While I’m obviously bias I’ll try to give some general information here.
To expand on what @CNC3D said. There is a HUGE range of differences in bit quality and design.
Bit geometry (rake angle, helix angle, lands, tip size / type, etc) can have huge effects on how the tool performs in different materials and systems. I’ll give a few quick examples:
This is the angle of the cutting face (in this case the flute) to the material. For softer materials you usually want a higher angle so you get a good clean cut of the material. However, if this is too high and you want to cut harder materials then you will have too weak an edge. It’s quite common for companies to either shoot for some middle ground or simply sell metal cutters as soft media. An even bigger problem is a tool with negative rake which is quite common in very cheap tools as it’s the easiest type to make.
This is the angle of the twists of the flutes up the tool. Think of it kinda like a screw pitch. This is another one of those things that effects soft and hard materials differently. As an example high helix upcut is more likely to chip out wood. On the other hand you want enough that you are clearing out the cut material to reduce or prevent re-cutting. Again though you often see high helix tooling used for metals with very good results…and sometimes sold as wood cutters with less ideal results.
Other changes in flute geometry, and tip style will also effect your cut but I don’t want to expand this to a crazy degree.
Also as @CNC3D mentioned carbide quality range is huge. You have the basic size grades (micron / submicron), then breakdown by ISO. However, it goes even further than ISO grade. Let’s use 3 carbide examples in ISO K20:
Chinese YG7 - T.R.S= 1.9GPa HRA=90
Sandvik DH20 - T.R.S.=2.8GPa HRA=92.3
Mitsubishi MF20 - T.R.S.=4.4GPa HRA=92.8
T.R.S. is transverse rupture strength and HRA is a rockwell A test. Clearly all these carbides are different even though they share the same ISO grade. Just the differences in these 2 properties will absolutely change the tool life, and stress the tool can handle. They will also greatly effect the cost of the blank.
The tolerance allowed on the tool can also have some obvious and subtle effects. I’ll give 2 quick examples.
Some of things are obvious like a 6mm (0.2362") tool being sold as a 1/4" tool. Even much smaller diameter changes can have a huge effect on things like engraving and inlay though.
This is the difference in the size of the flutes from the center of the bit. There’s a few things this effects but I’m going to just discuss wear here. A tool with high runout has a flute that is doing more of the cutting and wearing faster than the other flute. This means your tool is going to start giving you poor cuts faster. Additionally, this will also have an effect on the diameter of the cutter.
Think I’ll leave this here unless someone wants more information. To sum up quickly geometry, base material, and tolerance make huge differences in tool performance, bit life, and unfortunately price.
I doubt that this is what you’re looking for. These are not even listed as carbide in the specs further down the page "Material: blade carbide (tungsten steel) ". It’s not a down cut either if that’s what you’re looking for.
These are not engraving tools but drills. Drill bits are not designed to take side load at all. They will also give you a very poor cut if you can keep it from breaking.
Hope that’s at of some help.
Again, obviously I’m bias on tooling so I won’t make specific recommendations. But if there’s anything else I can help with please let me know.
Think & Tinker / PreciseBits