Carbide insert recommendations for student shop

Hi everyone,

I am tasked with teaching many students how to use the lathes in one of the school shops that I use often. For the kinds of speeds that people are comfortable running at, I know we are usually far under where carbide performs best. That is, until I get them on the CNC and it can actually run that fast and have stops so it is near impossible to crash.

I would just use HSS, but there is an entire art form in grinding HSS that I don't currently posses the skills to teach. Running the lathe is complicated enough for some people anyway.

We have a bunch of old carbide, but it is old carbide. Absolutely no information on speeds and feeds online and what I can find, it seems like someone ordered a bunch of specialty inserts for materials we don't usually work with. From what I have read online, carbide has come a long way since those inserts were made. Plus after years of use and abuse in a student shop, most of our insert holders are trashed. Something I am trying to avoid by teaching people how to use the equipment properly.

Not looking for mirror finishes like we are assembling hydraulic cylinders or anything.

We often run aluminum and cheap steel. I know that is very vague, but we have a ton of material in our shop but it isn't labeled in any way.

What are some basic insert recommendations for this case? Just basic OD turning and facing. Generally no heavy cutting.

Also, an actual class is taught in this shop once a year. One of their projects is to turn a basic part, but the GA orders cold rolled steel. I can not for the life of me get a good surface finish on that material. Is there an insert that will do well with cold rolled?

Thank you!

Bring in a teacher sub for the day to actually teach how to grind HSS.

Have large posters set up for the teaching, to explain clearance etc.

It's not an "Art Form", it is simple.

It's covered well in "how to run a lathe".... which is what your supposed to be teaching eh ?

I'd speak to Curtis (ExKenna on PM) at Lathe inserts.com LATHE INSERTS

He has a good rep on this board, knows his game inside out, understands ''the small user'' with varied materials etc etc etc and only sells quality gear, and at good prices.

FWIW I think you would be the sort of customer that's right up his alley.

NO PERSONAL EXPERIENCE as I live in the UK, ....were I in the US he'd be my go to guy.

QT Op:I don't currently posses the skills to teach.
HSS is required for one-ups and the like..being a teacher you should master that skill..not that big a deal and need not be perfect angles...

QT: [but it is old carbide.] Nothing wring with old carbide. Much of the old carbide is every bit as good as made today.. Yes chip breaker shapes do add some efficiency....Students need to know grades and cutting tool geometry..

Plenty good books on simple manual machining...

This is very basic you should know; (copy paste in brouser)
file:///C:/Documents%20and%20Settings/Jim/My%20Documents/Downloads/9781849960526-c1%20(1).pdf

Basic speeds and feeds:
Cutting Speeds - LittleMachineShop.com

Basic lathe terms;
Lathe Terminology — Sherline Products

You owe your students 20 hours of study time in a subject to think about teaching.IMHO.

I know we are usually far under where carbide performs best.

Click to expand...

ARRGGGGHHHH!!!!

Carbide does not have to be run fast.. The material has not one fricken clue what the
cutting tool is made out of, it could be crusty boogers and bubble gum...

Just like HSS, it all boils down to GEOMETRY!!!

Polished/ground/upsharp inserts act almost exactly like a nicely ground sharp piece of HSS.
Yeah, they are meant for aluminum, but they work a treat when you need low tool pressure and
they work well when you aren't running stupid surface speed.. I use them all the time in
non-aluminum.. They will help you get a decent finish on a crappy low carbon steel also.

Picking out inserts is a pain in the ass.. I've got too much other stuff to do, and too much
other stuff to remember... I now let somebody else make the decisions..

Give Curtis a call(exkenna on this site).. Saves you the headache of trying to figure out what you need.
Just tell him what you are doing and tools show up on your door step, and 99% of the time they work
really well, and 99.9% of the time you'll really like the price... He won't sell you crap, unless
you specifically request crap...

SMALL LATHE TOOLING, AXA TOOLPOST, ccmt inserts, ccgt inserts

So far as using cold rolled steel is concerned, that is perhaps not the best choice if you're trying to impress the students with how much fun machining is. I'd press for 12L14 or 1144 steels, as those are naturally short chipping and machine quite a bit better. Almost any old insert will work for rough machining in those materials. Then get a few finisher inserts for the final cuts.

