# Embarrassed to ask, but haven't found an answer to this with pictures - carbide angles relative to workpiece



## WobblyHand (Dec 20, 2019)

Have an LMS mini lathe.  I ordered carbide bits with it, since I didn't really know what I was doing.  So there are three bits in this kit.  These are triangular indexable bits.


Sorry about the focus, I thought it was on the bits.  How are they used?  Starting from the tool on the right, we can mount this on a QCTP.  For non facing, is the bit relative to the workpiece mounted like the picture below?
	

		
			
		

		
	



What should the angle be relative to the length of the piece?  90?  I've read conflicting things, or I'm confused.  So I'm asking for help.  There are a lot of pictures (on this site) on HSS tool angles, but I haven't found anything on carbide tool positioning.  As you can see from the 2nd photo, the facing that I did was ragged at best.


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## mikey (Dec 20, 2019)

Turn the tool so that the cutting edge on the left angles toward the chuck by about 5 degrees or so. That will work of both facing and turning. That tool has a huge nose radius and the cutting edges are pressed, not ground, so it will require relatively heavy cuts to work well. I cannot tell how big the tools are but it is possible that AR Warner might sell T-15 HSS inserts that would work better on your small lathe. Maybe check with them?


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## WobblyHand (Dec 20, 2019)

Thanks.  It isn't a very good tool for light cuts at all.  Even at 5 degrees.  I assume you mean a 95 degree included angle between the length of the workpiece and the length of the tool.  The tool has been kind of frustrating.  I'll check with AR Warner to see what they have.

In the meantime, I've been following the thread on grinding your own.  Have the tool steel and keystock.  Waiting for the sample example bits (they are in the mail), just trying to figure out the grinder part.


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## mikey (Dec 20, 2019)

Yeah, turn the tool counterclockwise 5 degrees. 

HSS will work much better on your little lathe. It will rough better but more importantly, it will take very fine cuts with ease so you can come in on size. I know that model tools thread is a monster but read through it if you can; there is a lot of good information there.


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## WobblyHand (Dec 20, 2019)

These are TCMT  2-1.5-1 carbide inserts: 0.093" thick, 0.015" radius, 7 deg clearance angle, 0.250 IC.  3/8 shank.  So 1/64" radius.  They chatter a lot more than I'd like.  Last time I checked, they were on center, how close to center do you need to be?  Does the ruler trick work for these carbide tools?


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## WobblyHand (Dec 20, 2019)

I've read that entire thread end to end    Thanks for starting it and keeping it going!  It's been very educational and helpful.
Still hope to be able to use these carbide bits for something...


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## BtoVin83 (Dec 20, 2019)

yes, it should have an angle. What that angle should be let your imagination take hold. Depending on the operations  I'll run them angled right or left or strait in. Negative rake tooling is pretty forgiving not like positive rake HSS


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## mikey (Dec 20, 2019)

WobblyHand said:


> These are TCMT  2-1.5-1 carbide inserts: 0.093" thick, 0.015" radius, 7 deg clearance angle, 0.250 IC.  3/8 shank.  So 1/64" radius.  They chatter a lot more than I'd like.  Last time I checked, they were on center, how close to center do you need to be?  Does the ruler trick work for these carbide tools?



Should be dead on the centerline of your spindle. Yes, the ruler trick will work for now.


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## Cadillac (Dec 20, 2019)

WobblyHand said:


> These are TCMT  2-1.5-1 carbide inserts: 0.093" thick, 0.015" radius, 7 deg clearance angle, 0.250 IC.  3/8 shank.  So 1/64" radius.  They chatter a lot more than I'd like.  Last time I checked, they were on center, how close to center do you need to be?  Does the ruler trick work for these carbide tools?


Look at tcgt 21.51 inserts they will work much better on your lathe. The inserts you have are molded with a large nose radius,these are ground and sharp.


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## Mitch Alsup (Dec 20, 2019)

Rule of thumb:: the smaller the nose radius the light the load on the lathe.

Rule of thumb:: negative rake angles are for very hard material; while positive rake are for soft materials.

So, TCGT are a positive rake version of the TCMT, and look for a nose radius of about 0.008 or smaller






						Sandvik Coromant
					






					www.sandvik.coromant.com


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## WobblyHand (Dec 20, 2019)

Thanks for your answers!  It's quite helpful.  I notice these inserts *TCGT21.51* are for non ferrous materials like aluminum and brass.
1. Is there a way to buy a few as opposed to a 10 pack?  Not sure I want to spend $50 just to see if they are marginally better than what I have.
2. What does one use for steel?  I'm trying to machine a Crosman 1322 airgun barrel.


