Hammer crimpers and the cheap import hydraulic crimpers have their place, and many people use them with very little issue. In applications where one is doing many, many crimps requiring a very high degree of reliability of, companies spend tens of thousands of dollars on highly engineered crimping equipment.
For low volume use you can spend well over a grand on something like a Greenlee or Thomas and Betts. The best compromise I've ever found is the
Quick Cable 4255-001R Crimper. I own and use it frequently.
What you're getting for your $250 is an engineered, precision tool that will perform reliable REPEATABLE crimps time and time again without failure. With hammer crimpers in particular you'll get crimps that appear to be solid, but actually are under crimped or over crimped, creating a less than ideal connection.
Cheap hydraulic crimpers invariably suffer from poor die design. There are actually about a dozen specifications for connectors for any particular wire size, meaning that one size-fits-all dies are simply not correctly engineered. Just in 0AWG, I have dies for 3 separate types of connectors that are commonly used.
The Quick Cable crimper I limked is made in the USA, if that matters to you. A connection properly made with this tool is UL Listed both in the United States and in Canada.
Realizing that $250 Is a big bite to take, consider that similar tools run well over $1000, and up to $50,000 for automated versions. It's a small price to pay in my opinion to have absolute confidence and pride in the work I produce.
I handle electrical repairs and upfitting for two police departments, a fire department, and an ambulance service. A failure of one of my connections could have life threatening consequences, but even still I'd recommend spending a little more on a good crimper for anyone doing this more than once or twice.
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