Carbide tooling help !!

[lather]

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 (http://www.glanze.com/indexable-tool-holders/turing-tool.html)

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 (http://www.shop-apt.co.uk/carbide-inserts-for-turning-apt/page/5/)
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.

[pipeclay]

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.

[bwal74]

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

[lather]

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 (http://bbs.homeshopmachinist.net/showthread.php?t=14809)

Advice needed on carbide inserts for lathe use - Practical Machinist - Largest Manufacturing Technology Forum on the Web (http://www.practicalmachinist.com/vb/general-archive/advice-needed-carbide-inserts-lathe-use-82640/)

[pipeclay]

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.

[Gavin Newman]

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.

[19brendan81]

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 (http://www.ctctools.biz/servlet/the-485/indexable-iso-Type-lathe/Detail)

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 (http://www.shop-apt.co.uk/carbide-inserts-for-turning-apt/tcgt-110204-al-ak15-carbide-inserts-for-turning-ground-and-polished-for-aluminium-apt.html)

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

[lather]

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.

[Gavin Newman]

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.


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

[pipeclay]

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.

[19brendan81]

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!

[19brendan81]

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.

[Stustoys]

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

[lather]

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.

[lather]

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.

[19brendan81]

Gday Lather,

Are you certain that you are grinding your HSS bits up correctly? You should easily be able to 2mm off the diameter with HSS...more with coolant. I mucked around for ages with HSS before throwing in the towell and getting carbide. I kept persisting though, and finally cracked it. Small errors in angle can make a tool pretty well useless.

The feed and speed chart I made up for my workshop assumes 100fpm for mild steel, so i would be cutting that at 400rpm with HSS. I think I erred on the side of caution when I made that chart though.

Also dont forget that the workpiece must be properly supported or it will effect the way it cuts. How much of this bar is protuding from the chuck and is it supported by a tailstock?

Lastly sometimes its the base materials fault too...some of that unknown mild steel you get from around the traps can be a pig to machine (in my humble experience).

Brendan

[lather]

learned a big lesson today, had reduced the rake angle, as someone mentioned on another site about using no rake on hss, on a rigid machine.

ground the angle to about half, at a rough guess it,s less than 10 degrees.
the feel and speed, now when making deeper cuts has improved.

hadn't realized that reducing the angle would improve the cut, tried various angles previously, but never reduced the angle much from the correct angle as stated in lathe user manuals.

[lather]

Brendon
About to place an order on ctc.
the tool height needed is 16mm.

being able to turn the CCMT insert and use it in another holder to make use of the other 2 surfaces is a good idea, problem is that it's difficult to actually find information of which tool holder allows this when using the CCMT09T3 insert.

plan to get he SCLCR/L1616H09 holder - CCMT09T3. insert
SCLCR/L INDEXABLE TURNING TOOL HOLDER #I28 (http://www.ctctools.biz/servlet/the-607/indexable-iso-standard-lathe/Detail)

trying to keep it simple and get 3 different boring bar sizes which also use the CCMT09T3 insert.

edit, forgot to mention, manged to cut 6mm off the o.d at a feed rate of 0.1mm each rev, a 2mm cut feels like butter compared to the way it cut previously.

[pipeclay]

Most of the angles stated in manuals are theoretical.

[Bryan]

I've read that for any question about lathe tool geometry (for general turning), an answer of "about 7 degrees" will work. One day I'll put it to the test.

[lather]

would drills cut mild steel quicker at a more shallow angle, normally grind the cutting edge from 9 to 14 deg depending on size.

[Bryan]

What you're grinding on a drill bit is clearance. The rake is the angle inside the flute and is set by the helix angle. It is sometimes flattened off (less rake) for brass. Don't think I would mess with it for steel.

[pipeclay]

Is there a particular reason why you are going to buy 16mm shank turning tools?

[Gavin Newman]

I can't speak for lather but I have the same type of lathe as him (AL960B) and a 16mm shank tool fits the toolpost with no shimming required so all my carbide tools are that size.

[Steamwhisperer]

Same with mine (AL340D) although I do have a QCTP

Phil

[lather]

tool height on the lathe is 16.9mm

[pipeclay]

Did they change the tool opening on their posts,they all seem to show 12 centres.

