But used PROPERLY there is nothing wrong with a good quality plier style crimper.
This is the hard part though, and the ratcheting styles help reduce some of the variables such as crimp force and terminal placement. Ratcheting types deal with some of these issues by applying a consistent crimp force by it's design, and might add a locater to assist in placement (not all do, such as some models with interchangeable dies).
It's a matter of reproducibility in order to insure it meets specifications, as well as saving on costs (reduces production time vs pure hand, and by reduced rework either at the factory or as a warranty repair).
Much harder to get a good crimp the more it depends on all factors done by hand (location, crimp pressure, strip length, nicks in the wire during stripping, ...), though not impossible.
So better tools were developed (ratcheting, electric, and pneumatic crimp tools), as well as automatic wire strippers to prevent variable strip length and nicks to the wire.
I got the Waytek Wire housing and a couple of the interchangeable jaws. Best $120 investment Ive ever made. I can knock out metripack and weatherpack crimps with the seal all at once, easy perfect crimps every time.
If it's the one I think it is, it's actually a
Pressmaster MCT.
I own one of these, and it's nice. Does require a bit more skill though, as there aren't any locators available, which makes terminal placement a bit more difficult (pay attention to where the seam is in the die, and experiment with the depth with different brands of terminals).
The other thing I've heard is that while solder joints are very mechanically strong when cold, when they get hot they are not. Crimped joints are still mechanically strong when they're hot. Something I think is especially important for automotive applications.
If it gets too hot, the solder can actually melt. But at that point, the insulation is also burnt off of the wire (i.e. insulation in automotive applications is usually rated to 80C, while 63/37 solder will melt at 183C, lead-free solders much higher than that). Insulated terminals can take more than that, as 105C is typical for vinyl insulated terminals.
The transition from solder impregnated wire to non is abrupt, so mechanical failure is prone to occur at that junction, such as that caused by vibration. Crimp terminals don't have this issue, so can tolerate vibration better.
Some terminals are better suited for vibration as well, such as
open barrel types, as it makes a better crimp on the insulation than insulated terminal can, especially on thinner insulation.
I don't like using insulated terminals myself. I only use non-insulated with ... heat shrink. I think heat shrink has the best strain relief. I like the adhesive lined type.
Better for **** splices than the insulated terminals.
What do you use for end connections, such as when you need female spades?
Hmmm...good food for thought. What stops a crimped connection from also breaking where the crimp ends?
Assuming it's flexing where the wire exits the metal portion of the terminal, it will eventually break (i.e an insufficient insulation crimp or none at all, and no other means of insulation support), but not as quickly as if it were soldered.
But the flexure issue can be solved by properly supporting the wire at the terminal, thus extending it's service life.
