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camdigger
07-13-2009, 12:29 PM
OK, can someone put on their secret decoder ring and decipher a couple of insert descriptions for me? I have 2 styles to describe, one is SDXT-90M405-NCM325 mf'd by Korloy Inc, the other is a CCMT 32.52-F3P PT20C NC3020 from Sowa Tool.

The SDXT is a free cutting square insert that works well for me, the CCMT is a 60* or so diamnd insert that has performed like an absolute POS.

The object of this exercise is to get a diamond insert that performs as well as the square ones...

Glenn Wegman
07-13-2009, 12:51 PM
One is a milling insert and the other is a turning insert. Different worlds.

The Korloy is for milling low carbon and soft steels.

The NC3020 is a turning grade for medium cutting of steel, not finishing.

What are you using them for?

camdigger
07-13-2009, 01:03 PM
Both inserts were supplied to fit holders that came with my lathe. Best recommendations from ACT.

I asked for inserts for turning:rolleyes:

Most of the work is in mild or tool steel. Some mystery metal too.

The holders have flat pockets that present the insert with the top face perpendicular to the work.

So.. the milling insert outperforms the turning insert for hand and power fed turning and facing operations?????????!!!?....

No wonder I'm frustrated!

Glenn Wegman
07-13-2009, 01:35 PM
The "milling" insert (possibly dual purpose, but I believe listed as milling) most likely has a different edge prep than the turning insert in your case. Most likely a sharper edge and possibly more "top rake" just behind the cutting edge? The turning insert most likely has a "duller" edge due to it not being a finishing insert.

Just a guess!

lazlo
07-13-2009, 01:41 PM
Like Glenn says, the SDXT is a square high positive (11) milling insert. You could certainly use it for a turning insert, but I think you'd be better off with the CCMT, which is a 7 positive turning insert.



the CCMT is a 60* or so diamnd insert that has performed like an absolute POS.

It's an 80 diamond, which is nice because you can turn and face without moving the insert. CCMT's are pretty popular with HSM'er's. Korloy makes good inserts, but I'm not familiar with "Sowa Tools." You might try a name-brand (Kennametal, Sandvik, Valenite) insert...

camdigger
07-13-2009, 01:53 PM
Like Glenn says, the SDXT is a square high positive (11) milling insert. You could certainly use it for a turning insert, but I think you'd be better off with the CCMT, which is a 7 positive turning insert.


The SDXT is being used in a 45 degree holder which allows both turning and facing, but will not cut a shoulder. I can cut .004 IPR and apply a DOC that will throw a chip 0.200 wide at 400 RPM on a 1" MS rod without complaint.

The CCMT diamond inserts are reserved for shoulder cutting in a +/- 20 degree holder that's supposed to allow both rh turning and facing. I say reserved because of the P!$$ poor performance of the CCMTs. The lathe complains so much, I'm reluctant to even use a power fed with them.

FWIW, SOWA Tools seem popular up here as both ACT and Thos Skinner and Son recommend them above some others.

From the SOWA Tool website, the CCMT has a 0 degree rake land behind the cutting edge and a chip beaker groove behind. The tip radius is 1/32". I haven't found the SDXT insert yet...

Glenn Wegman
07-13-2009, 01:59 PM
From the SOWA Tool website, the CCMT has a 0 degree rake land behind the cutting edge and a chip beaker groove behind. The tip radius is 1/32". I haven't found the SDXT insert yet...

Well there you go!

Try it on a .030" doc at high spindle speed and you'll see a big improvement in the finish. That's what it's made for.

Glenn

camdigger
07-13-2009, 02:07 PM
Glenn

Any suggestions as to IPR it should handle.. What SFPM? High spindle speed is a relative term and highly dependent on workpiece size.. All I know it is a POS at the settings the SDXT handles without complaint.

Cam

Any idea if the SDXT has a land behind the cutting edge? If so, how wide? FWIW, I've also used a TNMG insert with fair results.

lazlo
07-13-2009, 02:12 PM
From the SOWA Tool website, the CCMT has a 0 degree rake land behind the cutting edge and a chip beaker groove behind.

