# Insert shape comparison



## Tekno_Cowboy (Sep 14, 2009)

Does anyone know of a good pro/con type comparison of the different shapes of indexable carbide inserts, and their applications?


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## gadget_lover (Sep 14, 2009)

Not I. 

The shape of the insert makes a difference in several areas. Number of cutting edges is one consideraton. So is the size of the cutting surface.

A square insert has the most possible corners (8), but it takes a wide bite in relation to the depth of the cut. A triangle has fewer edges but also has a smaller cutting area so it takes less force to cut the same depth.

That's all (that I think ) I know on the subject. 

Daniel


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## KowShak (Sep 15, 2009)

The strength of an insert varies according to the angles of it's cutting corners. As an example, a square insert is stronger than a triangular insert assuming other factors are equal (e.g. corner radius, thickness, insert size).

What's more important than the basic insert shape is the cutting edge geometry, e.g. positive / negative rake, chipbreaker shape etc, that is not a simple subject.....


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## precisionworks (Sep 15, 2009)

> pro/con type comparison



That's a tough one. Most distributors figure that their customers already know that they want a certain ANSI shape, and provide tech support only for grades & types of coatings. PGS Tools does have a well done tech page, and they ship free if the order is $100 or more:

http://www.pgstools.com/servlet/the-template/technicalinfo/Page

Carbide Depot has a brief section on choosing an insert shape:

http://www.carbidedepot.com/formulas-insert-shape.htm

Discount Tools also has a short section:

http://www.discount-tools.com/catalogs/gen/239.pdf

Before you settle on a shape & size, make sure the insert is readily available from a number of manufacturers. I bought a nice Seco indexable end mill on eBay, about $20 delivered, and it came with 5 inserts. But only Seco made that shape/size, and the next 5 inserts were going to cost $125 - back on eBay it went 

Some insert shapes can be used for turning, facing, boring, and end milling.


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## Tekno_Cowboy (Sep 15, 2009)

Thanks for the links, the Carbide Depot one was just what I was looking for. :thumbsup:

Looks like the 55 degree diamond is pretty versatile, and the Trigon is a jack-of-all-trades, but a master of none. From what I keep hearing from the sales reps though is that trigon inserts are the hottest thing since sliced bread.

Can anyone shed some light on their pushing the trigon shape?


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## Anglepoise (Sep 15, 2009)

precisionworks said:


> Before you settle on a shape & size, make sure the insert is readily available from a number of manufacturers.



I think this is very important. For example, Sandvik do not make a small
1/4" Trigon insert so if you want to use this shape, you might not find it satisfactory for boring.

For my use, I want my preferred shape ( triangle ) and size to fit as many of my holders as possible.


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## precisionworks (Sep 15, 2009)

> trigon inserts are the hottest thing since sliced bread.



Every body and their mother offers a WNMG insert, and there are lots on eBay as well - an eBay search shows 73 listings for this shape. The 80 degree corner, while not as narrow as a 60 degree triangle, will still be able to cut to a 90 degree shoulder without problem. One big selling feature of the WNMG is three edges on top & three more edges on the other side. It's a popular shape, very strong, and easy to find holders for.

I use CNMG because it is even more popular - an eBay search shows 178 listings, more than twice as many as for the WNMG. You get four corners, two on top plus two on the other side, but they are so inexpensive that this is seldom an issue. There are face mills that use the "unused" corners of the CNMG, so the inserts are free if you use them first on the lathe. This one on eBay is almost identical to the 2" face mill that I use:

http://cgi.ebay.com/CNMG-2-0-FACE-M...ding?hash=item1e5789ecc4&_trksid=p3286.c0.m14

*NOTE* - that face mill has a 1.000" shank. That's fine if you use an ER-40 collet chuck in your mill, but very few places sell an R-8 collet in 1" - this company does list it:

http://www.engineering-supplies.com/subcat.asp?id=257


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## wquiles (Sep 15, 2009)

Tekno_Cowboy said:


> Thanks for the links, the Carbide Depot one was just what I was looking for. :thumbsup:
> 
> Looks like the 55 degree diamond is pretty versatile, and the Trigon is a jack-of-all-trades, but a master of none. From what I keep hearing from the sales reps though is that trigon inserts are the hottest thing since sliced bread.
> 
> Can anyone shed some light on their pushing the trigon shape?



Don't buy a Trigon holder/inserts yet - I have one set at home with 9 un-used inserts, and I will make you a smoking deal if you want it :devil:


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## Tekno_Cowboy (Sep 15, 2009)

It looks like you used it on your HF 8x12, so I'm assuming it's 1/2" shank? 

I'll take you up on that offer if the price is right. Thanks Will, PM incoming :thumbsup:

Edit: Now that I think about it, is that the one you tried using without an insert?


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## wquiles (Sep 15, 2009)

It is a SECO 5/8" holder/kit - ENCO Part #SU317-0801 - $112 plus shipping

I have only used one of the ten brand new inserts (6 edges per insert). The whole thing is yours for $25 plus shipping - lets say $30 shipped to you 

I no longer have the modified holder for it to fit right in the 8x lathe, but it is not difficult to modify. If you don't have a mill, or a friend that can do the small milling job, mail me the holder, and I will modify it for free if you buy the kit from me :devil:

Will


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## precisionworks (Sep 15, 2009)

One caution on any negative shape (C*N*MG, W*N*MG, T*N*MG, etc.) is that negative inserts require a machine with more power & more rigidity than the machines in many home shops. Lathes from about 10" swing & up seem to work well, but smaller machines may or may not. Smaller machine users often prefer positive shapes (T*P*G, T*P*C, T*P*GH, etc.)

Will's holder & inserts look to be Seco, which is high end tooling - equal to Iscar, Kenna, Valenite, etc.


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## Tekno_Cowboy (Sep 15, 2009)

"Sounds great!" just seems like an understatement. 



Just shoot me a PM or email on where to send the Paypal. 

Thanks a ton! :twothumbs:

Oh, did you happen to have a modded AXA toolholder you'd be willing to sell me too? I can have one modded by the local Carquest machinist, but I'd rather send my money to a fellow CPFer...


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## Tekno_Cowboy (Sep 15, 2009)

precisionworks said:


> One caution on any negative shape (C*N*MG, W*N*MG, T*N*MG, etc.) is that negative inserts require a machine with more power & more rigidity than the machines in many home shops. Lathes from about 10" swing & up seem to work well, but smaller machines may or may not. Smaller machine users often prefer positive shapes (T*P*G, T*P*C, T*P*GH, etc.)
> 
> Will's holder & inserts look to be Seco, which is high end tooling - equal to Iscar, Kenna, Valenite, etc.



Thanks for the info. I think for the price, I'd be crazy not to try it anyways. If It doesn't work out, I can always pass it on to someone else on the forums for the same great price. :thumbsup:


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## wquiles (Sep 15, 2009)

No worries - send me the holder and I will modify for free. Total for everything is still $30.

These negative inserts work really well for me on the 8x, so they should work well for you as well 

Will


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## cmacclel (Sep 15, 2009)

wquiles said:


> No worries - send me the holder and I will modify for free. Total for everything is still $30.
> 
> These negative inserts work really well for me on the 8x, so they should work well for you as well
> 
> Will


 

I just purchased that same holder kit from Enco a couple weeks ago. The inserts seem to hold up well in Titanium.

Mac


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## Tekno_Cowboy (Sep 15, 2009)

Hmmm... I wonder how it would work for turning some Ti chopsticks :thinking:


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## Tac (Sep 15, 2009)

I've used inserts just like that to cut titanium. (Think: Turning 4"dia down to .750, manual. Fun stuff.) Worked great. Trust me, as long as you're any bit experienced, they're easy to work with.


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## Tekno_Cowboy (Sep 16, 2009)

It'll be interesting to see how they handle 9 inches of 5/16" when cutting a taper. I havn't worked much with long, thin stock. Would I be better off with higher or lower spindle speeds?


