Hand Sharpening?

[BobWarfield]

Nope, I have nothing to contribute here. I am not very good at grinding HSS tools, but I am trying to learn. I have my carbide insert tooling nailed pretty well. Let's say 80%, so I want to learn HSS now.

I have achieved modest success on several HSS tools. One was a form tool, so was the only way to get a job done, and it worked very well. Another was a little parting off tool that worked well. I tried a large radius round nose with lots of positive rake to try to make a nice finishing tool. That one actually works really well, but it was dumb as a rock simple to make. I want the more sophisticated stuff!

I also attempted to make Swede's Patented 5Bears Precision Cutting "Secret Weapon":

I tried to make that shape, I got close. Mine is not nearly this pretty and has facets. I suspect I need to cut the edges with a jig that holds them consistently at the right angle. In any event, mine just didn't cut the way Swede describes. The shape wasn't quite right. Or, perhaps I didn't hone it properly. There is chit chat frequently about using a pocket hone (EZE-LAP) for the final touch up on the edge. I also saw a note from Widgitmaster on CNCZone who always gets outsanding finishes that he uses no carbide inserts. He just has a tool grinder with a diamond wheel and hand sharpens to the right shape. He talks about having just the right "hook angle", which I gather is the positive rake. I've asked him to post a picture and few notes over on the 'Zone, so hopefully I can learn from that.

Okay guys. Here is your chance. Let's make a thread that has all the hand sharpening tips and secrets you can deliver. How do I use that EZE-LAP exactly? You experienced hands help us out here. A chunk of HSS is a terrible thing to waste, and the HF Tool Grinder is pretty cheap.

Thanks in advance!

BW

 

[Powder keg]

When I was going to school. Before we turned on a lathe we had to be able to sharpen a HSS cutter by hand. I'll take some pictures this week of some of my tools.

Also, I've been fortunate enough to have some very skilled machinists teack me some tricks. I have to make a form cutter for some rings on a cannon I'm working on. I'll take lots of pictures when I doo that.

Later, Wes

 

[Tin Falcon]

BOB:
you opened a can of worms with this one. I went to machinist school about 11 years ago at the beginning of the lathe block of instruction we were taught the basics of the lathe and tool grinding when we got to the lab we were each given a piece of IIRC 1/4 mild steel and told to grind it like a cutter (general purpose). The cutters we actually used were more or less sharp and ready to go but we had to grind our own as needed. no insert stuff in school. I have been able to grind a usable cutter for whatever need since. Not necessarily the prettiest. As time has gone on they have fewer facets and look more like the text books and photos.
Experience has taught that stoning makes a huge difference in the way a HSS lathe bit cuts.
Entire books have been written about cutting tool material and geometry.
Here are a couple of charts that may help

I prefer 0 degree side cutting angle myself but the larger angles ar better for roughing.

The way a tool is ground also depends on the tool holder for instance a lantern tool post had built in back rake a QC does not.
I ground the form tool to do the little candle holder posted in the galley.
Hope this helps
Tin

 

[Mcgyver]

From reading various forums I get the sense newbies sometimes make this way more difficult in their minds than it is. you just need to think through what the tool is doing and where the cutting edge is. Then you can tell where rake is required, the other angles are clearance so things, other than the cutting edge, aren't in contact. The angles don't matter that much, hand held protractor accuracy is more than enough. When i was a newb i made this complex rest system for my bench grinder with adjustable angles and tables and little templates for quick setting to common angles etc. What a complete waste of time! It never gets used. Step up up to the grinder, hold the bit in your hands with the rest out of the way, and try to replicate, for example, what Tin posted, eyeball accuracy to say withing 5 degrees. all there is to it. within an hour you'll wonder what the fuss was. Maybe it'll take you longer, maybe you'll have to ask for some clarification, but my point is don't let it intimidate you from trying it, its no more difficult than say tapping. imo there is little place in the home shop for carbides and most would be better off with hss - you can do almost anything with it and its sooooo inexpensive.

