Suggest index toolholder set please

I like to think I’ve learned to check all the details so as to prevent such errors in the future. In fact, I found the problem before any parts arrived while building a spreadsheet of holders, compatible inserts, and inserts ordered or received.

At any rate, you’re right. I have plenty to work with for a while with positive inserts.
 
A literally exciting day. I have enough new parts in-hand to try out the carbide inserts. Now, I'll admit never tried to push the MRR with my hand ground HSS bits. I was just happy to get a nice finish and hit a target dimension. That said all the publish specs for speed and feed printed on the carbide bit box awoke the scientist/engineer side of me.
First the set up. I bought the Shars 5/8 shank set that I mentioned above. They arrived quickly and really look pretty nice. THEN I read @davidpbest book. That clued me in to the fact that I'd best use a holder with a shim for steel work. Thus I also bought kennametal SCLCRF 103B and SCLCLF 103B holders.
As of this writing I will use the Kennametal shimmed holders for steel and run the Shars holders with non-ferrous. I am pretty happy with that.

So, FIRST CHIPS:
I decided to run steel at the specified speed and feed. Or as close as I can get to that.
The stock is a piece of 1.5" diameter unknown alloy steel from my Dad's house. I have reason to believe that the it is a decent alloy for turning, but I can't say just what it is.
The holders are both of the Kennametal units set up as turning and facing. Here I must add that I have never put a 5/8" shank in my lathe. Setting the proper height (using a Shars BXA quick change holder) had the quick-change holder down against the top of the compound. I may slice a mm off the bottom of those holders.
The inserts are CCMT32.51from e-bay. Frustrating, I don't have much info these other the sellers claims.

I tried to achieve a first-pass cut at 700 SFM and 0.006"/rev. Could not get there as that would be 1780 RPM and my machine max is 1550 RPM. Still, 1530 RPM is 600 SFM. So I used 1550 RPM settings. The feed rate was set at 0.0057"/rev

Touched off and dialed in a cut of 0.016". This is the radius of the insert. Then I let fly.

I have never run steel so fast. VERY attention grabbing. Brown/blue chips spun off, also a first for me. And the finish is quite nice! I have no idea what dimensional control is available with this set up. Future project. here are some images.
 

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600 SFPM is within the insert's range, but is screaming fast for your machine. It's within the limit of your chuck, but close. In the future, keep in mind that the chuck will limit your RPM, not the machine itself. The chuck's limit must be observed. Bison has different ratings for the cast vs. forged chucks, and each diameter and chuck style has its own max RPM. Get the catalog, look the max up, and put the max on your chuck with a stamp kit.

I use 1/2 the calculated value for carbide tools as a guideline. Looking at your chips I'd say you are fine, but I wouldn't make a habit of dialing up the max value and running it. There is a point where the machine becomes too quick to operate well, if it doesn't fly apart from centrifugal force first.

The continuum of positive rake, in my opinion, begins at 14" of swing, but it's not driven dimensionally, it's driven by power and rigidity. I have a 4500 lb lathe with 8 hp, positive rake is default there. A 1500 lb lathe with 1.5 hp is, in general terms, going to be easier to hit dimensions with using neutral rake, but under some conditions will probably do okay with negative rake.

Rake is just one factor among many. There are dozens of insert geometries out there that have a larger effect on work than rake. Ultimately, the behavior of the tool will drive you toward the right selection. It will become obvious as your creep up to a dimension whether you can hit it all the way across the work, or not. You may find that negative rake tool digs and starts the cut, but a turn or two worth of longitudinal travel later, the work pushes the tip of the tool away and it rubs on the skin instead, leaving a taper. Or maybe you infeed for .005 to hit your nominal, and find you get a solid .007 cut instead- that's what happens with the wrong insert/holder for the material and setup. Anything with an edge cuts in a lathe if you can push it without burning the tool, but having the best possible tool for the job means you can reliably predict and hit your final dimensions.
 
pontiac428 said:
600 SFPM is within the insert's range, but is screaming fast for your machine. It's within the limit of your chuck, but close. In the future, keep in mind that the chuck will limit your RPM, not the machine itself. The chuck's limit must be observed. Bison has different ratings for the cast vs. forged chucks, and each diameter and chuck style has its own max RPM. Get the catalog, look the max up, and put the max on your chuck with a stamp kit.

