Hi Brian,
KBC tool in Canada has a fair amount of inserts. In the US they are a reputable supplier, so odds are they are in Canada as well.
If you happen to have a means of taking delivery at a US address, latheinserts.com is a good supplier. Only better to high grade products, not a "quality import" sort of place. Everything ever purchased from them has been excellent. Sadly they don't ship to Canada.
Carbide Depot is also a good supplier, but they charge UPS $50 to ship to Canada before added charges. You folks in the great white north really get hosed by shipping from the US from what I've heard.
A good carbide nomenclature chart is here:
http://www.carbidedepot.com/formulas-insert-d.htm
As you've already found, ignore the amazon 10 for $25 "first top rate to be cutting your metal much we like" garbage, just wasted money. Some reputable vendors do have quite good house branded inserts, I've gotten Kyocera, Iscar and other top quality inserts in OEM packaging with the house brand sticker partially covering the makers own labels.
If your Warner tool holders take the diamond inserts (CCMTxxxx) treat yourself to some good inserts and try them out. Good inserts last MUCH longer than cheap ones, the cost of changing tool holders to get one more tip may not be worth it.
If you already have triangular insert toolholders you're half way there. You need positive rake inserts (TCMT, TPxxxxxx) for steel to work well. The insert size is measured in 1/8's of an inch diameter of an inscribed circle, so a TCMT321 will have it's straight edges tangent to a 3/8 inch circle centered around the mounting screw. The second digit is thickness in 1/16s of an inch, almost always a "2" in these size inserts. The last digit is the tip radius in 0.016 inch increments. A TPG321 or a TCMT321 will have a 0.016 inch tip radius. Just as in HSS tools you grind, the larger the radius the longer the tip tends to last and the smoother the finish but the less tight the corners and the more spindle power needed for a significant depth of cut.
There is also an ANSI/ISO nomenclature that has 4 digits and a decimal. Same basic deal - a TCMT32.51 insert is the same as a 321 EXCEPT the thickness is 0.156 inch. Not a big deal, but it does change the cutting edge height when mounted in the lathe. Try not to have both thicknesses in stock, it sucks to replace a worn insert and not notice the new insert is either high or low by 30 thou. Done it, took a moment or two to realize what was going on.
The AR Warner tooling is nice, when most of my work was in brass I loved the fact that their inserts could be polished and had zero rake. In steel the use of small positive rake inserts such as CCMT221 or CCMT21.51 diamond and TPG221 triangular inserts improved finish quality noticeably over the zero rake inserts.
If you have lower cost indexed tool holders, look carefully at the insert pocket and see that it is truly flat and the corner(s) are relieved so the insert sits solidly. Lap/hone/use method of choice to make the pocket floor flat if needed. A rocking insert is a chattering broken insert. Really high end holders often come with a carbide anvil the insert sits on, but most of us don't spend that sort of money on our tool holders.
I'm guessing you already know that carbide hates to scrape and hates thermal shock. Cut hard, cut deep, cut to size, and don't spritz on a little cold coolant or thin oil now and then. Cut wet or cut dry, once it's at a blue chip heat hitting the cutter with cold liquid will likely either crack it or fracture the edge at a minimum. A 0.002 inch depth of cut and a tentative feed rate will give poor finish and high wear on the insert. It's OK once in a while if you must, but the real deal is to have most of the heat of cutting leaving with the chips, not hanging around in dust.
Hope this is of some help,
Stan
