There is a special rivet that uses the "splash" staking tool. The rivet comes with the retaining prongs already formed, the tool spreads them. The special rivets are available at
http://rivetsonline.com/rivets-en/semi-tubular-rivets.html but what is made and stocked is not the same as the originals. Originals have more prongs (I think either 6 or
then the current ones available (I think 4 prong). That's the difference. I researched this several years back looking for the exact original rivet but came up zero.
The heater box ones are usually different than normal semi-tubular rivets. The back side has a sunburst pattern when squeezed, probably to keep from damaging the heater box material and hold stronger.
Rivets installed on soft material (plastic, leather) usually use a washer to spread the load mostly at the tube end. The alternative is the multi-prong rivet that grips over a wide area - spreading the load. The prong design makes it difficult to remove without some damage to the material it holds.
The best option is to use the prong type even though it has less. The next option is to use a semi-tubular type with a washer as a backing. The semi-tubular requires a special pair of dies and an expensive rivet tool ($150-$300). Unfortunately, some of the rivets on a heater box are located where an extended post to mount the die and that requires either an arbor press of one of the large 20 ton types. Overkill? No, it's the best way of staking the rivets.
Jim