Edit: you might also inquire about 1045 steel in a cold rolled condition. Typically it comes as ground and polished, but if you're not using the finished OD, then no use paying for that. 1045 is the grade I call general purpose and I use it everywhere that the typical 1018 (crap rolled) would get used, except I'd use the latter if welding was the main consideration.

I really appreciate all of the feedback thus far.

One thing that it seems I didn't make clear is that I am also an undergraduate student. I am not in charge of this shop in any official capacity, nor am I compensated in any way for any of this. I have no formal training in machining besides what I have read and watched online and my own trial and error. Oh, and limited consultation from a local machinist. That being said, I have learned a lot about machining over the last couple of years, and my fellow students recognize that I have put in the effort to do so and have asked for my assistance in learning.

There is one shop class involving machining taught at this university. And I taught the GA that teaches that class. So it isn't a class anyone should take to actually learn machining. The purpose of that class is to give engineering students an understanding of the most common manufacturing processes in the hopes that they don't design something nearly impossible to manufacture. I sit in on the class and help for two reasons. The first is that I still want them to be capable of making decent parts. The second is that I don't want them to break anything that could slow progress of other projects done in the shop outside of the class. (SAE baja and robotics teams also use the shop)

This is not a formal class, though the progress made through this could carry on to the class mentioned earlier. The goal of this is to teach SAE baja and robotics team members basic lathe skills so they can make basic parts and hopefully make sensible designs. I am simply passing on what knowledge I do have in order to speed up their learning and letting them learn from my mistakes and successes rather than making them research from scratch. One of my goals in doing so is to simplify our tooling selection. A few sku numbers for inserts. A few tool holders. And documents explaining setup and feeds and speeds for the materials those inserts are best at cutting.

Our current selection is a drawer of random tool holders, inserts, brazed carbide, and custom HSS tools other people have ground in the past. We have many carbide inserts that we don't even have holders for. And holders that have clearly been damaged beyond safe or successful use.

My goal is not to train the next generation of machinists. It is to make basic lathe operations easy and give people the basic skills to run the lathes without any major mistakes or constantly tearing up tooling. All in order for everyone to have a better experience in the shared student shop. Most of the parts they will be making have rather loose tolerances and no need for a perfect finish.

I have watched hours of videos about grinding HSS. I have ground my own tools with some success. The purpose of choosing insert tooling over HSS is not because I think that HSS is a poor option. Grinding a good HSS tool is a lot more than making it sharp. Relief in multiple directions, and other tool geometry features have to be considered. Insert tooling takes care of that for them. It is just one less thing for them to worry about. I still show people HSS tooling. But I don't claim to be any good at making good tools from it. They are always free to do their own research and make any HSS tool they want.

Anything learning beyond what I have described is highly encouraged, but it is unfortunately on their own. We have a machinist available for basic questions and he can make more advanced parts for us. But he simply does not have the time required to teach. He has parts to make for university research and more than a full time job's worth of work outside of his job at the university. I don't think he ever gets a chance to relax.

Bobw said:

ARRGGGGHHHH!!!!

Carbide does not have to be run fast.. The material has not one fricken clue what the
cutting tool is made out of, it could be crusty boogers and bubble gum...

Click to expand...

Perhaps a better way of wording it on my end is that I know that we won't often take full advantage of what carbide tooling is capable of.

What is the name of said "Taxpayer fund wasting POS university" ?

HuFlungDung said:

So far as using cold rolled steel is concerned, that is perhaps not the best choice if you're trying to impress the students with how much fun machining is. I'd press for 12L14 or 1144 steels, as those are naturally short chipping and machine quite a bit better. Almost any old insert will work for rough machining in those materials. Then get a few finisher inserts for the final cuts.

Edit: you might also inquire about 1045 steel in a cold rolled condition. Typically it comes as ground and polished, but if you're not using the finished OD, then no use paying for that. 1045 is the grade I call general purpose and I use it everywhere that the typical 1018 (crap rolled) would get used, except I'd use the latter if welding was the main consideration.

Click to expand...