[bwal74]

Hi,

Pretty sure Chronos in the UK sell a boring bar set that uses the CCMT insert. When Xmas is over and have some spare cash will look at buying a set. CCMT insert are quite reasonably priced from CTC.

Ben

[Gavin Newman]

Did they change the tool opening on their posts,they all seem to show 12 centres.

Nope, this has been raised previously in relation to the 960B. Although the H&F website links 12mm tooling to the 960B every example I've seen will take 16mm tools with no shimming required. The AL320G I had previously was the same.

[lather]

plan to get the 16- 20 and 25mm boring bars that use the ct 093 inserts from ctc SCLCR/L INDEXABLE BORING BAR #I33 (http://www.ctctools.biz/servlet/the-612/indexable-iso-standard-lathe/Detail)
unsure if the S20Q-SCLCR/L09 bar would fit in my tool post.

does the "h" in the dimensions chart relate to the round diameter of the bar, or the flats.
it's 18mm which should fit as the tool height on the lathe is 16.9mm, the height to the top of the post is 26.5mm.

what does the l1 dimension refer to, is it the max boring depth ?

[pipeclay]

The H dimension is the width of the flats,generally you would want you hold down screws in the centre of the bar,so if the H dim was 20 you would need the centres of your screws to be at 10mm from the edge.

The l1 as far as I know allows clearance for chips around the head of the tool and coolant,it is smaller than the minimum bore size.

Is there any reason why you are looking at getting bars that are so close together in bore size?

[lather]

A 20mm bore is common with what i,m working on.
which the 12mm bar would suit,
next problem is the length of the bar, prefer the longest possible, so the job doesn't need to be turned around.
if the 16mm bar was longer the 20mm would not be needed

May need to purchase larger drill bits, the largest i have is 25mm, and bore up to 68mm holes.

unsure if these boring bars are suitable, when making hubs which have bearings inserted each end, i bore both the bearing recesses with out taking the job out of the chuck so they are inline, these bars wont be able to cut the inner recess.

edit, the post bolts are 9mm from the edge, would 1mm matter.

[Stustoys]

Hi guys,
I might be seeing this wrong but isnt h=distant across flats. 1/2h=center height? the distance from the center of screws to the edge would be 1/2d.
As I read the drawing I1 is the minimum distance from the tool rest to the tip?

SCLCR/L INDEXABLE BORING BAR #I33 (http://www.ctctools.biz/servlet/the-612/indexable-iso-standard-lathe/Detail)(turns out I cant link direct to the details. click on "detailed description" for a drawing of the bars.)

The 16mm bar is 160mm long so should be able bore 100mm deep or more.

I couldnt tell you if you are buying the correct bars for your inserts. These bars call for a CC insert(I can never remember what any of that means off the top of my head)

Stuart

[the fabricator]

for me, i would try to use a PWNLR tool holder and use WNMG inserts, i can machine with cutting speeds up to 350m/min, but this is at work where we are encouraged to run that fast, for home use i would slow it down to save money but they are still and very nice, rigid tool. can face and turn ( and some limited internal work )

we also have some Mild Steel Finishing tools, not sure of codes and what not but they come up like magic on plain old black bar, which is probably one of the hardest materials to get a nice finish

[Bryan]

I've read the praises sung of WNMG inserts on PM. They sound like a good all-rounder, and more economical than CNs by virtue of 50% more points. I was looking at the holders on the CTC site, here (http://www.ctctools.biz/servlet/the-510/indexable-iso-Type-lathe/Detail). Just going by the drawings the inserts don't look all that well located by the holder. Not tightly surrounded like the diamond shapes are. But I guess if people use them without dramas they must be ok. Don't mind me; just thinking aloud.

[pipeclay]

There are different methods of clamping the insert depending on the manufacture,although most have a similar amount of tip support in the tool.

Similar to the boring bars,you can get the smaller diameter bars in the lengths of the larger bars,it just depends on the manufacturer.

[lather]

purchased the tools, with out the 20mm boring bar, due to purchasing other gear.

Is carbide conductive, it's a strange ?, but it due to the reference system i use (for the tool tips distance to the center) needing to close a circuit, it saves time as there no need for measuring until it's close to size, whenever changing tooling, e.t.c.

[Stustoys]

Is carbide conductive,
Yes.

[19brendan81]

Nice one lather. Let us know how it goes.

