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View Full Version : Just Can't Make It Chip ..........!



JoeLee
12-09-2012, 01:31 PM
This has to be one of the worst jobs I've done in quit a while, turning down the flange on the 5C adapter plate. I don't know what the alloy is but it either streams and bird nests or winds springs some being over 5 ft. long. I've tried a few different style inserts all with various combinations of feeds and speeds and get basically the same results. With a .025 or more DOC it get a beautiful finish, the stuff comes off hot and ragged and if it starts to wind around the chuck I have to stop. After a pass I've found that pulling the carriage out fast leaving a slight thread look to the flange seems to minimize the streaming as the interuptions sort of make a breaking point for the stream. I've also found the the insesrt I'm using CNMG 432 does the best job. I could cut a lot deeper but that creates a lot more heat. Perhaps if I had coolant it may keep the swarf cool and brittle enough to curl and break small chips but I don't have coolant. Any suggestions?????? Having to turn off 1.25" on the dia. at .025 DOC chews up the better part of the day.

JL.................

http://i911.photobucket.com/albums/ac317/JoeLee09/Work%20Head%20Alignment/Image050.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/Work%20Head%20Alignment/Image048.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/Work%20Head%20Alignment/Image049.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/Work%20Head%20Alignment/Image047.jpg

Evan
12-09-2012, 01:42 PM
It looks like you have the power to use a negative rake tool. Have you tried that?

Scottike
12-09-2012, 02:11 PM
I've had the same problem - often. I'll be curious to see how others have solved it - or not.
I found that a shot of shop air will often direct the curl away from chuck at the beginning of the cut and
then using a wire L shaped hook to guide the curl to run in a safe direction.
It doesn't always work, but it's better than allowing the curl to run willy nilly, wherever it wants.
CNMG is a negative rake insert.

beckley23
12-09-2012, 02:20 PM
Increase the DOC to .100-.200", increase your feed to .0065 or higher, increase your SFM to 3-600 SFM. You may have to play with the numbers, depending on your machine size and HP.
The pull back marks are from spring, and are quite normal. You should be able to get rid of them by repeating the cut without changing anything else.
Harry

Peter N
12-09-2012, 02:46 PM
I bet that's an EN19/4140 steel or something very similar.
Same thing happens to me, cuts beautifully but *really* struggles to break a chip - you can have it coming off so dark blue it's almost black, and it's still long and stringy.
The only way I can get it chip is using a particular DCMT tool that I have that is loaded with a Sandvik GC4225 insert, with a funny moulded chip-breaker, and using an aggressive feed rate.
Using different speeds or DOC seemed to make no difference, but for me this insert works better than any other I've tried, although there may be far better solutions.

Picture here, although this is a CNMG rather than the DCMT I use.

http://www.sandvik.coromant.com/sandvik/0110/Internet/I-Kit1/se02674.nsf/116e3994e474f44ac12568db004d4af7/26b538821e47d982c12570f9004abb94/Rt_Body/0.38D2!OpenElement&FieldElemFormat=jpg

JoeLee
12-09-2012, 03:03 PM
I think I have some square inserts??? SNMG I think, I could give it a try. I could cut much deeper but I don't want to take the chance of the 5C slipping in the hex block.

JL................

oldtiffie
12-09-2012, 04:47 PM
If its any help - or not - I had quite a job drilling my similar ER-32 adaptor. The drill had to be dead sharp, slow and forced fed with cutting oil to keep a constant chip with no rubbing. It work-hardened in an instant once the drill blunted and rubbed. It was almost impossible to drill out - so I changed the hole pattern slightly - was OK.

There was no warning.

With the job you are doing its more likely that you will get work-hardening once the feed stops and it rubs a bit before retracting the tool - TC will rub more drastically then HSS due to its cutting action.

You may have to go back to "square one" - or perhaps make a new adaptor from scratch.

John Stevenson
12-09-2012, 05:17 PM
Clamp a bit of steel on top of the insert, play about with position and angles .
You want the chips to hit the packing and be forced to break up.

Years ago you used to grind chip breaking grooves into tools. Problem with the carbide inserts is the chip breakers are designed for 2" depth of cut and 10,000 revs

oldtiffie
12-09-2012, 06:18 PM
I would just about bet that the job is work-hardening during the cut and that flood cooling is inadequate as it needs to be jetted up to the point of cutting - which can make one big mess.

Work-hardening can start at the begining of the cut as the TC insert tries to force its way into the job and raise a chip as it may well rub at that point as well.

Just hope that the R8 and other finished surfaces have not distorted.

