Constructing Tamiya Tank Tracks

In the past, i've run put the tracks on last, and hold them in place with alligator clips, with the pins inserted in holes.  Then melted them with the tracks in place.

Now, I using join the before putting them on, either leaving the drive sprocket off until last, or put the tracks on the drove sprocket, streached around the ready idler, and slowly rotated the drive sprocket while working the flexible track slowly in to position over the roadwheels, kinda like putting a bicyle chain on.

As most Tamiya kits mount the wheels using poly caps, it's not often a problem. Often, the easiest way is to mount the sprocket and idler wheels, mount the track on those and then insert the roadwheels. The tracks on the Pz.IV range are moderately tight, but not overly so. It can be tricky, however, when the tank has interleaved wheels such as in the Panther and Tiger families.

I would glue the wheels and idler on and leave the sprocket off until you put the track on. Slip it under the tracks and assemble them last.  HTH.