[tpsimer]

Good Afternoon,
I have a part that has a bore that is deep. It is 2.5 diameter and drops down to .875 at the bottom 4.5 inches deep. I am having trouble with chatter and chipbreaking. This is 6061 and it is running out strings rather than breaking. Any suggestions for a cnmg insert chipbreaker and grade? Also any pointers on getting rid of chatter? I am running way to slow for any production but speeding up produces chatter.
Thanks,
Tony

[packrat]

I know this is BLASPHEMY on this site, but, insert tooling is not the best thing for aluminum cutting, Especially boring in the lathe. There is no way that you can get a insert that is as sharp as a correctly ground HHS tool. The metallurgy of the material makes it impossible.

I would switch to a HHS boring tool for this. and make sure the cutting edge is on center.

cary

[plasmator]

I know this is BLASPHEMY on this site, but, insert tooling is not the best thing for aluminum cutting, Especially boring in the lathe. There is no way that you can get a insert that is as sharp as a correctly ground HHS tool. The metallurgy of the material makes it impossible.

I would switch to a HHS boring tool for this. and make sure the cutting edge is on center.

cary

[citation required]

[roninB4]

Well I may get flamed for this too but I'll be in good company. I also don't care much for any type of machining (especially in the lathe) of aluminum with anything but HSS. With HSS you can adjust the nose radius, rake, and chip breaker fairly quick and easy with HSS. Carbide is great stuff, don't get me wrong. But it works best in a continuous cut with a rigid machine on ferrous material (mostly). Aluminum is so soft and gummy it sometimes takes some experimenting to get a good breaker to work per your speed/feed. A good finish seems easier to obtain with HSS also. I'm sure there's something out there with insert geometry that works well but if I can adjust/grind the right geometry mix myself I find it easier and less time consuming. Chatter will often come from too small a boring bar diameter. Use the largest one possible or make one for the job. JMO.

[PixMan]

Some shops just don't have the holders (boring bars i this case) for using HSS tools.

There are MANY good inserts out there for boring, turning, milling of aluminum that will break a chip.

What holder do you have and/or what is the insert size & shape?

[ImanCarrot]

Bore from the bottom out- that way the tool will drag the chips out of the bore instead of pushing them in the hole.

Drill a hole just inside the O/D required- the chips will break and no stringy things can form.

[Shane1234]

i usually use kenametal black inserts for boring aluminum on the lathe, and run high rpm and high feed with light passes. if possible, coolant thru the bar. also, a .005 radius insert works well. haven't used much of the hss bore bars.

[rowbare]

An old timer machinist told me the same thing packrat said about being able to get a sharper edge on HSS.

The Arthur Warner company makes HSS Inserts in standard sizes. You might find an appropriate insert there.

High Speed Steel (HSS) tool bits and blanks - Arthur R. Warner Co

bob

[mc_n_g]

If you are stuck using CNMx inserts you should try using a CNMP or CNMG.
You shoudll get a polished or ground insert designed for aluminum. The CNMP is a positive cut to sit in negative toolholder. An insert designed for aluminum will not work9 or have extremely short life) for other materials.

[packrat]

[citation required]

I can't point you to a specific website or book, BUT, stop and think about it for a minute;

HSS is an alloy, chemically combined at the molecular level. It can be ground/sharpened down to a single molecule width.


Carbide is a sintered mix of many larger compounds. There a carbides, binders and fillers in the mix. While the carbides are hard they are also larger than a single molecule, when sharpened/ground a inserts edge is comprised of much large particles than a tool steel.

That and 48 years of experience as a die maker/ machinist is what I based my answer on.

cary

[roninB4]

Some shops just don't have the holders (boring bars i this case) for using HSS tools.

There are MANY good inserts out there for boring, turning, milling of aluminum that will break a chip.

-I'm not going to knock using inserts I haven't tried but making a boring bar isn't that difficult. Take the largest piece of round stock that will fit (your stock rack may vary....). Drill a hole (on an angle if you need a blind hole bored) through to accept whatever HSS blank you have, drill and tap the end ( in line with the boring bar axis)for a set screw to hold the blank in place. Now grind your geometry on the HSS blank. Takes about 20 minutes to make and doesn't cost much either.

I've been a die maker & machinist for 25 years. Use HSS or carbide according to the application, don't reach blindly for one or the other.