[azzrock]

I've read the praises sung of WNMG inserts on PM. They sound like a good all-rounder, and more economical than CNs by virtue of 50% more points. I was looking at the holders on the CTC site, here (http://www.ctctools.biz/servlet/the-510/indexable-iso-Type-lathe/Detail). Just going by the drawings the inserts don't look all that well located by the holder. Not tightly surrounded like the diamond shapes are. But I guess if people use them without dramas they must be ok. Don't mind me; just thinking aloud.


ive been using one of these for a few years know. i like it a lot. its gone know and im looking for a replacement.

[the fabricator]

i did a bit of research on the inserts we have at work, as i have my tafe text book here with an insert identification guide in it.

for roughing on all materials, i seriously couldn't go past a PWNLR holder, with the WNMG inserts ( 0.8 nose radius), with a wedge clamp. i've run a 15mm cut at .58 mm/rev feed and the insert didn't go anywhere. its 85 degree included angle makes it very rigid and very supported with they hardly ever burn out (unless you accidently run them at 850 m/min on s/s like i did the other day, oops), an alternative would be an MNMG insert ( which we use at tafe, which are also quite nice)

for finishing on mild steel, bright mild and K1045 ( or S1045 ) a TNMG insert would eb the best ( 0.4 nose radius ) ( look for the polished ones by sumiyoto ( sp? ) electric ). use a high speed, fine feed and PLENTY of coolant otherwise you WILL burn them out very quickly, they are polished remember?

for finishing s/s, en26 and 4140 ( very nice material to turn for shafts, bolts etc ), my recomendation would be a VNMG insert with an 0.4 nose radius, with a 35 degree tip angle, these inserts are also liable to burn out, so plenty of coolant on these as well.

a 45 degree SPMR holder is a nice tool holder to treat yourself with, produces very nice chamfers, be wary at high speed with this tool as having a large cutting area to cut with can cause severe chatter, which can cause these tools to dig in

a parting off blade and block from iscar ( or more realistically for us, hare forbes ) would also be nice, use the IC 354 inserts, low speed and always a 0.1mm/rev feed, plenty of coolant. the nice thing about these inserts are that you can set them very short and do some grooving work with them ( and use any of the IC 354 inserts, be it parting off or radius etc.)

for screwing, it sure is a bit more expensive, but full profile inserts produce a much, much nicer thread, well worth it

for large radius's, use hss, it can't be beat

[19brendan81]

"i've run a 15mm cut at .58 mm/rev feed "

Fark thats a big cut!

I second the use of coolant on the TCMTs...I have burnt them out before with what I thought was a mild cut.

[pipeclay]

Dont forget that is a reasonable size centre lathe being used.
Some of the nose radious stated may not be suitable for a home workshop either.
One other thing to remember is not to exceed the nose radious ,when setting feed rate.

[jack620]

I bought a TC tool holder while I was O/S last week. It takes TNMG inserts. I've only given it a brief trial, but I was able to turn and face 4140 easily without adjusting the tool. I didn't use coolant, but I will try some next time.

I also got a few spare TNMG inserts made by Lamina Technologies in Switzerland. They were $4 each. Has anyone tried this brand of insert?

LOTS of data on DoC/feed rates vs material for each type of insert on their website:

http://www.lamina-tech.ch/eng/catalog/group/turning

[Bryan]

Hope I'm not intruding with this, but I gave my CN holder a good workout. I was pretty gobsmacked by the finish it produced. This wasn't even a new insert. It seemed quite tolerant of speed and feed, but not light cuts. But we knew that. Material was 1045. Had a lot of trouble controlling diameters though. Seemed to cut undersize, and not consistently. Had to resort to HSS for finishing. :(

PS, I found a use for my crappy CTC mag base - keeping the hot & curlies off Big Ben.

[jack620]

That's a much nicer finish than I got on either MS or 4140. Maybe I was turning it too slow? What RPM were you using Bryan? Did you use the power-feed (I didn't)?

I was taking a shallow cut. The manufacturer of the insert recommends a 3mm DoC and 0.3mm feed for 4140. I don't know if my 3/4HP machine would cope with that.

[Bryan]

Jack, that was 38 dia @ 960 rpm (100+m/m). Feed .2 mm, doc 1.1 mm. Deeper cuts worked, shallower didn't. Try it with powerfeed. There's no way I could have hand fed that fast. And that was at the slower end of the range given: .17 - .45.

