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What inserts do you like and why?

@Canadium - it is $75 Canadian. Is it really worth that much?
Hmmm ... I think value is an individual thing. Depends a lot on your expectations. I love books, saw many positive reviews, and I didn't see many others on the subject so I bought it. Learned quite a bit from it and probably will learn more as I reread multiple times. I'm not sorry I bought it. I've paid a lot more for books in the past. There are only 105 pages so if you think like a librarian and weigh value by number of pages you might not go for it.
 

Susquatch

Ultra Member
Moderator
Premium Member
I'm not sorry I bought it.

That's good enough for me.

I've paid a lot more for books in the past.

Me too. My machinery handbook was prolly the most I ever spent on myself besides university text books. At the office we bought whatever we needed - I once bought a full set of the Oxford Dictionaries. Several grand right there. But nobody would ever argue their authority.

I wish I could have brought them home with me when I retired.
 

PeterT

Ultra Member
Premium Member
About half of the David Best book is recommendations.

I know him from Hobby Machinist forum. He has done some really cool machine builds. Usually I throw money at books but strangely (for me) I did not click buy. I suppose price was a factor. Thought I'd wait for a few reviews, then I kind of forgot about it.
 

Tecnico

(Dave)
Just want to say this thread is full of interesting information. I'm going to have to block off some time to go through all the references.

Keep it coming!

D:cool:
 
This gets repeated often, but I am still struggling to understand why or what the basis is. I mentioned this in post #142 where I scribbled on the little operating window chart provided by carbide insert manufacturer. Particularly where I randomly flagged a faceted style finishing insert with a very small DOC range, 0.002-0.032" if I understand the specs correctly (excerpts below). There may be other carbides optimized with even smaller DOC than this, I just grabbed this one as example. This (0.002") seems to completely contradict 'a good amount of material'. Yes, there are heavy hogger carbides & I think that DOC is reflected in their respective operating plots, no? Isn't that how FT machinists choose tools?

Looking at this a different way, say you matched a HSS grind to dimensionally identically equal a carbide - rake, relief, nose radius, edge sharpness, surface finish.... (for now disregard carbides chip control features & coating to keep thing simple). What are we left with? The 2 tools differ only in their basic material properties: hardness & modulus & ?? Now all of a sudden they have dramatically different DOC 'bite'? That makes no sense to me. Now running them both for 1000 parts in production mode is a different thing. I'm just asking why does carbide 'need' a big bite?
I'm guessing the answer to your question is that because carbide is more brittle than HSS originally they were making inserts with bigger nose radius and duller cutting edges hence deeper depth of cut required and hence the reputation. Things change however and they now make better carbide compositions and as you point out finishing inserts.
 

Susquatch

Ultra Member
Moderator
Premium Member
I'm guessing the answer to your question is that because carbide is more brittle than HSS originally they were making inserts with bigger nose radius and duller cutting edges hence deeper depth of cut required and hence the reputation. Things change however and they now make better carbide compositions and as you point out finishing inserts.

I need to learn how to write simpler and better. That's basically what I said except I took 16 pages to say it.
 

PeterT

Ultra Member
Premium Member
Here is where I think 'speed' is entering the picture & probably influencing the consensus that carbides are outside the realm of hobby machines. BTW I shared this same view because that's what the manufacturers data suggests (and still does, read on). That is until I started using specific carbides myself and what can I say, the results don't lie. I've ran the same insert many many times, in different common materials, taken a thou off, measured the results. Its reality, no different than when I did the exact same thing with HSS. So possibly, as I mentioned before, perhaps the manufacturer operating parameters (bounding area graphs, bar charts, min/max) are not absolutes or hard boundaries. They could be softer edge boundaries that 'work' on the fringe or even outside the range to some extent, but other factors (disadvantages) may start to enter the picture.

