Thread: Carbide tooling help !!

looking at purchasing carbide turning tools, the range of inserts and choice does my head in.
Have a few questions to make the right choice when selecting carbide tooling and nserts.

the main material that will be cut is mild steel.

only need a left and right turning/ facing holder and a boring bar.
prefer to keep it simple, so all the holders use the same carbide insert.
Have been looking at the Glanze range, with all the holders needed using the CCMT0602 insert, not sure of the quality as they are made in india.

these inserts seem to be diamond shaped, and assume if a tip breaks that it can be turned around only once.
Is a triangular insert the better choice, as all 3 tips could be used if chipped or is the angle of the insert important for the finish ?

is the boring bar with a Thru Coolant Hole the better choice, or does the hole cause the bar to be less rigid ?

there are 3 types of clamping systems, whats the best choice ?
Glanze Indexable Tool Holders : Turning Tool

1-Turning Tool With screw Clamping System
2-Turning Tool With Top & Side Wedge Clamping System
3-Turning Tool With Lever Clamping System

to confuse me more came across this site
Carbide Inserts for Turning APT Associated Production Tools
had noticed that the TPMR type inserts which don't have a hole are cheaper, can only guess that they are used on the holder with the Top & Side Wedge Clamping System.

do all carbide inserts have chip breakers ?
had thought that the actual carbide the insert was made from cut the material, what does the coating do e.g. CVD coating?

are jobs much faster when using carbide over HSS ? this would be my main reason or using carbide.

does the quality of the holder also improve the finish ?

sorry about the questions, when doing a little research, seems there's much more to it than HSS.

Carbide can be quicker than HSS.

Not all Carbide tips have chip breakers.

A lot can depend on the HP of the machine,although a lot of smaller HP machines will work fine with Carbide,but the benifits of the Carbide would not be used to their full capability.

Are your jobs going to require a lot of stock removal or mainly just light cutting,this can have an influence on the type of tool holder/tips you use.

The through coolant bar is not required unless you can justify the extra exspence and you have a constant high flow feed of coolant.A normal bar with coolant going into the bore would be ok.

Hi,

Carbide tooling is generally quicker than HSS (approx twice the speed).

I wouldn't worry about having a coolant hole in your boring bar unless its a huge bar (like like a 20cm Diam or so).

The coatings generally make the inserts harder, wear longer etc.

Depending on how badly the insert is broken, you generally can turn the insert over. If your changing over due to wear, a triangle insert will give you more tips to use (6 tips).

Try a mob called CTC in Hong Kong, they are relatively cheap and of good quality. ctctools.biz/servlet/StoreFront They also have a pretty good product good.

Cheers Ben

pipeclay, the main use would be taking off material, mostly from boring,
when boring do the chips damage the carbide tips as they try to wedge under it ?

ben, didn't know the tips could also be turned over.

Have decided to hold back on the purchase and not rush in, seems easy to make the wrong choice when using carbide.
Plenty of science involved with carbide, as well as having a suitable lathe.

found a few threads with good information about carbide tooling / inserts,

Do you like your carbide toolholder for your lathe? - The Home Shop Machinist & Machinist's Workshop Magazine's BBS

Advice needed on carbide inserts for lathe use - Practical Machinist - Largest Manufacturing Technology Forum on the Web

Generally the chips when boring have no effect on the cutting of the tool.

That said there are times when they can interfeer,mainly if the diameter of the bore and bar are very close and if boring a blind hole of small diameter.

They dont normally get under the bar,but build up in front of it,and can load the bar up and cause the bar to dig in.If I am boring with a bar of similar size to the bore (generally I like at least 3 to 5mm clearance) I will withdraw the bar to remove the swarf,this generally is only when doing blind bores or occasionally stepped bores.

The tips that can be turned over are for negative rake tooling,machines using this style of tool usually have a minimum of 2HP.

The lower HP machines are better suited to run positive rake tooling which only uses one side of the insert.

lather, pipeclay is on the money - I've got an AL960B, same as yours, and the positive rake boring tips are the way to go. I use Taguetec bars (S12M-SCLCR09 & S16R-SCLCR09) with CCMT09T308 inserts and they work well in our model lathe.

Gday lather, below are my observations with carbide.