Ah, that means you need to take a DOC that's deeper than the land width to get a positive rake angle. If your DOC is equal to or less than the land width, you've effective got a negative rake insert.

You should really try another brand of CCMT insert.

Evan
07-13-2009, 02:18 PM
The CCMT has 7 degrees of clearance. That doesn't make it a positive insert, especially in light of the manufacturer description that says the cutting edge is at zero degrees. Since your tool holder is also at zero degrees it is absolutely essential that the cutting edge be either no higher than centre line AT ALL or even slightly lower than centre line. I would drop it just slightly under centre and run the sfm at three times HSS.

Evan
07-13-2009, 02:21 PM
Ah, that means you need to take a DOC that's deeper than the land width to get a positive rake angle.

Nonsense Robert. That won't make the cutting edge positive.

lazlo
07-13-2009, 02:27 PM
Ah, that means you need to take a DOC that's deeper than the land width to get a positive rake angle. Nonsense Robert. That won't make the cutting edge positive.

It makes the cutting edge a lot less positive if you don't take a DOC that's greater than the land length -- because the chip isn't making it to the chipbreaker.
If the insert is tilted down 5 like most CCMT inserts are, it will literally turn a positive rake insert into a negative rake insert.

But you still don't understand negative rake inserts, so I doubt you'd understand this nuance.

From Plastools:
http://www.plastools.com/insert_information.htm
http://www.plastools.com/insert3.gif

Figure 2 depicts three very basic Rake Surface Angles which would be regarded as major elements of the topography. The land length shown in figure 2 are somewhat misleading in that the transitions to the chip control groove and the groove itself is smooth rather than harsh angles as shown in figure 2,
a positive rake surface is possible with the TNMG-XXX insert if the DOC is greater than the cutting edge land length.

Evan
07-13-2009, 02:40 PM
It makes the cutting edge a lot less positive if you don't take a DOC that's greater than the land length -- because the chip isn't making it to the chipbreaker.
If the insert is tilted down 5 like most CCMT inserts are, it will literally turn a positive rake insert into a negative rake insert.

But you still don't understand negative rake inserts, so I doubt you'd understand this nuance.


You are not reading what the OP wrote. The cutting edge isn't positive at all regardless of depth of cut.

His tool holder is zero rake. The cutting edge has a land that is zero rake. That insert has a suggested DOC of as little as .008". That isn't going to turn it into a positive rake edge. There is no reason to tilt it down since it already is supplied with a 7 degree clearance angle. The insert is designed to cut with a zero degree cutting angle with a 7 degree clearance angle. Suggested speed is 850 to 900 sfm for low grade steels.

Glenn Wegman
07-13-2009, 02:49 PM
Glenn

Any suggestions as to IPR it should handle.. What SFPM? High spindle speed is a relative term and highly dependent on workpiece size.. All I know it is a POS at the settings the SDXT handles without complaint.


Sorry about that, should ave been more specific.

I don't know what you have for spindle speed or HP. Depending on part dia, you may not get near this sfm.

400 to 600 sfm in mild steel, if it's coated probably more. Try .003 to .005 ipr at .020 to .030 doc and see what you get. It's pretty light for sure as far as feed, but I understand that you are looking for finish. A spritz of coolant may help too. If not good, try more, or less. I'm just guessing as I don't have the specifics on the insert.

camdigger
07-13-2009, 03:33 PM
Ah, that means you need to take a DOC that's deeper than the land width to get a positive rake angle. If your DOC is equal to or less than the land width, you've effective got a negative rake insert.

You should really try another brand of CCMT insert.

If DOC is transverse to the main axis of the work when doing R to L turning, I rarely go less than 0.020" unless I'm turning to a finish diameter. With the SDXT inserts I go about 0.030 - 0.060" for fast stock removal. I don't recall for sure, but I think I had the IPR set about 0.004".

At a list price of over $8 per insert, and HSS blanks at +/- $5 per, I can't justify too many experiments.

I'd like to find out how wide the land is on the CCMT insert vs the land width on the SDXT but I can't find the spec on either one.

As it sits, the land converts the CCMT insert into a 0* rake insert

camdigger
07-13-2009, 04:24 PM
Sorry about that, should ave been more specific.

