Carbide insert lathe tooling

[kuksul08]

I've noticed a lot of people using the carbide insert tooling, with the triangular or diamond shaped removable cutter. I know this has been discussed here a lot since I have been reading the past threads. It's a bit overwhelming though. I'm doing hobby work and can't decide what is reasonable for me.

They make more sense than all the other cutting tools I have since you can turn, face, thread, and bore delrin, aluminum, and steel with a single tool. I am a little frustrated by the old I have that came with my lathe, some give nice shiny finished and some give a ridged, dull finish. So, a new tool is in order.

What are the basics and where do you all source the holders and inserts?

 

[precisionworks]

Small machines do better with positive inserts. Usually the second letter in the designation, like TPG, TPU, but sometimes well hidden like CCMT. The best single source for smaller machine tooling (IMO) is Curt at Lathe Inserts - great prices backed by a ton of knowledge & a nice guy to deal with. .

LatheInserts.com

 

[Th232]

Usually the second letter in the designation, like TPG, TPU, but sometimes well hidden like CCMT. The best single source for smaller machine tooling (IMO) is Curt at Lathe Inserts - great prices backed by a ton of knowledge & a nice guy to deal with. .

Out of curiosity, this is something I've always wondered about. In TPG and TPU, since it's a 3 letter designation instead of 4 letter, why is it only 3 letters? I presume that they've removed the 4th letter (geometry), but I've never known why...

 

[precisionworks]

If there's a 4th letter it indicates groove or hole - since both TPG & TPU are clamp down inserts there is no 4th letter.

A good ANSI/ISO chart

 

[kuksul08]

Great info in that link^. I like the kits that Curt has put together, it makes it easier for someone like me. Thanks.

edit: So I'm looking at the 3/8" hobby kit. Just curious - can you do boring with a square insert holder like that? I was thinking a round holder would work for most operations, but a square one is limited to external features.

 

[precisionworks]

can you do boring with a square insert holder like that?

The square shank holder has clearance under the insert for external operations only. Even a facing cut (which has the least clearance) allows free cutting action. A boring bar has a dramatically different shape with nothing but room under the insert. That allows it to be used for internal cuts.

 

[unterhausen]

can you do boring with a square insert holder like that?

You need a boring bar. But to answer your real question, no, you can never stop buying tooling for your lathe

 

[Th232]

If there's a 4th letter it indicates groove or hole - since both TPG & TPU are clamp down inserts there is no 4th letter.

A good ANSI/ISO chart

Thanks for that info. Looks like a better version of the chart I've got, never seen that "null" before. I presume there's no difference between nothing and "N" then?

And as unterhausen has noted, you can never stop buying tooling. Off the top of my head, if you choose to convert to carbide you'll need tools for:

* Turning. Recommend both left and right hand tools.
* Threading. Two, one for internal and one for external.
* Boring. Probably get a set of these.
* Grooving/parting. Might be able to get away with buying only one, but ending up with multiple widths (and an internal grooving tool) is a more likely scenario.

Then after that you'll realise you could get a nicer surface finish by having a tool that takes a round insert, or maybe you'll get different grades of carbide or coating for Al and steel.

Now... to find someone who sells CTAPL 08 and CTEPL 08 holders and ships to Aus at a reasonable rate...

 

[precisionworks]

To start with, a right hand turning tool (cuts toward the chuck) will do lots of ops. Add a left hand later if needed. My left hand tool gets used maybe 5% of the time.

Threading - start with external threads & get rock solid with the procedure. Internal threading then builds on external threading skills.

Boring - start with a bar sized for the work you plan to do. For flashlights (CR123 or 18650) that means 1/2" (12mm) diameter. For a tiny bar like that solid carbide is what you really need. Add larger bars as needed.

Parting - narrow inserts work better on a small machine. Something close to 2mm is a great size, and narrower parting tools are also available.

Grooving is where you can spend a ton of money so shop around. Mesa Tools USA has some nice low-priced tooling: http://www.mesatool.com/#

 

[kuksul08]

I have to remind myself not to cheap out because I'll end up buying the proper tools eventually anyway.

