cutoff and threading tool selection

[DanielG]

I'm tooling up a lathe (flat-bed, CNC, 8" chuck) and need to select a cutoff tool and threading tool.

I'll start off by saying that I'm a mediocre machinist (though a good engineer). I don't do production work; it's mostly custom one-off parts for equipment we're building. We don't run machines very hard, and I'm willing to pay money to make my life easier.

For threading, I've used top-notch on a manual lathe. The prior owner of this CNC lathe used Iscar tools, so I had the Iscar rep in. He recommended their Penta line, which I haven't used before.
https://www.mscdirect.com/product/details/02987675
https://www.mscdirect.com/product/details/46669552

For cutoff, he recommended
https://www.mscdirect.com/product/details/59548594
https://www.mscdirect.com/product/details/76847888
this is a different style of insert than I've used at previous jobs for cutoffs. The other option, of course is HSS. I'm terrible at re-grinding things though, so I tend to like inserted tools.

My other thing to consider is toolholding. If I go Aloris, I'm right on the edge between CXA and CA. This machine had CXA on it previously, but didn't come with the toolpost. On the multifix side, I've read that it's much nicer, but again, I'm on the line between B and C. The issue I see with B size Multifix is that it can only take a 7/8" tall cutoff tool, which seems very limiting from what I've seen. The 26mm tall tool linked above will cut 3" diameter. The 7/8" tall tools seem to be for smaller diameters.

Anyone have any thoughts/suggestions?

 

[gregormarwick]

For threading, Sandvik 266. Buy a full profile insert for the pitch you are cutting, put the thread dimensions and material specification into their online calculator, put the cutting parameters into your threading cycle, press go. Perfect thread, on size first time, zero fucking around. There are naysayers on here usually, but Sandvik's threading system is objectively better than everyone else's, and worth the premium.

For parting, the system recommended to you by your Iscar rep is good, I could recommend others, but that one is just as good as any.

Toolholders; IMO, the best toolpost for a CNC centre lathe is the old Dickson quick change, as seen commonly on Colchester and Harrison lathes since forever. More repeatable and less wear-prone than wedge style Aloris and the like, easier to clean and more fluent when swapping out tools. New toolposts and holders made by Bison these days (link below, pg.67). Multifix/Multisuisse is overkill on a CNC as you won't often (if ever) use the many-position indexing feature which is it's strongest selling point, and they are a little more clumsy to swap tools quickly.

https://bison-chuck.com/wp-content/uploads/2021/09/Spindle_Tooling_and_Quickchange_Toolposts.pdf

 

[RoundHouse M&F]

Aloris CXA or CA
For your tool post question look here and scroll down 2-3 posts and look at PMTOOL'S post. also we just got a knuth lathe that has the Multifix tool post that holds 1" - 1-1/4" tools and my preference would be the CA/CXA. Their easier to clean the chips and dust out when you change tools, the holders are cheaper and easier to get, and their lighter which helps when you have 5-8 tools and are constantly changing them.

Good notes about the multifix is it does seam to have a greater dampening effect on the boring bars we use and it is solid when you tighten it. we did have to send one holder back as it was so tight it wouldn't slide down onto the posts clamping fingers.

Not familiar with Iscar turning but On turning tools we use all Sandvik coromant. Threading is a corothread 266 and grooving is the corocut QD. The thing I like about sandvik is the simplicity in how they have all the different grades and cutting info arranged. we have a few seco milling tools and every time I needed to find a different grade i would have to call and ask their support center, when i could have found it in the sandvik book or online in like 5 minutes. I think i have only called sandvik to help trouble shoot cutting conditions 2-3 times and it was with some really weird alloy of a cast Heat resistant 316Stainless with extra evil... i mean nickle.

Also on the threading find something like the corothread 266 with a replaceable insert seat, that way if you loose/crash the insert you don't risk loosing the holder. Holders may be $150-200 but a pack of 10 seats may be 100$ and you dont have to wait for a new holder to arrive unless you really crash it..

 

[Ox]

For threading/grooving - I use the Top Notch as well, but I am sure that the Penta is a good choice as well, but I have no experience with it.


However, for cut-off, I have been forced from my Manchester this last year - after <25 yrs of running them, and I ended up with the Iscar, but not the blade style that you showed. I think that would be a flexible and chattery issue when stuck out very far. (???)

The units with the 4 sided blade put a lot more "blade" to the job of keeping the insert where it is s'posed to be.

Log into Facebook

I wish that they offered sharp corner inserts, but the small rad inserts have done surprisingly well at parting off without leaving too much burr up in the hole, and of course, if you are running a sub-spindle, then that is a non-issue anyway.

I get little to no chatter, and the inserts last a long time.

I was concerned with the perishable blade being costly/part, but the perishables has been surprisingly low as well.

I have found that I prefer the 908 grade, and 80% of what I got on my initial buy was 808's, but they doo OK I guess...


As for the toolpost, I can only comment on Aloris, and per that I would say "Get the biggest one that fits".
I have had a CA for 30 yrs. It's the only one that I have ever used to speak of.


---------------------

Think Snow Eh!
Ox

 

[mmurray70]

For threading, Sandvik 266. Buy a full profile insert for the pitch you are cutting, put the thread dimensions and material specification into their online calculator, put the cutting parameters into your threading cycle, press go. Perfect thread, on size first time, zero fucking around. There are naysayers on here usually, but Sandvik's threading system is objectively better than everyone else's, and worth the premium.

+1 for Sandvik 266. Everything he said is right on the money.

Sandvik is really good at almost everything, but I dont really like their part off tools. Iscar will probably be better choice. The dirt cheap MGMN300 tools on ebay come in handy every now and then for some jobs. They work amazingly well for price.

 

[Orange Vise]

We use Iscar for all of our threading and parting.

Not sure I see a benefit in the Penta line for threading. You're paying more per edge compared to laydowns. We use laydown topping inserts which clean up the crests of the threads. Sandvik laydowns are very good as well.

As for parting, the blade you linked with TAG inserts are excellent. They're the most reliable partoff tools we've used, including Iscar's own Penta IQ Grip.

We even have the XXXL size that'll part off 5" bar: