There are a few US based eBay sellers that seem to sell surplus non-counterfeit inserts, I also purchase some from European sellers. Often hard to detect the difference of OEM vs. counterfeit but often it can be detected by the the labeling and enclosure differences if you know what you are looking for. The Mitsubishi, Sandvik and Korloy seem to be in abundance from Chinese sellers, not saying they are all counterfeit as some state that they aren't. I have purchased from a few of these sellers who guarantee OEM and performance wise they seem to hold up well. There is (and will continue) to be quite a debate as to using inserts vs. HSS on smaller lathes, they each have their merits. But smaller less rigid machines do better with HSS. A lot also depends on the tool holder, geometry, and type of insert. A positive or neutral rake insert pocket can produce some very nice cutting performance with reduce Hp requirements.
I would not recommend a negative rake insert geometry for smaller lathes, with a few exceptions. I would avoid unbranded or generic brands like Cobra, Rishet, NWP, tried some Cobra inserts years ago and they would break very quickly. So you are not saving any money in the long run if the insert is not durable and the cutting performance is poor.
I usually recommend finding insert brands/configurations/coating that work for you and then sticking with those. Inserts, in particular many of the older traditional styles, can be picked up for around $2 a piece. Example below would be for general turning in ferrous materials, the Mit's VP15TF coating holds up very well. Seco, Kennametal are more expensive, but seem to be rarely counterfeited.
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Seco, more expensive, TP2500 coating is a durable general machining coating for ferrous metals.
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TCGT (ground edge as opposed to molded) would be used for softer materials like aluminum. I have purchased inserts from this Chinese seller and the same to be authentic.
Find many great new & used options and get the best deals for KORLOY TCGT110204-AK H01 TCGT21.51-AK Carbide Insert 10PCS/Box at the best online prices at eBay! Free shipping for many products!
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Some US seller's like Shar's seem to be trying to carry a bit better quality on some items, so also may be worth a try. Inserts for me can last 2-3 months, so a cheap investment even if they cost a bit more for a quality insert. I tend to also standardize on inserts for different holders, for ferrous materials I mostly use CCMT inserts, and also use the same insert for my boring bars.