Korloy example. I lifted this chart which shows cutting speed on Y axis. It shows a range of inserts & corresponding materials. Just for visual reference I made a line at 100 m/min.
1668704084445.png

Now I plug in some numbers (red cells), a recommended surface speed from chart, a bar diameter & compute resultant RPM which is what I need to set on my lathe
Here we see the issue. My lathe can run between 70-1350 RPM. The calculated resultant rotational speed is already 1273 RPM, 94% of my top speed.
1668704452225.png

Worse yet, make the diameter smaller & RPM climbs accordingly
1668704816725.png

Working backwards, if I set RPM to max, what is the resultant surface speed? (approximate)
1668705133333.png

using above example, shows as green line
1668705200494.png

This is what I'm wondering out loud. Is the boundary hard (manufacturer blue) or is the boundary soft (orange shade just for visualization).
Because going back to my original statement, there are millions of everyday examples where hobby machinist are happily cutting materials to a satisfactory combination of finish & dimension. So somehow the data has to facilitate that reality.
1668705929492.png

Its unfortunate that an equivalent diagram isn't readily available for HSS. Or maybe it is, tucked away in a text book. Because an 'overlay' would be inteersting
I'd like to hear from people who have been down this path where this is familiar territory, maybe do it for a living. Is this the workflow of how they select carbide cutting tools? What are typical spindle speeds of CNC lathes?
 

PeterT

Ultra Member
Premium Member
btw, the Korloy documentation does have generic charts & discussion about the tradeoffs of different machining parameters. I'm sure other suppliers do much the same

1668706254496.png

This kind of table shows feed & cutting speed by insert. They don't really say min/max/average but presumably corresponds to the graphs & bar format
What's interesting is once you zoom in or define operating parameters, there are many available corresponding insert shapes that satisfy that same criteria.
1668706438638.png
 

little ol' e

Jus' a hobby guy
I'm surprised at your view on this, I regularly do cuts of 0.001" and achieve the results required along with great finishes.

My suspicion is that you have not set up tooling correctly, either too high or too low with carbide does effect finish quality greatly as it smears or grabs when cutting. Correctly set up carbide cuts as it should.

What tool, insert grade and material are you taking the .001 DOC in to get the nice finish? Can you give us the speed and feed you were running that particular cutter at as well please?
I do not know of any indexable tool/insert that will perform well in steels when trying to skim .001, I will certainly give it a try.
Thanks!
 

Degen

Ultra Member
Premium Member
What tool, insert grade and material are you taking the .001 DOC in to get the nice finish? Can you give us the speed and feed you were running that particular cutter at as well please?
I do not know of any indexable tool/insert that will perform well in steels when trying to skim .001, I will certainly give it a try.
Thanks!
Steel was 4140 - about 6" dia speed about 360 rpm, feed slow don't remember, insert triangular, style don't remember other than non coated and extremely limited options of inserts because of size (one of my first insert cutters) on the Logan Model 200. Light passes done without lube.

I was surprised at the ease of the cut and finish produced

Biggest thing is ensuring proper cutter height, high tends to smear (not enough pressure on edge as its distributed over a larger area), low tends to grab (too much pressure because too little insert is in contact).
 

little ol' e

Jus' a hobby guy
This gets repeated often, but I am still struggling to understand why or what the basis is. I mentioned this in post #142 where I scribbled on the little operating window chart provided by carbide insert manufacturer. Particularly where I randomly flagged a faceted style finishing insert with a very small DOC range, 0.002-0.032" if I understand the specs correctly (excerpts below). There may be other carbides optimized with even smaller DOC than this, I just grabbed this one as example. This (0.002") seems to completely contradict 'a good amount of material'. Yes, there are heavy hogger carbides & I think that DOC is reflected in their respective operating plots, no? Isn't that how FT machinists choose tools?

Looking at this a different way, say you matched a HSS grind to dimensionally identically equal a carbide - rake, relief, nose radius, edge sharpness, surface finish.... (for now disregard carbides chip control features & coating to keep thing simple). What are we left with? The 2 tools differ only in their basic material properties: hardness & modulus & ?? Now all of a sudden they have dramatically different DOC 'bite'? That makes no sense to me. Now running them both for 1000 parts in production mode is a different thing. I'm just asking why does carbide 'need' a big bite?
Hey Peter,

If your looking for inserts that can turn .001 they can be had for around $260 each. They are specifically for hard turning on CNC. Those inserts are not carbide or coated carbide . Those are ceramics and CBN's, not what your going to be running on a manual lathe IMO.
Not to say some aren't doing it. I don't, simply because, my manual lathe couldn't handle it, and to be honest, I don't know of a manual lathe that could handle those inserts.

I figured this thread was about manual machining- turning inserts. That is why I tried to simplify things in 3 categories when considering carbide inserts.

