Is it time for ME friendly inserts resource?

[Clive FosterParticipant @clivefoster55965]

Given the steady trickle of insert related queries I wonder if its time for some sort of Model Englneer friendly inserts resource to be developed. As there are about 16 bazillion different types of inserts out there and most of our usage will be outside the official design use parameters anyway the chances of ending up with a plain wrong or merely "inappropriate for me" insert are high unless exhaustive research is undertaken. Not something that could be done overnight but given time it ought to be possible to end up with a decent lists of safe types along with speeds feed and depth of cut information suitable for our machines taken from practical experience. It would also be really nice if edge and chip breaker geometry on friendly inserts could be included to help verify if something similar to known friendly one is worth a try. Some of the stuff turning up on E-Bay at attractive prices is fearfully exotic. But when you can get a box of 10 inserts for the price of 2 retail temptation is hard to resist.

Problem is that modern inserts are mostly specifically developed metal removal systems designed to operate at high speeds and feeds on CNC machines removing large quantities of material very quickly at the cost of a very short, by our standards, lifetime. Hours or even minutes whilst we expect months or even years. That said the lifetime when used as intended may be short in time but the amount of metal removed probably approaches, or exceeds, a decades worth of ME swarf. Working at these rates the cutter is generally over the peak of the power needed per unit volume of material curve so power needed increases more slowly than the amount of swarf generated does. Which is more than a little counterintuitive and can demand rather different cutting geometry than is ideal for us working towards the bottom end of the curve where power needed goes up in line with or probably a bit faster than the amount of swarf increases.

Its generally agreed that a safe insert pattern for our smaller lathes is a polished type intended for use on aluminium. These tend to have sharp edges which work well in lower speed cutting with relatively low forces in a range suitable for machines generally both smaller and weaker than industrial machinery. Even then there is considerable variation as to how well they hold up on different materials and how sensitive they are to cutting speeds. Nominally identical, as in being designed for the same duties, cutters from different makers can behave very differently under our conditions of use. Unlike HSS tooling, where a poor choice of cutting parameters merely necessitates premature trip to the grinder for resharpening, early demise of an insert costs real money. Using up a box by trial and error isn't really on. In my experience inserts crave speed and need to cut. Hoping to baby a longer life out of an edge with light cuts and slower speeds frequently has the opposite effect drastically shortening the life. I have some DCMT inserts that last well in difficult steels when run close to the design 1400 surface ft/min cutting speed but dropping significantly below 800 sfm kills them in a foot or so. Finding the aluminium type inserts needs a reasonable understanding of the type codings. They are logical but it can be a complex business especially when working through manufacturers website catalogues.

All that completely ignores the fact that many non aluminium inserts work just fine in smaller machines. Albeit a fairly aggressive approach to cutting usually works best. Trying to trim a few thou all too often just wrecks the finish. Those of us with industrial size machines are better served as there are still ranges of inserts designed to be used at manual machine speeds and feeds, mostly rather above HSS levels tho' so success on smaller machines lacking the strength and rigidity to reliably generate high cutting forces cannot be guaranteed.

Starting out shopping for lathe inserts is bad enough but mills are a complete nightmare. I run a Bridgeport, wimpy by industrial standards but hefty compared to most of ours, and wouldn't find it easy to go insert. All I have is a Little Hogger set from Chronos and 3" face mill taking TPKN inserts. TPKN is common and old fashioned but finding decent cutting speed, feed and depth of cut data is less than easy. The Chronos Little Hogger set works well but all the guidance I got after fairly determined phone chasing was about twice HSS speed. Nothing with the set at all when I bough it approaching 10 years back. At least my handy dandy Osborne HSS speed & feed cardboard slide calculator is reliable for HSS and gave good starting point.

One thing that really should be stopped is the selling of inexpensive "no name" insert holders taking their own specific non standard insert types with no data as to material type or conditions of use. At least if we had an ME Friendly resource folk could safely be directed to commonly available ISO standard shapes and materials from reputable makers. I'm old enough and ugly enough to make a fair fist of finding my own way through the maze but its awfully easy for a novice in the field to waste serious money. Model Engineering or Home Workshop hobbying is expensive enough as it is without such errors.

