Round lathe inserts, what are your opinions?

[CarbideBob]

Not a fan of round inserts.
The chip formation/thinning on leading edge is all so wrong.
Yes there are operations when it is the only solution.

 

[EmGo]

Not a fan of round inserts.

Then you must hate this thing of 3d surfacing in a mill

Agreed they are a little goofy, wouldn't be my first choice for just turning but there's parts where they work well. I haven't had the grief with them that some people describe here ... maybe because I do manual programming and can tune the toolpath for optimum performance, considering the tool itself

Also there seems to be a lot more choices for geometry than there were twenty years ago ..

But since you're here, these are intriguing. There's a lot of the advantages of a round insert without some of the shortcomings. Have you seen these commonly ? What's their designation ?



(That thing you posted of the pimple-faced teenager making his integrex do stupid stuff ? This insert would kill that job, for about a quarter million $$ less)

 

[gregormarwick]

Then you must hate this thing of 3d surfacing in a mill

Agreed they are a little goofy, wouldn't be my first choice for just turning but there's parts where they work well. I haven't had the grief with them that some people describe here ... maybe because I do manual programming and can tune the toolpath for optimum performance, considering the tool itself

Also there seems to be a lot more choices for geometry than there were twenty years ago ..

But since you're here, these are intriguing. There's a lot of the advantages of a round insert without some of the shortcomings. Have you seen these commonly ? What's their designation ?



(That thing you posted of the pimple-faced teenager making his integrex do stupid stuff ? This insert would kill that job, for about a quarter million $$ less)

Posturing about programming aptitude aside, I have used round inserts a lot, in lots of different materials. They are extremely effective at roughing out deep grooves and complex contours with high feed adaptive toolpaths. They are poor for finishing, by any metric. They do not form a chip unless they have enough engagement to cause the chip to curl, which usually requires per revolution feedrates of >10% of the insert diameter. And that means a very high surface roughness. Also, because lathes tend not to have very fast controls, doing your finish pass at 250ipm will absolutely destroy any chance you have of turning an accurate profile.

The B axis turning that bob linked to earlier is an extremely useful method of turning complex contours with a single tool and preventing collisions. I used it a lot when I was programming the NTX. It's true that I have seen a lot of youtube videos where it's not necessary but just because it looks fancy.

 

[angelw]

Posturing about programming aptitude aside, I have used round inserts a lot, in lots of different materials. They are extremely effective at roughing out deep grooves and complex contours with high feed adaptive toolpaths. They are poor for finishing, by any metric. They do not form a chip unless they have enough engagement to cause the chip to curl, which usually requires per revolution feedrates of >10% of the insert diameter. And that means a very high surface roughness. Also, because lathes tend not to have very fast controls, doing your finish pass at 250ipm will absolutely destroy any chance you have of turning an accurate profile.

The B axis turning that bob linked to earlier is an extremely useful method of turning complex contours with a single tool and preventing collisions. I used it a lot when I was programming the NTX. It's true that I have seen a lot of youtube videos where it's not necessary but just because it looks fancy.

Hello Gregor,
Yes, the round insert needs a lot of Feed Rate. One client's job I was tasked to lower the cycle time, was a very deep, truncated triangular, face groove, the Major, Minor diameters of which were 250mm and 100mm respectively. The DOC using a 12mm Diameter Insert, was 0.5mm in Z, with the X Feed in both directions at 3.0mm per rev. Roughing with this tool in the manner described pulled 30 minutes out of the cycle time.

Regards,

Bill

 

[BT Fabrication]

I've never messed around with an insert that had such a big contact area. Are these inserts okay for chip management?

yep, I use them all the time in a 10MM diameter insert from walter tools. cuts everything like butter. the application that works best for these is intermittent cuts, I use them to clean up welds or cut out welds on tube parts.
just used it on some S7 steel from a jackhammer pin. cut well enough, just need to find yourself a good chip breaker and hardness.

 

[Mechanola]

I should happily use an R insert for turning that concave face. The secret to success lies, as always, in the geometry of chip formation, to be precise, in the width-depth-length ratio. You remove a certain amount of metal per second which is conversion of a certain amount of energy to heat (most of it should go into the chips).

Width is increased by the round tool, depth of cut you define, and length is given by the feed rate (tool advance per rotation of work). Steels and all stringy cutting metals are best dealt with under shallower cuts but more aggressive feed rates. You want the stock to fold onto itself in order to break. Try an R insert at medium speed. Depth of cut 0.008" is better split into two 0.004" passes. Then seek for the best feed rate.

 

[Fancuku]

I hate those useless things. I refuse to use them.

 

[EmGo]

I hate those useless things. I refuse to use them.

Cool. So what would be your method for making this part ?

 

[CarbideBob]

EmGo,
If that third groove will end up looking like the first two this is the wrong tool.... positively no doubt.
Costly and losing production time.
The big problem with round tools is the chip thickness variation and entrance.
Why does climb mill work better than convention often? Could it be entry chip thickness?
Yes in places it is the only option.
Last resort in my book but in a cnc maybe get all the metal out with a real tool and do the finish with a round ended guy.

Other is screw machines. Plunge and make the form. Full rad tools in the form die a shorter life but no way around this.
Hence Manchester grooving tools. Why where they so good and loved by many?
Bob

 

[EmGo]

If that third groove will end up looking like the first two this is the wrong tool.... positively no doubt.

If you're referring to the facets, they are artifacts of the photo. If you are bitching that it is faster to use a form tool, not everything is made in quantities of 800,000/week

Costly and losing production time.

Damn car guys Doesn't explain how he plans to get the radius bottom by refusing to use a round. Even if it's a partoff style with a full radius nose, it's still a round -- and even more subject to chatter.

Made some parts similar to the photo and the finish was much better plunging a partoff then running a full-round over the profile, otherwise got scrapes and scratches and it wasn't as pretty. Pretty counts to some customers ... this is niche manufacture, not 1970 pontiac wagonville. (Nice nose, buddy ! You and karl malden related ? )

Hence Manchester grooving tools. Why where they so good and loved by many?

If you're making a full radus root, they still have a totally round nose, yes ?

I'd say the Manchetsrers were popular because they were well-made and substantial, pretty good about avoiding chatter. The support blades were replaceable without buying a whole new tool, and those support blades were subject to wear and breakage. Clamps same. The inserts were supported well and clamped well, which made the tool perform well. There were a lot of styles that no one else made for specialty operations, such as face grooving or the really narrow, high-performance cutoff tools.

Probably last on the list was any special geometry or carbide grade they had.

But back to the mystery - is that strange round-nose triangle common ? Or even sold in the US ? The more I look at it, the more I want to try one.

 

[michiganbuck]

Worth a try but the round insert has the radius of the insert. might not be what your machine can handle.
50-60 parts is not bad

 

[FeelthySanchez]

Unless you already have the holder for the recommended milling insert: R300-0828E-PL 1010, CoroMill® 300.

I would have to agree here w/ Dan, EmGo & MtnDew: 180 pcs/insert is fair.