and i can only get the screw to turn like once around in the holes before they stop dead and will not turn anymore.

The screws they come with are not very long to begin with, 5mm long flatheads. Should i get new screws for each of these? How can i fix this problem? Am i going to have to drill out each of these holes? If so, whats the best way to do this? Tap and dye? What size whole should i drill them out to if i have to do this? Again its a metal frame these wholes are in, so if i have to re-drill/extend the holes, i would have to have to go through metal.....

Any help is appreciated, and thanks in advance.
Josh Mader

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#2
Josh....When I've run into this situation I use a 2-56 tap and screw to do the job (mostly because that's what I have...left over from my R/C days...). The 2-56 is a mite small, but since I use a little silicone washer to center and "cushion" the trucks, it works OK.
Gus (LC&P).
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#3
I will agree with Gus - a 2-56 is my "standard" modeling screw. If you can possibly drill and tap the hole for a 2-56, go that route. Ace hardware sells 2-56 screws, but the tap you would likely have to go to a hobby shop for. "classic" (pre atherarn) MDC used 2-56 screws for many things - so it is possible you would not even need to tap the hole.

But I am confused as to your description of the problem. Any way you can post a picture? Make sure the parts are actually fitting tight and not binding anywhere and that you are not cross threading the screw.
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#4
Thanks guys, i think this is most likely what ill be doing, is doing 2-56 screws. Im not sure if thats what these screws i have is or not though, how do you know?

Here is a pic of what im talking about, as you can see, this is as far as the screw will go into the whole for the coupler mounting hatch, and its the same for the truck mounting hole as well. I was only able to turn it at the most one full rotation in the hole before it would not turn anymore, even with force.....

[Image: SL373059.jpg]

[Image: SL373060.jpg]
Josh Mader

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#5
On second look, it appears the screw is crooked in the coupler mounting whole, i took it out and straightened it out, but it still does not turn any further then it did before, and the truck mounting hole will will not go in straight at all, it wants to sit in there crooked Curse grrrrr i seem to have problems with every single rounhouse kit ive ever built, yet i still keep buying more of them :oops:
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#6
Josh - I see now. That is actually some kind of sheet metal screw that taps its own way into the pot metal frame. These were common in roundhouse kits. Some times they take a bit of force to tighten them all the way down. You have a few choices:

1) continue tightening and hope that you don't strip out the screw or crack the frame.
2) drill the hole all the way through the frame to a slightly larger size. The screw will be easier to put in, and less likely to mushroom the frame or strip out the slot on the screw. The drawback is if you enlarge the hole too much, the screw may not stay tight.
3) Buy a 2-56 tap and the appropriate drills, drill and tap a new hole, and put the coupler box on with a 2-56 screw.

I would go with #3 personally, as i already have a tap and a source of screws. I have several roundhouse kits that I did this to - especially locomotives that need to be disassembled on occasion. The 2-56 is simply easier and more reliable for repeated disassembly.
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#7
It looks from the picture that you may be using the screw intended for the trucks on the coupler pocket instead. Most of the "classic" MDC kits I have picked up have two or even three different sizes of screws, and there's almost always an odd number too...! Eek

Anyway, since all screws of this type are small, and their lengths may differ only slightly, you might need to experiment a bit.

If that does not work, generally the metal underbodies can be drilled (slowly and carefully) with multipurpose bits. Since the screw has a chunky enough thread to be more or less self threading in the soft metal, you do not need to tap.

Good luck!

Andrew
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#8
Kevin is correct: those screws are self-tapping type, which work fine, but not if the hole is too shallow. You could deepen the hole by using a drill bit that will fit in the existing hole, or drill it out (and deeper) using a #50 bit, then tap with a 2-56 tap. Lubricate the tap and/or back it out frequently as you work, to clear the chips and keep the tap from seizing in the hole and breaking.

Wayne
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#9
Kevin, Andrew, and Wayne, i cant thank you guys enough for the help!!

I went to the LHS today and picked up a 2-56 Tap and a packet of 2-56 x 1/4" and 1/8" screws. There were only 5 in each package and they were $2.99 per package, so i only got one of each just to try them out and see how they worked lol The dang Tap was $7.49 and the screws were $2.99 a package Curse lol

I called my grandpa when i was at the LHS and asked him if he had something i could use the Tap with to turn it, of coarse he did so i did not need to buy anything else but the tap and the couple screws. I ended up putting the tap in his pin vise, he has a nice one that i wanna get lol (hes a jeweler and owns his own jewelery shop so he has everything lol). I also got a #50 drill bit (one of them was $1.39 which is ridiculous considering i got a pack of 10 for $1.99, i just didnt have #50's Curse ).

Brought it all home and my grandpa tells me the tap is a piece of crap, good old china imported crap lol. He brought out a massive book from a local tool supply warehouse, where we found a good old American made tap, that will do a better job, and its $5.99, so ill be going to get one of those along with a couple other tools next Monday with him lol.

Anyways, i put the #50 bit in a drill press and drilled all 4 of the holes out on all the frames (to bad i only brought 4 cars with me to there house, the other 10 will have to wait till next week when i come back over.... lol). The i used the pin vise with the 2-56 tap in it and taped all 4 holes in each frame all the way through, put them in an ultra-sonic solvent machine (he said it gets alot of the chips out that are left behind and also cleans the newly taped hole up real nice and smooth) then i blew all the holes out with the air compressor. Nice and shinny new taped holes!! Man they looked good lol. Put the brass 1/4" and 1/8" screws in there appropriate holes and bam, problem solved Misngth

Now all's i need to do is put some .10 fiber washers under the trucks to stop them from hitting the underside of the frames and put some nice Kadee Couplers on them when i get them lol

Just thought i would share how my problem got resolved Icon_lol

Thanks again for all your help guys Misngth
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#10
glad to hear it worked out okay!
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#11
nachoman Wrote:glad to hear it worked out okay!

Thanks Kevin!! Cheers

I just got back from True Value Hardware store, cleaned them out of 2-56 screws in both Phillips and Flathead in the 1/4" size lol, they didnt have 1/8" 2-56 screws, but i used 1/4" on the coupler pockets, and they worked fine, they just stick up a bit on the other side of the frame on the ends of the cars, i think i can trim them if i wanted to too....

They had them priced at $.32 and $.35 a piece, much better then $2.99 for 5 screws LOL, i got 29 1/4" screws all together from True Value, just over $10.00 lol
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#12
I am glad that Josh posted this! The ability to drill and tap a hole for a machine screw
is a powerful modelling aid and really not difficult as Josh's posts have pointed out.
Without it you can really be stuck sometimes; those self tapping screws have very
limited capability. Curse
This same skill can be very useful in many other applications as well. Larger sizes of
taps and tap drills are at HD or any hardware store. Another example of MRR helping
out in your real world!! Goldth
Thanks, Josh!

PS: The tap drill for 2-56 is listed as #50 or #51 in different places. If you have one
of those #51 through #80 sets you can use the #51. It is only .003" smaller than the #50.
If you have a deeper hole or harder material then maybe the #50 would be a better choice.
If the drill is too small, it's easy to break the tap. Nope
Cid
Cid
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#13
Thanks Cid Misngth

Indeed it is not very hadr to deepen a whole and tap it, it can however take some time, and if you have alot of them to do, you might want to do a few at a time, unless you just want to get them all over with and do them all at once lol. Its a very repetative process.....

Im thinking im going to have to do this process again with the 30 E&C Shops Coalporter kits i got coming lol
Josh Mader

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