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## mattthemuppet2 (Dec 20, 2019)

I get my inserts from Banggood or ebay, usually for around $10 a pack and they work fine for me. TCGT21.51 I think is TCGT110204 in metric, you might find more using that search term. The xxGT inserts work sooooo much better on smaller and lighter lathes, that's pretty much all I use unless I'm roughing out steel. Even then I'll use the xxGT inserts for the finishing cuts.

the xxGT inserts will work fine on steel, but they might not last as long. They do give a beautiful finish though.

If you want a better system, rather than throwing more money at what you have, I suggest looking into SCLCR holders, that use CCMT/ CCGT inserts. They can do turning and facing and boring all with the toolpost square to the work. Only 2 cutting tips vs. 3 for the TCMT/TCGT inserts, but a bit more versatile.


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## Cadillac (Dec 20, 2019)

You can get turning facing and boring tools that hold a tc.. insert. I also use on facemill and flycutter. I get mine through eBay forget the sellers name but come from China under 10 bucks for a box of that size. They work great as said above on just about any material except hardened stuff.


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## brino (Dec 20, 2019)

@WobblyHand,

You started this thread title with "Embarrassed to ask, but.....".

Rest assured that you NEVER need to feel that way here!
If you are asking the question, then that means there is likely no easily accessible/understandable existing thread or tutorial on the subject.
You will NOT be flamed here, you will NOT be ridiculed here, our (amazing!) moderators will NOT stand for that.

I personally do not use a lot of carbide in my shop, but I learned some useful information from the responses.
Thanks for asking the question!

Ask what ever you want, no shame, no embarassment!
We are all here to learn.

-brino

by the way: what diameter is the workpiece and what rpm did you use? My understanding is that carbide likes it fast .


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## Larry42 (Dec 20, 2019)

Seems like on a very small lathe using HSS would be better. It is easy to grind. If you don't get an ideal shape it will still work and you can simply refine the shape as you go. HSS can be easily ground to a fine edge so it will take very little force to start it cutting.


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## WobblyHand (Dec 20, 2019)

@brino, workpiece diameter is 0.438".  Tried various RPMs, chattered a lot at higher RPMs, so I backed off.  So probably < 1000.  Nothing really seemed to work well, which is the reason for me starting the thread.

@Larry42 I've got some HSS blanks (actually cobalt) now, waiting for HSS to come in.  Also have some keystock to practice on.  The example tool bits have been sent, but have not been received.  I was just trying to accomplish something with what was in house.  Ordered a belt grinder.  Ahem, what an expensive hobby...


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## DAT510 (Dec 20, 2019)

@WobblyHand,

Welcome to the H-M. 

A couple of things come to mind....

Regarding the angle of your cutter.....
One way to think about angles of your inserts or cutters in general, in relation to the surface you wish to cut, (especially with smaller and lower HP lathes), is the more surface of the cutter in contact with the material being cut, the more force that needs to be applied to cut.  As the energy is being spread over a larger cutter area.  In other words the Force per Area is lower.  Think of 1 lbs force over 1in^2 =1psi   That same 1 lbs force spread over a 1/10 in^2 = 10psi.  So the smallest amount of the cutter in contact with the part being cut, will have the greatest cutting force (PSI), and will require less power to cut your part.  Also smaller tip radiuses will cut better, though the finish will not be as nice.

In short turn your cutter so only the tip is in contact with the surface you wish to cut.

Same applies to the sharpness of the cutter.  HSS bits are not a brittle as Carbide, and can take more abuse to a sharp edge as compared to carbide.  Therefore, HSS often ground to quite sharp edges.  Carbide brittleness is the reason most carbide inserts are not ground to a sharp edge from the MFG, as the sharp edge can chip more easily.  But this also means Carbide inserts typically need quite a bit more pressure and a larger depth of cut to cut effectively,  as compared HSS. 

Stefan Gotteswinter is an impressive machinist who machines parts on smaller lower power equipment using carbide.   He regrinds his carbide to sharper edges to work with lower power machines and to take finer cuts. 






In addition to the angle of you cutter, another thing to check is.... whether the height of you cutter is correct.  If it is above the center line of your lathe, the contact point will be below the cutting edge and it will not cut well.  Of the two, being slight below the center line is better than above, though we all strive to be dead center.

Hope this helped.