Clive.

 

Edited By Clive Foster on 03/10/2015 19:46:23

[Clive FosterParticipant @clivefoster55965]

[AjohnwParticipant @ajohnw51620]

APT Carbide brake down the material groups which I find helps. Their prices aren't bad either but come in packs of 10 apart from a few they sell for hobby use in smaller numbers.

I've used several types over the years on a lathe. One thing I am certain of is that loose head stock bearings don't do tips any good at all even causing them to chip at times. Another thing I have learned is not to trust ebay bargains. I'm sure some have been used. I don't buy that way any more but to be fair some list now with no mention of either new or used. Some state new but having been bitten and disappointed with performance I just don't buy them from this source any more.

Personally I feel rigidity is more important for finish than speed. I actually wonder if some people find that speed must be high are getting better results because their lathe head stock bearings will heat up more and more quickly the faster the lathe is run and this will tighten them more as a result. Not an approach that suites me as I adjust on the basis that the lathe wont run much over circa 500 rpm. In any case max speed is circa 1300rpm.

One pet hate I have is model engineering suppliers that sell tooling with no mention of the tip type reference number or even sizes. Eg I recently bought a 25mm parting off blade and holder from RDG. From the onset as there is no info on the tip fitted I have mostly bought it for the holder as I can easily buy another blade and tips to suite. The tip supplied looks unusually short too.

I'm looking at face mills at the moment. As raked inserts look best on a lathe to me I suspect I will go for APMT1604. However a Chinese listing mentions that APGT1604/APKT can also be used in these. That will mean spending some money to find out.

John

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Edited By John W1 on 03/10/2015 22:05:27

[Enough!Participant @enough]

Hopefully, something may happen along the lines discussed here.

[AjohnwParticipant @ajohnw51620]

Books wont be much good for inserts as they keep evolving so have little chance of keeping up to date.

John

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[Tony IdleParticipant @tonyidle14205]

I haven't found insert type to be a critical issue. I have a Colchester Bantam with Dickson tool post & max speed 750rpm. I use a set of no-name 20mm holders that take TCMT16 xxx 03 tips. I buy quite literally any TCMT16 inserts that turn up on eBay with complete success. Note needs to be taken of tip radius for critical work to a shoulder but other than that minor changes to speed & depth of cut accommodate the differences. Grey (carbide?) inserts chip easily on intermittent cuts but that's about the only characteristic of note (at least for hobby use).

[AjohnwParticipant @ajohnw51620]

I did buy what ever of ebay but found that some didn't last as long as they should so am pretty sure that they were used and had been on cnc machines being used for production work where they are removed before performance drops off. Actually I saw a whole bucket full of tips like this at a dealers who was thinking about selling them. He invited me to look at them with an eye glass and no problems could be seen but the coating will have been part worn out.

Following suggestions from some one else I tried TCGT types. These are representative of the latest ideas on inserts. The form on the top of the insert is changed to provide a sharper cutting edge with rake. I went for 11mm ones as they fit holders such as these

**LINK**

Those are actually fitted with this style of tip and even come with torx screws. Mine had something else on them and used hex keys which are hopeless, the key soon rounds over. 16mm tips and holders are also available. The triangular shape is good because they can be used up to a shoulder even for facing it. I think 9mm are also available. I've since bought a proper holder but can't find one with the V pointing forwards so will have to stick with the 10mm ones or make one myself.

I feel that these tips do compete with HSS but I haven't tried highly polished HSS with more extreme rakes – yet. The performance drops of when the coating wears off but there are versions about that are polished and have no coating at all. These are mainly aimed at none ferrous and abrasive materials but some are also suitable for finishing stainless so I will be trying these on all materials at some point. I have used coated finishing tips for stainless as these were what I originally bought. They work well on ms, silver steel, brass and al. Al is probably the stuff that tends to wear the coating off.

