Lathe turning square stock with replaceable insert?

[WilliamR]

I watched one of the video's on (most hated tool) knurling thread, and couldn't believe the guy could turn square stock (and the eccentric) without that tiny diamond shaped insert grenading on first or second revolution. By colour and shine it doesn't look like any of the carbide I have, or is it just that much better of grade?

Whatever it is I could use a few of them.

Thanks.

 

[Susquatch]

I watched one of the video's on (most hated tool) knurling thread, and couldn't believe the guy could turn square stock (and the eccentric) without that tiny diamond shaped insert grenading on first or second revolution. By colour and shine it doesn't look like any of the carbide I have, or is it just that much better of grade?

Whatever it is I could use a few of them.

Thanks.

OK, that's worth watching. Do you have a link to the video and a play time for the slice you refer to?

Without looking, could the insert be HSS instead of carbide? HSS is much better at handling interrupted cuts.

 

[WilliamR]

I've had to use HSS tools on some of the things that would have destroyed my carbides. Huh, didn't realise there were HSS inserts? They were definitely bright and shiny like steel.

Would have posted a link but don't think I have enough thread posts? It was the video in post 45 on the (most hated tool) knurling thread.

 

[Dabbler]

The insert in the "Universal cut knurling tool" video by We Can Do That Better starting at 3:28 is a VCMG insert. This is normally used for finishing, so it is very sharp and he takes very light cuts. He also takes the scale off the corners, as the scale will destroy these inserts.

If you have trouble with interrupted cuts try a CNMG in the larger sizes/thicknesses, using the 100 degree point as the cutting corner. This is the most robust configuration for carbide on lathe also (except specialty ones, but they are very spendy), and is much harder to destroy.

 

[Susquatch]

I've had to use HSS tools on some of the things that would have destroyed my carbides. Huh, didn't realise there were HSS inserts? They were definitely bright and shiny like steel.

Would have posted a link but don't think I have enough thread posts? It was the video in post 45 on the (most hated tool) knurling thread.

After having a quick look, I agree with @Dabbler. That isn't a HSS insert. But yes, you can get HSS inserts. In fact Arthur Warner is an outfit in the USA that specializes in HSS Inserts.

https://www.arwarnerco.com/

I especially like their HSS threading kit:

Kit #18 1/2 inch Threader NV

www.arwarnerco.com

And their 35 degree profile VCMW kit (which is similar to Carbide VCMT).

Kit #16 35 Degree Profile (V) Right Hand Left Hand

www.arwarnerco.com

 

[WilliamR]

The insert in the "Universal cut knurling tool" video by We Can Do That Better starting at 3:28 is a VCMG insert. This is normally used for finishing, so it is very sharp and he takes very light cuts. He also takes the scale off the corners, as the scale will destroy these inserts.

If you have trouble with interrupted cuts try a CNMG in the larger sizes/thicknesses, using the 100 degree point as the cutting corner. This is the most robust configuration for carbide on lathe also (except specialty ones, but they are very spendy), and is much harder to destroy.

Thanks, that is very useful info for me. The ones I'm using are definitely econo grade as well. The insert classification system makes my head spin...

 

[WilliamR]

After having a quick look, I agree with @Dabbler. That isn't a HSS insert. But yes, you can get HSS inserts. In fact Arthur Warner is an outfit in the USA that specializes in HSS Inserts.

https://www.arwarnerco.com/

I especially like their HSS threading kit:

Kit #18 1/2 inch Threader NV

www.arwarnerco.com

And their 35 degree profile VCMW kit (which is similar to Carbide VCMT).

Kit #16 35 Degree Profile (V) Right Hand Left Hand

www.arwarnerco.com

Thanks for info and links. Will check them out. Definitely a whole new world to me. I've tried super light cuts but the inserts I use shatter on anything that isn't constant load. Really surprised me he could turn bar stock with an insert.

 

[Susquatch]

Thanks for info and links. Will check them out. Definitely a whole new world to me. I've tried super light cuts but the inserts I use shatter on anything that isn't constant load. Really surprised me he could turn bar stock with an insert.

You are not alone. It surprised me too. I wouldn't even think of doing it that way. Why would anyone? Anybody with a lathe with no HSS is crazy (Flak Jacket On). Why take delicate cuts to turn square bar round when you can use HSS and have at it. But I wouldn't use a Warner insert for that - I'd grind a 1/2 or 5/8 inch bar of HSS for that and then switch to whatever I needed to finish the job.

@Dabbler has a crap load of really cool ideas about how to do things. He is also darn good at figuring out how someone else did something. But I couldn't help but notice that HE DID NOT SAY that is how HE WOULD DO IT..... LOL!

Btw, I've been using a lathe for 40 years. I still find the insert terminology confusing too. Plus my brain is not wired to remember 2D data. I keep a few key types on reference sheets and notes in my tooling drawers. I also wish there was an android app for that!

 

[RobinHood]

Carbide inserted tooling with a carbide backing plate under the insert are much more robust and resilient to interrupted cuts. Typical 3/8” or even 1/2” (10mm or 12mm) offshore tooling does not usually have the carbide backer plates (probably to save height space and cost). The lager stuff 3/4”, 1” and 11/4” shank tooling most always does have the support plate.

I have not (yet maybe?) shattered a supported insert doing interrupted cuts (yes, they are all 3/4” or larger tool holders). I have had quite a few of them bust when they were not supported. Could also be the quality of the insert - the unsupported ones I have are offshore specials…

To the video: the fellow is a very good craftsman. He knows the limitations of his mini lathe/tooling. He has made a lot of extra tooling/fixturing so he can get the most out of his machine - and he does!