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## Tac (Sep 16, 2009)

Given titaniums properties, I'd say a *high* speed with a smaller cut would produce better results. Also, titanium in small cuts just loves to spark and light up, which isn't really a problem with the giant stock I used before. (No expert here!) I rarely do anything over 6" long in Ti, and I'm not the expert at turning anything long and of a fairly small diameter with that metal. 

I hope someone else can give you a better answer, but that's just my opinion.


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## KowShak (Sep 16, 2009)

I think precisionworks has covered all of the major points.

One advantage that 80 degree diamond (e.g. CNMG) and trigon (e.g. WNMG) have over other insert shapes (e.g. triangle, 55 degree diamond) is that one tool will both turn and face and will turn up to a shoulder, i.e. you won't have to change tools part way through the job the way you would with some other insert types.

I'm using triangular (TNMG) inserts in my lathe tooling, if I was buying a new set of tools I'd probably be buying CNMG, they're the most easilly available which makes them the cheapest (especially on ebay) and they're more robust than TNMG or WNMG. The advantage of not having to change tools so often is something you appreciate more when you're changing tools in the middle of one of those jobs that's taking longer than it should.


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## precisionworks (Sep 16, 2009)

> I havn't worked much with long, thin stock. Would I be better off with higher or lower spindle speeds?


The spindle speed should be around 100 sfpm for roughing, around 150 sfpm for finishing - for 5/16" diameter, that means roughing at 1200 rpm, light finishing at 1800 rpm. Ti6-4 is machined at 1/3 to 1/2 the speed of mild steel.

The insert has to be sharp, and must be replaced as soon as it dulls. If in doubt, look at the insert under magnification & compare to a new insert - a worn edge will look wider because of flank wear.

Ti6-4 has a relatively low modulus of elasticity and the stock will "push away" from the tool much more than steel so good support is a necessity, which means a follower rest or traveling rest. If you don't yet have a follower, this is a great time to make one in the shop (or purchase one if available). They aren't hard to make if you buy a surplus one on eBay that's close to the correct size & adapt it to your compound. The two contact points on the follower are positioned directly across from the tool point and the thin rod is unable to move.

Take as much DOC (depth of cut) as your machine will handle, as you have to get under the tough skin. Combine that heavy DOC with a slow feed. Machining Ti generates tremendous heat at the tool point, and any type of coolant will help - flood is best but an air jet directed at the tool is a pretty good alternative. Or use a mister like the one that Will uses.

IMO, if you can machine 316SS you can machine Ti 6-4. It isn't and more difficult to machine - nor is it any easier :nana:


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## cmacclel (Sep 16, 2009)

Good info as always Barry 

I found in my experience with 6al-4v that I get obtain the best results by roughing at 150SFM at 0.006 IPR and finish at a .002 Depth of Cut at 200SFM at 0.002 IPR.

Mac


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## precisionworks (Sep 16, 2009)

> roughing at 150SFM at 0.006 IPR


That's good to know. I see quite a few references to 150 for roughing & 200 for finishing, but I tend to usually run on the low end of the range. You'd laugh if you saw me drill mild steel with a 1" twist drill at 25 sfpm (100 rpm) ... but the cutting lips stay sharp for a long time


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## wquiles (Sep 27, 2009)

Tekno_Cowboy said:


> Hmmm... I wonder how it would work for turning some Ti chopsticks :thinking:



You are going to find out soon - your holder is ready:
https://www.candlepowerforums.com/posts/3100458#post3100458


Will


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## Tekno_Cowboy (Sep 27, 2009)

I can't wait :twothumbs:

Did you have to take much off the holder to make the tool fit?


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## wquiles (Sep 27, 2009)

Tekno_Cowboy said:


> I can't wait :twothumbs:
> 
> Did you have to take much off the holder to make the tool fit?



I cut the bottom of the tool (instead of the holder since there is a lot more metal on the tool). I did two passes, and took about 0.085" total.


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## Tekno_Cowboy (Sep 27, 2009)

That works out fine for me. :thumbsup:

I can't wait to see how it does turning some 1.75" Al down to 1.3". :naughty:


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## Tekno_Cowboy (Sep 30, 2009)

I got the tool and modded holder in today 

The holder just barely fits, but that's a good thing in this case.