[jack620]

Thanks Bryan, I was running 38mm diameter at 600RPM. I'll up the revs and engage power-feed.

Did you use coolant?

[Bryan]

No I don't have coolant set up.

Edit: But if I did I would use it for this.

[jack620]

Bryan,
I just checked the manufacturer's data and they actually advise against using coolant on FC, MS and even 4140. I had another go with a piece of 32mm MS using the power feed. Holy s**t, it absolutely tore thru the metal! I had metre long coils of dark blue swarf all over the place. 1200RPM, 0.1mm feed and 1-2mm DoC seemed to work well. The recommended 3mm DoC at 0.2mm feed just stalled the 260.

The finish was good, but not as good as yours.

I like carbide. :2tsup:

[Bryan]

Yeah it's a bit scary when you're not used to it. I tried heavier feeds and they worked great but it was just too fast and too hot for me. I couldn't dodge the chips quick enough. Interesting that coolant isn't recommended. I thought I was doing it all wrong by working dry.

Edit: Metre long chips is not what you want. You may get them to break by fine tuning your settings. I'll let more experienced carbide users advise on that.

[pipeclay]

Increase your feed rate to get the swarf to chip,but do not exceed your nose radious,1200 RPM is ok but try around 800 RPM,try these at 2mm cut.

[jack620]

OK will do. Radius is 0.8mm. Am I right that higher feed equals rougher finish? What's the aim here- do I shoot for the minimum feed that results in swarf chips rather than coils?

[pipeclay]

Your feed rate is well under the optimum,the max you can run is .8mm.
.8mm tips for a 260 are a bit too big,if possable look for .2 or .4 mm tips.
What you should find is that if you increase the feed rate you may experience vibration .
Higher feed wiill not give a rougher finish as long as you dont exceed the nose radious.
For your .8mm tip I would suggest to try it on a .4/.6mm feed,you will probably find that this will possably stall your lathe.
If these are the only Nose Radious tips you have at the moment you will need to play with feeds speeds and depth to achieve a reasonable finish.

[the fabricator]

sometimes you can increase your speed to get the chips breaking.

i'd say a .6mm/rev feed on a hercus 260 would probably stall it.

usually my roughing feeds on large diametre jobs ( 200mm plus ) are about .2 to .3, depending on my set up, finishing about .1 to .15. speeds on this job get up to around 400m/minute, this relativly low feed creates a lot less force trying to rip the job out of the jaws, even with a 10mm cut

for small diametre work ( ie they have given me a peice of bar and i have a small overhang out of the chuck, full length grip on the jaws, very rigid set up, i run at the highest speed the lathe has ( 1350 rpm ) and up to a .5 feed, with 5mm deep cuts.

both these combinations result in chipping shavings, in fact i have a notebook with all my speeds and feeds for good finishes, getting chipping shavings etc that i have written up just from experimenting

i never rough with coolant ( except maybe on 15mm doc's at .6 feed )

always finish with coolant

my point after this rant is that you should just experiment with your speeds and feeds, try anything from .1 feeds and 500m/min speeds all the way to 100m/min speeds with a 1mm feed

and look out for those long stringy shavings, i copped a VERY thick VERY hot one to the face once and my face looked like it was attacked with a knife, not pretty

[lather]

Received the carbide tools, tested the boring bars on a small job.
bored out a short piece of mild steel, from 20 to 22mm.
the bar is left handed, set the insert tip to center height e.t.c.
was not impressed with the results, the bars flex easily, tested both the 12mm and 16mm bar, must be vibrating as it constantly sqeels,
using the CCMT09T304 korloy inserts from CTC.

must be doing something very wrong, ran it at different speeds up to 650 rpm, still sqeels, feels like a blunt hss tip when cutting,
even a 0.5 mm deep cut causes the bar to visibly flex.

[Jekyll and Hyde]

Received the carbide tools, tested the boring bars on a small job.
bored out a short piece of mild steel, from 20 to 22mm.
the bar is left handed, set the insert tip to center height e.t.c.
was not impressed with the results, the bars flex easily, tested both the 12mm and 16mm bar, must be vibrating as it constantly sqeels,
using the CCMT09T304 korloy inserts from CTC.

must be doing something very wrong, ran it at different speeds up to 650 rpm, still sqeels, feels like a blunt hss tip when cutting,
even a 0.5 mm deep cut causes the bar to visibly flex.