I use 1/2 the calculated value for carbide tools as a guideline. Looking at your chips I'd say you are fine, but I wouldn't make a habit of dialing up the max value and running it. There is a point where the machine becomes too quick to operate well, if it doesn't fly apart from centrifugal force first.

The continuum of positive rake, in my opinion, begins at 14" of swing, but it's not driven dimensionally, it's driven by power and rigidity. I have a 4500 lb lathe with 8 hp, positive rake is default there. A 1500 lb lathe with 1.5 hp is, in general terms, going to be easier to hit dimensions with using neutral rake, but under some conditions will probably do okay with negative rake.

Rake is just one factor among many. There are dozens of insert geometries out there that have a larger effect on work than rake. Ultimately, the behavior of the tool will drive you toward the right selection. It will become obvious as your creep up to a dimension whether you can hit it all the way across the work, or not. You may find that negative rake tool digs and starts the cut, but a turn or two worth of longitudinal travel later, the work pushes the tip of the tool away and it rubs on the skin instead, leaving a taper. Or maybe you infeed for .005 to hit your nominal, and find you get a solid .007 cut instead- that's what happens with the wrong insert/holder for the material and setup. Anything with an edge cuts in a lathe if you can push it without burning the tool, but having the best possible tool for the job means you can reliably predict and hit your final dimensions.
Click to expand...

There is a lot that I want to unpack from your post. Safety being the most important. I’ll query the rest later.

I had never considered that my lathe might be able to spin the chuck that was provided with it at a rate that was unsafe or beyond specification. I thank you for bring this potential to my attention. Now, I am a big fan of manuals and I do read them. My lathe manual makes no mention of a max chuck RPM. It speaks only of spindle RPM capability.

The chuck is a 6” 3-jaw from Hua Pai (China). I just now made a limited effort to find such a spec for Hua Pai chucks. I failed. If anyone has a link to this info, please post it.

Thus, let’s have a look at Bison. The specs I found are here:

https://www.bison-america.com/pdf/Chapter_1/Specs_1_1.pdf

Let’s assume that my Hua Pai is a basic garden variety cast iron body and look at Bison’s specs for “cast iron body”, “3105, 32**, 36**”

here are some of the numbers

Chuck Size [in]. Max RPM
5” 4000
6” 3600
8” 3000
12” 2000
16” 1600

This suggest to me that my 1550 RPM setting is well within the 3600 RPM maximum for a 6” chuck

Only if I fit a 12” chuck am I capable of spindle speeds near the chuck RPM limit of 2000. Such a large chuck would barely clear the 13” swing of the machine.

Am I misunderstanding something here?

NOTE ADDED IN EDIT:
I just went to Precision Matthews. They spec a max RPM for their 6" 3-jaw at 4200 RPM
 
AllenV said:
There is a lot that I want to unpack from your post. Safety being the most important. I’ll query the rest later.

I had never considered that my lathe might be able to spin the chuck that was provided with it at a rate that was unsafe or beyond specification. I thank you for bring this potential to my attention. Now, I am a big fan of manuals and I do read them. My lathe manual makes no mention of a max chuck RPM. It speaks only of spindle RPM capability.

The chuck is a 6” 3-jaw from Hua Pai (China). I just now made a limited effort to find such a spec for Hua Pai chucks. I failed. If anyone has a link to this info, please post it.