The tool works wonderfully :thumbsup:

It was amazing that, in combination with the speed-reduction gear, I was able to take a .100" pass on a piece of 6061 Al, with the motor hardly noticing it. I think I'd even be able to take a .150" pass, if I'd want to. It's a far cry from the .020" I've been limited to with the tooling I've been using.

It's really amazing what a difference a well-made tool makes. :twothumbs

Thanks Again Will!


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## Atlascycle (Sep 30, 2009)

Tekno_Cowboy said:


> I got the tool and modded holder in today
> 
> The holder just barely fits, but that's a good thing in this case.
> 
> ...



Now was that DOC or off of the diameter?

Jason


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## wquiles (Sep 30, 2009)

Tekno_Cowboy said:


> I got the tool and modded holder in today
> 
> The holder just barely fits, but that's a good thing in this case.
> 
> ...



You are welcome 

Now we need a picture of your setup with that new-to-you tool :devil:


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## Tekno_Cowboy (Sep 30, 2009)

Atlascycle said:


> Now was that DOC or off of the diameter?
> 
> Jason



That be DOC :devil:

I found that it's about half that without the speed reduction gear.



wquiles said:


> You are welcome
> 
> Now we need a picture of your setup with that new-to-you tool :devil:



Oh, I'll get there, it's just going to have to wait until they're done with my compound rest at the local metal shop. I'm having them take about .150-.200" off up to the oil ports, to move all my tooling lower.


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## bluwolf (Oct 6, 2009)

Am I hijacking this thread if I ask some more questions about inserts? If so let me know. But I thought it might be nice to keep all the info in one thread.

Using CNMG432 as the example. I get it all but M (tolerance) and 4 (size). Is there a fairly simple explanation?

Then there coated and uncoated, and different radii. Again is there a fairly simple answer for what you're looking for when cutting different materials.

For example what to use with Al, Ti,SS, basic steels like 1018 or 12L14?

I would guess there's no simple answer. But a basic rule of thumb, maybe?

Mike


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## unterhausen (Oct 6, 2009)

seems to me that the size is the easiest part. It either fits your toolholder or it doesn't. I'm still in the confused newbie state myself. I looked at the info in the second post in this thread, and I really only understood one of the links.


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## bluwolf (Oct 6, 2009)

unterhausen said:


> seems to me that the size is the easiest part. It either fits your toolholder or it doesn't. I'm still in the confused newbie state myself. I looked at the info in the second post in this thread, and I really only understood one of the links.


 
So how do you know if it fits your holder? Like, there are different shapes but there are different sizes within those shapes also, isn't there? I know there's stupid question I should know the answer to in there somewhere.

Mike


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## precisionworks (Oct 6, 2009)

Each letter & number in the ANSI chart specifies something about the insert:

http://www.carbidedepot.com/formulas-insert-d.htm

On a CNMG-43x, the last number is the radius, which is the most common variable you can specify. 

43*1* = 1/64 which is a finisher radius

43*2* = 2/64 which is a medium or general radius

43*3* = 3/64 which is a rougher

You can also pick the grade & the type of coating.



> what to use with Al, Ti,SS, basic steels like 1018 or 12L14?



Aluminum machines best with aluminum specific inserts. http://www.latheinserts.com/category.sc?categoryId=43

Ti and Stainless steels are somewhat similar, and can sometimes use the same insert.
http://www.latheinserts.com/category.sc?categoryId=16

Low carbon (under 25 carbon points, like 10*18*) and medium carbon (under 50 carbon points, like 11*44*) take another grade.
http://www.latheinserts.com/category.sc?categoryId=15



> But a basic rule of thumb, maybe?


Aluminum, Ti, SS and steel all have different machining characteristics. For aluminum, the carbide substrate is very hard but not too tough. For titanium, the substrate is very tough but much softer.

There are lots of people who buy whatever they can find on eBay and use that particular flavor on every job that comes into the shop. It's a lot like flashlights ... there isn't one flashlight that does everything well, which is why most of us own quite a few. You'll get much better results when the insert is made for the material.


