help with indexable inserts

[savarin]

I need some help in translating the numerous terms used to describe indexable inserts.
I would like to start experimenting with them on my Asian 9x20 lathe.
I believe I would need positive rake inserts due to its pack of power and stiffness.
Can anyone point me to a reasonable definitive list of common designations and what they are good for.
I would like them for turning and facing stainless, mild steel and aluminium mainly.
Someone posted an image from TSI tool supply that I thought was good until I tried to relate it to what was available in ebay and failed hopelessly.
Thanks.

 

[talvare]

This site has a lot of info:
http://www.carbidedepot.com/formulas-insert-d.htm
Also, most of the manufacturers of inserts have good info on their websites (Kennametal, Valenite, Iscar, etc.)
Here's a good basic video from This Old Tony:

Ted

 

[Bob Korves]

A lot of the carbide for sale used on eBay is mystery carbide, and the stuff new in the packaging is not much better because the manufacturers use different grading systems. They try really hard to get us locked into using their products exclusively by keeping us too confused to try to figure out another manufacturer's equivalents. The shapes and sizes have become fairly standard now, but the grades are just about impossible to get my head around before they change yet again. It doesn't really have to matter so much, some of the differences are only really applicable to production work where time is of the essence. Learn what the first four digits mean and you are on your way...

 

[mksj]

I would keep it very simple and focus on either 1 type of insert holder, possibly two if you need to do very narrow work. You will have an issue with rigidity and power. You can get different types of holders for an insert that works for you.

One of the most common inserts is the CCMT/CCGT if 1/2" holder than use a 32.51 size insert, if you use a smaller 3/8" holder than a 21.51 insert. The inserts come in CCMT which is a molded insert so the edge is not as sharp as a CCGT type which is ground. A ground insert will take less power and give a sharper finer cut, but is more fragile and not as good for deep cuts. A CCGT should take less cutting power because of less cutting resistance from the sharp edge. There is both the angle of the holder itself (negative, neutral and positive) but also the shape of the insert effects the cutting angle. You may want to get a DCMT (diamond) for narrow work and angular. So I often get the toolholders in a set of 3, right hand, neutral, left hand set. Carbide Depot carries a wide assortment, but you might try a starter kit first and see how it works.

Aluminum one normally uses a polished uncoated CCGT type of insert, you can get very clean cuts. Steel and stainless, more common a CCMT which is coated (like CVD, TiCN....) for wear resistance. I do use the CCGT on steel for very fine cuts. There is a whole host of coatings, breakers, designs, ...., as Bob mentioned I think it is to confuse people and always trying to sell the next best thing and sell their proprietary holders. These changes may make a difference in dedicated high production machines, but will not have a significant impact at our level.

This is what I recommend as a starting set, great price and includes inserts for the materials indicated. I use several sets of holders, one set is for steel, SS, the other holders are setup for softer materials like Al, brass/bronze, etc.
http://www.latheinserts.com/3-8-HOBBY-LATHE-KIT-375-Lathe-kit.htm
http://www.latheinserts.com/1-2-HOBBY-LATHE-KIT-500-Lathe-kit.htm
http://www.latheinserts.com/TURNING-TOOL-HOLDERS_c157.htm

Lathe inserts:
http://www.latheinserts.com/LATHE-INSERTS_c149.htm

 

[carlquib]

I would suggest using good name brand inserts. When I started out I was buying the cheapest stuff I could find, mostly tcmt or tnmt. I didn't realize what I disservice I was doing to myself. I had my eyes opened when my tool dealer talked me into an Iscar threading tool. I was amazed at the difference in quality between the cheap inserts of unknown origin and the name brand stuff. I haven't actually tried to figure it out but I think I am saving money paying for the better quality. I plow through stuff now that would have trashed cheaper inserts and the insert doesn't look any worse for the wear when I am done. They just laugh at cutting down weld build up and interrupted cuts. I also switched to wnmg and cnmg inserts, so I get more cutting edges per insert. You might not get really good finishes with a negative tool and a light machine. The negative tooling really likes rigidity and horsepower, they will work on light machines you just can't take full advantage of what they have to offer.

Hello, my name is Brian and I'm a toolaholic!