650rpm still sounds too slow to me for a start, I would have said about 1500rpm for that bore diameter in mild.

[lather]

may test at higher RPM, though prefer to keep it on the low speed belt, had queried about carbide and speeds earlier in the thread, and assumed that 650 rpm would still give a reasonable performance, due to using the positive rake inserts.

it seems to grind more than cut, could the insert be the wrong type for boring, due to the downward tip angle of the boring bar, causing more of the upper lip of the insert to make contact when cutting or does the bar need to sit lower than center height ?

using the same inserts for all the holders, the insert was recommended for the boring bar.

[pipeclay]

The tip of the tool needs to be on centre.
You say you have a left hand tool,I take it you are running the lathe in reverse.

[lather]

the lathe is run in reverse, the insert has a 7 degree positive relieve angle,
when viewed from the front of the bar, 1 bar angles downwards 10 degrees the other 12 degrees,
wouldn't this affect the overall cutting angle, as it has a 7 degree positive relief angle (when the top surface of the insert is in a horizontal position,same as when used in the turning tool holders),
the boring bar is angled downwards x degrees, doesn't this expose more of the upper tip of the insert into the surface of the material

[Stustoys]

Hi lather,
How much over hang do you have?

I set my boring bars a little high if the hole is on the small side, it makes sure the bottom of the tip isnt rubbing. (yes I know it can mess with the rake angles a little).

Pictures?

Stuart

[pipeclay]

The bars are designed that way,as long as everything is on centre there should be no problem.
The vibration issue could be caused by a number of factors,these you would need to eliminate by trial and error.
Any particular reason why you went for the left hand bars.

[lather]

Pipeclay, the LH bar was preferred, due to using a reference system that reduces wasting time measuring.
it's a simple idea, a small thin metal shim has been super glued on the side of the chuck, it's isolated. a multimeter is used, it's set to beep when completing a circuit.
1 probe is earthed to the lathe the other is placed onto the insulated metal plate on the chuck.
the multimeter beeps as soon as the tip of the tool makes contact with the small metal plate on the chuck.
the distance to the center on each different chuck is worked out by cutting a bar and measuring.
once known, the dial of the cross slide can be set so when the tool tip is at the center of the chuck, it reads zero.
e.g. when the tip makes contact with the insulated plate on the 4 jaw chuck, the dial is set to read 7.40mm, now when the dial is on a whole mm value, the work piece is also cut to a whole mm value.
Had made a quick reference chart for the dial readout and o.d. for each mm.
e.g. on a 20 mm o.d the dial reads 4.0, a 40mm o.d it reads 0.0mm.

the only problem at the moment is counting the dial turns as it's 8mm per turn.

will be easier when the poor mans dro is fitted, do not intend to set the dro to the work piece o.d., as it is not designed for a cross slide, so each mm is 2mm of the o.d.
in the case of the 4 jaw, once the tip makes contact, the dro will be reset to zero, now need to wind the slide in 0.30mm and reset the dro to zero to match the dro to a whole mm (or 2mm o.d. in this case).
a chart will be made for an easier reference for each mm of the o.d, if the dro reads 100mm it would be the lathes center, 90mm would be a 20mm o.d. e.t.c.

so now when ever a tools position is changed, or switching tools the reference makes it easy, no need to measure until about 0.1mm from the final cut.
will still set the dial as a backup reference.

Can't understand why the top of the insert sits in a horizontal position for the turning tools, but not for the boring bar, without affecting it's cutting angle.

basic image attached.

[pipeclay]

When you get your system working as you want will it still be easy to get an accurate reading if the tool post is off set or the compound rotated.
Not being up with all the different tool geometry,as a guess I would think the difference between the angle the tips sit out or due to tool shank clearances.A different clearance is required for an OD tool compared to a boring tool,others who are more up with geometrical terms and books will be able to give you the correct terminology.