I had hoped that I would be able to find a face mill that used the same tips. No luck but it looks like APMT1604/APGT1604/APKT can all be used on the same holders so there is plenty of scope for tip geometry including micro polished. These can also be used on rather large end mills. Smaller sizes use smaller tips. This is one of the problems with the technology as I see it so it pays to spend some time determining what shape and size of tips to go for. The volumes sold seem to have a direct bearing on price.

I've decided to try my own theory on face mill size. Cranky – what? Say I buy a 50mm one and run it at some cutting speed. As my miller uses a belt drive the cutting torque available for the same cutting speed would be the same for a 100mm one as it would be running at a reduced speed via the belt. I don't expect to be able to take a large cut with either size. I've no idea how deep a cut I will be able to take.

John

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[Clive FosterParticipant @clivefoster55965]

Although I agree with John that a book is probably not the best way of providing this sort of resource I don't think obsolescence and ever evolving insert technology is the major worry. Inserts for industrial size manual lathes have been around for along time and show little evolution as already being more than good enough for use when the man in the loop is the main factor in setting operating rates. Cost is probably the driver heard. Cheaper but just as effective.

Mainstream insert evolution is more concerned with faster metal removal whilst maintaining dimensional accuracy when used in high speed CNC machines. Under these conditions the chip breaker is almost more important than the cutting edge itself. Folk who have used modern inserts on steel at design rate will have noticed how the blizzard of nicely curled chips comes off blue, or even red, whilst the work remains relatively cool. This ability to put the heat into the chip just before it is removed weakening the fracture line for easier removal is one of the major secrets behind modern machining. According to my Sandvik book the chip breaker does most of the work and an insert operating under optimum conditions ought to fail by chip breaker erosion not tip blunting. No way are typical ME machines getting into that territory.

Tonys Bantam is at the lighter end of industrial machinery with the strength and mass to exploit designed for purpose inserts so its no great surprise to find he gets decent results with pretty common, easily sourced inserts. Its the smaller machines where things get difficult. I believe Greenwood Tools were the first folk in the UK to source inserts that worked well and reliably using straightforward book values for operating parameters on ME class machines. Albeit best at the stiffer end of thing Boxford, Denford, SouthBend, Myford ML7 et al. Inconsistent operation and odd failure modes, as noted by John W1, were reported on older, less stiff, machines. User experimentation often enabled successful parameters to be evolved for such machines but thats an expensive way to go about things for individual users and the variety of both inserts, machines and machine conditions makes sufficient testing for an authoritative book impractical.

We have to accept that no one is going to design nice versatile inserts for us so we need to exploit crowd feedback through an online resource. Given sufficient results in the usual "worked fine for me", "OK I suppose" "abject fail" and, probably most important, "my lathe is similar to yours but this insert did / didn't work for me which is the opposite of what you found" categories we might be able to make some sense of things. Ideally we should be able to evolve useful tip shape, tip sharpness and maybe chip breaker data with the expectation that something very similar to a known good performer would be worth a try. With luck given some "known good" to start with we should be able to find what sort of variations add up to "better performer on MY lathe". Given the variety of machinery and fiscal resources one size fits all isn't going to happen. If nothing else there will be clear blue water between those who are able to finance several types of inserts to have specialists on different materials and those who can only afford one universal performer. Obviously the universal performer will not only work a bit slower than the specialist inserts but also needs to last much longer lest the users wallet empty before the model is finished.

Clive.

 

Edited By Clive Foster on 06/10/2015 10:46:21

[AjohnwParticipant @ajohnw51620]

I can't say that I agree with that Clive. They have moved on from the initial flat inserts and also the ones with rake obtained with a small groove along the cutting edge. In part the changes reduce cutting forces = less HP and then micro polishing for aluminium so that there is less trouble with the stuff melting and sticking to the tip. Then there are ones for milling designed for high feed rates. On the milling side I have noticed that many of the used cutters sold on ebay use old obscure inserts. Many of them are fine, some damaged. I decided to order something relatively modern and versatile from Hong Kong. It also comes with a lot of tips – in some ways I would rather have picked my own because I have gained the impression that micro polished are the best option for home use. Mainly from what they state they can be used for. As I see it a tip which is basically intended for aluminium but can be used for finishing stainless should be suitable for just about everything.