In the"early days" before TC became common it was quite normal to use "Stellite" tools as they took a lot of load and rubbing and heat and could be ground as you would for HSS.

http://www.google.com.au/#hl=en&sugexp=les%3B&gs_nf=3&gs_rn=0&gs_ri=hp&cp=7&gs_id=s&xhr=t&q=stellite&pf=p&tbo=d&output=search&sclient=psy-ab&rlz=1W1IRFC_enAU360&oq=stellit&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=17bd62e69f0feaab&bpcl=39650382&biw=1920&bih=846

motorworks
12-09-2012, 07:16 PM
Hi
Not sure how many you have to make and if this is in your budget, but I found the
Fix-Perfect from Kennametal the best turning insert for most work.
(It's a turning tool only..i.e. can not face).
I use it in a 7.5 hp Colchester 15 x 50. No problem taking anywhere from 0.010" to 0.200" cuts in
stainless to stressproof. Excellent chip curling....the best I have used...tried lots over the years.
Tool holder (5/8'' square shank) runs ~140.00 each....inserts from $ 30.00 each (come in a box of ten)
See link:
http://www.kennametal.com/kennametal/en/products/20478624/47535256/56193772/56193777/56193782/43292.html

Just a happy camper
eddie

RussZHC
12-09-2012, 07:17 PM
I wish you did not have it but sorry to say, I like your problem...as a newb, sort of thing I wonder how to solve too/all the time. Awaiting more suggestions.
I found some materials (can't help much, "mystery metal") the DOC is the key and that sometimes there almost seems to be a very small range as far as feed rate goes, faster or slower than a fairly narrow window and the same things happen.

Re: chips...can I make a sort of wild/stupid stab...would there be any value (or way) to make a cut (saw, really small end mill) along the direction of travel...artificially create an interrupted cut?

lane
12-09-2012, 07:23 PM
If it does not chip ADD more feed . Keep adding feed until it does.That is the trick.

JoeLee
12-09-2012, 07:40 PM
Lots of good points and tips, etc. The insert is a Kennametal KC 730......... dead sharp, not a honed edge.
I don't think it's work hardening as I've drilled these with out a problem, it's just tough stuff. I'll see if I can come up with something to clamp down over the insert so the stream hits a wall and possible breaks. What would happen if these were being turned in a CNC enclosure. One couldn't have to keep stoping to weed it out.

JL....................

John Stevenson
12-09-2012, 08:07 PM
What would happen if these were being turned in a CNC enclosure. One couldn't have to keep stoping to weed it out.

JL....................

As Lane says high feed , bags of revs etc, remember they are using 25 HP spindle motors for a reason.
modern tooling is designed for this not us lot gnawing and chewing in a home shop :D

Boucher
12-09-2012, 08:08 PM
I second what Lane said. Also up the speed until the chips are at least straw color. I really prefer them to be blue. I use an NS 730 ceramic from the Carbide Depot. If the KC 730 is a ceramic it works better as you turn it faster.

becksmachine
12-09-2012, 11:49 PM
Breaking a chip can sometimes be impossible, but it is almost always a function of how tight the curl is in relation to chip width and thickness. Tighter curls mean broken chips.

No matter if it is an insert or hand ground brazed or HSS tool, there are a number of factors that will determine how a chip forms. Width of step, (chipbreaker) nose radius, positive or negative top rake, feed rate, depth of cut, even the approach angle of the cutting edge can make a tremendous difference.

In general, a thicker chip (greater IPR feed) will break more readily than a thin, flexible chip.

Greater DOC usually makes it more difficult to break the chip.

Tighter (shorter or deeper) chip breakers will facilitate making short chips, but this in turn limits feed rate as a heavy feed will make the chip pack into the groove and possibly break the tool or insert. Consequently finishing and roughing operations usually need different configurations to achieve the same result.

Larger nose radii usually make it more difficult to break the chip.

As was mentioned previously, negative top rake facilitates making short chips. If you think about it, the top rake itself is tending to direct the chip back at the workpiece which is one way that they break.

Dave

Evan
12-10-2012, 12:26 AM
A CNMG 432 may be called a negative insert but so are inserts with zero rake. The effective cutting edge is positive on the CNMG 432. That is obvious in the pictures above. True negative rake cutting means the cutting edge is actually negative rake at the work surface.

JoeLee
12-10-2012, 12:31 AM
I am using a negative rake angle and with the CNMG insert, you can't really change the approch angle of the tool holder too much.
I suppose I could try a smaller radius insert. It is all hit and mis. Hot rolled isn't even this bad.
The deeper I cut the hotter it gets.
I was thinking of clamping a TPG insert down on top of the CNMG to act as a chip breakere and play around with the chip curl and direction if the clamping screw is long enough. I think if I can get a tighter curl I may get it to break.

