Carbide inserts not lasting long?

[martik777]

I find the Chinese dcmt's with the small radius (.4mm) are prone to chipping especially with interrupted cuts but they last many hours on steel otherwise - good value for <50cents each. These dcmt's (VP15TF 070208) have a much larger radius (.8mm) which provides more strength and a better finish but not as good for plunge cutting. https://www.aliexpress.com/item/33037657777.html?spm=a2g0s.9042311.0.0.55f04c4dO64OPl

Both work well on 1144 and 4140

 

[Winegrower]

I have wondered whether expensive name brand inserts are worth it. I found these Kyocera inserts on eBay for about $2.50 each, looked up their characteristics in Kyocera's catalog. These are designed for steel, stainless, cast iron, with medium interrupted cuts and heavy roughing. And wow, these are terrific. Taking 0.100 on the diameter is easy, the surface finish is good, and with the speed up around 1000 on a 1" chunk of mystery metal, feed at 0.009/rev, the chips break just right. Maybe I'll try pushing it further just for the thrill of it.

Perhaps there is something to the name brand stuff, especially if they don't cost that much more. I've ordered some similar Kyocera square inserts for about $3.00 each. We'll see.

 

[MrCrankyface]

I've played around a bit more and my lathe is definitely on the weak side for this particular material(mystery steel).
I upped the RPM to 710, DOC of 1mm/0.039" and a feed of 0.175mm/0.007" per rev and the inserts are lasting a tiny bit longer but the material removal I get done before they start cutting badly is probably three times as good and the finish is almost like a mirror.
It's almost constantly sparking at this RPM but I'm not sure it's from the inserts, could be from the material coming off.

I can't up the RPM more due since I run out of torque and I can't lower the DOC since the chipbreaker stops working and it immediately creates a birds nest.
Lower feed also makes the chip breaker stop working.

Maybe I'll try grinding up a HSS rougher some day but will also give brand inserts a try the next time I place an order.

 

[Tozguy]

HSS is the way to go. This is the HSS system I adopted several years ago to minimize grinding requirement while getting excellent results. Once I added up the cost of all the carbide inserts I previously went through, this became an investment that is easily recuperated.
https://www.eccentricengineering.com.au/index.php?option=com_content&view=article&id=32&Itemid=297

 

[Mitch Alsup]

For the feeds and speeds you present, I have successfully used CNMG on milde steel at 360 RPM on a 12×36 lathe which 2HP and 1200 pounds of weight.

I suspect the rigidity of your 10×?, possibly the HP of the motor, and the positive rake CNMT:: while sharper they are basically for softer material. I even use CCGT in my CNMG holders for aluminum for a fine finish.

 

[Buffalo21]

HSS is the way to go. This is the HSS system I adopted several years ago to minimize grinding requirement while getting excellent results. Once I added up the cost of all the carbide inserts I previously went through, this became an investment that is easily recuperated.
https://www.eccentricengineering.com.au/index.php?option=com_content&view=article&id=32&Itemid=297

I could never get mine to work worth a crap. I have 2 friends who use them, love them, I basically resharpening it about every 5 minutes, or the cut quality was terrible, rendering the parts all but useless. I probably should dig it out the box in the basement and try again.

 

[martik777]

If you are using Chinese HSS they likely won't last as long. I still use HSS for parting, form tools and when I need a very fine cut < .002" but import inserts are my main cutting tools even at slower rpm on a 9" South Bend

 

[Buffalo21]

If you are using Chinese HSS they likely won't last as long. I still use HSS for parting, form tools and when I need a very fine cut < .002" but import inserts are my main cutting tools even at slower rpm on a 9" South Bend

I was using the piece of HSS that came with the tool.

 

[Tozguy]

I basically resharpening it about every 5 minutes, or the cut quality was terrible

I found it helpful to slightly break the sharp edge with a diamond hone after sharpening. The edge seemed to last longer. That and use of cutting oil.

 

[Illinoyance]

Buying inserts from China or from flea bay can be a crap shoot. There is a lot of counterfeit name brand carbide out there. I have some Chinese inserts that perform very well. I think buying inserts from Amazon is as big a crap shoot as buying from Banggood i China.