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## brino (Dec 20, 2019)

Chatter near the suggested sfpm is usually caused by something loose in the set-up.
If feeding by cross-slide, lock down your compound-slide.
Also, try to minimize any slop in all your dovetail slides.



WobblyHand said:


> Ahem, what an expensive hobby...



You have no idea!

.........but seriously, there are so many ways to do any operation that you can likely find one to meet your budget.
just keep asking questions and searching for answers.
Some people here do amazing things with less than perfect conditions.

-brino


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## WobblyHand (Dec 21, 2019)

brino said:


> Some people here do amazing things with less than perfect conditions.


Totally agree!  You can see it on this and other forums.  What people have been able to accomplish using "non-optimal" methods is humbling and inspiring.


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## WobblyHand (Dec 21, 2019)

@DAT510 Thanks for the insight and video.  Stefan has some pretty cool tools.  My current capabilities are nowhere near his!  That's a pretty neat diamond grinder.  I'll use more of the point of the tool.  
@brino Compound slide was locked down.  I'll check and adjust the gibs.  One of them was pretty stiff, the other was quite a bit looser.  I'll tighten up the looser one.
@mattthemuppet2 Ordered some TCGT110204 inserts.  What's another $10?

Back to the dungeon


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## WobblyHand (Dec 21, 2019)

Bit was centered.  Set a 5 degree angle of attack.  Cross slide gibs were tightened.  Now minimal chatter running at 2500 rpm.  Facing cuts on steel are much smoother now, but still not showcase.  I was able to take 0.001" cuts although they weren't as nice and smooth as I remember using HSS.

To get a smooth burr free chamfer using carbide what does one do?  I still feel a burr.  It's like the metal wasn't cut that cleanly.  Almost pushed aside.


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## T Bredehoft (Dec 21, 2019)

WobblyHand said:


> It's like the metal wasn't cut that cleanly.




That's why we   recommend HSS for the hobbyist. Carbide is great for production, but not so good for playing.


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## WobblyHand (Dec 21, 2019)

Slowly, but surely, I'm getting the message.  Big grin.  
It will be a week or so before my belt grinder comes in.  Then I'll pester the tool grinding thread.  

Oh, I call it the dungeon because it's underground and like a cave.  54F.  Got to get a little heat in there.  It gets cool after a while.  I have a dehumidifier running to ensure it doesn't get too damp.  Don't want my new stuff rusting!

Thanks for at least getting me going.  Everyone has been incredibly helpful, it's greatly appreciated.


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## DAT510 (Dec 21, 2019)

Carbide needs a deeper depth of cut.  Since it’s cutting edge is more “rounded” than sharp, 0.001” cuts are too small, carbide would tend to rub or smear the surface more than cut it at 0.001” depth of cut. 

With carbide try 0.010” or 0.015” depths of cut. 

Also what material are you cutting. Some steels are more gummy and getting a nice surface finish can be difficult.


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## WobblyHand (Dec 21, 2019)

Yes, seeing smearing.  I don't want to go much further on facing this end.  Going to run out of total length if I'm not careful.  Wish I knew the kind of steel.  It's a Crosman airgun barrel, not some high end barrel steel.

My example bits came in from @Z2V.  Also a belt grinder, which I'm not sure if I can modify appropriately.  Hoping to try out HSS within a week.


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## mattthemuppet2 (Dec 24, 2019)

WobblyHand said:


> Ordered some TCGT110204 inserts.  What's another $10?
> 
> Back to the dungeon



I think you'll be amazed at the difference - free cutting and beautiful finish. I used a CCGT insert to turn and bore a couple of CrV sockets this evening, worked beautifully. They also work really nicely with aluminium too, no edge build up which I found to be a problem with HSS. Honestly, HSS works fine and is cheap as chips. xxGT inserts work better and are almost as cheap - all I use HSS for on the lathe now are parting blades and form tools.


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## WobblyHand (Jan 16, 2020)

mattthemuppet2 said:


> I think you'll be amazed at the difference - free cutting and beautiful finish. I used a CCGT insert to turn and bore a couple of CrV sockets this evening, worked beautifully. They also work really nicely with aluminium too, no edge build up which I found to be a problem with HSS. Honestly, HSS works fine and is cheap as chips. xxGT inserts work better and are almost as cheap - all I use HSS for on the lathe now are parting blades and form tools.


Just as a follow up, these TCGT110204 are pretty darn good!  Both on steel, aluminum and brass.  The turning finish was mirror like on aluminum and brass.  Facing steel is so much nicer than those awful inserts that were originally supplied.  Very little chatter, even when I was playing around trying to make a square out of a round.  Fortunately the stock was 6061, and the carbide didn't break.  As I understand, interrupted cuts are bad for carbide.