It's best to stone them from there before use. Some like Arkansas stones etc i prefer one of those double sided water stones (that i keep in bucket) because they cut so fast. The only trick part is making sure your stoning motion has zero chance of opening a finger or wrist - its not really tricky but be aware of safety when stoning tools.

to anyone wondering how, have a go, show your attempts and we'll help set you straight if it isn't working

PS, same holds for threading tools, using a thread gauge or acme thread gauge, you can grind these by hand, grind, hold up to the light to check, etc. Bob, just read your note on the right hook, we'll see what Eric has to say, but I'd guess he's referring to creating the positive rake via a chip breaker. This is the advanced class (2nd half hour of the 1 hour masters hss lesson ) basically you don't grind a rake angle (angle on the top of the bit, slanting away from the cutting edge) but you grind a chip break that comes up to the cutting edge - the rake comes from the side of the chip breaker 'trough' itself. I'll see if i can sketch it.

 

[BobWarfield]

Guys, let's advance to chapter 2 in the course, second semester. Been there, seen the basic lathe tools shapes, ground some of them, got the T-shirt. Got a half dozen books that repeat that information including the South Bend lathe book and a number of others. Got the online Army manuals with the same stuff.

Let me be ornery here just briefly to make my point. Unlike Mcgyver, I think carbide is wonderful in the home shop because it gets you immediately doing interesting things without having to master the tool grinding piece. I've had tremendous success with it, and it does a great job for me. I don't need HSS to save money, and it doesn't save that much anyway. An insert for any of my tools is $3 and I don't break one very often. Modern carbide works great for interrupted cuts and my cheezy Asian machines have more than enough rigidity and performance to achieve great results with modern positive rake indexable tooling. And I am not going to settle for the classic educational method that says we have to learn the old ways and pay our dues before we'll let you get close to the new ways.

It's a hobby, let's have fun. I want HSS tooling to open up new horizons. Instead of telling me (as I do my kids!), gee Bob, when I went to school, I walked up hill both ways in the snow, so you need to go back and start over doing that too, I want to know, "What can I do with HSS that I can't do with my carbide and how do I go about doing it?" I've got form tools covered. Not a hard concept to grasp. Been there, done that.

So what's chapter 2 look like?

You've mentioned stoning/honing, lots of people mention honing, there's a thread on PM as we speak, but nobody I've yet found says how to do it! There's a lot of technique to good honing. Scrape one way and things get sharper. Scrape another and they get duller. Knife makers go into intricate detail about how they sharpen their blades. We need more detail on honing HSS tools. Heck, we need any kind of detail at all. How exactly are we honing these tools? Give us a picture. Put arrows and show the motions.

Let's take the Widgitmaster case. He's doing Turner's cubes. The two chief things he has said directly he is doing is using a tool that cuts the whole surface for good finish. This is pretty automatic on a lathe, but on a mill, it's a reason to own a big flycutter and not just use your multi-insert face mill. Use the latter for the roughing, then get out the fly cutter for final finish. I've got one of Widgit's mini-routers, and let me tell you, his finish coming right off the mill is amazing. He's also just posted a link that's all about the relationships of tool radius, feeds, and speeds. Also important, but that's pretty cut and dried for me. There's also some coolant tips, such as use liquid dishwashing soap for plastics. Great, good, very helpful. Now I want tool geometry and sharpening/honing info.

Brings me to an interesting point: there's tons of pix of basic lathe tools, but I've seen precious little about boring bar (what Widgit is using for the Turner's Cubes) or fly cutter geometry. What exactly are those tools supposed to look like? There are tantalizing glimpses of tools that have a hook-like feature, and Widgit's reference to "hook angle". Look at Swede's tool I posted the picture of. That's a very hooklike shape.

Now Mcgyver, lest you think I haven't been listening and watching, I have. Here's a picture from a discussion you were very active in about fly cutter geometry:

That's very interesting. That got me thinking about what you're saying above. Where is the cutting edge? Hmmm. Not where we thought it was. The fly cutter doesn't cut down in Z, it cuts in X and Y along an arc in the horizontal plane. BTW, there's that little curved hook again in that pic. Here's some more hooks relating to fly cutters:

Now here's one that looks more like one of my overly faceted tools:

What's really the best? Commercial flycutters slap a lathe tool in, usually brazed carbide, that's not really the right thing according to those geometries. There are better mousetraps, but what's the best? Why? How do I get that shape?

