Author Topic: Carbide Conundrum... (Read 29406 times)

AdeV · « **Reply #25 on:** December 11, 2009, 03:37:32 AM »

Quote from: Darren on December 10, 2009, 08:18:37 PM

Quote from: AdeV on December 10, 2009, 07:45:37 PM
My lathe's top speed is 670rpm

Ah ..... not quite sure what to say ....

Erm, that does seem slow .. what's your lathe again? Has someone altered the drive, what type of bearings does the headstock use?

It's a 1930's design Edgwick, and gives speeds between 17rpm and 670rpm...

The headstock shafts are on ball races & the spindle is on taper roller bearings, according to lathes.co.uk

The Mk2 range offers the same spindle speeds, and suggests that with a faster motor will go up to 1000rpm; I dare say with a 2-speed motor I could push it as hard as 1200rpm; but tbh, it sounds quite fast enough doing 670....

Darren · « **Reply #26 on:** December 11, 2009, 06:41:47 AM »

I think you are going to struggle with tipped tooling of the insert type with smaller diameters as they are not sharp like HSS. This is why they need to be worked, ie higher speeds and feed rates.

TBH I'm not sure what to advise, I've done hardly any lower speed turning. Maybe brazed tungsten tip tooling would be more suitable for you as you can hone the edge on those to a razor sharp edge with the right stone on the grinder.

Perhaps Bogs or someone else could advise here ...?

ksouers · « **Reply #27 on:** December 11, 2009, 07:13:17 AM »

Ade,
There is another possibility...

There is a company here in the US that makes insert tools out of HSS.

http://www.arwarnerco.com/index.html

You might be able to find a local vendor that carries them.

Kevin

AdeV · « **Reply #28 on:** December 11, 2009, 02:35:04 PM »

Kevin - that looks like a really interesting set. LMS seem to sell a selection of HSS inserts, no sign of any in the UK; but I will keep looking. Thanks for the link

Darren - no problem, you are probably right. The only reason I was really interested in inserts is because I have these three holders, it seemed a shame not to use them. Especially the rhomboid one, as that's the one I can get closest to centre height with relative ease. Until John pointed out that Glanze toolset, I hadn't planned on buying any more holders. Now that my top speed is an issue, I'll probably steer clear & stick to HSS. If I can get any of those inserts that Kevin spotted for reasonable money. which happen to fit my holders, then I'll go down that route rather than carbide.

I'd hoped to have time to buy some tooling this morning, but didn't; so I'll be going tomorrow morning instead.

Hopefully, I'll be able to make my QCTP soon, which will solve the biggest problem I have with regular HSS tools (centering the cutting edge).

75Plus · « **Reply #29 on:** December 11, 2009, 05:57:05 PM »

Quote from: AdeV on December 11, 2009, 02:35:04 PM

Hopefully, I'll be able to make my QCTP soon, which will solve the biggest problem I have with regular HSS tools (centering the cutting edge).

This is the way I solved the tool height problem. I milled a slot in a piece of aluminum to a depth that would put the tool bit on the center line of the work piece. One piece can locate two different sizes of bits. I like to use smaller sized tools for small work pieces. I even made one with a 7 degree slope to use tool bits that had been ground for use in the old Atlas holders.

ksouers · « **Reply #30 on:** December 11, 2009, 09:44:35 PM »

Quote from: AdeV on December 11, 2009, 02:35:04 PM

Kevin - that looks like a really interesting set. LMS seem to sell a selection of HSS inserts, no sign of any in the UK; but I will keep looking. Thanks for the link

You're welcome.

Might want to send A R Warner an email to see if they have a UK, or at least an EU, vendor. If not I'm planning to place an order with LMS after the holidays, I can have a couple extra put in the order and I'll drop them in the post for you.

Kevin

AdeV · « **Reply #31 on:** December 12, 2009, 05:47:52 AM »

Quote from: ksouers on December 11, 2009, 09:44:35 PM

Quote from: AdeV on December 11, 2009, 02:35:04 PM
Kevin - that looks like a really interesting set. LMS seem to sell a selection of HSS inserts, no sign of any in the UK; but I will keep looking. Thanks for the link

You're welcome.

Might want to send A R Warner an email to see if they have a UK, or at least an EU, vendor. If not I'm planning to place an order with LMS after the holidays, I can have a couple extra put in the order and I'll drop them in the post for you.

Kevin - that's a good idea; and many thanks for your kind offer. If I don't succeed in finding a UK seller, I'd definitely be interested in taking you up on that one.

Darren · « **Reply #32 on:** December 13, 2009, 01:44:03 PM »

Ade, No dis-respect to Kevin I really can't see the point in using HSS inserts

Might as well use regular HSS blanks.

