Piston Link Arm Screws – To Apply Force or Not?

[JTrains]

 So I took apart the #8204 C&O that my father bought for me sometime in the early 1970s to replace a minimally-performing smoke unit.  It’s possible I had a couple of refreshments during the disassembly process, so it took me a few minutes to get all of the parts back to their original intentions.  I was ready to declare victory and finish up by screwing in what I believe to be the two piston link arms (parts #30 and 31 in Lionel diagram/BoM 3-15 & 3-16) via the pair of “crosshead screws” (part #32).  However these screws don’t seem to want to go into the cast body unless I apply a level of force I’m not sure I should.  They look like they could perhaps be self-threading – but, to admit my apparent noobie-ness, are of a threading I’ve not seen before.  The two pics below show their location as well as a close-up of the screw itself.

 

 

I don’t want to create a situation by applying force unless force is what is really called for.  Can anyone provide some guidance on what I should be doing?

[webenda]

Apply Force. 

Try to locate the old thread by rotating backwards and feeling the "click" as the threads line up, then push in. It might go in with light pressure while turning with socket or wrench. If not, you will have to take everything out of the way until you can back up the casting inside and force it in. I would squeeze it in with slip-joint pliers. It can be pressed or hammered in if casting is backed up with something like an anvil.

Reference: http://www.fastenerdata.co.uk/fasteners/screws/self-tapping-screw/hammer-drive.html

[JTrains]

webenda

Apply Force. 

Try to locate the old thread by rotating backwards and feeling the "click" as the threads line up, then push in. It might go in with light pressure while turning with socket or wrench. If not, you will have to take everything out of the way until you can back up the casting inside and force it in. I would squeeze it in with slip-joint pliers. It can be pressed or hammered in if casting is backed up with something like an anvil.

Thanks for the link - this does indeed appear to be a "U (hammer) drive screw".  It at first seemed a curious choice Lionel made, though - a bit of research showed a manufacturer that indicated that "...they are more comparable to nails than screws...not intended to be removed after installation".  How else, I wondered, was one supposed to remove the motor if not by removing these screws?

Now looking more closely, I see that the screws on the driving wheels that attach the driving rod come off easily.  Looks like I over-dissambled it under the influence of refreshments - perhaps a lesson to be learned here...

[JTrains]

Some slight inward force combined with a bit of wiggling via a pair of mini VamPLIERS (which are quite handy, if you've never seen them...) got the job done last night.  Thanks again!