You see where I'm coming from? Chapter 1 is out there, many have read it, we can go to Sherline and dozens of other places to review, but there is no chapter 2 that I can find. That seems to be lore passed by word of mouth within the trade. Let's bust that out and make it available to those of us not in the trade to get hold of. The trade has mostly gotten on to indexable tooling and CNC button pushing anyway. That's part of why chapter 2 isn't getting out there.

That's why I want "tips and secrets". What can you talk about that hasn't been talked about? Not how do we help the noobs quit making this more difficult. Not let me tell why it is so wrong to use carbide at all. Don't talk down to, educate up to. It ain't difficult at all unless nobody tells you the tips and secrets. Then its easier just to buy the inserts, LOL!

Cheers,

BW

 

[Tin Falcon]

Bob:
for starters here is a pic af a couple of BB s I have. The round one is one i made out of drill rod the other is one ground from a HSS blank.

I will try to take some pics of the stuff you ask.
I read a post at some point IIRC on th HSM board from a shop instructor . He gives the students good sharp bits of proper geometry to start out so they learn how the bit is supposed to cut . Then they learn how to duplicate those tools.
IMHO tool grinding is a basic skill. But in the home shop I do not see a need to learn all the basics at once or up front. I hope I never get the well "You are not a real machinist unless you can ___________"(fill in the blank!! attitude. If someone chooses to use brazed carbide or carbide inserts for weeks months or years before learning to grind HSS what does that matter to me.
Hand grinding is kind of like riding a bike or drawing a free hand illustration. Once learned,it is easier to do than explain. But I will do my best to get some pics and explain the details you asked for.

The other thing to keep in mind published geomerty are the Ideals based on years of research. In the home shop closes counts.
Tin

 

[Bogstandard]

I totally agree with Tin on this one.

It is a thing that can be picked up in stages, as and when required.

Just remember, when you see pictures and charts of grinding angles and such, these are usually geared towards production. In the environment we work in, these ground up tools are used for everything, a bit of steel first, then a bit of brass. If you were to grind up dedicated tools for every material and type of job, you would hardly get anything done. So as you gain experience (by just trying things out), you will strike a happy medium where one ground up tool will 'do' a multitude of tasks.
I only ever grind 'special' tools for a certain job when one of my 'universal' ones won't fit the bill.
But I do agree with everyone else when it comes to final sharpening, I use Arkansas stones, I have never had much success with diamond laps, but that is just my preference. Ground tooling HAS TO BE SHARP, if it isnt, you may as well be using a bit of mild steel to cut with.

John

 

[Mcgyver]

Bob, Lots of good points and questions.

Got a half dozen books that repeat that information including the South Bend lathe book

i wish more people would develop libraries - reading a thoughtful treatise on a subject answers all kinds of questions you never knew you had. This advances ability. read them and put it into practice, in this sport those aren't theoretic ivory tower texts, they're great practical play books.

I think carbide is wonderful in the home shop because it gets you immediately doing interesting things without having to master the tool grinding piece.

I too use carbide to, for certain things. In the context of a grinding tools discussion, it was more an opinion of whats best to use given the particular circumstances and that "I don't know how to grind a tool bit" shouldn't factor in; its not that hard and there's lots of willing help. Since you've raised the point, there is another more pragmatic reason why HSS might be the best tool for the job - remember the shear plane lecture ? more rake is possible with hss, that means a smaller shear plane, that means less cutting force which betters suits light duty home machines. its not a matter of wonder imo, its just sharing mechanical & engineering knowledge....whether that's followed or not, because someone doesn't thing they're ready or even doesn't believe well, like Tin says doesn't matter or bother. I just want people to be empowered to try it by harping on how easy it is.

