1.5 vs 2mm parting insert

[martik777]

My 2mm inserts tend to break. Would a 1.5 be less likely to? Material is 1018 5/8"
Holder is a MGEHR1010. Inserts are import

 

[davidpbest]

Not likely. It's more likely that the "import inserts" are at fault, or your setup isn't as precise as it needs to be. Have a look at the attached.

 

[martik777]

Thanks - good article.

It's probably the inserts. I can part 40-50 pcs without an issue then suddenly one will fracture. They also tend to get tiny chips if I do an interrupted cut. I don't have the nerve to try a power feed parting op I have no idea where to buy genuine inserts.

Edit: I indicated the parting tool (was way off) and slowed the RPM from 700 to 450. It's much smoother now and no failures yet!
I face off until the nib disappears to adjust my tool height.

 

[mattthemuppet2]

I only use my 1.5mm mggn inserts for when I want to groove and turn a feature, ie. plunge cut a couple of times to make a groove, then turn the bottom flat by moving along the bottom of the groove. For parting they suck, neither the steel or alu specific inserts do a good job curling the chip out of the cut, so eventually it'll jam.

 

[pontiac428]

How about inserts suck in general for parting? Carbide needs to run on a precision setup, from bearings to floor bolts- it hates intermittent loads, interrupted cuts, tool chatter, and spindle vibes. Carbide is nearly hard as diamond, and shatters like glass when flicked with a finger.

M2 and Cobalt are okay for parting, but even they are a little too brittle.

For many years before high speed machining, T15 was the go-to for parting tools. It's a tungsten precipitate steel, not a moly/tungsten like HSS, and it is true to toughness rather than hardness. These tools cut and don't break. You can burn them, like every other material but carbide, but they are easily retouched with a stone or bench grinder. But they don't shatter or explode, which I find nice.

Carbide is not always the best choice. It is usually the most expensive choice, though.

 

[Ischgl99]

I’m using Iscar GFR 2mm wide inserts for about 4-5 months now and they work really well. I wouldn’t want to go any thinner than that unless I was grooving. I was using a P type HSS previously that worked OK, but the carbide inserts are a significant improvement. I have a PM1236T bench lathe on a wooden stand, so while rigidity certainly helps, it is not imperative to use carbide. I have been power feeding since the first few times using the inserts, I set my infeed to about 0.001” and get nice and consistent curls.

I bought my inserts on Ebay, I buy partial packs since I feel it is more likely they are genuine from a shop getting rid of old stock than a full pack that could have been sourced from China and being sold locally to look like they are genuine. For your inserts, you can try Curtis at Lathe Inserts, I don’t know if he ships to Canada, but he sells good stuff. Some of the inserts he sells are from China, but he used to work for Kennametal and tests everything he sells to make sure it is good. I have purchased some Chinese inserts from him, not parting, and they are good quality.

 

[pontiac428]

I guess I can also add that a thinner parting tool does not mean easier cutting. With very small lathes, thinner tools might be needed to overcome infeed deflection. But in general, a 1/4" blade can cut smoother than a 1/8 blade, so thicker works better for general purpose use. I'm using mostly 3/16" blades now, they need less sharpening and plow out parting cuts with less noise and vibes overall.

Just something to think about. Maybe even try it someday. Or not. It's your shop, your rules.

 

[martik777]

I think my problem was not being 100% perpendicular. Since indicating the tool I have had zero issues and it cuts like butter. Not bad for a 20 cent /cutter insert with a $7 holder lol. I even had my first power crossfeed experience but I still like to do it manually!

 

[Boswell]

I think it was Blondihacks where Quinn sets the parting tool to perpendicular every time she uses the parting tool. I generally have not had many problems with parting (Carbide inserts and mostly on Aluminum but since I started confirming perpendicularity each time, I have not even had an occasional problem. (yet).