I think you would be much better off using these http://www.iscar.com/Ecat/familyhdr.asp/fnum/919/app/105/mapp/IS/GFSTYP/M/lang/EN/type/1/cat/3602210/relation/TI/tool/I

OK so they are meant for alloy turning. But I'd bet that though not designed for steel they will last a whole lot longer than HSS inserts.

I'll let you know as I've just bought a load for myself ............. too cheap to leave behind ... nobody wants them.

The are 09 size, but you can find 06 easily enough.

http://cgi.ebay.co.uk/CCGT-09T304-AS-IC20-ISCAR-10-inserts_W0QQitemZ260522934017QQcmdZViewItemQQptZUK_Home_Garden_PowerTools_SM?hash=item3ca8607f01

jgroom · « **Reply #33 on:** December 13, 2009, 03:27:37 PM »

I think it would be pretty slick. You gain the advantages of inserts, i.e. no grinding, just spin to a new point when dull, without the big disadvantage, the edge chipping when the belt slips, motor stalls, you look at it wrong, or it just feels like it. Unfortunately it looks like the price is the same as carbide

, sooo....... I guess I'll keep practicing my grinding.

Jeff

Darren · « **Reply #34 on:** December 14, 2009, 08:38:56 AM »

Quote from: jgroom on December 13, 2009, 03:27:37 PM

I think it would be pretty slick. You gain the advantages of inserts, i.e. no grinding, just spin to a new point when dull, without the big disadvantage, the edge chipping when the belt slips, motor stalls, you look at it wrong, or it just feels like it. Unfortunately it looks like the price is the same as carbide , sooo....... I guess I'll keep practicing my grinding.

Jeff

If you are having undue problems with chipping then it may be that you are selecting the wrong grades for the job in hand? Or even shapes.

Take for example a common Sandvik CMMT 06 02 08-UR 235 P45 tip,

We have already discussed shapes further up with CMMT being quite versatile having two different angles for us to make good use of. One being stronger than the other.

The No's relate to size, thickness and corner radius. But what about the letters at the end? xxxx xx xx xx-UR ? Anyone take any notice of these?

Well the R stands for Roughing, (they will also finish fine as well in my exp) This gives us an indication of how tough a tip may be. You will also find F=fine and M=medium

Then we have 245. This relates to the specification of the makeup of the tip in more detail. In this case 235 is an extremely tough grade with a three-layer coating of TiN, TiC and TiN. The total thickness is only 3 micrometer. GC235 is an exceptionally good grade for intermittent machining, the machining of stainless and carbon steels at low speeds and parting operations.' - 'For toughness demanding operations in steel and steel castings. Suitable for low speeds and unfavourable conditions. Extremely good edge security.

Considering this grade is also suitable for low speeds then it may be a good choice for some of us with older machinery.

Lastly there is P45, This relates to P=Steel of a hardness of 45, which is pretty hard.

As I have said before we can use most types of different tips for most of our machining. But if you are experiencing excessive chipping or a limited top speed, then a tougher tip as described here may be a good choice for you.

AdeV · « **Reply #35 on:** December 14, 2009, 10:45:32 AM »

If the P45 matches the P-values in Machinery's Handbook, then it's a very resilient cutter which is ideal for nasty metal & interrupted cuts, but will be subject to wear. So it's strong rather than hard, if you see what I mean.

Darren · « **Reply #36 on:** December 14, 2009, 10:50:53 AM »

Yes, I was referring to the metal being hard not the cutter

jgroom · « **Reply #37 on:** December 14, 2009, 12:18:19 PM »

Hi Darren. The main problem I have is the leather belt on my 9" South Bend. If I take a big enough cut to make the cutter happy it tends to slip occasionally. Of course it doesn't help that my indexable set is from Horrible Freight (and worth every penny

) and shop funds don't allow a big outlay for good inserts at the moment. I have a few brazed carbide tools that work ok for (careful) hogging, but I get a much better finish with HSS.

I plan on updating the drive to Poly V-Belt (Hot-Rodding a 9" South Bend Lathe, HSM, July/Aug 2006) which should take care of the slipping problem.

Hmmmm... looks like it's -12C in the shop at the moment, not gonna happen today!

Jeff

Darren · « **Reply #38 on:** December 14, 2009, 12:22:54 PM »

Why not swap the belt for what you over there call a serpentine. That will run on flat pulleys and will not slip.

I did the changeover on my other lathe and now you'd stall the 1.5hp motor before the belt slips. Meaning if you take a huge cut the motor will stall.

jgroom · « **Reply #39 on:** December 14, 2009, 01:46:55 PM »

Hi Darren. Serp belts are Poly V-Belts, don't know if that's a trademark or what. The mod replaces the three sheve flat belt pulley with a five sheve poly v pulley. Sounds like a better deal overall and since I'll have to remove the spindle either way......

