Turning Insert questions | The Hobby-Machinist

I 'd like to buy some spare turning inserts for my Atlas 12" lathe. The lathe came with 1 holder & 1 insert.
I tried to sort thru the pages of offerings in the Enco Catalog, but just not sure what I need

The holder is marked Kennemetal MTDR-62.

Most of what I do is turning cold roll & some hot roll round stock & sole aluminum

Thanks for your help Is this your holder? A 3/8" shank tool?



If so, the generic starting point for your inserts will be like the box behind that example. TNMG-221. The you need to figure out what grade, what nose radius, and what, it any coating you want on it. Kennametal catalog online will have guidelines for those items, generally. For roughing, a larger nose radius is preferable, but may try to chatter in a small machine. For finishing, a smaller radius is generally used, but with a lower feedrate. Tony Tks for the response
The shank is 3/8

I use light cuts & feeds on my atlas. so TNMG-221??
Probably a smaller nose radius
No idea what coating to get..
I'd trust your suggestion
Tks Here's a few links to MSC with a few suggestions for general purpose steel work. http://www1.mscdirect.com/cgi/NNSRI...re=ItemDetail-_-ResultListing-_-SearchResults

http://www1.mscdirect.com/eCommerce...xsj87?refinement=&searchandizedOk=N

You might want to try eBay also and pick up a 5 or 10 pack for 20-30 bucks.

Here's a chart from this website: http://www.carbideprocessors.com/pages/carbide-parts/tungsten-carbide-grades.html


C grades classification

C-1 to C-4 are general grades for cast iron, non-ferrous and non-metallic materials
C-1 Roughing
C-2 General Purpose
C-3 Finishing
C-4 Precision
Steel and steel alloys - these grades resist pitting and deformation
C-5 Roughing
C-6 General Purpose
C-7 Finishing
C-8 Precision
Wear Surface
C-9 No shock
C-10 Light shock
C-11 Heavy shock
Impact
C-12 Light
C-13 Medium
C-14 heavy
Miscellaneous
C-15 Light cut, hot flash weld removal
C-15A Heavy cut, hot flash weld removal
C-16 Rock bits
C-17 Cold header dies
C-18 Wear at elevated temperatures and/or resistance to chemical reactions
C-19 Radioactive shielding, counter balances and kinetic applications

It has been a few minutes since anyone has brought up carbide tooling, so here goes. I'm shopping for a decent carbide insert and holder setup for my lathe. Details are below but my biggest questions are these:

What is the practical benefit of a 3/8" vs. a 1/4" or a 1/2" vs. a 3/8" inscribed-circle size insert? Cost seems to go up with size somewhat. Are the bigger hold-down screws a benefit? Other practical benefit?

How much of a practical difference might I see with an insert holder with a larger cross-section than the 1/2" ones? My tool holders can easily handle 5/8" or 3/4" but is there much benefit? (Assuming I'll probably not need to hog out industrial level amounts metal per pass.)

I have a budget of $- to get this off the ground. (I sold some equipment and that $ has to be spent, you know, for the good of the economy.)

Thank you.

Background:
I have the same set of cheap triangular inserts and holders that came with my lathe and they have worked "ok". I've used HSS quite a bit but really like the results I get with quality carbide threading tools and parting tools. I did an internal acme thread with a carbide tool that was just excellent. It was a happy day. So I'm shopping for a basic profiling/facing setup with right-hand and left-hand holders for 80 Deg. diamond and 135 Deg. for more intricate profiling. I have a 16" lathe with a CXA tool post. My max RPM is , 5 HP. I work on aluminum, various steels, and sometimes stainless. I prefer to go bigger.. the bigger the better...
In my opinion, bigger is always better when you are not constrained by a tight fitting cut.
I prefer to fit the biggest tooling I can fit in a holder and maintain center.

I liken it to more absorption of vibration. Smaller usually will flex more..

I have been on small carbide cutters, and didn't like them. On my little SB9 I prefer 12mm and up shanks. I can and do fit 16mm. I did in the past have to remove some material to fit it in the tool holder, but I have since found out about the XL holders, and they work for me. I was involved in a conversation where the user was unable to come to center with a 16mm. Definite advantage to bigger boring bars, similar but less so for turning tools because of less overhang. No real advantage to bigger inserts unless your machine is powerful/rigid enough to use the entire face of the insert.

I've purchased a full assortment (turning, boring, internal and external threading) of inserted tooling from Aliexpress and eBay . It has all been of good quality, none of it is junk. I realize this barely touches your budget, but I'd recommend a 16mm set like this, plus a pack of every insert.

full disclosure: I haven't used one of the inserted parting tools. I had bad experiences years ago and have stuck with HSS ever since.

edit: If you want to blow some money, buy the brand name inserts. When I had this question, I called Carbide Depot. They are in the American South (AR, AL?), & I had a long conversation with some guy that had worked there for a very long time. He answered all of my questions in the one call, & sold me everything that I needed. I chose Kennametal tool holders.

I think I spent about $500 on that order. Carbide Depot has a house brand (for carbide inserts) which is made in Switzerland. It seems to be just as good as the quality name brand stuff, but it is significantly cheaper.

It was a nice change of pace these days to make an old school call, & have a conversation with a knowledgeable person.