I also posted a photo of the main 4 inserts I use on my manual lathe, that I felt others could benefit by.
The two triangular inserts with a .03 rad for roughing and semi, along with two triangular inserts for finishing with a .015 rad.

Just pick a holder and insert of choice that matches best with what material you happen to be machining.
I think I posted what materials the 3 simplified grades would perform well in as well IIRC...
If I didn't, let me know.

-When you ask why does carbide 'need' a big bite. -

Carbide inserts in its form, is a compressed dense material, some think its brittle.
This is why Carbide needs to be engaged into the material to keep everything stable, this is why we always like to leave at least .012 - .015 for a finishing inserts.
Can you take a lighter DOC with a carbide insert, of course you can, as long as you back the RPM down while keeping the feedrate up for the bite to happen. That way your not grinding, skating or rubbing rather than cutting.

Does that explain things any better and make sense?
 
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little ol' e

Jus' a hobby guy
Hey Eric, can you post part numbers for what you recommend as well as for the associated holders?

I see you have several different types as well as several sizes of that type. With time I may come around to that but not just yet. I'd prefer to stick with one size and maybe several different point radii and maybe 3 types (Stainless, Steel, Aluminium) unless one type will do all which would be a bonus!
I missed seeing your post Susquatch, these pages go by quicker than I can type ... I hope to stay in line here eventually haha

Unfortunately, I have not come across any 1 insert that will work well for all 3 material groups yet lol . I wish...
Could get away with 1 insert for like 304 stainless, P20 , 4140 but that's pushin' it really.

Depending on the diameters your machining, I like to have 2 sizes triangular for roughing, and 2 sizes for finishing since my diameters can be anywhere from a 1/4" round up to 6".

Not sure what your budget is but if you could let me know what your lathe specs are I'm sure we could pick something out together that would work.

Just need a couple weeks to get caught up on a few things.
I also need to get something sent out to another member here to try that has been sitting on my desk for well over a week now, my wife has been sick so... I only have 2 hands and 1 is usually half full;)
 

PeterT

Ultra Member
Premium Member
This is why Carbide needs to be engaged into the material to keep everything stable, this is why we always like to leave at least .012 - .015 for a finishing inserts.
Can you take a lighter DOC with a carbide insert, of course you can, as long as you back the RPM down while keeping the feedrate up for the bite to happen. That way your not grinding, skating or rubbing rather than cutting.

The 0.001" DOC kind of came out as home machinist shop example we can relate to. We know from experience we can shave off that much off with HSS tool. I've done it myself, I'm familiar with it, I'm not opposed to it. I just added that I also shave that amount off with carbide inserts. Many, many times. Which differs from experiences that you can't, or not for long, or special inserts or mods are required. I probably do 60/40 aluminum alloys / other. But other are mild steel, tool steel, occasional 4140, brass, bronze etc. Sorry no rusty bolts from the forest haha. I don't think my micrometer or DRO is lying or I would not have gotten very far in machining, so what remains is explaining it. Because as I mentioned, it doesn't agree with the insert catalogs so there must be more to the story. BTW when I tried braze on carbides I hated them. I went back to HSS. Those carbides seemed to be very friable (edges chipped easily). I chocked it up to offshore quality because I tried a better USA braze-on & it was much better, but also more expensive. Then I tried some CCMT for both OD turning & boring bars. Some cut better than others, as one would expect, but basically I never looked back.

My vocabulary/web plagiarism might not be quite right but I'll give it a shot. Hardness is the ability of a material to resist deformation. Brittleness is relative inability to sustain plastic deformation before fracture of material occurs. Modulus is the slope of stress/strain curve before elastic deviation occurs. Toughness is the ability of a material to absorb energy and plastically deform without fracturing, the area under the stress strain curve. Ceramics for example are very hard, harder than most tool steels. That property makes for a good cutting edge. But they are also brittle, therefore when it fails the fractured edge no longer resembles a useful tool. Hardness & brittleness generally correlate in many natural materials.