[iknowyoudo]

When I bore I use a G74 (drill chip break routine) I set my retract (K) at .01" and hog out .08" per pass 5" deep 1" ID. I use carbide Circle brand boring bars. The one I use to hog has a hole in the center for through coolant. I soldered one end closed then filled 3/4 full with sand then soldered that end closed. The sand absorbs the vibration leaving a silky smooth finish when I do a clean up pass of .007" to .01". I hope this helps

[kwhizz]

The "New" guy's are to tuned in to getting an Insert out of the Drawer.....and.....the skill acquired prior to the Insert era are quickly being lost.......when you had to make your own toolbits and use them......you learned real quick what worked and what didn't.......Inserts are great in most applications, But.........Hitting the "Sweet" spot in cutting tool geometry for certain applications is what seperates the "Experienced" from the parts changers.................

Ken

[Shane1234]

The "New" guy's are to tuned in to getting an Insert out of the Drawer.....and.....the skill acquired prior to the Insert era are quickly being lost.......when you had to make your own toolbits and use them......you learned real quick what worked and what didn't.......Inserts are great in most applications, But.........Hitting the "Sweet" spot in cutting tool geometry for certain applications is what seperates the "Experienced" from the parts changers.................

Ken

I think that in the current aspects of business that time = money, swapping inserts is the easy choice on part runs, whereas taking the tool out to resharpen/replace & re-touchoff will cost you time.

[kwhizz]

I think that in the current aspects of business that time = money, swapping inserts is the easy choice on part runs, whereas taking the tool out to resharpen/replace & re-touchoff will cost you time.

You are missing the point......For certain applications, an Insert tool is not the answer.........That's where the Experience part comes in.......It's knowing how to sharpen the tool to do the Job at hand and maximize what needs to be done, rather than get an insert that is "Close" to doing the job.....Experience is the difference between getting it close and doing it correctly...........If you don't know the difference, then you wouldn't understand.........

Ken

[PixMan]

Personally, I know well how to grind tools and do so when it makes sense @ my dad's home shop. If it's a matter of a one-piece non-repeating job in the commercial machine shops, same story.

However, if the job is something that's got several dozen (or more) parts and/or it's going to be a repeating job then it's best to find repeatable tooling for the job. This means find tool holders and inserts to get the job done the same way every time. If you don't, your competitor will.

[kwhizz]

Personally, I know well how to grind tools and do so when it makes sense @ my dad's home shop. If it's a matter of a one-piece non-repeating job in the commercial machine shops, same story.

However, if the job is something that's got several dozen (or more) parts and/or it's going to be a repeating job then it's best to find repeatable tooling for the job. This means find tool holders and inserts to get the job done the same way every time. If you don't, your competitor will.

Nevermind...............LOL

[MikeZee]

You cnc guys make me laugh, the only thing you know is inserts and how to push a button.
I've ground drills (by hand) to cut within a .001, bored 16" deep, holding .002 in a 4"bore manual lathe (not with insert) and probably forgot more than you know. Yes, I'm old school, every thing I do is custom and I do some tricky **** - maybe I'm in the wrong forum, just looking for some skill. You're debating what to use to cut AL. c'mon, it's as soft as ****, you could use a clog iron and get good results,if it was ground right.

[PixMan]

MikeZee, I don't know who you're addressing that to, but if it's me....

Maybe you consider me a "cnc guy" who makes you laugh, but I'm 51 and have been doing this since I started trade school at 13 years old. I too have ground drills by hand that cut within .001 of their stated size (very recently, and witnessed by a guy who was surprised by it.) I can and have for many years also ground hundreds (if not thousands) of turning tools from HSS and brazed carbide, and more than just a few milling tools as well.

And I also know quite a bit about CNC machining and carbide insert tooling. Despite what you seem to think, it can take quite a bit of knowledge to select and successfully, gainfully employ carbide insert technology to increase productivity while lowering production costs. Even in onesey-twosey situations on manual machines, there are many times when only the right coating on the right carbide insert substrate can get a job done. Hard turning or milling is an example of that.

I have also bored larger diameter bores, and far in excess of that simple 4 to 1 ratio using brazed carbide tools, and held similar tolerances. I'd much rather do it with the right coated carbide insert and get it done much faster. I've got better things to do that wait for that cut to finish.

In today's world of actual work for pay, it's rare to find a shop where it's appropriate (or approved) to be grinding tools instead of making parts. There are some shops (such as your own, apparently) where it makes perfect sense to do that, but it's rare now. Quality tooling doesn't cost, it pays.

[holbieone]

You cnc guys make me laugh, the only thing you know is inserts and how to push a button.
I've ground drills (by hand) to cut within a .001,

so you have a hard time centering a drill point , .001 you need glasses !!