JL..............

becksmachine
12-10-2012, 12:55 AM
Some good information and illustrations here.

www2.coromant.sandvik.com/coromant/pdf/...061/tech_a_1.pdf

Can't seem to make the link work, copy and paste should.

Dave

Evan
12-10-2012, 01:03 AM
That link isn't working.

I know the holder holds the insert at a negative rake. That is because the sides have no rake. Because of the shape of the actual cutting edge the effective edge is still positive. I have inserts that have absolutely flat tops and bottoms with no chip breaker groove. When used at the proper negative angle the cutting edge is also negative to the work. The causes the chip to curve directly into the work and break instead of making a curly chip.

oldtiffie
12-10-2012, 01:19 AM
Some good information and illustrations here.

www2.coromant.sandvik.com/coromant/pdf/...061/tech_a_1.pdf

Can't seem to make the link work, copy and paste should.

Dave

Start here:

http://www.sandvik.com/en/sitemap/

JoeLee
12-10-2012, 08:31 AM
This was going to be my next question but you beat me to it. Altough the insert is held in the negative position relative to the work center line the actual cutting edge is actually positive because of the groove just behind it. I do have some tool holders that have a negative rake that take flat top inserts with no chip breaker geometry. I'll try one to see what happens. I have a feeling though that it's going to stream off the side and I won't be able to take as heavy of a cut. But since this is all trial and error you never know.

JL.....................


That link isn't working.

I know the holder holds the insert at a negative rake. That is because the sides have no rake. Because of the shape of the actual cutting edge the effective edge is still positive. I have inserts that have absolutely flat tops and bottoms with no chip breaker groove. When used at the proper negative angle the cutting edge is also negative to the work. The causes the chip to curve directly into the work and break instead of making a curly chip.

bborr01
12-10-2012, 09:47 AM
I don't really see the problem here. I keep an 8" mill bastard file with a proper screw on wooden handle on it at all of my machines, including the lathes. When the chips refuse to break, I use the tip of the file to guide them down into the chip pan. They generally break off at some point. This may sound unsafe to some here but it is how I was taught back in the late 70's and it has never been a problem for me or the guys that showed me the trick.

Also, Joe. You should back off your tool bit when you come back across your part.

Brian

JoeLee
12-10-2012, 10:32 AM
Also, Joe. You should back off your tool bit when you come back across your part.
I purposely let the tool bit drag comming back out because it left a thread type groove which helped to break the spiral stream comming off the work. I do use a paint stick to try and direct the stream and help it to break. I don't think I would want to stick a file that close to the chuck.

JL................

I don't really see the problem here. I keep an 8" mill bastard file with a proper screw on wooden handle on it at all of my machines, including the lathes. When the chips refuse to break, I use the tip of the file to guide them down into the chip pan. They generally break off at some point. This may sound unsafe to some here but it is how I was taught back in the late 70's and it has never been a problem for me or the guys that showed me the trick.

Also, Joe. You should back off your tool bit when you come back across your part.

Brian

JoeLee
12-10-2012, 10:35 AM
I purposely let the tool bit drag comming back out because it left a thread type groove which helped to break the spiral stream comming off the work. I do use a paint stick to try and direct the stream and help it to break. I don't think I would want to stick a file that close to the chuck.

JL................

MrFluffy
12-10-2012, 11:08 AM
You probably thought of this, but on the occasions I get long curly endless chips, I let them grow till they can be directed into the chip pan safely then periodically tickle the feed lever clutch on the traverse when they start looking like theyre long enough to go supernova and ball up on the chuck fingers or something. The momentary pause breaks the chip and starts another.
I like them... makes clean up a matter of grabbing 30 wiggles and folding them into the swarf drum :)

JoeLee
12-10-2012, 12:01 PM
The problem with letting the long spiral continue is that it's spining like a drain cleaning snake. On occasions I try to direct them off the side and let them spin on the floor until breaking. The other problem is that on one pass it may spiral and on the next pass it may stream all in taking the same DOC and same feed rate. That is why I run the tool across the part on the way out and cut what looks like a coarse thread, it makes for an interrupt point and helps the stream to break.

JL........................

Toolguy
12-10-2012, 12:18 PM
If you can't get them to break up with the cutting tool, you can grab the spiral with long needle nose pliers. The chip will break off when you stop it from turning.

Boucher
12-10-2012, 08:06 PM
Again feed and speed need to be increased. Hot is good. If that is a ceramic insert it will take the heat. Your surface finish looks good but, Don't drag the insert back across the part. That is the wrong move.