So the way I visualize it, HSS can be conditioned to a razor edge. It is tough & can withstand rough & tumble machining, vibration, harmonics. Its going up & down the more ductile green curve & absorbs more energy doing so. A disadvantage might be how long does the edge last? Its softer by definition. The HSS edge may not be fracturing but its rounding over by abrasion. There is no free ride. It may behave differently at elevated temperature, more time consuming to create &re-create geometry...but now we're getting into the weeds

1668789122725.png 1668790043607.png 1668788563040.png

But here is what I was wondering. Lets say we operate a carbide & HSS in the red box, meaning stress level. Same tool geometry. Neither tool edge has failed. Maybe I'm operating in that zone?
I can think of lots of reasons why ceramic would get pushed into failure, wrong insert geometry for DOC, loose lathe ways, highly interrupted cutting....
1668790852363.png
 
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PeterT

Ultra Member
Premium Member
If your looking for inserts that can turn .001 they can be had for around $260 each. They are specifically for hard turning on CNC. Those inserts are not carbide or coated carbide . Those are ceramics and CBN's, not what your going to be running on a manual lathe IMO. Not to say some aren't doing it. I don't, simply because, my manual lathe couldn't handle it, and to be honest, I don't know of a manual lathe that could handle those inserts.

Like I mentioned above, the 0.001" was maybe more of a discussion parameter or what we achieved in the shop vs. a specific shopping list requirement. At least from my perspective. But the random finishing carbides I pulled from the Korloy catalog are not exotic, they are pretty common off the shelf inserts AFAIK. $260 would buy me about 100 of them LOL. I'm just saying many are referenced in the 0.1mm (~0.004") DOC range as per manufacturer minimum. And I am guessing they are conservative to keep customers happy. I don't think they explode with 0.002" DOC and now the gap is narrowing. For sure many inserts show higher recommended DOC, but its all spelled out in the catalogs. Now if you buy some random inserts with no corresponding part number or specs, then yeah, could be a bad machining experience. No different than grinding a HSS with incorrect rake geometry or tool placement.

1668799406167.png
1668792683868.png

1668792801271.png
 
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Susquatch

Ultra Member
Moderator
Premium Member
Have a look at post #163.

I am sorry to take so long replying to your post. I confess that I have been studying the material you provided in post 163 in my mind all afternoon and all night.

I almost want to keep my mouth shut...... but can't. My own need to understand exceeds the embarrassment of the admission.

I believe the photos and the implications and conclusions Sandvik provides in a few of those photos is wrong......

I know, I know. Who am I to challenge the technical information provided by the likes of Sandvik...... But I've looked at it every which way of Sunday and I keep concluding the same thing.

Perhaps I am missing something. If so, I'd sure like to know what it is.

How can Sandvik be wrong? These characters are insert experts! How can I be right when I am not worthy to walk in their shadow?

Perhaps so, but I know from my own personal experience in the auto industry that the marketing folks often take complicated technical information and turn it into simplified information that is just plain wrong. If I am correct in my assessment of this particular information, then I'd bet that is what has happened at Sandvik too.

Please look at the drawings closely to see if you see what I see. First and foremost, (and what caught my attention in the first place), I see an insert that is cutting air, not metal. There should be metal above the insert that subsequently gets peeled away by the insert. If there is nothing above the insert as shown in their drawings, then there will be no chip. But yet, they show a chip anyway as though it will magically appear out of thin air. In my opinion, the shape and location of the cut section is correct, but only for below the insert. Above it, the shape is also correct but should be shifted to the right by the feed rate. What they show is what it would look like if the feed was disengaged and the lathe left to run for at least one revolution. In this case the cut is already completed, the forces are all gone, and there is no chip.

In my view, the problem that results from this error, is that the resulting forces are shown incorrectly too and so is their derivation and their consequences.

The description completely ignores the downward force on the top of the insert. This force is not minor. In fact, I believe it is the dominant cutting/shearing force by a VERY wide margin. In my mind, it is unreasonable and misleading to ignore this dominant force in any discussion of insert performance and resulting forces. Furthermore, I believe it is the downward cutting force that drives all the issues that we have been discussing here. I'm not saying that the other two forces don't play a role, just that I believe that their role is minor compared to the cutting/shearing force itself. Basically, they guide and direct the cutting force, and I don't think they really do much more than that.

Screenshot_20221118_121242~4.jpg

When I think about forces and the structure needed to support those forces, there is no rock of Gibraltar to the right or front of the tool. The vast majority of the support structure is under the tool down through the cross-slide to the bed because that's where the vast majority of the forces are and must be reacted.
 
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