# Carbide tooling



## DavidR8 (Nov 13, 2019)

Hey all, I see many people using carbide tooling in their mini lathes. 
I was of the understanding that carbide needed high feed rates and spindle speeds to be effective. 
Can someone educate me?


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## MontanaLon (Nov 13, 2019)

Many of the mini lathes have plenty of spindle speed for carbide. The feed rates are likewise high enough. Where they lack is in depth of cut because of a lack of horsepower. It is all about what surface finish is needed. Most hobbyists aren't needing mirror like finishes and when weighed against the extra work of grinding tools in HSS most will accept a pretty good finish over the extra time and skill needed to grind HSS. 

I have gotten into a habit of roughing out with carbide and using HSS when I can to finish. To me it is the best of both worlds. But then my lathe isn't "mini" except maybe to Abom79.


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## ttabbal (Nov 13, 2019)

I have both. I don't have a mini, but my 1127 is pretty small as lathes go. I reach for the HSS 90% of the time. It gives me a better finish with lower cutting forces than the inserted carbide I have. I can take deep roughing cuts or shave a few tenths off. Inserts have a minimum depth of cut to work well. Combined with the increased forces, that can cause problems for smaller machines. 

That isn't to say that the inserts are useless, I occasionally work material that eats HSS. My boring bars are also carbide. 

As for time and skill, a good grinder limits the time required. And if I can do it, I think most anyone can.  it looks far more difficult than it is.


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## Tozguy (Nov 13, 2019)

Carbide tools are more brittle than HSS and the edge will chip easily from chatter or other mishaps.
My adventure into carbide started with cheap brazed carbide bits which was self defeating. 
You need to sharpen brazed carbide from the start.
Inserts don't need sharpening but are expensive and just as fragile. 
So now I use carbide only when the hardness of the work dictates it. My 12x36 is rigid enough to run carbide successfully and I have the confidence to run the speeds and feeds high enough. But HSS cobalt and Crobalt style bits in a tangential holder are my go-to for most one off jobs on the lathe.


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## Downunder Bob (Nov 13, 2019)

Ash been said, it comes down to horses for courses. Carbide tools certainly perform better when worked hard. The problems you have with a mini lathe is HP and rigidity. However there are times when you should use carbide and that is when you are machining a hard material. Times when the HSS just doesn't stand up to the cut, even when you slow it down. so go the carbide.

For light finishing cuts HSS will usually give you a better finish. Also when cutting softer metals like aluminium, copper, brass, even free cutting mild steel HSS is generally best. I also prefer HSS for single point thread cutting even on a larger lathe with the rigidity and HP, it's just that most thread cutting is done at a relatively low speed.

You should try everything and then use what you find suits you best.


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## DavidR8 (Nov 13, 2019)

Thanks gents. 
As a newcomer to the hobby it’s tough to sort out the whys and wherefores!


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## mikey (Nov 13, 2019)

Dave, you've gotten some good answers but let me muddy the waters a bit more.

The problem with mini-lathes is that they lack rigidity, speed, power and size capacity. When speaking about carbide tooling, and especially inserted carbide tooling, all of these things matter. A deficiency in any one of these capabilities will impair your ability to use carbide as intended. A lot of mini-lathe guys use inserted carbide and think they work well but it isn't until you see how carbide works in a high horsepower, high speed spindle situation that you understand that there's "work" and then there's work. 

Inserted carbide tools will work on your little lathe. I mean, it will cut. However, you lack all of the things above so do not expect carbide to give you all the benefits it would normally confer. I own a Sherline lathe and I've used inserted carbide, brazed carbide and HSS with it so I'm not guessing here. Inserted carbide will work for you, and you don't have to grind anything to do so. What you will also find, however, is that the cost for this tooling will be much higher vs HSS and you will not be able to cut to tight tolerances as easily. Yes, carbide works better for harder materials but you still need enough power, speed and rigidity to cut it and you may not have it ... just saying. 

If you still want to try inserted carbide tooling, probably the best geometry for a small lathe will be an SCLCR tool holder with CCMT and CCGT inserts. If you go this route, ask the guys and they will guide you.

Regardless of what the Youtube guys show you, lathe work is not really about deep roughing cuts; it's more about accuracy at the small end of things. A good HSS tool will usually cut what you dial in, whereas an inserted carbide tool requires a lot more skill and experience to do the same thing. You can definitely cut accurately with a carbide tool but you have to know how to work with the insert geometry and nose radius of the tool, and there is a whole lot more to it than you might think.

If you wish to work with HSS but either cannot grind it yet or just prefer inserted tooling, look at the AR Warner line of inserted HSS tools. Their inserts are flat on top and can be easily sharpened by honing the top of the insert so the cost per insert, while high, is not bad considering how long one insert will last. 

Of course, your best bet will be to learn to grind your own HSS tools. It will work better for most materials, will be easier to use and will cut more accurately on your little lathe.