The diamond shaped inserts (CCMT) whilst less economical than the triangles (TCMT) due to having only 2 primary cutting edges are better able to fit into corners and seem to cut better than the triangles. You can also buy holders from CTC tools that will allow you to use the broad corners of CCMTs for certain operations (like putting a 20mm bar between centers and reducing its diameter accross the entire length), so technically thats 4 cutting faces versus 3 (although granted, 2 of them would not be used much) I.E:

MCBNR/L INDEXABLE TURNING TOOL HOLDER #I01

My 1 HP lathe was easily able to take a 5mm cut (2.5mm DOC) in mild steel with TCMT inserts, resulting in blue chips forming and an outstanding surface finish, so your 2HP machine should be capable of cuts twice that depth...which will allow you to get the most out of the relatively expensive carbide vs cheap HSS

In your wanderings on the web you might stumble accross a page that reccomends using TCGT or CCGT alloy inserts to take very fine cuts on steel to achieve extremely fine surface finish. The inserts referred to are these...

TCGT 110204 AL AK15 Carbide Inserts for Turning Ground and Polished for Aluminium APT Associated Production Tools

In my experience, these are extremely fragile and when they break they break through to the center hole ruining the whole insert. I played around with $50 worth of these on mild steel trying to get a really nice finish on a bore and ruined all but 2 inserts. I gave up on them in favour of the CCMTs in finishing grade which do a much better job.

Lastly, ebay USA and UK have thousands of listings for inserts. Most of the post to AU and its only a few bucks. You can get very cheap inserts shopping for them this way compared to anything local.

Brendan

Thanks in helping clear this up, almost went ahead with purchasing negative rake, until coming across the other threads.

Gavin, what type of rpm for example on a 30-40 mm bore would the lathe be running on and can the quick change gear box be used up to the highest rpm, had been mentioned in an earlier thread not to use it at high rpm, have not used it above 300 rpm, unsure if the statement was correct because it defeats the purpose of using carbide for a smooth finish.

tested a home made carbide tool, which is simply the carbide tips from a circular saw, placed at about the same rake angle as when using hss.

Ran the lathe on 650 rpm, to test the tools cutting action, it worked well, except the lathe was shaking, the 4 jaw was equally spaced and double checked the 4 jaws positions with an indicator, besides if the work piece is centered the jaws should be as well.
at 300 rpm which is the max speed i use with hss, this shake isn't noticeable.

performed a test, machined at 300 rpm, ran a fine finish cut with the cross slide being locked.
then ran it at 650 rpm, some more material was unevenly removed without touching the settings of the slide.
the shake seems to affect something causing an uneven cutting action, this was noticeable as it created a shine when cut at higher rpm, which was not even, so the shake of the lathe causes something to slightly move.
have not tried it on the higher speed belt, the lathe has never run on the higher speeds.
will test it today at the higher rpm with the chuck removed, perhaps the chuck is unbalanced.

Brendon
came across it, there was a recommendation to use the clamp over system without the hole, due to the threads failing on the screw type clamp system, as well as reducing breakage.
are these cheap inserts reliable compared to the more expensive brands ?
even a 5mm cut would be a big improvement.

Originally Posted by lather

Gavin, what type of rpm for example on a 30-40 mm bore would the lathe be running on and can the quick change gear box be used up to the highest rpm, had been mentioned in an earlier thread not to use it at high rpm, have not used it above 300 rpm, unsure if the statement was correct because it defeats the purpose of using carbide for a smooth finish.

I generally leave my lathe in the low range on the belt so my revs range from 70 to 650 depending on the gear used. I've used the power feed through the QCGB at all these speeds. For a 30 - 40 mm bore using carbide I would probably run at the 420 rpm ratio or even the 650 ratio in conjunction with a bit of neat cutting oil (I don't use suds on my lathe). The QCGB gears do get noisy at the higher speeds but they are open straight cut gears so that's to be expected 0 I just make sure they have plenty of oil before I use them at that speed.

I'm not sure how the QCGB would go if you were in high range on the belt and used the 900 & 1400 rpm extra ranges that gives but the chinglish manual doesn't specifically warn against it so it seems that it should be possible.

Originally Posted by lather

Ran the lathe on 650 rpm, to test the tools cutting action, it worked well, except the lathe was shaking, the 4 jaw was equally spaced and double checked the 4 jaws positions with an indicator, besides if the work piece is centered the jaws should be as well.
.

I have the same problem when using the 4 jaw (and my 4-jaw is a Fuerda direct mount unit - no backplate, the pins are direct into the chuck) I took the jaws out and had the same issue so it appears that the chuck body is unbalanced. I generally use the 4 jaw up to 300 and it seems OK as you've found. At some stage I'm going to try balancing the chuck dynamically but at the moment I live with it.