You've mentioned stoning/honing, lots of people mention honing, there's a thread on PM as we speak, but nobody I've yet found says how to do it! There's a lot of technique to good honing.

mines pretty simple, draw the ground surface across the stone away from the edge. a few strokes on the coarse side, a few on the fine and have a look. keep in mind a tool bit imparts force that sets up a shear plane - it is not slicing - so its maybe not as critical as say stroping a razor.

That got me thinking about what you're saying above. Where is the cutting edge? Hmmm. Not where we thought it was. The fly cutter doesn't cut down in Z, it cuts in X and Y along an arc in the horizontal plane. BTW, there's that little curved hook again in that pic.

you've got it. most slap a knife tool and and plough away, but the cutting direction is as you noticed not straight down but horizontal. the second, grey bit image, is one i did showing how i grind both a lathe facing tool and a flycutter.

the knife tool works, mostly. same way you could take a knife tool and do a light facing cut. heck you could jam a screwdriver into the work and material would be removed....but the point is to create geometry that is efficient - that will remove a lot of material and leave a good finish, it better to do a 150thou facing cut with a properly ground tool that 15 10 thou cuts facing with a knife tool.

What's really the best? Commercial flycutters slap a lathe tool in, usually brazed carbide, that's not really the right thing according to those geometries. There are better mousetraps, but what's the best? Why? How do I get that shape?

what commercial fly cutters? most i've seen come without a tool bit. the large, straight up and down kind will work fine with a knife tool. for each tool, its just a matter of figuring out where the cutting edge and where clearance is required. as i said though, the knife tool will work in the flycutter for light cuts, but its not ideal.

 

[DICKEYBIRD]

Great thread fellers! I picked up a few Eze-Lap sharpeners of various sizes from the local Bass-Pro Shop and they work great for putting on a final keen edge. I got a 1/4" square one, a 1/4" round and a 2" x 6" flat one mounted on a nice wood block.

I had an idea while finishing a HSS tangential bit sharpening exercise over the weekend. After roughing out a blank on the standard ol' grey rock/bench grinder, I smoothed it further on the AO plate wheel on the H/Freight grinder and started to finish it on the medium grit diamond wheel I bought for the other end of the H/F grinder. I remembered where it is said that HSS dissolves the diamonds when grinding it at high speeds so I held the bit against the diamond wheel and turned it by hand. It worked great but was a little awkward. I think I may make a crank handle to engage the big nut that holds the wheel on and try that. A bit of stoneage technology but it should work a treat.

 

[BobWarfield]

Bob, Lots of good points and questions.
read them and put it into practice, in this sport those aren't theoretic ivory tower texts, they're great practical play books.

These books, and many more, have all been read. As I mentioned, they don't cover this topic, only the basics. It's amazing what things are left to be passed on by word of mouth. There are no hard and fast rules in the books for when to use tailstock and/or a rest. All they say is that they may be needed when working on "long skinny" work. When you're in a pro shop surrounded by lots of veterans, you'll hear soon enough what's right or wrong. The problem for the HSM is they're not surrounded by pros and much is left to the imagination. Too much.

Since you've raised the point, there is another more pragmatic reason why HSS might be the best tool for the job - remember the shear plane lecture ? more rake is possible with hss, that means a smaller shear plane, that means less cutting force which betters suits light duty home machines.

Now you've got to totally color me skeptical on that. You're saying you can get more positive rake out of HSS than carbide. I'd like to see a close up picture of the tool that's doing that.

The thing is, indexable tooling can achieve tremendous positive rake in two ways. First, I can buy inserts that have tons of positive rake built in. Check out this CCGT aluminum finishing insert, for example:

For home machines, it works great on steel too, and you can plug it into any CCMT holder. Most folks have never seen one, they're hard to find, and they're pure magic to use. It's primary disadvantage is it will be unhappy on interrupted cuts because the edges are quite thin.

I want to see the HSS tool in regular use that has more positive than that. If it does, it isn't much more.

