Thread: Carbide insert experience

I have always used HSS for my lathe tools (small lathe), I was given a Chinese set of holders + inserts, they have been sitting on a shelf for two years, I am currently machining some stainless steel so I thought I would try them out. Well the finish is exceptional, however I made one cut and all was fine so doubled the cut depth ( I do this with HSS all the time ) the result,,, the insert immediately grabbed and shattered like glass. so is this the result I should expect from a small lathe, or is it a result of inferior inserts or something else.

China,

How small is small? Smaller than a 9" Hercus?

I use carbide and other than some nondescript parting off inserts breaking, I have never had an insert shatter. Can you post a photo of an unbroken insert? Joe H put me onto some inexpensive inserts a few years back and a variation of those inserts might suit your needs.

Bob.

Hi Guys,

Yes carbide does that, and SS work hardens rapidly. Its quite possible that you found a particularly hard bit embedded in the workpiece.

One good reason to wear safety glasses.

Ive had carbide break off before, but only when its being abused. They haaaate chatter and interupted cuts, you can trash a corner in seconds doing either if youre not careful. If we're talking smaller than a hercus 9in, hobby lathe sort of thing, the real benefit to carbide will be higher RPM running, not the ability to take huge depth of cuts. Rigidity is everything, carbide needs it to function.

My lathe is a Al 50G commonly referred to as (9x20), I will give another go I think it was too much I may invest in some better quality holders and inserts I am now having difficulty finding inserts
I always wear safety glasses these days I can't see without them, I will post a pic of the inserts

What inserts are you using ?
Not all inserts types are created equal

Looking at your lathe
https://www.machineryhouse.com.au/L157
it takes 10mm height tools

On the cheap end there is horrible sets that are poorly designed and If it's a kit like this
https://www.ebay.com.au/itm/10mm-3-8...t/392096484278
Throw it in the bin.

For a small lathe like yours would suggest looking at CC**0602** inserts. Normally CCMT060204 for steel ones.

Tool holders would be ones like
SCLCR1010E06 / SCLCL1010E06
SCMCN1010H06
SCACR1010H06 / SCACL1010H06

Can easily get boring bars that take the same inserts.

While they won't give you the most possible edges at 2 cutting edges per insert they don't require as much force to cut so will be a bit more forgiving on a lighter duty machine.

Originally Posted by MasterSpoon

What inserts are you using ?
Not all inserts types are created equal

Looking at your lathe
https://www.machineryhouse.com.au/L157
it takes 10mm height tools

On the cheap end there is horrible sets that are poorly designed and If it's a kit like this
https://www.ebay.com.au/itm/10mm-3-8...t/392096484278
Throw it in the bin.

For a small lathe like yours would suggest looking at CC**0602** inserts. Normally CCMT060204 for steel ones.

Tool holders would be ones like
SCLCR1010E06 / SCLCL1010E06
SCMCN1010H06
SCACR1010H06 / SCACL1010H06

Can easily get boring bars that take the same inserts.

While they won't give you the most possible edges at 2 cutting edges per insert they don't require as much force to cut so will be a bit more forgiving on a lighter duty machine.

MS

This holder will enable the use of the 100 degree corners - https://www.ebay.com/itm/10-100mm-Ne...gAAOSwGzxZibWO

BT

In my experiences with ebay insert tooling so far, its worth noting that bigger (and more rigid) holders arnt necessarily going to yeild better results. Bigger inserts for general purpose turning tend to have larger edge radius', which means the feed rate required to get the insert to cut will be higher, and thus the demands on the machine higher too. Ive got a few holders that take TNMG1604xx inserts and they, realistically, are just about past the limit of what a hercus 260 can handle. Ive got TNMG160408 inserts, you can forget using those on steel, the nose radius is too big. I then bought some 160404 inserts and, while the edge radius is the same, the nose radius reduction made the machine significantly happier. For ploughing material off, theyre not too bad.

At the other end of the scale, I bought some boring bars off ebay, super cheap ones with CCMT060202 inserts, thinking I could just use them to get in tiny spaces while my bigger brazed tooling does the heavy removal for bigger holes. Turns out that the smaller insert has a much sharper edge radius and theyll take a 1mm doc easily. They have been surprisingly capable bars, the SCLCR12 bar has been my go to bar for a little while now. Im starting to consider more holders to use the CCMT inserts for other work, im that happy with the bars.

So smaller isnt necessarily worse!

Bob,

How do you find that holder for the 100 degree points. Are cutting forces noticeably higher than when using the other two points? Can you take the same minimum depth of cut?

Graham.

China check that your tool post is sitting firmly on the compound, i have seen them sitting on the top of the T nut that holds the toolpost in place.

Cheers, shed

"On the cheap end there is horrible sets that are poorly designed and If it's a kit like this https://www.ebay.com.au/itm/10mm-3-8...t/392096484278"

Hi Master, I don't disagree re the quality of these - these were the first ever set of carbide tools that I bought, about 10 years ago. There was not much else around for the hobbyist at that time. I never intended on keeping them as the quality was so low, however in their defense I still use these tools often! Obviously the original carbide is long gone and I have replaced it with new stuff (kolroy brand TCGTs). I have them setup as my dedicated fine finishing tool for taking light cuts (up to .5mm max generally) and they work admirably.

I wouldn't recommend someone buy them now as there are better options around, but I did feel I should come to their defense somewhat as it was just the other night I was marveling how much use I had got out of those crappy tools.

Whilst on the topic of carbide for small lathes - my two bob on the matter is that I far prefer the triangular TC inserts. I have some CC tools too but don't seem to like them as much.

Originally Posted by Oldbikerider

Bob,

How do you find that holder for the 100 degree points. Are cutting forces noticeably higher than when using the other two points? Can you take the same minimum depth of cut?

Graham.

Graham,

The 100 degree corner's only real drawback is that it obviously won't cut to a square shoulder. The holder I currently use is not the same as the one I provided the link to.

DSC_9044 (Large).jpg

I have ordered one of those for a CC..06.. insert and if it works well I'll buy another to suit the CC..09 inserts I most frequently use. I don't notice that more effort is required to remove the same amount of metal as when using the 80 degree corner. As far as minimum depth of cut goes I can't say. I most often use the blunt corner for removing as much material as possible.

The best thing about the holder it that it uses the corners that you can't use otherwise. By the time I acquired the holder I had accumulated quite a stash of expensive broken 80 degree tipped Kennametal CCGT09T304 inserts which I had used in the "normal" holder below-

2012-05-29 017 (Large).JPG

Bob.

Thanks Bob, that's useful information. I've only recently got organised with a variety of insert tooling, when I start to get a stack of blunt diamonds I'll look into these holders. At that time I should be able to justify the purchase as a money saving one

Graham.

Graham and Anyone else interested,

These are the inserts I use, as recommended by Joe H, and the seller I have purchased them from. While they suggest they are intended for non ferrous metals, I have used them on 316 stainless, 4E cast iron, 1045, 4140 and gumby 1214 with, IMO, reasonable success. They do work beautifully on aluminium too.

I use them on my 1 horsepowered 9" Hercus at about 1000rpm ( the lathe will run up to 2650rpm ) and as end mills and fly cutters on my 2HP mill.

For the price I would imagine that they are counterfeit.

https://www.ebay.com/itm/10pcs-Super...UAAOSw8vZXMmmb

Here is an example of the finish on aluminium using the above insert at about 600 rpm.

DSC_7523 (Large).jpg

Bob.

I can vouch for the inserts Bob recommended. They cut beautifully on aluminium and Delrin. I haven't tried them on anything else. I'm impressed to hear they work on 316.