As @Dabbler states above, that VCMG insert has very sharp edges (like an HSS tool would have) and depending on the carbide, might actually have similar properties to a good HSS tool. Since it is being used on a mini lathe, only shallow DoC are usually taken because the lack of rigidity and torque (you can see/hear these limitations when he is drilling/counter boring). To be sure: I am not knocking the mini lathes!

Do I use carbide on rusty metal that require interrupted cuts - absolutely. Do they grenade - no. Do I use the most expensive “finishing” inserts - no. I use roughing inserts - they are made to withstand the stresses better.
I also slow right down and try to take a bigger bite (big DoC) to get first of all, under the rust/scale in one go and, two, to reduce the number of passes requiring an interrupted cut.

 

[WilliamR]

You are not alone. It surprised me too. I wouldn't even think of doing it that way. Why would anyone? Anybody with a lathe with no HSS is crazy (Flak Jacket On). Why take delicate cuts to turn square bar round when you can use HSS and have at it. But I wouldn't use a Warner insert for that - I'd grind a 1/2 or 5/8 inch bar of HSS for that and then switch to whatever I needed to finish the job.

@Dabbler has a crap load of really cool ideas about how to do things. He is also darn good at figuring out how someone else did something. But I couldn't help but notice that HE DID NOT SAY that is how HE WOULD DO IT..... LOL!

Btw, I've been using a lathe for 40 years. I still find the insert terminology confusing too. Plus my brain is not wired to remember 2D data. I keep a few key types on reference sheets and notes in my tooling drawers. I also wish there was an android app for that!

That's good to know, thanks. The HSS is pretty forgiving for me, and easy to touch up. Maybe down the road I will have better success with carbides. Coolant would sure be nice.

It would be great if they could unify the insert sizing system.

I have similar years of experience on lathe (brake lathe ) Unfortunately no help at all haha.

 

[Dabbler]

But I couldn't help but notice that HE DID NOT SAY that is how HE WOULD DO IT..... LOL!

There are many ways to get to the same result. I'd use my stand up 6X48 belt sander, and take off much of each corner. I don't own CNMG or VCMG inserts, so I'd use either one of my 1/2" HSS tools, or one of my TCNG inserted carbide tools to take tensy cuts until I got to about 80% round. My TCNG 322 inserts are very thin, and don't take abuse - and then I go to the deeper DOC and finish the round (in case you were curious)

-- and YES I have done this countless times, for one reason or other.

My ambition is to get tooled up for CNMG 433 inserts one day.

 

[WilliamR]

I was curious, thanks. When necessary I use angle grinder or belt to smooth as much as practical. Pretty much only choices I have-good to know it's not that uncommon.

 

[phaxtris]

I have turned lots of garbage, torch cut, interrupted torch cuts, square to round etc, with carbide inserts, the wnmg's seem to do ok.
I've never had one explode, they do chip, but I can usually get what I need to get done with one corner....feels like it takes for ever tho, all a guy wants to do is get that *bang!bang!bang!bang!......" Over with


What's worse is it definitely beats the sh!t out of your machine.....at least it seems pretty hard on it to me

I agree with the other posters about taking as much of it down with a grinder or other methods before putting it on the lathe

 

[WilliamR]

Thanks, will check out the wnmg. That knocking is the sound of broken dreams at my house haha. Sometimes I can sneak underneath but usually doesn't end well. Gun shy now, will use HSS until trying out the cnmg/wnmg technology.

Maybe it's the small size cheap insert, cheap insert holder, flexy tool post coming into play. Hesitant to try parting with it. The whole thing is cheap but don't know how I managed without one for so long.

 

[Susquatch]

Thanks, will check out the wnmg. That knocking is the sound of broken dreams at my house haha. Sometimes I can sneak underneath but usually doesn't end well. Gun shy now, will use HSS until trying out the cnmg/wnmg technology.

Maybe it's the small size cheap insert, cheap insert holder, flexy tool post coming into play. Hesitant to try parting with it. The whole thing is cheap but don't know how I managed without one for so long.

I spent 30 years with an old flat belt driven 1880s lantern style tool post lathe. Things could only improve after that.... Best of all, that old girl taught me more than you tube ever could! Still have way more to learn than I know though!

 

[WilliamR]

I spent 30 years with an old flat belt driven 1880s lantern style tool post lathe. Things could only improve after that.... Best of all, that old girl taught me more than you tube ever could! Still have way more to learn than I know though!

Wow that would be an interesting piece. Lots of old stuff like that in your area? I was trying to buy an old foot treadle lathe in perfect shape, but ferry to Nanaimo was shut down due to covid at time and it eventually sold.

 

[phaxtris]

Oh man how I would not want to try to machine steel with a treadle lathe, that sounds like all sorts of terrible, probabaly need a walker after an hour of that

 

[Darren]

Nice machine....but i'd rather smash my jewels between two bricks than sit at that all day! We don't know how lucky we are to have the machines we have.

 

[Susquatch]

Wow that would be an interesting piece. Lots of old stuff like that in your area? I was trying to buy an old foot treadle lathe in perfect shape, but ferry to Nanaimo was shut down due to covid at time and it eventually sold.

Mine is quite similar in many ways. No foot treadle. It was run off a ceiling drive along with everything else in the original shop. I replaced that with an electric motor.

It mostly gathers dust now.

 

[WilliamR]

I wanted it sooooo bad haha. 1890 WF Barnes