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## mattthemuppet2 (Jan 16, 2020)

very neat, I'm glad that they're working well for you. Your experience pretty much matches my own  Interrupted cuts will be fine, just don't get too crazy if you're doing it in steel. Thing is these inserts are so cheap you can push things a bit until you chip a tip, rotate the insert and try and remember not to do that again. Stalling the tip in the work kills tips in my experience, other than that they last a good while in steel and a long time in everything else.


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## ThinWoodsman (Jan 17, 2020)

DAT510 said:


> Carbide needs a deeper depth of cut. Since it’s cutting edge is more “rounded” than sharp, 0.001” cuts are too small, carbide would tend to rub or smear the surface more than cut it at 0.001” depth of cut.



You can use a diamond hone on the edge of the carbide insert. Sharpen it enough to take those 0.001, 0.002 cuts.


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## rwm (Jan 17, 2020)

That link that Mitch posted is a very slick site with a good description of turning theory. I like it! Everyone should review it.
I am confused about this:
"So, TCGT are a positive rake version of the TCMT " That doesn't sound right.
Position 3 is the tolerance of the insert if I understand correctly?
I do not understand how the rake angle is coded. Is it based on the tool holder or the insert? All my tool holders are zero so far. Do I need a negative rake holder?
Cutting radius is coded in position 7 in 64 ths of an inch?
Position 5 is inscribed circle. Is this based on the radius or diameter?
I am running a "TT321" insert routinely on aluminum. (1/2" tool holder) That should have a 1/64" tip radius. Does any one have a better recommendation? If so please explain why it will be better. I like to know the theory behind all this.
Robert


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## rwm (Jan 20, 2020)

After measuring my inserts, the Inscribed Circle would seem to be based on the radius, not circumference. In my case TT*3*21 would be 3/8" radius. I am not clear why the letters are only expressed as TT.
No takers on the rake angle question?  I would really like to understand how that works with inserts. It's weird also that the HSS knife edge tool demonstrated by Mikey works so well with aluminum since it has a very high rake angle?
R


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## Shootymacshootface (Jan 20, 2020)

This is a great topic, thanks op. This makes me ask something that I haven't been able to figure out on my own. I have noticed that carbide tooling does work best with heavy cuts and rather poorly with very light cuts, like when sneaking up on your final dimension or making spring passes, the surface finish goes to crap. How does one get consistent good final finishes with carbide tooling?  I have been enjoying a lot of success with hss, but stopping to sharpen bits after a lot of roughing could be avoided with carbide tools.


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## mikey (Jan 20, 2020)

rwm said:


> That link that Mitch posted is a very slick site with a good description of turning theory. I like it! Everyone should review it.
> I am confused about this:
> "So, TCGT are a positive rake version of the TCMT " That doesn't sound right.
> Position 3 is the tolerance of the insert if I understand correctly?
> ...



Debugging inserts can be really confusing when you first look at them. Every manufacturer is supposed to adhere to ANSI or ISO standards; here in the States, we usually use ANSI.

Rake is complicated because the insert and/or the tool holder can have rake, and you can have a negative rake tool holder that produces a positive rake at the cutting edge. There are tooling specialists who work in this field that can make recommendations to shops because there are so many inserts that confusion is actually not uncommon.

For my simple mind, I keep things simple. I look at the relief angle (pos. 2). If it is an N then that is a 0 degree rake insert (it has no relief angle under the cutting edge) and that means the relief MUST be provided by the tool; this is a negative rake insert that fits into a negative rake tool. Anything else is a positive rake insert but the tool holder can still give you a net negative rake when the insert is bolted down. This perspective is not entirely correct but it is useful for my limited insert use.

The chip breaker configuration and wiper configuration complicate this further because they depend on usage and material. You need to decide what is appropriate for the job at hand.

Nose radius is in 64th's but there's more to it. A 1/64" nose radius is 0.016", although many inserts are actually 0.015". This is a common radius but is on the big side for my use. I much prefer a 0.5/64", or 0.008" for most work and a 0.20/64 or 0.004" if I can get it. The reason this matters is because the nose radius determines how small a cut you can take before radial forces get too big to cut reliably. Your minimum depth of cut should be at least as large or larger than the nose radius, so a minimum accurate cut with a 0.016" nose radius is about 0.015". If you try to go shallower, it might cut but you have to try it and see if it cuts accurately enough for you. I have found that I can go down to about 1/2 the nose radius and it sort of cuts okay; you don't get what you dial in but it tends to at least be consistent. If you try to go shallower then radial forces will deflect the tool and it skates and will not cut. Your finish goes out the window, too.

I have to run some errands now but my advice to you is to choose a tool holder and download the manufacturer's info on it. They will have insert recommendations for use with that tool holder. Then figure out which insert configuration will suit your needs and then learn everything you can about that insert.

If I had to choose a single tool holder, I would choose the SCLCX class. Inserts are cheap and they work well for hobby class machines because they are a positive rake tool holder and insert. Buy the smallest nose radius you can get for finer work. You will find that the bigger the tool holder, the bigger the nose radius; and the bigger the nose radius the deeper you must cut for accuracy. Try taking a 0.001" depth of cut with a 5/8" square tool holder and you'll see what I mean. Bigger is NOT always better.


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## Grandpop (Jan 20, 2020)

Those TTxxx inserts seem to not follow the standard lettering/numbering scheme. They have a 7 degree side clearance, and the molded in chipbreaker adds another 4 degrees. You often see these stated as 11 degree rake angle, which would be correct if the tool holder insert seat is parallel to bottom surface.

 I use those in my big dovetail cutter in TT431 size, as TCMT431 are expensive and harder to find. While TTxxx and TCMTxxx are both 7 side angle, their center holes are different, so can't use the same screws. Not a problem for my dovetail cutter, as I built it for the TTxxx inserts.

I last bought the TT inserts from Richett on ebay, in coated grade for $20. Hold up pretty good milling in hrs and 4130.


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## rwm (Jan 20, 2020)

So can I find an insert that is triangular i.e. TTxx32.5? (TTxx320.5?) I don't see to find ones with that small of a tip radius.
Robert


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## mikey (Jan 20, 2020)

You may find it a challenge to find small nose radii in larger tools. You appear to be using 1/2 shanked tools; might have to go to 3/8" shanked tools to find a 0.008" NR insert. Yeah, I know that the consensus is that bigger tools are more rigid and "better" but I use 3/8" tools on my 2HP Emco lathe and they cut just fine. I also own 1/2" tools and find no significant difference in how they cut. 

If you have not tried an SCLCR tool holder, this might be a good opportunity. The generic tool holders are cheap, as are the inserts. They use CCMT and CCGT inserts that are common on ebay.

I meant to mention the AK inserts in my other post but ran out of time. AK inserts are found in many different insert configurations. They are uncoated and ground to a sharp edge. They also have very positive rake angles that works well with Aluminum and plastics. They also work fine for harder materials but the edge doesn't last as long when doing so. It puts a really nice finish in most materials, though, so if you haven't tried it, you should. 

The other thing I wanted to mention is that most insert tool holders are intended to be used perpendicular to the work. The tool holder geometry is set up like this and lots of folks fix or pin their tool posts to take advantage of this fact. However, many tools work better if you alter their lead angles. If you take almost any inserted tool and angle it back toward the tailstock a bit (maybe 10-15 degrees or so), you will be amazed at how much better it finishes. Play with it and you'll see what I mean.

Similarly, you can cant the tool holder towards the headstock a tiny bit so the tool cuts with the nose radius and the end cutting edge. This also improves finishes significantly but you will need to play with depth of cut to see how it affects your accuracy.

Finally, I wanted to mention that you need to determine how your insert likes to cut. Most roughing cuts are accurate when the depth of cut is slightly greater than the nose radius; a good setting is NR + 0.010". This fully supports the nose radius in the cut and reduces chatter and increases accuracy. Most inserts will cut consistently at this setting.


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## mikey (Jan 21, 2020)

Shootymacshootface said:


> This is a great topic, thanks op. This makes me ask something that I haven't been able to figure out on my own. I have noticed that carbide tooling does work best with heavy cuts and rather poorly with very light cuts, like when sneaking up on your final dimension or making spring passes, the surface finish goes to crap. How does one get consistent good final finishes with carbide tooling?  I have been enjoying a lot of success with hss, but stopping to sharpen bits after a lot of roughing could be avoided with carbide tools.



I meant to address this and forgot; sorry. 

As in the above posts, inserts require sufficient depth of cut for the nose radius to bite. If your DOC is too small, the nose will deflect and skate on the surface. Under these conditions it will not cut consistently. What is happening is that radial forces are excessive and the tool is actually pushing away from the work surface but this is not consistent. Hence, your finish will look ratty as the tool tip moves toward and away from the surface. 