I am not the one that orders cold rolled for machining. That would be the actual graduate assistant in charge of the shop. I will certainly pass along the information to him. I think he realized his mistake last year when we spent hours trying to get a decent finish on it. The only way I could do it was with a certain insert and on the cnc lathe well out of his comfort zone for teaching. Granted, neither of us have a machining background. I just followed some settings I found online and plugged them into the cnc lathe.

QT: [that HSS is a poor option.].. When you can buy an insert (catalog item)for a task doing that is very often the best choice for sure.. and you can often change that insert and not reset you set-up for higher and expected productivity....
Where their is not an insert for the task designing a special and waiting for delivery can be a problem.
So only inserts or only HSS is not an option if parts are to be made....in house grinding carbide is often not an option for the average tool maker or lathe hand...learning tool geometry for off hand making bits or carbide inserts is essential..also considering the size and power of the machine.. IMHO.

Think of all the special you might need such a certain corner radius, a oil seal groove. a snap ring groove, a threading bit nose flat, a one up machine machine part needing a simple special feature. Most all a HSS bit needed..even if it is a catalog item and you don't have that insert on hand and perhaps 10 minuets to make the bit and the part..

digger doug said:

What is the name of said "Taxpayer fund wasting POS university" ?

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Well, it is in Illinois, so not so taxpayer funded right now.

This is a great university, it just doesn't offer any sort of real machining courses. Or courses on any trade for that matter. Just because we don't have that, doesn't make it "POS university". Nobody looking to be a machinist would ever come here for that reason. There are many other places that offer that education.

michiganbuck said:

QT: [that HSS is a poor option.].. when you can buy an insert for a task doing that is very often the best choice for sure.. and you can often change that insert and not reset you set-up for higher and expected productivity....
Where their is not an insert for the task designing a special and waiting for delivery can be a problem.
So only inserts or only HSS is not an option if parts are to be made....in house grinding carbide is often not an option for the average tool maker or lathe hand...

Click to expand...

I am having some trouble understanding your point here. You quoted "that HSS is a poor option" out of context.

I have no problems with HSS tooling. Just that with modern insert tooling and the basic operations we usually use, there is no reason for ME to teach HSS tool grinding when that time could be used to teach them the basic lathe operations.

I have absolutely no desire to ever have to grind carbide.

Guess you are missing the point...been there and done that to almost every thing in the trade..no not a master of all the skills but a hand in many.....never said you should grind carbide or teach same.

QT op: [You quoted "that HSS is a poor option"].... QT: means I am quoting a post that said that...was it yours, perhaps not?

QT OP:[This is a great university, it just doesn't offer any sort of real machining courses.] then why ask about carbide and lathe operation..do they have a lathe there?

Good luck with teaching shop, Buck

michiganbuck said:

Guess you are missing the point...been there and done that to almost every thing in the trade..no not a master of all the skills but a hand in many.....never said you should grind carbide or teach same.

QT op: [You quoted "that HSS is a poor option"].... QT: means I am quoting a post that said that...was it yours, perhaps not?

QT OP:[This is a great university, it just doesn't offer any sort of real machining courses.] then why ask about carbide and lathe operation..do they have a lathe there?

Good luck with teaching shop, Buck

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Ok. That is an oddly specific few words to quote just to say that you are talking about that entire post.

We have multiple mostly equipped machine shops for student use. Just no real classes on how to become handy at machining. Which is what I am very informally providing to fellow students that have an interest in it. The shop that I use most frequently has 3 manual lathes and 1 cnc lathe.

nerdyrcdriver said:

We have multiple mostly equipped machine shops for student use. Just no real classes on how to become handy at machining.

Click to expand...

To ME, that doesn't even make sense..

One of the first manufacturing/engineering classes that I took was essentially an introduction
on how to make shit. 2 lectures and 2 labs a week. I don't remember exactly what was covered
in the lectures (classes and info gained kind of blend in together after years)..

Holy crap.. Apparently that class now has its own web page...

About ME18 - ME18

Its apparently changed a bit since I took it 20 something years ago..

something that stands out to me.

It is our believe therefore that engineers that have an understanding of manufacturing processes and manufacturing science (the study of manufacturing processes) will be better engineers. We are with this course trying to manufacture engineers who understand how things are made so that they will be able to design things that can be made.