Second, we can mount the insert at an angle to increase whatever rake is built into the insert. Good cutters are made that way. Consider these two facemills. Here is a TPG-insert (no inherent rake in the insert) advertised as having "90 degree positive rake":

There's no positive rake there, and as someone in another thread commented, it will hammer as a result. For more money (of course!), I can buy this face mill:

You can visibly see how the inserts (which again have no inherent rake) are "laid back" in their pockets to create positive rake.

There are more sophisticated cutters that take positive rake inserts, and lay them back, sometimes in 2 dimensions (axial and radial positive rake).

See why I'm skeptical that HSS can inherently have more positive rake and always has lower cutting force than carbide inserts? Maybe it's true, but I'm definitely in the "show me" camp on it. That's why I'm hear, to learn how to do that.

I am certainly not surprised that pro shops have to rely heavily on their tooling reps to keep up with all the ins and outs. Just keeping up with all the insert variations is a huge amount of information.

Cheers,

BW

 

[Mcgyver]

carbide is wear resistant and can withstand heat but isn't very tough. it does not matter whether you angle the insert or whether the rake is built in, it's the included angle of rake and clearance forming the cutting edge that need be considered....you can get a more acute angle with hss than with carbide for any given load requirement. granted that insert you pictured looks like it has a lot of rake... most positive rake inerts I've seen are not hugely so. if you have more info it would be good to read, i suspect there's a trade off involved else why are they using them on the mill for example. mind you, I'm a eons away from having seen all and there are smart people working on improving these materials.

The only advantage I've heard here for using carbide in the homeshop (Macona and his monarch excluded ) is that its easy for the complete beginner. I want to challenge people by saying that's a non-reason - give it a try, its easy and if i can, help show them how.

Use what you fancy, now back to hss grinding.

Bog, mostly I agree with what you're saying, however not between between brass and steel. a couple of flat topped shapes with small radius covers it all and it can make a mess using positive rake, steel dulled tools on brass. hss blanks are inexpensive enough you do build up a collection over time of specialty things, grooving tools, profiles, thin little ones from crank shaft journals etc.

I should point out with all this rake talk, for the benefit of those newer to this, you don't have to have it to cut steel or anything else. Its there to minimize the cutting force and we usually want it, however sometimes, like in making a profile tool, your are better off with zero rake (flat tops) - the easier to shape, cut the actual profile indented. A thread cutting tool is the simplest example.

 

[rake60]

This is a great thread. A lot of very good information.

My earliest attempts at grinding tools often resulted in heat blued
HSS that didn't cut at all, or very ragged finishes.
That all went away with practice.

As time went on I got lazy. I'd grind the clearances on the sides and front
edges but no rake at all. They cut just as well. I've been using these four
for many years.

They're not pretty by any means. All of them were ground freehand on a bench
grinder. The clearance angles are not calculated or measured. I just grind them
so there IS clearance, and they cut just fine.
There's really no Black Craft to it. It can be as simple or as complicated as you
wish to make it.

Rick

 

[Tin Falcon]

Rick brings up a good point about Zero rake.
At the cabin fever show I finally invested in a set of indexable insert holders from Arthur Warner Co they are top shelf and work great. In retrospect It probably would have been cheaper to get a set of made in USA holders from Enco then HSS inserts from Warner.
But the point here is these tools have no rake. And so far they work great. So the KISS method can be applied to HSS tool grinding.
Tin

 

[deere_x475guy]

Tin, your post is timely for me. I was just looking around for the name of the company that handled the HHS inserts. I just picked up a holder from Production Tool last weekend. It came with one carbide but I wanted to use HHS in it. It's an AR style holder.


I have been grinding my HSS and am not to bad at it. I have been using that hook posted below for along time. Well long for me...last couple of years. If I have a lot of material to get off before I get down to the last .040 I use a negative rake cutter. Then from there I step down to an HHS cutter. I use the hooked one for when I am trying to eeck out a .002 cut that I can't get off cleanly by using a file or sand paper. I'll post back with pics.

A
Ok..got the pics taken and uploaded to photobucket. The hook that I have is no where near that showed in the drawings. Actually after looking at it more it looks like just normal back rake, just exaggerated a little more than normal

 

[te_gui]

Just a little tip on clearance angles;

For most of our work the radius formed by your standard bench grinder wheel is just fine. I will echo the thoughts abut stoning though, a couple seconds with a stone can make all the difference in the finish.