TRX
12-10-2012, 08:42 PM
A squirt bottle with soapy water often helps break up stringy chips. I use liquid hand soap, about 10/90 mix.

Sometimes a brush with cutting oil will break up the chips, but it tends to be smoky.

Co2 mech
12-15-2012, 10:31 PM
I bet that it is 4140PH. Getting that to break a chip is tough. High feed,deep cut, and low SFM (30to 50) is what it likes. Finnish passes at high SFM low feed keep the birds nests managable with a pair of pliers.
Regards

beanbag
12-16-2012, 06:18 AM
Joe, is that the HP or the LP chipbreaker? It is hard to tell from the pic, but the LP has a short, almost flat ramp, whereas the HP has the long, positive rake ramp. If it is the HP, then yes, the chip will gently slide down the ramp and not break. It is more designed for Aluminum where you can take huge cuts, and then the chip will break. Taking these little cuts on steel will cause the curly strings. Also, it appears that your feed and DOC are actually too small for your nose radius. In this case, you are actually cutting the with corner of the insert instead of the front edge. This also affects the way the chip flows.

As everybody else said, you need more feed to get the chip to curl tighter. You need more DOC so that the front of the insert cuts, thus the chip curls up and hits the workpiece.

Or you just need an insert with a differently shaped chipbreaker.

Peter.
12-16-2012, 06:56 AM
Some good information and illustrations here.

www2.coromant.sandvik.com/coromant/pdf/...061/tech_a_1.pdf

Can't seem to make the link work, copy and paste should.

Dave

You must copy link instead of highlight & copying text, or it misses the bits it shortened out of the link.

http://www2.coromant.sandvik.com/coromant/pdf/Metalworking_Products_061/tech_a_1.pdf

PixMan
12-16-2012, 08:23 AM
I can't believe some of the misinformation and unsafe practices posted here about carbide inserts and turning in general. For safety's sake, which should always be the first priority, please don't be "guiding" stringy chips. Get them to break.

The insert being used is an excellent one....for austenitic stainless steels. The "GP" chipbreaker on the KC730 grade is good for 300 series stainless because it's "upsharp" and helps reduce work hardening in the cutting zone. Since few carbon steels or alloyed steels do that, you need a tighter chipbreaker geometry and a grade better for steels. In Kennametal, their grades for steels are KC850, KCPx5 series, and 91xx series. Sandvik Coromant steel grades are 4215, 4225, 4235. Valenite is 55xx, 56xx, or older SV235, SV310 or VN8. In iscar it's 8350 or others.

Grade is usually far less critical than the chipbreaker geometry, though consider that you generally find good geometry for steels in steel turning grades. Makes sense right? This is why the GP chipbreaker, in a grade for stainless, isn't working all that well. The photo of the CNMG432-MM grade 4225 is an example of an excellent choice for the application, in both chipbreaker geometry and grade. Each maker will publish recommended ranges of speed for grade, and recommended feed rates and depth of cut for every chipbreaker. Information like that is found on the maker's packaging, catalog and/or website. It's not secret. The range for that "MM" chipbreaker, for example, is .020" to .220" D.O.C. at a feed rate of .004" to .018" per rev.

If increasing a feed rate within the maker's suggested range doesn't break chips with a given material, you can either go beyond recommended rates or get a tighter chipbreaker. Be aware of chip form, and cautious that the feed rate isn't so high that you override the form. That's what happens when you use a finishing geometry on a roughing cut. In the case here, I'm sure the feed rate is nowhere near what the "GP" chibreaker can take, but the insert grade probably wouldn't take it in steel.

Here's two steel cutting inserts, both Valenite. On the left is a VNMG331-F3 grade 5515, on the right a DNMG432-M5 grade 5625. The feed rate and D.O.C. range for the F3 is .004" to .012" per rev at .010" to .150" depth. The M5 is .006" to .022" per rev and .025" to .200" D.O.C. You can see the difference in the "finishing" vs. "medium-rough" in how close the "bump" is to the cutting edge. The edge itself will have more hone or "T-land" when the insert is for roughing, a sharper edge when finishing.
http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/422322392_photobucket_39767_.jpg

The average home shop person isn't going to have the resources to stock all kinds of grades and chipbreakers, but a couple of choices is really all you need. Having something like the GP is always good, and when the opportunity arises by bumping into a guy like me or grabbing a couple off eBay every now & then helps grow the choices. When you have a few more to choose from, you can usually find something that works. As you get more experience in trying different things, there's less confusion and you start knowing instinctively which to try first.