Rgds - Gavin

Is the lathe sitting level.
Even at high speed with the chuck attached I would think that it would have to be out by at 250gms if not more before it would create balance problems.

Hey lather,

Re cost of inserts - The inserts I have owned are...

1) TCMT inserts of unknown brand or pedigree that came with the super cheap 5 piece Ozmestore indexable tool kit. These are all worn/used up now.

2) Replacement TCMT inserts for the above toolkit. They were unbranded,but are Ti coated. I think they were $3 each and I bought them from a guy in tassie. Im still using all of these.

3) Kennametal CCMT inserts from the US - paid $5 AU per insert delivered. I have only had them for a couple of months.

4) Kennametal TCGT inserts from the US - paid $8 AU per insert delivered. Bought 6, smashed 4 in one sitting...havent used the others.

I started shopping for these OS when I went into the local place and they wanted $15 per insert or something stupid.

Of these, the best have been the Kennametal CCMTs, The cheap TCMTs fared about equally...and as mentioned I have had no luck with the TCGTs. Its worth noting that I did heap of brutal machining with my original, supercheap TCMTs. I machined down the HSS shanks of a bunch of drills ranging from 16mm to 25mm so that theyd fit in my 1/2inch cordless drill chuck. The inserts performed flawlessly even though the chips were coming off glowing, and left a mirror finish on the drill shanks.

Its worth mentioning that besides the TCGTs I have never had an insert break through the the center, nor strip out a holding screw. For what we are doing the ones held with a screw through the middle should be fine.

Re feeds - I often use the powerfeed at high RPMs (1000 - 2000)...if this is bad for your lathe its news to me!

P.S here is a pic of me getting stuck into a part for a tube bender I made. Im using the original Ozmestore inserts and I think this is a 3mm DOC for a 6mm reduction in diameter. Its free cutting steel (12L14). This was at 1000rpms and under powerfeed with no coolant. Note the colour of the swarf - bright blue. It was coming off very hot.

I never take cuts this big when boring though.

Hi lather,
The QCGB can be used at the highest rpm, but you need to watch that gear you are in. The longest feed on my chart is 7mm(a slightly large feed is possible), the max speed on my lathe is 1400rpm, the leadscrew is 3mm pitch. So "if" you were ever to try that the leadscrew would be turning at 3266rpm........ I doubt much good would come from that. But it would be over pretty quick as it would be feeding at 163mm a second.

Maybe thats what the warning you read was about?

Older lathes used to have a warning "do not engage course feed above XXXrpm" Which is one of the few useful warning labels I have seen, I guess is had to make way for all the other much more important warning labels we have these days.

Stuart

thanks for the replies, its definitely helped, glad it can be run on the lower speed belt,
was concerned that it needed the higher rpms.
will purchase some tooling soon.

pipeclay, the bed is level, had bored some flat bar which was about 10mm off center, the lathe definitely shook at 300 rpm, so dropped down to 110 rpm, seems it doesn't take much for an imbalance.

have just started working out cutting speed, is 120 fpm correct for a 25 mm mild steel bar when using hss, worked it out as 650 rpm,
even at 420rpm and feeding by hand, cutting using a fresh ground tip suddenly becomes hard to feed.
the tip gets a build up of crap almost instantly, unsure if it's got too hot or some of the mild steel starts to weld itself to the tip, it can be scraped off with a blade.
the swarf is still the same color and does not turn blue when this happens.
use a diamond tool holder which would be difficult to grind incorrectly, and have tried various angles to work out why i cant get as deep a cut as other members using hss.
of coarse i can get a deep cut but overall it is much slower than performing 2 or 3 shallow cuts.

have put up with it and generally run it at a slow speed, which is probably why a simple job takes forever.
normally use 300 rpm for shallow cuts, but for deeper cuts, about 3mm on the dial it's much faster to cut at 110 rpm.
Am i doing something wrong ? as there is a big difference in the cutting speed

brendon, would be happy with at least taking off 4 mm from the diameter, the majority of the time i take off 0.5mm to 1 mm off the diameter when using hss.

Pipeclay, the question about the lathe being level, reminded me about the cross slide not sitting at the same level as the bed, the longways level was slightly uphill compared to the bed.
just found out that the topslide runs upwards 0.15mm in its full range.