Thanks

Jeff

Darren · « **Reply #40 on:** December 14, 2009, 01:56:56 PM »

Oh I see, Poly V is Serpentine

I also put one on that really old Union lathe I have and it worked well on that as well..... they get a thumbs up from me ....

udimet · « **Reply #41 on:** December 21, 2009, 02:08:59 PM »

The positve rake inserts are more suitable for small machines ie the CC** DC** TC** SC** and VB** THE SUFFIX GT after the aforementioned letters
denotes that the insert has a high rake angle [very sharp geometry] that are mainly designed for non ferrous metals and plastics. They do however
produce a superb finish on STEELS provided they are used for small depths of cut ie finishing passes. The negative rake inserts are designed to
be used with high power and high rigidity machines at very high metal removal rates. Some of the negative inserts are as follows,
CN** DN** VN** WN** SN** [so unless you have a very rigid machine with lots of horses behind it ,avoid].
Regards,
Udimet.

Darren · « **Reply #42 on:** December 21, 2009, 03:02:19 PM »

Thanks for that

Where does XXMT come in as opposed to XXGT?

Is GT a sharper geometry then MT ....

I notice GT is usually specified for Aluminium and often comes uncoated ?

udimet · « **Reply #43 on:** December 22, 2009, 02:53:13 AM »

Hello all,
Yes,GT is a far sharper geometry than MT. **GT inserts always have a very high rake angle are uncoated and polished [due to the applications that they are designed for]
The coating that is used on coated inserts regardless of the coating process [either CVD or PVD] will have the affect of decreasing the "sharpness" of the cutting edge as opposed
to uncoated inserts. The MT and MX geometries are designed for Ferrous metals from bog standard EN1 right through to the heat resistant "super alloys" only the grade of carbide and the chip-
breakers differ [but that is a subject all of it's own] Also there are many of the **MT and MX geometries that are known as WIPER inserts [From Sandvik Coromant] Also bear in mind the ISO
classification system P, M, K, N, and S Which relate to in order, Steel, Stainless steel, Cast iron, Aluminium and Super alloys.
Regards,
Udimet.

udimet · « **Reply #44 on:** December 22, 2009, 12:05:53 PM »

Hi Everyone,
Re The post by AdeV the tool that you have is for the following series of NEGATIVE inserts of the following types
CNMG, CNMA, AND CNMM. and the inserts will be 1204** the 2 stars denote whichever nose radius, you have a choice of the
following 04, 08, 1.2, 1.6. As I stated in my previous post These are negative inserts that require a lot of power and rigidity
to be effective, I note that the toolholder size is 25mm, that size of shank would be best suited to a lathe of about 215mm
center height. If you have that size of lathe [or larger] then negative rake inserts would be fine. If your lathe is smaller then
god knows how you got a 25mm shank into the toolpost [ bit of ingenuity there

] Really most small lathes are best suited to
positive rake inserts If you can get hold of a toolholder type SCLC* they utilise the CC** series inserts and you should see a
great difference compared to the CN series.
Regards,
Udimet.

AdeV · « **Reply #45 on:** December 22, 2009, 03:15:09 PM »

Hi Udimet.

Thanks for your detailed and informative responses! My lathe centre height is approx 165mm - so, from what you are saying, probably not suited to negative rake bits. No problem, I've pretty much put the carbides to one side for now, I'll concentrate on HSS.

As for fitting the tool, that's no problem: My toolpost will take upto 50mm tool steel!! This seems a tad excessive to me, and when I get around to making a QCTP, it will not be on quite such a massive scale... Well, maybe. I already got the steel, and it's pretty damn big...

I think, once I've got the hang of latheing (still a newbie here), then I'll look at carbide again. Although, as mentioned above, my lathe's top speed is only 670rpm, so maybe it'll never be suitable for carbide?

Darren · « **Reply #46 on:** December 22, 2009, 03:56:14 PM »

I do have one reservation with using sharper carbide insert profiles. They would be even more prone to chipping.

Prob why they seem to be reserved for alloys by the manufacturers?

udimet · « **Reply #47 on:** December 23, 2009, 02:32:06 AM »

Hello AdeV,
You should have no problem by sticking to HSS. For your further info HSS lathe blanks are available in a few grades [thankfully not as numerous or complex as carbide].
the most common are M2 and M42 the latter has Cobalt added and has slightly more hardness and heat resistance, but is more expensive.
Re your toolpost size, 50mm on a 165mm center height

your right that is just a wee bit on the large side. My machine at work:450mm center height
Takes up to 70mm but weighs in at 12.400 kgs and has 60 kw behind it. so whatever you do dont stick a 50mm blank in it

Keep on practising it's the best way learn. and don't worry about producing scrap early on [I've been there].
Best wishes,
Udimet.

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Author Topic: Carbide Conundrum... (Read 29406 times)