Chip breakers are another factor that for me don't seem to work that well on these tips. This could be down to both speed/feed and or size of cut

High speed – red hot swarf. I find that hard to accept unless oil mist or coolant etc are used. I have seen large cnc machines machining aluminium. There are several reasons why I wont be able to do the same thing at home or achieve the same finish they do. One is speed, the other is rigidity which has a large effect on finish. Cooling too. My boxford is not exactly a light weight machine. The bearing in the head stock are most definitely not suited to cnc machine speeds. Having seen these machines being set up things aren't a lot different to using a lathe really. The speeds and feeds needed are often determined by the part that is being made on them not manufacturers tables. Tip choice – same. The company I worked for spent just short of £2M on a few of them. 3 if I remember correctly. They went to India some years ago. Company policy – hardly any labour content in the UK at all. One setter part time. A few people to palletise the parts then assemble. I'd guess that they are now being made in Germany. Moan over.

John

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Edited By John W1 on 06/10/2015 11:41:07

[Mark CParticipant @markc]

Clive,

"blizzard of nicely curled chips comes off blue" too right! It is a problem I have found on my Boxford when I go at it – my hair is disappearing at an alarming rate without having it singed off when the damn stuff lands on my head and it is a definite problem when the stuff goes down the back of your shirt….. I have one type of roughing insert that makes short tight curly chips about an inch long and fires them out like a machine gun all over the place to the point that they are a fire hazard. I don't have a chuck guard and have considered fitting one just for this tool.

Mark

PS. The tips are DCMT 11T312 Sandvik items and the finish is excellent when you get them working as described.

Edited By Mark C on 06/10/2015 12:17:13

[AjohnwParticipant @ajohnw51620]

I used to have the flying chip problem on a Myford Mark. ML7 I put it down to loose headstock bearings and that proved to be true. It didn't much matter what sort of tool I used. i recently bought a used Wabeco that seems to have a slight chip breaking feature built in. Not sure what needs adjusting yet. The lathe is covered in rather short bits and the owner used DCMT's similar to Mark's. I tried the tips I use and had similar results but the finish on ms was marginally better.

You could always upgrade to the latest tip in that sort of line Mark

**LINK**

Even turn carbide then.

For interest here is the tip Mark is using

**LINK**

Some don't have the serrations. Chip breaking depends on feed rate as mentioned.

John

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[Mark CParticipant @markc]

Aerial assault by chips is not a machine problem (other than lacking some separation medium between me and the work, AKA chuck guard). It is a function of insert design (chip breaker) and use (speed, feed & material). It indicates that the insert is getting close to the operating conditions it was designed for.

PCD (Polycrystalline diamond) and CBN (cubic boron nitride) inserts are really designed for "exotic" materials where carbide is simply not hard enough. The last time I used them for a job was on a special coating applied to a cast iron mould for forming optical lens blanks. The stuff they sprayed on (some sort of propriety metal alloy was too hard for coated carbide and they specified a particular type of insert that was suited to their material. They are certainly not in the category of ME workshop fodder…..

The inserts I am using are not quite the same as the ones in the link, they are Sandvik as I say and are in a grade of coated carbide suited to steel (and to some extent, Stainless) with the appropriate chip breaker for "getting it on" in steel. They are capable of taking a significantly higher cut/feed rate than I have power for but upping the feed to compensate for the reduced cut keeps the power down to a point I can manage but they don't want to take little tiddler cuts off – they need to get their teeth (tooth?) into the stock and do some work! This means that taking small cuts so you can sneak up on the desired size is out of the question – you have to plan ahead and understand how to get consistent results and go straight to size with a "proper" cut, just like you would in a production environment.

On the plus side, they are almost indestructible on our size machines, I try regularly just to check their quality control…..