[lather]

pipecaly, if the compound is rotated and the tip of the tool is too far in to reach the side of the chuck, it can't be used.
plan to place a small plate on the tailstock quill for left hand tools which could perhaps be used when the compound is angled to far in to reach the side of the chuck.

as long as the tool tip can make contact with a sturdy reference point, e.g. the chuck or tailstock quill, the system should work.
The only problem i have had when using it, is due to the tool slipping down in a diamond tangential holder, or due to a build up of crap on the tools tip, hopefully this will improve when using carbide, or the new HSS tool.
the reference is quite accurate, and within 0.05mm when constantly testing.
the reason behind it was to reduce the time measuring.

The chuck reference is always the same distance to the center, so as long as the tool tip can make contact with the insulated plate the distance to the center won't change.
the beeper is used for more accuracy, when contacting the plate lightly, forcing the tip into the plate would put it out.

usually i take the first measurement when it's about 0.2 mm from the final cut, even if i was using an accurate dro i would still measure near the final cut, mainly due to the problem mentioned earlier about a build up of crap that welded itself to the HSS tool tip, this had caused it to cut an extra 0.1mm, unsure why this happens, needed to tap it off with a box cutter blade.

the tool needs to be at center height, use the chuck for setting the height, have scratched a line on the spindle/ gearbox body, so the chuck will be in the correct position, and scratched the side of the chuck with a centered tool.

edit:, i know it's an unorthodox idea, got frustrated from constantly taking measurements, especially on single jobs requiring many tool changes.

[pipeclay]

Have you been able to work out what you were doing wrong in the set up and use of your boring bar/s?

[lather]

haven't had a chance, have been making shelves, that sit behind the lathe, including modifying the lathe guard which can easily slide back, and is no longer attached to the lathe, needed a little more clearance between the cross slide and guard to attach the dro.
decided to allow it to slide back further making it easy when cleaning the cross slide gibs.

only used the bars to bore out the parts for the guard slide system.
trying to organize the work area, so every tool has it's place.
should be running in a few days

[19brendan81]

Hi Lather,

Is that image how you are holding the boring bar in your job? If it is, that will be your problem. Presenting the carbide to the job like that will result in heaps of negative top rake, and thats where you will be having problems. Present it to the bore horizontal, exactly as if you are cutting an external diameter and im sure your problems will disappear. This is how I bore with carbide.

Brendan

[Gavin Newman]

Hi Lather,

Is that image how you are holding the boring bar in your job? If it is, that will be your problem. Presenting the carbide to the job like that will result in heaps of negative top rake, and thats where you will be having problems. Present it to the bore horizontal, exactly as if you are cutting an external diameter and im sure your problems will disappear. This is how I bore with carbide.

Brendan

My Taguetec boring bars present the insert at roughly the same angle as the diagram lather posted and they are obviously designed to sit that way because they come with flats machined to sit in the tool post.

They cut well with the insert at that angle, I assume it's at that angle to provide clearance from the base of the insert to the wall of the bore.

Although it would seem that this angle would end up giving huge amounts of negative rake, the edge of the insert actually presents a positive rake at the point of the cut as they have a cutting lip around the edge of the insert.

[lather]

brendon, the carbide bore bar is designed to sit at that angle, the angle can't be changed, as this is how it sits on the flats when held in the post.

took off the cross slide, when replacing adjusted the gibs prior to fitting the screw,
the cross slide must have had some slack, as the adjusting screw was turned 1.5 X in from the previous adjustment.
adjusted both the top and cross slide with out the screws connected,
adjusting the gibs while the screw is connected seems to give a false feel, compared to sliding the slides by hand.

have not had time to use the lathe, due to making mods which took longer than planned.

[19brendan81]

How strange. I had no idea they were designed like this. I built my own carbide boring bar and it holds the insert flat, and cuts like a dream.

[lather]

finally had a chance to use the lathe, the bars work much better.

The 12mm bar with only 50mm of the bar extending out from the post still squeals loudly and need earmuffs to put up with it, even on a very light cut.

didn't realize that the carbide inserts were very easy to damage, tested the turning tools, machined a small section, which seemed to work fine.
changed speeds, accidentally very lightly hit the end of the job with the insert before starting the lathe.
when turning down the bar it was rough and a struggle to cut, due to the tip being damaged.
must have been a very small chip as it was difficult to see any damage with the eye.

another tip had been damaged within a short time when boring.

The feel through the handle is much more jerky compared to HSS, is this normal and due to the chip breaker ?

[pipeclay]

I would say no its not normal.
The squeal you refer to should not be present.
What is the swarf like when taking a depth of cut greater than 1mm.