 

[Hilmar]

What and where is
"" Swede's Patented 5Bears Precision Cutting "Secret Weapon":""
Hilmar

 

[BobWarfield]

What and where is
"" Swede's Patented 5Bears Precision Cutting "Secret Weapon":""
Hilmar

That's my made up name for the cutter described on this page: http://www.5bears.com/cnc16.htm

Speaking of which, if you have an unusual or different HSS tool, or special tip for them, post to this thread. Let's keep the knowledge flowing.

FYI, Widgitmaster is sending me a flycutter tool he ground himself. What a nice fellow! He says the shape is not like any of those I pictured above, so I'm eager to have a look at it and learn how it works.

Meanwhile, I will continue to play with HSS off and on. I can grind the basic tool shapes, but had been hoping to see some special advantage in them, which I haven't yet. I've about concluded for most typical lathe operations, there aren't any advantages of HSS over my carbide tooling. If that's the case, it's more a matter of what you prefer to work with. In my case, it looks like I'm an indexable tooling guy. It works great, I get just as good and often better finishes as I can from my HSS efforts, and it is a lot faster and more reliable way for me to get on with building whatever I'm on. Meanwhile, HSS is nice for form tools and other special purposes. I also think there is a good opportunity for me to use it on boring bars and perhaps (thank you Mr Widgitmaster!) fly cutters.

Cheers,

BW

PS Mcgyver, you'd asked for more information on the CCGT inserts. I'm preparing a short article for my cnccookbook web site, but here is the long and the short of it:

- I don't know why they're classified as "CCGT" rather than "CCMT". In theory, ISO says that simply means the dimensions of the insert are made to tighter tolerances. Clearly there is also a radically different cutting geometry at work.

- Most of the major insert manufacturers have one of these special very high positive rake inserts. They tend to have a special designation for them:

Iscar uses "CCGT-AS"

Kennametal uses "CCGT-HP"

Valenite uses "CCGT-1L"

and I'm sure there are others. I can find no consistent terminology. You have to be able to see the picture to tell, so I went onto those manufacturer's sites and figured it out. You can get other insert shapes too. For examle, CCGT-AS has a TCGT-AS triangular counterpart for boring bars and such. I hadn't known that, but will be interested to try one out.

- Each manufacturer has a slightly different sales pitch about why you'd use the insert. Iscar is pushing them as offering such a fine finish for aluminum that no grinding is needed, for example. The recommended materials start from aluminum, but most manufacturers have a formulation for most steels (including stainless) all the way to even high temperature alloys. One would have thought the inserts would be too delicate with their fine edges, but I find they work great on steel.

- Carbide Depot has all those lines, but they're not cheap! $10 an insert. I've bought all mine on eBay at prices ranging from $2-4 an insert. Finding them requires being able to see a picture of the insert and they aren't all that common. Hence I will buy a box of 10 if I find it.

- If you've only ever used the "blunt" carbide inserts in CCMT, or worse, an even less sophisticated geometry like TPG, please try these beauties. You'll be amazed at what they can accomplish. It just might convert you to a carbide guy! LOL

 

[Mcgyver]

the CCGT is a bit irrelevant (that is shape - relief - tolerance - hole and afaik is the same for iso and ansi). ansi or iso determine where its metric or imperial and are the numbers follow the letters. The part that'll make you mental is the chip breaker info seems to be manufacturer specific. for example, the Kennematal HP says the chip breaker gives it 15 degrees top rake - this, the HP, is what distinguishes it from a CCGT with say 0 or negative rake.

i looked into these wondering if maybe material advancements had changed the relative merits of hss and carbide however as i suspected, there is no free lunch, everything is a trade off.
These 15 degree top rake tools are recommended for finishing cuts in aluminum and with a caution that it is a weak edge and is not recommended for steel.