The thing to note is that a carbide inserts require an adequate DOC. It would be nice if you could take a huge roughing cut and come back and take 0.001" DOC to come in on size but that just doesn't happen. What you have to do is find out the minimum DOC your tool will reliably take and rough to that point, then dial that cut in. For example, say your nose radius is 0.016". A DOC of about 0.020" or so will probably cut pretty consistently. You have to test it but if you dial in 0.020" and it reduces the OD by 0.040" consistently then you've nailed the number. Now just rough until you are 0.040" from final size and dial that 0.020" cut in and you're there. 

You may be able to get the DOC smaller but there will typically not be a direct correlation between what you dial in and what you get. However, if what you get is consistent then use it. For example, say you're using that 0.016" NR insert and you find that you can take a 0.008" DOC consistently, meaning it takes off the same amount for each pass, then use it. If a 0.008" DOC produces a consistent 0.014" reduction in diameter per pass then just rough until you're 0.014" away and dial in that 0.008" DOC. You have to determine how small a cut you can take. If you drop much below that 1/2NR, radial forces will be excessive and your consistency will drop off. Get much below 1/3NR and your insert will likely skate. That's just how this stuff works so you need to sort it out and go from there.


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## Grandpop (Jan 21, 2020)

The TT xxx series appear to older less common inserts, but still available. I've never seen the TT32x series in any smaller nose radius than .015 (so TT321). So that is right back where this thread started!

But yes, you can buy the TT321 inserts on ebay for $20 for 10, typically coated C5/C6 equivalents. They cut OK; much better than the really cheap ones that come with the cutter sets! 

Make sure you are pretty close to being on center if you are taking light cuts; makes a big difference. As with any carbide insert, if you want to finish with light cuts, you need to index the insert just before finishing (I mark one with Dykem so I know which one to use), or keep a different toolholder just for finishing. If that insert is slightly dull at all after your roughing cuts, taking light cuts is going to be an issue (as described above). With a new cutting edge, I don't have much trouble with light cuts, including the final .001 to .002 off the diameter). 

Having said that, I do not use the TT series for finish cuts when I am looking for great precision; I have other choices. I have an old TPG32x series holder. Prices of TPG321 inserts are stupid cheap these days, especially the uncoated ones. I have zero issues taking .001 cut off diameter with these, or taking several spring cuts. It may not be the worlds greatest finish, but good enough for anything I need. My 12 x 24  is like most lighter lathes, in that it typically cuts with slight taper (further away from chuck is slightly larger than close to chuck). I pretty much always sand/file to final size to get rid of that taper. Last night I was turning 1" dia O-1 tool steel down to 3/8 diameter x 2.5 inches long to fit inside a collet. This was the shank of a cutter I am making, so wanted it close to size and decent finish. I used the TPG321 with final cut of .001 on diameter (1400 rpm), and took 3 spring cuts. I ended up .0004 larger at the far end, so about 4 short strokes with good smooth mill file eliminated the taper completely.


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## Shootymacshootface (Jan 21, 2020)

Thanks Mikey,  you couldn't have explained that better. 
Thanks!


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## mikey (Jan 21, 2020)

Shootymacshootface said:


> Thanks Mikey,  you couldn't have explained that better.
> Thanks!



You're welcome, Sir. 

I've been in situations where I had a lot of work in a piece and I'm almost there, within just a few thou of final size. When the job requires a good finish and an accurate diameter, what do you do if you only have an inserted carbide tool that you know will not make the cut? I run into this situation when fitting bearings; you know how those fits can be finicky. 

The answer, for me, is to have a really good, really sharp HSS tool to make that cut. A good tool will be able to take off a thou reliably if the geometry is right. 

A lot of hobby guys, especially newer hobby guys, go with inserted carbide because they cannot grind or are not interested in grinding HSS tools but they eventually learn that the tool you use in not as important as getting the job done. There is a place for both kinds of tools in every shop. I use HSS the vast majority of the time because they work better for me on my small lathe. However, there are jobs when inserts are the right tool and I sort of know enough to use them in those instances. 

For me, it is not an either/or; it is a both/and.


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## Suzuki4evr (Jan 21, 2020)

brino said:


> You started this thread title with "Embarrassed to ask, but.....".
> 
> Rest assured that you NEVER need to feel that way here!


Brino is hitting right on the head. There is no such thing as an stupid question or nothing to be embarrassed about on H-M


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