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## KC2IXE (Oct 6, 2009)

Many Years ago, I wrote the various carbide Mfgs and asked these questions (aka what grade) and I put what they said here

http://www.thegallos.com/response.htm

One thing you have to remember, we (well, MOST of us - the pros here excepted) are rarely pushing our inserts anywhere near the levels that a shop with big, high HP lathes do. We simply don't get up into the SFM numbers!

A good "general purpose" coated carbide works fine for most of what we do. Special Aluminum grades WILL last longer, as they are harder, BUT until you are getting WAY up there in speed, you probably are NOT going to get much cratering wear, where the harder grades make a big difference. 

Let's face it, some of the real fancy stuff (PCD etc) is designed to be used at 20000 sfm!! Think about that number for a second

To get numbers like that, you's have to spin a 3.5" diameter part at 20000 rpm!! I don't know about YOUR lathe, but mine tops out at just over 1/10th that, and it would scare me to spin anying not deeply in a collet at 2000 rpm (6" chucks really don't like that)


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## precisionworks (Oct 6, 2009)

> A good "general purpose" coated carbide works fine for most of what we do.


Most people can get by with a general purpose insert for steel, Ti and SS. Insert life will be short on both Ti and SS, but they will work. 

Aluminum is a different story. General purpose inserts will cut aluminum, but do an awful job. Edge build up is a constant problem and the finish is far from ideal. The aluminum specific insert, with a sharp tip, high positive geometry & polished rake face, is night & day better. Try one and you'll never again use a general insert on aluminum


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## wquiles (Oct 6, 2009)

precisionworks said:


> The aluminum specific insert, with a sharp tip, high positive geometry & polished rake face, is night & day better. Try one and you'll never again use a general insert on aluminum


+1

I am one of the converts - all hail the alu-specific insert :bow:


The cool thing about it, is that it does pretty good with mild steel as well :twothumbs

Will


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## KowShak (Oct 6, 2009)

wquiles said:


> The cool thing about it, is that it does pretty good with mild steel as well :twothumbs



Whats the surface finish like on steel, is it as good as a steel specific insert? Have you done enough mild steel to see whether they chip or not?

I think you're right that a carbide insert will cut a material that it's not the right insert for and will do it almost as well as the right insert unless you're talking about a difficult material or talking about running the job as fast as possible on a CNC machine.


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## gadget_lover (Oct 6, 2009)

The "Tolerance" is talking about how accurately you can start the next cut after rotating the insert. An 'M" bit may be several thousandths difference when you rotate the insert or replace the insert with a new one. 

This makes a difference if you are turning a part and the insert breaks or chips. If you have a G insert the cutting edge will be very close to the exact place that it was on the old one.

I use M inserts a lot, and recheck positions ( height, Y and Z ) after changing the insert. In a production shop it probably makes more difference.

The links in post #35 will tell you how close the tolerances are for each grade.

Daniel


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## darkzero (Oct 6, 2009)

wquiles said:


> +1
> 
> I am one of the converts - all hail the alu-specific insert :bow:
> 
> ...


 
Me too but not CNMG though. Haven't tried steel yet but works great on titanium!


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## wquiles (Oct 6, 2009)

KowShak said:


> Whats the surface finish like on steel, is it as good as a steel specific insert? Have you done enough mild steel to see whether they chip or not?
> 
> I think you're right that a carbide insert will cut a material that it's not the right insert for and will do it almost as well as the right insert unless you're talking about a difficult material or talking about running the job as fast as possible on a CNC machine.



The finish on mild steel was better with the Al-specific insert, but I have not used it enough to see if they will chip or not.

Will


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## wquiles (Oct 7, 2009)

KowShak said:


> Whats the surface finish like on steel, is it as good as a steel specific insert? Have you done enough mild steel to see whether they chip or not?
> 
> I think you're right that a carbide insert will cut a material that it's not the right insert for and will do it almost as well as the right insert unless you're talking about a difficult material or talking about running the job as fast as possible on a CNC machine.



I am working on a custom 1xD for a customer in the UK, and I need a Copper "plug", so I used my CNMG 4xx tool with the Al-specific insert, and I got an almost polished finish:













Will


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