I don't know what you have for spindle speed or HP. Depending on part dia, you may not get near this sfm.

400 to 600 sfm in mild steel, if it's coated probably more. Try .003 to .005 ipr at .020 to .030 doc and see what you get. It's pretty light for sure as far as feed, but I understand that you are looking for finish. A spritz of coolant may help too. If not good, try more, or less. I'm just guessing as I don't have the specifics on the insert.

So, for 1" OD at 190 rpm I get +/- 50 sfpm? so at 1" OD, I should be running 1600 rpm? +/- 418 sfpm....

HP should be too be a concern, I've got 2 HP to play with. Most of my turning has been done at leass than 1000 rpm so maybe more speed is the answer with the diamond inserts. Still don't explain why the square ones work so much better at what seems to be too low rpm.:confused:

Glenn Wegman
07-13-2009, 04:48 PM
Different edge configuration.

Mark McGrath
07-13-2009, 05:02 PM
http://www.pgstools.com/servlet/the-template/carbideinsertidentification/Page

camdigger
07-13-2009, 06:26 PM
Different edge configuration.

So the obvious question following that statement is what 80 degree insert C??? will have similar free cutting characteristics to the square SDXT inserts that I know how to make work?

Evan
07-13-2009, 06:37 PM
Try the ones you have slightly below centre. You will be surprised.

camdigger
07-13-2009, 06:49 PM
Try the ones you have slightly below centre. You will be surprised.

I'm reluctant to do that as I'd have to bodge up a different holder (PITA with my limited shop time of late) or skim the bottom of the existing holder (so I'd need shims for the rest of it's life) for the experiment I don't have a lot of optimism for. At best I have one afternoon a week in the shop due to assorted circumstances and obligations, hence my reluctance to mess with an insert I have no confidence in....

IIRC, when I checked the alignment, the holder presents the insert to the work on center.

Glenn Wegman
07-13-2009, 06:53 PM
Is your SDXT insert bare or coated?

Evan
07-13-2009, 06:57 PM
The reason I suggest this is because it will have the same effect as tilting the insert to a slightly negative top rake. Try shimming the insert then in the holder ever so slightly to tilt the top toward the work. Keep the speed way up. According to the Sowa specs that insert is recommended to run at 800 to 900 sfm or so for soft and mild steels. If you can't run it at that you should at least try it on a larger diameter workpiece to see if it really performs better at the recommended sfm.

camdigger
07-13-2009, 07:02 PM
Is your SDXT insert bare or coated?

Both inserts are coated. The SDXT inserts are slightly more pure yellow than the CCMT which seem slightly brownish yellow.

Glenn Wegman
07-13-2009, 07:27 PM
A CCMT that is recommended for finishing is what you should try.

Another consideration is the geometry difference between the two types you have. The SDXT, mounted in the holder as you have it, gives a 45 lead angle which will be a more free cutting configuration than a CCMT mounted for turning and facing to a shoulder, which would be a negative lead angle so to speak. What you are doing is comparing a 45 lead free cutting finishing (relatively sharp) insert with a higher rake cutting edge that won't cut to a shoulder to a dull edge negative lead insert with 0 top rake that will cut to a shoulder. Basically apples and oranges although, as far as finish goes, a CCMT configured for finishing should give good results, but require a little more power to do so.

If your concern was fast stock removal, you would want a 45 lead oriented, negative rake, roughing insert and a bunch of HP and spindle speed. Set it for full depth of cut of the insert and grab a garbage can lid for use as a shield whan you engage the feed lever and stand back!

There are many different insert configurations and orientations for a reason.

Glenn

Glenn Wegman
07-14-2009, 08:02 AM
As far as Korloy....

They recommend trying a CCGT insert with a HFP chip breaker in a NC3010 grade for mild steel.

http://img.photobucket.com/albums/v647/Fighter1/korloy.jpg

camdigger
07-14-2009, 10:31 AM
Thanks, I'll check with the supply houses in Cowtown while I'm at work here.

lazlo
07-14-2009, 11:54 AM
If you look at the picture of the CCMT's at the bottom of Glenn's chart, it shows the land width and the minimum DOC to make the insert positive: the first insert, which is a finishing insert, needs a minimum DOC of .1 mm, an optimal DOC of .5 mm. In other words, it's .1 mm to the edge of the chipbreaker.

