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View Full Version : Chip breaker not chip breaking!!!!



jeremy13
03-09-2011, 10:38 PM
Well something like that. I hardly ever push my lathe hard at all. But I was in a hurry to night and all I had was some old hydraulic rod that was about ˝” to big. So I turned it down with a negative rake, chip breaker insert. I ran it at 600rpm .100”doc and .0045”ipr. But still ended up with a bird nest. With direction do I need to go to get small chips? The rod was 2.5”OD
http://i53.tinypic.com/2rnwxsm.jpg
http://i56.tinypic.com/6fy2rl.jpg

Toolguy
03-09-2011, 11:00 PM
I would try pushing the feed harder. Even if you have to back out to .05 or .06 on the depth of cut. Hard feedrate is what makes the chips break.

Carld
03-09-2011, 11:33 PM
Depending on the metal, DOC, feed and rpm a chip breaker may or may not break the chip. When I am turning something at a certain DOC, feed and rpm and the chip doesn't break I try hand feeding the cut to see if slower or faster will do the job. Sometimes I have to increase or decrease the rpm as well to find the combination. That's the fastest way I have found to do it. Using auto feed and changing everything takes to much time to find the right combo.

Of course you have to be a good judge of how fast your feeding by hand to convert it to the auto feed but you can get close and fine tune it.

BadDog
03-10-2011, 12:40 AM
I had some 4" dia tool steel I got for a project (some seemed to thing 4340 IIRC) that did not want to break a chip. And I had to drop the OD on the end to thread 30mm (LH) while reducing over all diameter to just over 3" for about 3" length. I played around a bit and finally got it making nice heavy tight blue chips about 4" long. The final setting was something like 0.375 DOC with 0.024 feed and about 400 sfpm. Tried several different inserts too. Of course, by the time I had it running nice, I was about done... :(

Black_Moons
03-10-2011, 01:06 AM
Adjusting the tool (post) angle can make a big diffrence too.

But yea, I find more RPM's, Higher feed/doc often get the chip to break. Some materials just need more serious chipbreakers too.

beanbag
03-10-2011, 02:42 AM
First of all, you need to mention what insert you are using. Different inserts are designed to break chips at either roughing feeds or finishing feeds. One of the Sandvik technical guides had a section about chip breaking, although I can't find it right now.

PixMan
03-10-2011, 06:29 AM
First of all, you need to mention what insert you are using. Different inserts are designed to break chips at either roughing feeds or finishing feeds. One of the Sandvik technical guides had a section about chip breaking, although I can't find it right now.

This is correct.

In this case (shown in the photos) the problem is far more likely to be an overriding the chipbreaker problem. Increasing the feed rate isn't going to help,it's going to make it worse.

A DNMG insert is usually used for profiling or finishing, but there are some with roughing chipbreaker designs. I have some. Each reputable manufacturer publishes depth-or-cut and feed rate data for each of their chibreakers...somewhere. I have a pretty good chart myself showing many, but it's a HUGE file that I can't share, sorry. What I can do is help. If you tell me the spec of the insert you have, I'll see if I can find the data for it.

Failing that, you can often find the charts for this on each mfr's website or certainly in their catalogs. Most times you can download a PDF of the catalog if you can't ask them to send you one.

In the course of applying carbide insert tooling to turning applications, you match the grade and coating and the cutting speed to the material type, then the chipbreaker to the desired depth of cut and feed rate. Sometimes you find that a maker doesn't have a chipbreaker that works and in the grade that does, or vise-versa. That is why we gt so many choices.

A home shop simply cannot have a wide array of different grades, coatings, chipbreakers and sources. It's too expensive and we have nowhere to put them. What we can do if find a couple of gems that work well for 90% of what we do, and learn how to use them.

For the problem at hand the solution would likely be to take a shallower depth of cut and try feed rates of .005", .010", and .015" per rev to see which provided the best chip form. Adjust from there until it works.

Spin Doctor
03-10-2011, 09:09 AM
If you look at the linsert the land on the edge of the tool is were a lot of the problems with chip breaking/bird's nest come from. The feed has to be agressive enough that the frazcture point of the material is high enough above the cutting tool (the material actually fractures instead of "cutting") that is flows past the land and into the channel that froms the curl.

jeremy13
03-10-2011, 02:44 PM
It was a US made generic TNMG insert.

PixMan
03-10-2011, 02:55 PM
It was a US made generic TNMG insert.

And so you got US made generic chips from using it. :D

You get what you pay for.

If you were to post a close-up photo of the insert, I might be able to match it up to a chart I have and give you some depth-of-cut and feed rate recommendation for it.

jeremy13
03-17-2011, 01:11 AM
Sorry for the long time between reply’s. But hear is the pic of the insert.
http://i55.tinypic.com/2i1iob8.jpg

wierdscience
03-17-2011, 08:36 AM
An insert with an MP chipbreaker (the ones with the extra dipples and bumps) do a better job of breaking a chip.

Also you might try bumping the RPM down to 450 and increasing the feed rate to .014-.018" per rev. on the inserts you have,assuming you have the HP and rigidity to do so.

PixMan
03-17-2011, 02:29 PM
That's really more of a roughing chipbreaker meant for materials that break chips because of the long distance from the cutting edge to the start of the chip groove, and the big, long radius of the chipbreaker groove at the inside.

I'd use that for roughing out something like 4140PHT or a H900 condition 17-4PH stainless, and use a feed rate over .018" per rev.

jeremy13
03-17-2011, 11:29 PM
I will play with the speed and feed rate. I have a 16X60 lathe with 7 ˝ hp. I do most of my roughing with that insert. The tool holder has a 3 deg. lead angel. I need to push this insert harder. I end up with a burnt out tip and hardly any side wear. I’m not getting my money’s worth out of the insert.

Jaakko Fagerlund
03-18-2011, 03:14 PM
If possible, use flood coolant when cutting, gets the most life out of that insert and cools down the work also.

PixMan
03-19-2011, 10:28 AM
If possible, use flood coolant when cutting, gets the most life out of that insert and cools down the work also.

Yes, but perhaps not always the best thing to do. Some coatings (such as AlTiN) work better and last longer cutting dry, with heat. You also shouldn't really need to cool down the work much, because the goal of carbide insert turning is to get the heat of the cut out with the chip.

That particular insert, probably a TiN, TiCN or multi-coating of the two processes, may benefit from the added lubricity in the cut from applying coolant, but if the grade is a P10/M15/K10 class it may be very sensitive to thermal cracking. If that's the case, it must be absolutely flooded or totally dry.