I need some recommendations on CCMT inserts

[D.sebens]

The setup you posted looks pretty conventional, so that's good. For the geometry to be correct you want the shank of the tool parallel with the face of the chuck. I use a 123 block against the chuck face, then move the carriage towards the chuck until the tool shank is pressing on the 123 block, then tighten things down. That will give the correct relief angle. Also, make 100% certain the tool is on center. This is for both turning and facing.

Chipping when facing often happens when you get near the center and the surface feet per minute drops to nearly zero, which carbide doesn't like. Unless you're already running really high speeds, I would try going faster when you face. Also, it's a good idea to at least lightly tighten the carriage lock on smaller lathes when making a facing cut.

What sort of RPM are you using when you get the chipping?

488 rpm. 1.375” stock starting size. It turns good at that speed. I can go faster but it really starts to eat in to my doc. I was taking .030” radius cuts at 488RPM. I don’t know what I could do at the next speed of 788 but probably half or so? I need to do more experimenting. I use the machine to make stuff(obviously lol) I find something that works and just keep doing it. I should try experimenting with speeds more when I have a lot of stock removal.

 

[D.sebens]

To add to that. For fun I tried back gear and a .060 or .080” cut at 87 RPMs. It was doing it but it was also pushing the stock back In the chuck. 488 and .030” was a MUCH higher MRR

 

[GeneT45]

For the geometry to be correct you want the shank of the tool parallel with the face of the chuck. I use a 123 block against the chuck face, then move the carriage towards the chuck until the tool shank is pressing on the 123 block, then tighten things down. That will give the correct relief angle. Also, make 100% certain the tool is on center. This is for both turning and facing.

I disagree with this. You can swing the tool around to any arbitrary angle and as long as the cutting edge is presented to the work, and on centerline, it's fine. There's nothing magical, nor necessary about getting the toolholder parallel to the chuck except that it ostensibly lets you face and turn without adjusting the toolpost.

GsT

 

[G-ManBart]

I disagree with this. You can swing the tool around to any arbitrary angle and as long as the cutting edge is presented to the work, and on centerline, it's fine. There's nothing magical, nor necessary about getting the toolholder parallel to the chuck except that it ostensibly lets you face and turn without adjusting the toolpost.

GsT

The OP is talking about facing and turning to a shoulder giving him problems. To do those operations you need the tool set so there's a relief angle between the insert and the work. With the SCLC tool he pictured you want the tool parallel to the face of the chuck so there is a 5 degree relief angle that prevents the entire side of the insert from making contact with the work. You can't just put the tool at any arbitrary angle and have it work for what the OP is talking about. Sure, if it was slightly off and only a 3 degree relief angle it would still work, but to keep it simple for someone having a problem, make the shank parallel to the chuck and the geometry built into the tool will be acceptable. That's why I said it was for both facing and turning....he can set the tool parallel to the chuck and should be able to do both operations without a geometry problem or having to change anything. It simply eliminates a variable to help find where the problem lies.

 

[mmcmdl]

This is where CNCs shine . Auto retract eliminates chipping and constant surface speed is used . Once again, carbide wants to cut , not push material .

 

[Huub Buis]

1.375” stock starting size. It turns good at that speed. I can go faster but it really starts to eat in to my doc. I was taking .030” radius cuts at 488RPM.

For turning steel, I use CCMT060204 VP15TF inserts from LYYZ that cost about 4$ for a box of 10.
My desktop lathes aren't rigid so I never can get the recommended feed and depth of cut. Most of the time I can't get the recommended speed of 120 m/min (410 SFM). My lathes max out at 1900 RPM.
I would turn/face 35 mm (1.375") steel at 1090 RPM, 120 m/min (410 SFM) using a feed of 0.1 mm/rev (0.004"/rev) and 0.1 to 0.4 mm (0,004" to 0.016") depth/width of cut. For finish passes or bearing fits, I reduce the feed to 0.05mm/rev (0.002"/rev). I could take heavier cuts but this would put to much stress (wear) on the lathe and results in a bad finish.
If I would face steel at 488 RPM taking 0.76 mm (0.03") cuts I also would get chatter and chip the inserts.
To keep the cutting forces low, I use inserts with 0.4 mm nose radius. On the mill, when using the boring head, I even use 0.2 mm nose radius inserts.
The specs on insert boxes are based on industrial type machines.

 

[SouthernChap]

I disagree with this. You can swing the tool around to any arbitrary angle and as long as the cutting edge is presented to the work, and on centerline, it's fine. There's nothing magical, nor necessary about getting the toolholder parallel to the chuck except that it ostensibly lets you face and turn without adjusting the toolpost.

GsT

What you said above has always (well, for a year and a bit since I started up all this expensive malarkey!) seemed like a sensible, intuitive perspective to me, but I've recently had my views on that challenged by a couple of videos that talk about chip formation (and also a video on tapping) by ThatLazyMachinist.

 

[WobblyHand]

There's optimal conditions for cutting, but it seems from experience that there's a broad range about that optimal point. I've seen some tooling that you scratch your head and wonder how it works but it does. I've used all sorts of non optimal arrangements and surprisingly many of them work. To be fair, some didn't work well at all. It's part of the learning process, especially if you haven't had any training. So the best cutting arrangement doesn't appear to have a cusp maximum, at least for presentation angle. So I don't take out my protractor for setting tool angle often. I still manage to get stuff done, despite being a bit lazy. Your process may differ.

 

[GeneT45]

I worry about alignment for parting and threading. Pretty much anything else, I'm just "ballpark". I've done it every which way and there really isn't a discernible difference when using carbide (because it will have the same edge and clearance all around) while conventional HSS cutters can be more picky because they are not usually symmetric. Nothing wrong with setting everything square, it's just not a requirement, nor would I expect one to see any improvement from it.

GsT

 

[D.sebens]

I will see how the new inserts do. I did some testing on the same steel and it was happy with .060” doc while turning. This left no reverse spring pass when I would retract so it was positively engaged in the cut. The steel was more like 1.25-1” at this point.