Thus, let’s have a look at Bison. The specs I found are here:

https://www.bison-america.com/pdf/Chapter_1/Specs_1_1.pdf

Let’s assume that my Hua Pai is a basic garden variety cast iron body and look at Bison’s specs for “cast iron body”, “3105, 32**, 36**”

here are some of the numbers

Chuck Size [in]. Max RPM
5” 4000
6” 3600
8” 3000
12” 2000
16” 1600

This suggest to me that my 1550 RPM setting is well within the 3600 RPM maximum for a 6” chuck

Only if I fit a 12” chuck am I capable of spindle speeds near the chuck RPM limit of 2000. Such a large chuck would barely clear the 13” swing of the machine.

Am I misunderstanding something here?
Click to expand...
I'd wager that the quality standards for that Hua Pai are considerably less than for a Bison. That being said, your 1500-1600 RPM is probably ok for your chuck.
 
Excellent! I am glad you checked, because now you know. 6" bench lathes aren't exactly health hazards, but it pays to stay informed. Independent chucks are usually rated for a good bit less RPM than scroll chucks.
 
AllenV said:
I have never run steel so fast. VERY attention grabbing. Brown/blue chips spun off, also a first for me. And the finish is quite nice! I have no idea what dimensional control is available with this set up. Future project. here are some images.
Click to expand...
Your Kennametal SCLCRF 103B is neutral rake, and the CCMT inserts designed for it have a 7° relief angle. So you're good there. I will say that your are really maxing out MRR. I typically run that toolholder and a quality insert at 900-1100 RPM on my PM1340, but often with higher DOC. Yes, I can push it a lot harder but the pucker factor goes way up. And depending on the position of the QCTP relative to the center of the compound point of rotation will have a big impact on rigidity and the tendency at those RPM's for the tool to start hobby-horsing which will lead to insert crack. Chuck limits were my first concern reading your post, but I see you've checked that.
 
AllenV said:
There is a lot that I want to unpack from your post. Safety being the most important. I’ll query the rest later.

I had never considered that my lathe might be able to spin the chuck that was provided with it at a rate that was unsafe or beyond specification. I thank you for bring this potential to my attention. Now, I am a big fan of manuals and I do read them. My lathe manual makes no mention of a max chuck RPM. It speaks only of spindle RPM capability.

The chuck is a 6” 3-jaw from Hua Pai (China). I just now made a limited effort to find such a spec for Hua Pai chucks. I failed. If anyone has a link to this info, please post it.

Thus, let’s have a look at Bison. The specs I found are here:

https://www.bison-america.com/pdf/Chapter_1/Specs_1_1.pdf

Let’s assume that my Hua Pai is a basic garden variety cast iron body and look at Bison’s specs for “cast iron body”, “3105, 32**, 36**”

here are some of the numbers

Chuck Size [in]. Max RPM
5” 4000
6” 3600
8” 3000
12” 2000
16” 1600

This suggest to me that my 1550 RPM setting is well within the 3600 RPM maximum for a 6” chuck

Only if I fit a 12” chuck am I capable of spindle speeds near the chuck RPM limit of 2000. Such a large chuck would barely clear the 13” swing of the machine.

Am I misunderstanding something here?

NOTE ADDED IN EDIT:
I just went to Precision Matthews. They spec a max RPM for their 6" 3-jaw at 4200 RPM
Click to expand...
As a point of reference, I wouldn't use the Bison numbers as a generic spec because there are a lot of variables.

For example, Precision Matthews uses San Ou chucks for at least some of their machines. As you mentioned, the 6" 3-jaw is listed at 3,600rpm and if you look at a San Ou sold by the importer (which I believe is CME Tools here in Michigan) their picture shows 3,600rpm on the chuck itself. But if you look at their set-tru style 6" chuck it's only 2,500rpm...pretty big difference.

There are others that are the same style (non-adjustable) where they don't appear remotely close to what Bison lists. My 8" 3-jaw San Ou is marked with a max of 2,000rpm, so a full 1,000 lower than Bison.

I actually was looking at a 10" chuck for my 14" Logan recently and several I saw weren't rated for the 2,000 rpm the machine capable of...almost forgot to check that!
 
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