[lather]

on a 1mm deep cut or deeper the swarf was still the same color as the steel, and was breaking.

on a shallow cut it was coming off stringy.

[RayG]

Hi Lather,

Hmm.. as PC says something is wrong, do you have a picture showing how it's set up, if you can show the angle of the cutter relative to the work.. that would help, can you see the relief on the cutter... at a guess I'd say it's possibly rubbing.

Regards
Ray

[lather]

The insert has clearance, will post a pic tomorrow.
could the problem be due to the spacers used for the height.
using a 3/8 length of HSS, and in desperation in trying to find a spacer had cut up a 6 "
ruler.

[pipeclay]

The packers that you are using should not be a problem as long as the tool is supported along the full length of the Toolpost.
Is the flat on the Bottom of the boring bar sitting on your packers?
When you check centre height do you have the tool clamped tight in the tool post,or do you place the packers,check height then tighten the tool post clamp screws?
Are your packers under the front of the boring bar in line with the front edge of the tool post?
Which order do you use when tightening your tool post screws?

[19brendan81]

Is there any evidence that the boring bar itself is rubbing on your job somewhere?

From what you described on the other page something is rubbing, its just a matter of finding out what. There shouldnt be any squealing noises when a carbide bit is cutting properly.

What size hole are you trying to bore and what size is the bar? What material is this in?

Edit - Just read your old posts....are you still doing 20mm to 22mm bore in mild steel with a 12mm boring bar? That should be fine. In any case, squealing = rubbing...its just a matter of finding where its happening. Some photos of your setup would really help.

[lather]

Brendon, had bored out a 20mm hole using the 12mm boring bar which had clearance all the way around.
switched to the 16mm boring bar which didn't squeal and has a minimum 20mm start bore.

[lather]

the 12mm bar works fine now.
checked the inserts fit while sitting in the bar, had noticed small gaps which a 0.04mm feeler gauge could fit.
gave it a clean and bolted down the insert, still had a small gap until tightening the screw down harder than i thought was needed.
checked the 16mm bar, unless tightening it down hard the 0.04mm fits under the insert.
the torx screw hole in the bar is not centered compared to the inserts hole, it's positioned closer to the corner that the insert sits against.
is this done to clamp the inserts tight against the ledge ?

now need to get holders to save time shimming each tool.
have seen holders for quick change tool posts, are there holders for a normal post ?

[pipeclay]

No they are suited to the quickchange tool post they are designed for.

[19brendan81]

So the problem was that the insert wasnt tightened up enough?

[the fabricator]

if you break an insert lightly bumping it against the job, the inserts are cheap
good quality inserts should dint the job, not crack the insert

the squealing you hear isn't just rubbing, it can be due to overhang ( most likely cause ), loose bar or insert, speed way to fast, feed to slow

tcmt tools ( or other triangular insert tools ) are notorious for vibration

always use the biggest bar you can, sticking out the least you can

and yes you can make boring bar holders, peice of hollow bar bored to fit the bar, welded to a flat bar to fit in toolpost. drill and tap the pipe in 3 places to fit grub screws



or heres an expensive solutions, anti-vibe bars ( Silent Tools ), these things are awesome

[the fabricator]

if you break an insert lightly bumping it against the job, the inserts are cheap
good quality inserts should dint the job, not crack the insert

the squealing you hear isn't just rubbing, it can be due to overhang ( most likely cause ), loose bar or insert, speed way to fast, feed to slow

tcmt tools ( or other triangular insert tools ) are notorious for vibration

always use the biggest bar you can, sticking out the least you can

and yes you can make boring bar holders, peice of hollow bar bored to fit the bar, welded to a flat bar to fit in toolpost. drill and tap the pipe in 3 places to fit grub screws



or heres an expensive solutions, anti-vibe bars ( Silent Tools ), these things are awesome

[lather]

Brendon
the screw originally was tight, just needed a touch more which was a struggle using the small handled torx wrench supplied.
the underside of the screws heads on the boring bars already look worn, mostly in the area that it forces the insert against the corner ledge due to the off center hole,
almost feels threaded when loosening.

the turning tool holder screws don't show signs of wear yet and don't need to be as tight, they worked fine.
the hole is still off center, but looks less than the boring bars threaded hole

i guess the screw eventually wears itself in.