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## pontiac428 (Nov 13, 2019)

Count my vote for HSS.  I don't have a mini lathe, but it is small enough to need to understand its limits with rigidity.  My impression of carbide is that it loves being ripped in RPM and driven no less than .040 DOC into the work to produce a nice result.  Most of the time I cut .020-040 based on my lathe's performance, and carbide just doesn't do that well.  HSS does great at any DOC, is sharpenable for a lifetime, and highly customizable.  There are some really great rinds that can be employed for incredible versatility.  It's cheap, with 3/8" M2 blanks costing about the same as one middle of the road import insert.  I never liked the idea of paying so much for inserts that will dull or chip then be thrown away, especially when the performance drops so much as they approach that point.  If I need something harder or more heat tolerant, I can use cobalt.  If I'm cutting a piece of stainless that is getting feisty, then the inserts come out, but they don't see the light of day much when I have 20 or so HSS tools ground, sharpened, and ready to work.  ...aaand that's worth exactly two cents.


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## DAT510 (Nov 13, 2019)

Stefan Gotteswinter has a number of great videos regarding the use of carbide on small parts and lower HP machines.  From my understanding carbide is typically ground/formed to a less than sharp or razor sharp edge due to it brittleness and risk of damaging/chipping of the cutting face.  Stefan regrinds his inserts and solid carbide bits to sharp edges, to allow him to use carbide in less traditional ways.  

His latest video is a DIY Slow Speed Carbide Grinder


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## pontiac428 (Nov 13, 2019)

I've sharpened both inserts and cemented carbide lathe bits on my Deckel clone, even at high speed it works well.


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## Tozguy (Nov 14, 2019)

As a newbie carbide tooling looked like a way to dodge the tedious grinding of 1/2 '' HSS. For the cost of learning the ropes with carbide (brazed and inserts) I could have bought a decent grinding set up for HSS.
Grinding HSS can be fun when you have the right equipment.
Then I tried the eccentric engineering tangential holder and after a few days of using it declared that the war was won. 
Now I use the TT holder for most outside cutting, carbide inserts for threading and boring (Mesa Tool), and home ground HSS when special form tools are needed. 
No matter how you cut it you are faced with spending some money. Have a look at the eccentric engineering site while you are at it and enjoy your new hobby.


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## tmenyc (Nov 14, 2019)

David,
I'm not far ahead of you, and had zero experience before I started, almost a year ago.  With all the confidence of near complete ignorance, but with a head that relishes a new challenge, I went Mikey's way.  Got the Precision Matthews 3/8" SCLCR/CCMT, CCGT set and a grinder, and now finally have the carbide AND a good, and expanding, set of HSS tools that are working well for me in 12L14 steel and a lot of softer stuff I need for my niche work.  I use the carbide for roughing cuts, particularly in removing the skin, and at my highest speed, 1440 rpm, and at higher feeds.  I also got, again per Mikey's recommendation, Micro100's solid carbide boring and internal threading tools, and they're a treat to use, like a fine dessert.  He and others have also been on the mark in telling me to try every combo of speed and feed on scratch stuff to see what works, and my old Logan definitely tells me what works. 
Tim


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## lpakiz (Nov 14, 2019)

Try this.  I searched EBay with “carbide insert lathe tool holder”
Very cheap tooling.  I bought several variations and they work great!


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## DavidR8 (Nov 14, 2019)

I'm looped in on the HSS tooling mega-thread, in fact I received the models yesterday so I hope to get in a bit of time this weekend sharpening my grinding skills 

As a newcomer to the obsession, I'm really interested in building up a base of skills that will serve me as my skills and abilities expand.


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## Dan_S (Nov 14, 2019)

Imo when it comes to inserts and hobby equipment what maters most, is the type of insert, and the chip breaker geometry.

The Major manufactures  usually break inserts down into 3 general types roughing, medium, and finishing. For hobby sized machines (< 14") you don't want to be running anything other than finishing inserts.  Finishing insets are specifically designed for low feed rates,  depth of cut, and toll pressure.

With regards to chip breaker geometry you want inserts with almost no land, and positive rake.

These are the insets I use for steel on my little 8x14.




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						Sandvik Coromant
					






					www.sandvik.coromant.com
				





Here I'm pushing them pretty hard in 1144 stressproof,  0.1" doc (0.2" of the diameter).


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## macardoso (Nov 14, 2019)

I'm going to throw a dissenting opinion out here. I have a 12x36 lathe and use carbide inserts 90% of the time (pretty much except for parting off). I find that it is beneficial to:

Always have a properly shaped tool
Have indexable toolholders always are positioned 90 degrees to the work (don't move the toolpost). This makes it very fast to change tooling.
Have tool materials/geometries ideal for my workpiece material
Quickly change cutting edge without having to re-zero the tool (except for very precision applications)
Run workpiece as fast as possible without worry of burning up tooling
Cut very hard materials when needed
No need to grind tools or make a mess in my basement by running the grinder!
I *very *rarely chip my tooling and I buy inserts from Shars at very reasonable prices. I love the ground edge inserts (e.g. CCGX) for aluminum and can get extremely good finishes right out of the box.

EDIT: I do want to add (because I think many people misunderstand this) that carbide is most *productive* when run fast and hard, however it doesn't *need* to be run hard. The carbide will cut up to these super fast speeds, but still does fine if you cut at 50 rpm. It isn't like it magically falls apart at low speeds. Just cut hard enough to not rub the tool and deep enough to fully bury the nose radius.


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