Mark

[Neil WyattModerator @neilwyatt]

I've come to the conclusion that CCGT and CCMT inserts probably meet all the needs of most small lathe owners.

1 They work well with small lathes of modest power

2 between the two types you can machine steels (CCMT), stainless steel and aluminium alloys (CCGT) (and they work on brass, to be honest)

3 they work with fine finishing cuts as well as hefty blue-chip cutting

4 they cope with moderately irregular/interrupted cuts

5 they (and their holders) are relatively inexpensive and available from a many sources

6 they will continue to be readily available for the foreseeable future

No doubt other inserts will be better for specific jobs, lathes, styles of turning., users etc. but because of their low cost, ubiquity and capability CCGT/CCMT have to be the best choice anyone starting out with inserts?

Neil

[Roderick JenkinsParticipant @roderickjenkins93242]

I completely agree with Neil, with the addition that CCGT tips are also very good for fine finishing cuts on steel. They are a bit delicate though so it is better to rough out with CCMT.

Rod

[AjohnwParticipant @ajohnw51620]

It would take some effort to switch me off TCGT 11's now. I don't like square inserts. There are plenty of cheap holders about for 11mm triangular inserts. More substantial holders for them are reasonably priced too – if bought from the right place. Some people go for the 16mm tips. I think 9mm is available as well.

I have used DCMT's in the past and still have a couple of holders for them and tips. One box of tips and holder is yet to emerge. The box of tips that have now been put in the right place is so old and tattered it's hard to read what they are. Something like DCMT 312 512 -11M. The first 2 1's in that might be something else. Sandvic coromant. Bought when Graham Engineering of Alpine brand fame were alive and well in West Brom along with a large show room.

Personally I feel micro polished is a very good idea if aluminium is being turned. Some of the tips Neil mentioned are available in that state also raked but I find square tips a pain when working up to a shoulder. I'd rather square it off and finish it with the same tool.

John

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[JasonBModerator @jasonb]

John, the CCMT and CCGT are not square they are 80/100deg rhomboid and what I use 90% of the time too.

[Mark CParticipant @markc]

The square tips are not square (unless they are "s" prefix), they are rhombic so you can get into a corner – something like 80 degree corners for the "c" prefix.

I also agree with Neil about the type he mentioned for the reasons he stated for the smaller lathes in hobby use.

Mark

beaten to the enter button!

 

Edited By Mark C on 06/10/2015 18:39:59

[MuzzerParticipant @muzzer]

CCXX tips aren't square – they have an 80 degree angle which allows you to get into a square shoulder. Admittedly this means that 2 of the corners are 100 degrees but if you want to use them (for roughing typically), you can get a holder that presents them correctly.

As noted above, CCGT is good for finishing cuts and light duties in steel (not roughing) – and light machinery. They are razor sharp and pretty tough. Probably the first type to try on both steel and aluminium, especially if your machine isn't very heavy.

There are some interesting milling inserts available nowadays, eg as noted by John W1 (APMT etc) that are industry std geometries at reasonable prices (see the link to APT) so you can buy holders (cutter bodies) from a variety of places. I've not had a chance to try them here in my armchair but they come in ground (aluminium) and coated (steel).

Naturally the Mercans have come up with their own imperial equivalent that costs more and seems to do something similar (look up the Shear Hog) although they seem to be loominum-specific. The point is though that the cutting forces are less, so you can remove more metal with less power and on smaller machines. Some of the inserts like the one posted by the OP look brutal in comparison and side-by-side tests seem to show a significant difference IIRC.

Murray

[Mark CParticipant @markc]

I have a couple of milling cutters that take AP type inserts (with the helical cutting face) and run them on my omnimil with a 3/4 HP motor. The problem I have with them is the rate of material removal – they are ok but no comparison to a modern roughing cutter on my mill. You are limited to the length of cut and there is no option for plunging unless you ramp down. I have a 40mm shell mill which works quite well for surface cuts and a 20mm end mill that can manage to rough out but neither are good for much else. They would be much better on a bigger CNC machine (or manual mill with a decent power). The inserts are not as sharp as a conventional mill but I might be specifying the wrong inserts. For what they cost, I took the advise of the rep from Cromwell and buy HSS/Co (or what ever they call them) and bin them when I am finished destroying them (which takes longer than I imagined when he suggested them).