as you do more, you'll discover the advantages of hss. any shape you need, always a sharp tool on hand, knowing how to put an edge on that easily take off less than a thou, or hog off .300" thou, put the radius on to suit the situation, make a super narror groover or parting tool, grind up an internal grooving tool, trepanning on steel or brass, perfectly turn a crank journal, have every size of acme threading tool instock, not caring about an interupted cut, be able to make that tool that will thread 40 tpi to a shoulder or cut a high helix 4 start thread, etc etc etc all for a neglible cost and never wasting time order and waiting.

you say you can do the basic shapes - are they not working for you as well as carbide? Maybe we can figure out why? my advice is stick with it - learn how to grind them, stone them and use them. and I bet you'll see an improvement in workmanship and wonder why you didn't go this route before. All this of course assumes you don't have some $40,000 monolithic lathe that can take advantage of carbide's high removal rates.

back to hss....

here's a couple of images of common tools that use a chip breaker to create the top rake. (my POS P&S is in repair so no pics)

facing tool: this is a most useful facing tool shown to me by a tool and die maker friend. I usually on a small corner radius...by mininmal, i mean bearly discernable. just enough so that its not a sharp corner. this is exactly the same form of tool to use in the common type of flyer where the tool lies at say at a 20 or 30 degree angle to the work

here's the same idea but as a knife tool. great for hogging off stock and will also put a fine finish on. stone on a small radius

 

[BobWarfield]

the CCGT is a bit irrelevant (that is shape - relief - tolerance - hole and afaik is the same for iso and ansi). ansi or iso determine where its metric or imperial and are the numbers follow the letters. The part that'll make you mental is the chip breaker info seems to be manufacturer specific. for example, the Kennematal HP says the chip breaker gives it 15 degrees top rake - this, the HP, is what distinguishes it from a CCGT with say 0 or negative rake.

i looked into these wondering if maybe material advancements had changed the relative merits of hss and carbide however as i suspected, there is no free lunch, everything is a trade off.
These 15 degree top rake tools are recommended for finishing cuts in aluminum and with a caution that it is a weak edge and is not recommended for steel.

Mcgyver, I would be interested in seeing the link to where there is a caution about only finishing aluminum with these inserts. I found quite the opposite both through personal experience, but also in what the manufacturers say. Try this page for example:

http://www.carbidedepot.com/Dynamiclanding.aspx?CategoryID=594

The application note for Kennematal CCGT-HP says:

"Exceptional edge wear resistance combined with very high strength for machining titanium, cast irons, austenitic stainless steels, non-ferrous metals, nonmetals, and most high-temperature alloys."

High-temperature alloys = Inconel, FYI, so this insert is not afraid to go against some tough stuff.

The Iscar insert is available in two grades:

IC20: Used for semi-finishing, finishing and semi-roughing of aluminum, cast iron and stainless steel. Used at low to medium speeds and feeds.

IC520: Suitable for turning austenitic stainless steel and soft materials.

Two points. First note the "low to medium speeds and feeds". Translation: you don't need a Monarch at 4000 rpm to run carbide. This is not surprising to me, because I've been running it for years and it works great. Second, there is a wide range of materials here that clearly suggests these are not just for aluminum, but also consider the differences in need of a home versus pro shop. The home shop will run at lower speeds, feeds, and material removal rates. It will likely take a shallower cut. What looks like finishing in the pro shop is general use for most home lathes. Home shops won't want to carry 10 different varieties of inserts, but a pro shop carries a lot more. I've run these inserts on all sorts of material, through interrupted cuts, and to the limit of depth of cut my lathe will do. They're fine.