The roughing CCMT at the bottom has a big land -- you need to take at least a 1 mm cut to get past the flat land, and a 2 mm DOC is optimal. I'm guessing that might be the insert you have.

Notice that there's an open box for the third letter -- that's indicating that the land size/geometry is the same whether it's ground or molded. So if you switch from a CCMT (molded) to a CCGT, you're still going to have the same minimum depth of cut. The edge on the CCGT will definitely be a lot crisper though.

The CCMT's I've have from Sanvik don't have that flat land -- they have a linear transition straight from the edge.

camdigger
07-14-2009, 02:00 PM
If you look at the picture of the CCMT's at the bottom of Glenn's chart, it shows the land width and the minimum DOC to make the insert positive: the first insert, which is a finishing insert, needs a minimum DOC of .1 mm, an optimal DOC of .5 mm. In other words, it's .1 mm to the edge of the chipbreaker.

The roughing CCMT at the bottom has a big land -- you need to take at least a 1 mm cut to get past the flat land, and a 2 mm DOC is optimal. I'm guessing that might be the insert you have.

Notice that there's an open box for the third letter -- that's indicating that the land size/geometry is the same whether it's ground or molded. So if you switch from a CCMT (molded) to a CCGT, you're still going to have the same minimum depth of cut. The edge on the CCGT will definitely be a lot crisper though.

The CCMT's I've have from Sanvik don't have that flat land -- they have a linear transition straight from the edge.

So... How does the DOC/feed per rev IPM affect the cutting relief angles? Intuitively, I'd say you need the same feed/rev as DOC to have the same effect on the swarf in both directions. Otherwise you have a different effective backrake angle along the axis of the work. Cutting a 1 x 1mm spring seems a tad agressive even in an industrial setting:confused:

lazlo
07-14-2009, 02:36 PM
So... How does the DOC/feed per rev IPM affect the cutting relief angles?

Just the DOC, the feed rate doesn't matter. I'll draw a picture later this afternoon, but picture the insert with the flat land pressed against the workpiece. If you take a smaller DOC than the width of the land, the insert acts like it's flat across the top. If you take a chip that's wider than the land width, you get the back-rake from the chipbreaker:

http://www.plastools.com/insert2.gif

That only happens when the chipbreaker has a flat land. If the Chipbreaker runs up to the edge like most positive inserts have, you don't have the DOC effect.

camdigger
07-14-2009, 02:51 PM
Hmmm... Not what I would have expected. The illustration clearly shows what I thought was happening at the nose of the insert, but the same thing should be happening along the side of the insert. I visualize a step being cut into the side of the work as the insert does its' job. I'm surprised there isn't some requirement /consideration for the effective back rake along the side of the insert ie, the "riser" of the step being formed as the insert cuts.:confused:

Again, intuitively for me, it would seem that the side of the tool's geometry would have more effect on chip flow than the nose as the feed is along the axis and not a plunge feed like a form tool. Most HSS tools I use are ground to a point and the tip has little to do with chip flow.

lazlo
07-14-2009, 02:58 PM
it would seem that the side of the tool's geometry would have more effect on chip flow than the nose as the feed is along the axis and not a plunge feed like a form tool. Most HSS tools I use are ground to a point and the tip has little to do with chip flow.

A CCMT toolholder has 5 side clearance: if you look down on the insert from the top of the toolholder, the insert is rotated 5 towards the headstock -- it's a single-point cutting tool. So the chip should be flowing over the tip, across the land, and down into the chipbreaker, like the diagram shows.

Most CCMT inserts don't have that flat land, which I think is what's screwing you up...

Edit: here's a picture I just drew that shows how a chipbreaker with a flat land can interfere with the insert rake angles. Until you take a DOC deep enough that the chip passes the flat land, you effectively have a flat-topped insert:

http://i164.photobucket.com/albums/u15/rtgeorge_album/CCMT.jpg