Mark

PS. I should have added that I imagine they would be a waste of money on anything smaller than a machine my size but others might report otherwise?

Edited By Mark C on 06/10/2015 19:25:57

[AjohnwParticipant @ajohnw51620]

Posted by JasonB on 06/10/2015 18:33:11:

John, the CCMT and CCGT are not square they are 80/100deg rhomboid and what I use 90% of the time too.

Thanks Jason. I just look at the pictures. So I could have one extra tip to wear out. However I mostly use a tool with the V pointing forwards. I did look at the diamond shaped ones with only 2 tips but went for the 3. The only problem is I don't seem to be able to buy a substantial holder that holds the tip like this

That's one out of the cheap sets that Chronos and others do – 10mm / 3/8". Not that the lack of a hefty holder matter really. Actually I posted a link to some one selling these holders along with the raked tips fitted. They usually have the ones with a groove round the edge on them. They will turn both ways and dig in if needed. Same in HSS even though the rake will be -ve in one direction. I only grind straight bar turning tools if I feel lazy and need a new tool. It takes a lot longer to grind the V without over heating.

One problem on a wabeco so could be the same on a mini lathe – when I orientated it to face the cross slide didn't have enough travel. The tool was about 25mm short of centre. Ok for normal turning but I may need a specific tool for facing – which I have.

When I ordered 2 holders off APT one turned out to be the wrong type. It takes the diamond type. They sent me the right one so I will probably modify the wrong one to gain a holder like the above.

John

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[JonParticipant @jon]

Incidentally these are the only tipped cutters I could get to work on an ML7, in fact this one but a silvery colour meant for cutting cast iron on a capstan. Stunning for intermittent cuts (wear hard hat and visor) in hardened steel, cast iron, aluminiums, plastics ok **LINK**
Do have the square style as well.

I acquired a load of quality tooling 5 years ago used in high volume production with boxes of tips. They work well on low speeds as seen by prog/setter/operator so throws that argument out the window, its the rigidity of the tool and machine that counts.
I gave away all the Sandvik tools after past performance and their idea of numerical part numbers that have to be translated.
Not much worse are Kennametal though Ceratizit a little better for identifying inserts needed to fit a tool, why do they make it so hard.

[Bill PudneyParticipant @billpudney37759]

For what it's worth, don't forget the A.R.Warner HSS inserts. I use a few of the triangular ones, but have recently gone over to the CCMT type. They certainly are not cheap, but they work well, and can be sharpened/honed/touched up with a diamond thingy. Despite the flat top, they work well on aluminium, steel, and brass.

cheers

Bill

[Rod AshtonParticipant @rodashton53132]

If this admirable resource comes to fruition. Could appropriate details/dimensions of d.i,y, toolholders also be included, if available. There are many threads on making holders. But collating them would be a real valuable asset.

The two things seem natural bed mates? I.D. for tips is one thing. Having the holder to hand is another.

[Neil WyattModerator @neilwyatt]

If someone is interested in writing an article for MEW on this subject, please could teh PM me?

Lots of people asking, but so far no-one offering…

Neil

[Roger HeadParticipant @rogerhead16992]

Just to add a bit more fuel to the fire… this thread

http://www.practicalmachinist.com/vb/general/chatter-turning-255043-print/

extols the virtue of the TNGG160404R-S PR1125 (see the post from carbidenz about halfway down the page). They aren't cheap, but with six edges it isn't so bad. They are listed at the very end of this page

http://www.carbidenz.co.nz/store/index.php?subcats=Y&type=extended&status=A&pshort=Y&pfull=Y&pname=Y&pkeywords=Y&search_performed=Y&q=TNGG160404R-S+PR1125&x=0&y=0&dispatch=search.results

Have any of our Kiwi friends tried these?

Roger

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