I expect many people have had some of the bad carbide experiences described, but that it was for two reasons. First, home users operate differently than pro users, so you have to know how to shop differently. Pros like negative rake tooling because there are more edges to harvest on an insert, so it comes out cheaper. Pros make money removing gobs of material fast with deep cuts. But that is changing as more discover the advantages of positive rake even for pros, and as the CNC manufacturers keep making lighter and lighter machines and cranking up the speeds and feeds while reducing depths of cut. Ironically this results in technology more applicable to lightweight home machines. So you have to know what to look for, such as realizing that "finishing" might mean "general purpose" in a home shop context. Pros are also much more conscious of wear characteristics. Home shops want to be frugal, sure, but if an insert breaks sometimes in a manual machining op, we see it immediately, change it, dial back on what we were doing so it doesn't happen again, and go on. The pro is running a CNC lathe at ridiculous material removal rates (we've all seen the cool videos!) with a bar feeder for many hours in the day. If an insert breaks, a bunch of parts pop out the other end that are wrong. In fact, when the next tool hits the material thinking it was already cut, and it wasn't because of a broken insert, even worse can happen. So the definition of what's "fragile" for a pro is different than for the home.

Second, the exact details of what to look for and how to use it are the "secrets" of carbide tooling. For example, the choice of tooling and insert geometry matters hugely with carbide, and I can certainly understand someone having a bad experience and deciding it was because their machine wasn't "up to carbide." Let me assure you, that isn't the case, you just haven't gotten hold of the right tooling yet. I don't mean to pick on them, but I have one of the Plastool turning and facing holders and found it performs poorly next to even regular CCMT tooling let alone CCGT. I can definitely grind an HSS tool that gives a better result than the Plastool and have done so. If that was my only experience with carbide, I'd be taking Mcgyver's position 100%.

I chalk that up entirely to the insert being used. I've seen similar things with indexable tooling for the mill. TPG tooling just doesn't cut nearly as nicely as something like a high positive rake Iscar Helimill or my Lovejoy 225 face mill. So, a "secret" for carbide turning tools is to run tooling with CCGT inserts. Another is to stick the biggest holder in that your QCTP will accomodate. I saw marked differences when I went from 3/8" Glanze up to 1/2" Micro100 holders. I made my own dovetail cutter using TPGB inserts originally and found performance improved greatly when I switched to TCMT. I haven't tried TCGT but will soon!

Most of the time you read about guys buying the cheapest possible bargain because that's what the budget permits. I understand, and HSS will easily outperform the cheapest indexable tooling. No contest. The tools I grind are already there. If you can either wait for the right sale, spend a little more, or get lucky on eBay, you can get some awesome results out of indexable tooling that are well worth it.

Okay, enough carbide. I definitely didn't start out to debate carbide vs HSS, but we seem to wind up there. That's fine. Perhaps its because most guys do one or the other while I'm basically trying to do both and am neither fish nor fowl. Just please be aware there is a LOT of misinformation about carbide in the context of the home shop. I've enough experience with it to be completely comfortable on that. I hope I've passed along some information that will make others more successful with carbide than they otherwise might have been.

What I hoped to get here was the genuinely new and hard to find tips about HSS. Sort of like the "secret CCGT" insert info I've presented on carbide. Several have suggested there is no such information on HSS, that's its very basic and you just do it. That's cool, I'll take that as my working assumption and keep experimenting and asking questions. At the moment I can get surface finish from HSS that is equivalent to my CCGT tooling and that I consider good. But, if I can't get HSS to do something better than the carbide, I'm a carbide man. It's easier and more consistent. I'll keep the HSS for form tools and other things for which there is no purpose-built indexable tooling.

Towards that end, I am really looking forward to seeing and trying out Widgitmaster's flycutter. I have also ordered today a set of diamond EZE-Laps so I can keep playing with honing/stoning my HSS. I have also heard you can touch up an insert with them.

Cheers,

BW

 

[Tin Falcon]

The idea of a general purpose bit suitable for most materials has been mentioned.
The recommended geometry for a GP bit is as follows.
End cutting edge angle 30 degrees
Side cutting edge angle Zero degrees
Side relief 10 degrees.
End relief 10 degrees.
Side rake 15 degrees
back rake 5 degrees.
Nose radius 1/16th inch
For definitions of these terms see the charts posted earlier.
well what does this look like?? since bits are generally small a while back I did a wooden demo to illustrate the concept.
Here is a photo of a right hand bit.

and here is the top view

A left hand version of this would likely work well as a fly cutter.
Hope this helps
Tin