Click to expand...

My ME1800 project is still in my tool box, and I just took a pic... Nothing fancy, we cast it
and machined it, then we had to make a print of it(majority of the grade, I missed one dimension and
got a 94)...




Fun class.. It was an engineering course, but it was also an intro to working
in a shop type of course..

This book should be known by anyone teaching a machine tools skills class.
Audel Machine Shop Basics, Fifth Edition / Edition 5 by Rex Miller, Mark Richard Miller | | 978764555268 | Paperback | Barnes & Noble(R)

A Journeyman tool maker or the like likely to know everything in this book. $19.00 a bargain.. and then something on basic programming..but those books can be expensive.

For a decent lathe mild steel perhaps 10-`12 side clearance (side cutting edge)
perhaps 8* end or radius nose clearance
perhaps 10 -15 side rake
perhaps 5 to 12 * back rake
Grade c-5 to c-8 (c-8 for finishing)..
A chip breaker that rolls the chip as you wish..
A nose radius getting larger with larger machine and more HP perhaps from 1/64 to 1/4 depending on the lathe

This just for starters/ball park... as some steels like a negative insert
*Just tell the boys to pick the catalog one that says "For Steel" and if it does not work find another catalog and pick "For Steel" again....Not

Good for boys to learn this: http://www.carbidedepot.com/formulas-insert-d.htm

Bobw said:

To ME, that doesn't even make sense..

One of the first manufacturing/engineering classes that I took was essentially an introduction
on how to make shit. 2 lectures and 2 labs a week. I don't remember exactly what was covered
in the lectures (classes and info gained kind of blend in together after years)..

Click to expand...

Yep. We SHOULD have that. But we don't. Our campus machinist wants that to be a thing, but that would require another machinist to be hired.

I work a lot with senior design teams that either come up with a project or are assigned a project to design and build. It is just sad how bad people are at designing things as seniors in mechanical engineering. But at the same time, they have no idea how things are made. Often times they need stuff 3D printed (I run one of the printers on campus). I constantly have to tell them that the only way to make their parts is to 3d print them with dissoluble supports. Some stuff could be done with some crazy multi stage injection molding, but that still isn't cost effective or efficient for what can be simplified greatly.

WITHOUT UNDERSTANDING A FUCKING POINT HERE .......... not reading any parameters of what you are MAKING, on what
model of machine, and sfm's you are dealing with... NOBODY HAS THE ANSWER to such a question.

ok, get a TNM_ 4__ toolhoder and TNMP 433 and TNMG 432 inserts . use the positive chip-breaker for aluninum
and the negative one for steel . that's the best i can offer.

tnmgcarbide said:

WITHOUT UNDERSTANDING A FUCKING POINT HERE .......... not reading any parameters of what you are MAKING, on what
model of machine, and sfm's you are dealing with... NOBODY HAS THE ANSWER to such a question.

ok, get a TNM_ 4__ toolhoder and TNMP 433 and TNMG 432 inserts . use the positive chip-breaker for aluninum
and the negative one for steel . that's the best i can offer.

Click to expand...

Whoa there. No need to shout. The information at the end of your response is exactly what I was looking for. General recommendations. You are the first to ask for this information.

Unfortunately I simply do not have much material information available. Most of what we use is leftover scrap laying around the shop.

Our main lathe is this Leblond Regal. My second favorite lathe. My only complaint is that it doesn't have any way to read distance traveled on the z axis. We get around this with a 2in indicator, but that is not always convenient to set up and only allows accurate measurement of 2in. Sorry, I don't have the specific information on it handy as I am home for break.

We also have this Enco 110-2075. Though we do not have a toolpost for it at the moment.


Additionally, we have what I think is a small brown and sharpe (could be wrong on that). Very worn out though. Usually only use it for small parts the 6 jaw chucks can't grip.

My favorite is our Bridgeport EZ Path SD. The downside of that lathe is that our 3 jaw chuck is not adjustable and is currently not holding parts as concentric as I would like. The 4 jaw is great, but makes quick jobs take longer than they would on the manual lathes with the adjustable 6 jaw chuck.