 

[Al Combs]

Barry, please forgive the noob question. I'm still trying to learn about indexable inserts without buying a Machinery's Handbook. In post #2 you mention the second letter of the insert's designation refers to whether or not it's positive. If the letter 'P' is positive, does 'N' means negative? I've seen that mentioned before and didn't bookmark it. But the ANSI/ISO chart in your 4th post say that a 'P' in the 2nd letter refers to an 11° clearance or relief angle.

Is there more than one type of designation for indexable inserts? Your ANSI/ISO chart is the most comprehensive on the subject I've come across. One of these days I'll figure it out.:shakehead

 

[gadget_lover]

P and N tell you the clearance of the cutting edge. You need more clearance if the insert holder is going to tilt the insert because you still need clearance so the tool does not rub as it cuts.

The greater the clearance, the more you can tilt the insert ( or the tool).

Dan

 

[Maglin]

Barry, please forgive the noob question. I'm still trying to learn about indexable inserts without buying a Machinery's Handbook.

You really should get your self a machinery handbook. It's pretty invaluable and helps you make about anything. I would look at just getting a few tools to start off with that share a common insert. So you won't have a lot of different inserts to buy and stock. I like the CNMG inserts I think it is. They have no rake and require a good holder that presents the insert with a negative rake. This gives me 4 cutting edges per insert to use and I can use one tool to face, turn, rough & finish, and turn to a shoulder with a RH tool. For boring bars I went with the Shars set that was a good starting point. They use CCMT inserts just like the TMX tools that latheinserts.com sells. I would get at least 5 CCMT and CCGT inserts for cutting steel and aluminum. Being they only have 2 cutting edges because they are a positive rake insert you might want to have 10 of each.

I personally like using HSS lathe tools. It doesn't cost near as much when you chip one as you can resharpen it and also kept a keen edge on it with a oil stone. I tried out the Diamond Tool Holder which is a really cool idea and works very well for the hobbiest. You don't have to know how to sharpen tools just one edge which you have a fixture for. You can put a .250" round bit in it and it's a finishing tool that gives a very good finish. With a .250" square tool it's a roughing, turning, facing, and turning to a shoulder tool.

 

[precisionworks]

+ 1 on Machinery's Handbook. It is helpful in every area of machine shop work. You will not find more useful information in any one volume.

 

[PhotonFanatic]

Barry, please forgive the noob question. I'm still trying to learn about indexable inserts without buying a Machinery's Handbook. In post #2 you mention the second letter of the insert's designation refers to whether or not it's positive. If the letter 'P' is positive, does 'N' means negative? I've seen that mentioned before and didn't bookmark it. But the ANSI/ISO chart in your 4th post say that a 'P' in the 2nd letter refers to an 11° clearance or relief angle.

Is there more than one type of designation for indexable inserts? Your ANSI/ISO chart is the most comprehensive on the subject I've come across. One of these days I'll figure it out.:shakehead

Try this page at Carbide Depot.

 

[Al Combs]

Thanks guys.

 

[kuksul08]

I'm a little confused about the part off tool inserts. They are really small, looks like you could only go 1/4" deep, and I'm not quite seeing how they are secured in the holder.

The problem I am having now is that my parting tools are HSS, .050-.125 widths, and when they cut they flex and leave a sort of ugly surface finish.

Any insight on these?

 

[gadget_lover]

If they flex you probably do not have the tool at exactly 90 degrees to the work. I use a machinists square to ensure the blade is exactly at 90.

And that tool you post there will go as deep as the cut-out allows. probably 1 inch.

Dan

 

[pmath]

I've been remiss in acknowleding the help I got here directing me to Curt's inserts. I cannot believe how much better my tiny lathe works with these beauties.

Peter

 

[kuksul08]

Well, turns out I will have to buy some new tools. I broke my only right hand turning tool as well as a left hand tool I was using for facing tonight. I was feeding into a steel bolt and I felt a little resistance, then suddenly the bolt walked up the cutter and chunked it before walking out of the chuck. What a nasty sound...

Now correct me if I'm wrong, but don't you need a left hand tool for facing and a right hand tool for turning? How are you supposed to face work with these insert holders since they are only right hand?