Rakes?

[stevec]

I'm a bit confused(normal) but is there dispute over the info in the links Ed provided? I found them pretty clear and easy to understand.
So, unless they are wrong, why the ongoing rehash?

[Mayhem]

(08-01-2012, 07:25 AM)stevec Wrote: I'm a bit confused(normal) but is there dispute over the info in the links Ed provided? I found them pretty clear and easy to understand.
So, unless they are wrong, why the ongoing rehash?

Nothing wrong with the links Ed posted but Jerry seemed a little confused between rake and relief, so I linked to a video. From an educational perspective, audiovisual instruction is more effective for some people than straight text-based instruction.

[TomG]

(08-01-2012, 07:25 AM)stevec Wrote: I'm a bit confused(normal) but is there dispute over the info in the links Ed provided? I found them pretty clear and easy to understand.
So, unless they are wrong, why the ongoing rehash?

There's nothing wrong with Ed's links but it never hurts to offer a few different ways of looking at things. Besides, Jerry needs all the help he can get.

[ETC57]

(08-01-2012, 07:53 AM)TomG Wrote:

(08-01-2012, 07:25 AM)stevec Wrote: I'm a bit confused(normal) but is there dispute over the info in the links Ed provided? I found them pretty clear and easy to understand.
So, unless they are wrong, why the ongoing rehash?

There's nothing wrong with Ed's links but it never hurts to offer a few different ways of looking at things. Besides, Jerry needs all the help he can get.

Now there's an understatement if I ever saw one!

Jerry.

[ETC57]

Steve,
you have to understand I'm kind of the community project

the more input I get the better the chances I'll get it!

Jerry.

[stevec]

Good for you Jerry, The more input I get the more confused I get.

[Mayhem]

(08-01-2012, 07:45 PM)stevec Wrote: ...The more input I get the more confused I get...

Don't worry Steve, that is the plight of man - the more I know, the more I know I don't know.

[PixMan]

There is one way that the term "rake" is often used even though it's really a misnomer. That is when referring to carbide turning inserts as "negative rake" or "positive rake".

In reality, they're almost ALL positive rake. What I mean by that is most negative rake inserts have straight sides, so the holders tip the insert to a -5º angle in two planes as a means of offering front and side clearance angles. That would mean the TOP RAKE would be at a negative 5º. In reality, the vast majority of negative rake inserts have top form geometry (a.k.a. chipbreaker) which compensates for the tilt and usually adds more positive rake. Only flat-top inserts, primarily used for cast iron, would be true negative rake though the moniker will go on forever.

Inesrts referred to as "positive rake" are single-sided ones that have side clearance angles either moulded-in or ground. Many modern ones have a countersunk srew hole in the middle (making them "screw down inserts), though older designs were and still are meant to be used in holders with a top clamp. These inserts sit in the holders flat, usually giving a 0º top rake angle. Nowadays there are a great many positive rake inserts that have chipbreakers moulded-in, adding to the amount of effective top rake angle. Those are typically weaker than negative rake inserts of similar geometry, though modern grades help tremendously to solve that problem.

Too much information? If you've got questions about carbide insert technology, always feel free to ask me. If I don't know, I'll make a up a believable story...er...I mean....find out the correct answer.

High positive milling insert, SEKN43. Top clamp, has chipbreaker.


Negative rake CNGG431-SR turning insert with two upsharp chibreakers on the 80º included angles. The obtuse 100º angles would be considered true negative rake.


Two SPEB09T308 screw-down positive rake milling inserts. One flat-top, one with chipbreaker making it high positive.


Negative rake WNMG542 insert in holder. This one is a strong edge chipbreaker design for high feed rate roughing operations. You need lots of HP to run one of these!

[stevec]

(09-01-2012, 01:04 PM)PixMan Wrote: Too much information? If you've got questions about carbide insert technology, always feel free to ask me. If I don't know, I'll make a up a believable story...er...I mean....find out the correct answer.

And it only takes him a month to fake..I mean... find and post the answer.

[DaveH]

Ken,
Thanks, nicely explained

DaveH