I look at it this way, if the Chinese fuses were that bad, it would catch up to them and no one would buy them anymore.
You are treating these as if the supplier cares about repeat business. Many of these fakes are produced in batches by random factories which don't care if anyone ever purchases again.
Counterfeit parts are very different from legitimate parts made in China with proper ISO-9001 tracking and certification from U/L, etc.
Here is a short writeup with pictures:
http://www.pat-testing-training.net/articles/fake-fuses.php
One aspect of PAT testing that is becoming an increasing problem is identifying counterfeit and non compliant electrical equipment. Trading Standards report that around £30 million worth of counterfeit electrical equipment enters the UK each year and 90% is made in China.
To take a look at this problem, we have randomly purchased 4 packs of BS1362 fuses from a popular online auction site.
...
Three of the four fuse packs purchased can be confirmed as counterfeit!
A photo is included of the aftermath of failure plus a video is included of a poorly constructed fuse exploding.
Fake Bussman fuses:
Research by Electrical Testing specialists, Intersafe, reveal fake fuses in circulation on the UK market. These counterfeit fuses can be extremely unsafe and could cause severe injury.
The Department of Trade & Industry Standards & Technical Regulations Directorate 6 (STRD6) reported that the presence of fake fuses in 13 amp BS 1363 plugs could be dangerous and cause the fuse link to “blow." This may explode violently and may blast the top off a plug or blast a plug from the socket. Reports suggest these fake fuses could cause severe injury.
The problem of counterfeit parts is pervasive, but usually ignored in the civilian channel. The Pentagon, however, has an incentive to find them, and this is the source for most of the documentation on how bad the problem has become. For example, here is a recent article:
https://www.scientificamerican.com/...-destroy-mission-for-counterfeit-electronics/
The Pentagon's Seek-and-Destroy Mission for Counterfeit Electronics
DARPA is developing microscopic chips to help crack down on knockoff parts destined for weapons and satellite systems
By Larry Greenemeier on April 28, 2017
The Pentagon has known for years that a significant number of the replacement parts it buys for its missile guidance and satellite systems contain substandard counterfeit microchips. But finding these fakes—as they make their way through a complex global supply chain of fabrication facilities, assembly plants and parts distributors—can be like searching for a needle in a haystack (made entirely of other needles). The military estimates that up to 15 percent of all spare and replacement parts for its weapons, vehicles and other equipment are counterfeit, making them vulnerable to dangerous malfunctions.
Counterfeit microchips—integrated circuits in particular—have turned up in replacement parts for U.S. Missile Defense Agency mission computers (pdf), ship-based aviation antenna equipment and in helicopter night-vision systems. Between November 2007 and May 2010 alone, U.S. Customs officials seized 5.6 million counterfeit microchips destined for military contractors and the commercial aviation industry, and the problem has only grown since then.
This, of course, is more than fuses. But the question remains: how can any part be known to function as advertised?
Because fuses are a complicated issue, to simply the issue for everyone, I located on the internet an ISO-9001 guide to fuse replacement. These are all alternatives to using counterfeit Chinese fuses.
so the edges don't hold up .
