Need help ID'in a screw thread

[Konga Man]

I'm looking for screw from an old Lionel/Ives 610 Pullman car. It's the screw which attaches the light lead to the pickup. It seems to be some very odd thread; it's got the diameter of a #3, but neither 3-48 nor 3-56 is a match. (Definitely not a 4-36.)

Anyone have any ideas what this thread could be -- and where I could get another screw like it?

Thanks.

[Texas Pete]

Try Chuck Sartor, Mizell Trains.  [e-mail]

Pete

[lionelsoni]

I don't know why it would be metric; but an M2.5 is almost exactly the same diameter as a number 3.  Could it be an M2.5x.5?

[servoguy]

Prior to WWII, there were more standard threads then there are today.  Some of them were eliminated in WWII.  For example, the threads on many Lionel screws are 4-36 rather than 4-40 or 4-48.  Most likely the screw you need is a coarser thread than a standard #3.  You may be able to find a company on the Internet that has odd ball screws available.  The 4-36 screws are still available.  

[TrainLarry]

  You need to know the threads per inch of the screw. If you have access to a thread pitch gauge, or a machinist friend with one, it would be easy to find this out. If not, just put the screw next to a ruler and count the number of threads in an inch. It would also be nice to measure the diameter of the threads accurately with a micrometer to the nearest thousandth to know for sure what size your screw really is.

  Are there any other screws in your Pullman that match this screw? Could be that at some point someone just replaced a lost or stripped screw with something they had laying around, and forced a re-thread of the pickup.

Larry

[lionelsoni]

I assumed that he must not have a screw or he would simply have made that measurement.

To expand on my earlier comment about a metric screw, the diameter of a number-3 screw is .099 inch, whereas the diameter of an M2.5 (a standard metric size) is .098425 inch, so close that you couldn't tell them apart.  If it has the most common .5-millimeter thread pitch, it would have 50.8 threads per inch.  They are commonly found in modern computer cases.  I agree that someone may have rethreaded the hole the hard way, to be able to use a screw that he had on hand.

[TrainLarry]

  Sorry if I assumed incorrectly that the screw was in hand, and a second screw was needed.

The parts diagram shows the roller pickup to be part # TS-21

http://pictures.olsenstoy.com/cd/b123%5C000910.pdf

Hennings Trains sells them online:

http://www.ebay.com/itm/Repro-Lionel-TS-21-Truck-Crossbrace-w-Pickup-/310314755326?pt=Model_RR_Trains&hash=item48403364fe

You probably will need to purchase the replacement pickup to get the screw you need if you can't identify the screw outright.

Larry

[servoguy]

http://www.mcmaster.com/#machine-screw-fasteners/=ffo8do

McMaster Carr machine screws