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Dampened bars vs reg solid carbide ?

SND

Diamond
Joined
Jan 12, 2003
Location
Canada
Have you guys tried any of the "dampened" bars in the smaller 1/2" to 3/4" size and is there much improvement vs a regular solid carbide bar? These are 2-4x the cost and I'm not sure how much dampening they can really do in such a small coolant thru bar vs the bigger 1.5+dia tuned bars that actually seem to work if set right. I couldn't find what they use to try to dampen the smaller ones, probably isn't slugs/rods and such like in the big bars? maybe a waste of $ on a little one?
 
While talking boring bars, do you guys have any easy tricks to set them to be sure they're dead on center at the insert tip since it looks like most rounds shanks can just spin right round? I'm thinking of buying a few extra ID turning blocks for the turret so I only have to center/set the bars once and hopefully not touch them again and just change the block with it in it each time. Gotta make it as easy and fool proof as I can, so any other ideas are welcome.
 
as far as dampening bars, we've had great success making our own bars from solid tungsten.

Would that be a bit like those heavy metal bars that aren't carbide, but not steel either? I always assumed they were just some in between thing that wasn't quite as good or as rigid as real carbide shank bars? Do these chatter less than a carbide shank of same size/length? never used one but I see ultradex makes the heavy metal type too.
 
Would that be a bit like those heavy metal bars that aren't carbide, but not steel either? I always assumed they were just some in between thing that wasn't quite as good or as rigid as real carbide shank bars? Do these chatter less than a carbide shank of same size/length? never used one but I see ultradex makes the heavy metal type too.

They chatter way less than carbide. Tungsten is extremely dense. I buy the blanks from McMaster. Turn them and mill the insert pocket in a 5C rotary. The stuff is hard, but machines nice.
 
I dampen my bars with coolant, doesn't seem to help with vibration at all :D

If you have to cut a carbide bar so it doesn't stick out the back side of the turret, then you've 'detuned it'. So I was told when I had to shorten a 1.25" carbide bar. It couldn't be used at 14" long and couldn't realistically be used at more than 8", because my turret is only 2.5" thick. So mostly I use very stubby bars, compared to what I use in manual lathe. And my CNC lathe doesn't bore worth a shit without vibration on extended overhangs. Best remedy is to stay away from long CNMG and WNMG bars and use T, D or V shapes to alleviate the 'heel dragging' of C inserts which is what causes them to build vibration unless you use only very coarse feeds. C's will work better if set at -10 lead angle, but then you can't bore to a shoulder with that.

I prefer to use one of the quick change systems like Kennametal Kmod 40. If you leave the base adapter in the turret, then the interchangeable heads can potentially be positioned with great repeatability in the correct attitude. You can record the tool offset for that tool permanently. I even use G10 somewhat in lathe programs, so as to preserve the tool offset numbers for my Kmod bars within the program itself, thus not having to remember to get the correct number from a list. List maintenance is kind of a bitch, because I might have 8 different bars to fit that turret position. Each one has to be meticulously charted by its engraved name so the correct one is mounted. My lathe has no tool eye, and I don't like setting tool offsets if I don't have to.
 
To verify center start with an angel finder and finish by facing some scrap. I'd like to hear quicker if anyone has it.

Kennametal 1"+ aren't too expensive but I don't have much need for that large. Sandvick makes some small stuff and Iscar does now too. Was able to bump up the SFM by more than double swapping from carbide to vibration damped. The 10xD ones sure are spendy!

I've read some about using an accelerometer and some software to get into higher RPM with no vibration. I need to do some more research to figure it all out.
 
I'm definitely not getting into making my own bars for regular stuff, done a few for weird things but, not this.
It's interesting that tungsten is about 24% more dense than tungsten carbide, I wasn't expecting that much difference.

I just downloaded the ultradex catalogs, looks like the small tuned bars have a set screw to adjust from the end to tune it for the application. Interestingly the regular(not dampened/tuned) Heavy Metal ones say a 6:1 ratio, and their carbide ones say 8:1.
I'll see how the carbide bars do in this machine and if I'm not happy I'll give a tune-able one a try. Doesn't sound like very many have tried them.
 
One trick that blew me away in the past, was to remove the tool block that holds the boring bar, and put a layer of electrical tape between the tool block and the turret. I was fighting chatter badly on a new machine, and none of the other tricks worked. My only thought is that the tape acted as a damper that absorbed any deflection, before you could excite/resonate the boring bar. All I know, is that it worked fabulously, and still had no trouble holding a tight tolerance.

I would not hesitate at all to try this trick on a conventional steel boring bar, before spending more on a carbide bar. Heavy-metal bars are not very common, at least from what I've seen available in the catalogs...



Regarding boring bars, for steel boring bars, Mitsubishi makes be best, hands down - I wish I could sell them... They have some kind of "dimple" design behind the insert that works some magic and stops vibrations.


For inserts, get away from double-sided inserts, and go with CCMT inserts for boring. You'll have thousands of options, as these inserts are quite literally designed for boring. Since it has clearance on the sides, the insert doesn't have to be tilted on a negative incline to avoid rubbing the bore. This gives you a more positive cutting angle, which reduces cutting forces, and therefore, the tendency for deflection & vibration. Going with a PVD grade insert will give you a sharper cutting edge too, and again reduces cutting forces & the tendency for vibration.
 
If you're actually going to be hanging them out 10-14xD, the dampened boring bars are worth twice the money they charge.

If you can get away with 6xD, get a carbide bar. The extra stiffness is really nice for small holes.
 
Heavy metal bars will have a lower L/D than carbide. They will chatter sooner than a carbide bar but there are frequency stability nodes to any setup.
It's not just a density thing and I've seen plain ole steel do 12:1 24 hours a day.
In volume production there are all sorts of tricks, different deal for a smaller job shop environment where you can't afford the testing or playing time.

The tuned bars from U-dex are made under a patent license from a big giant tool company. They paid big dollars for the rights to use this tech.
I was told that it took 4 years of production to begin making money off this product line.

Also, please, please don't get married to nailing centerline height here. Often above or below runs better as it changes the rake/clearance angles.
OD and ID, there is only one line that counts and it is from the tool tip to center of rotation. Facing, yes you have to rid of the center tit.
I look, taste and smell an op and tool wear and then tell people to raise or lower the tip 0.030-0.250.
They look at me like I'm a crazy man yet what I am doing is making their catalog standard holder into a custom rake holder designed for their cut.
You can't use this trick if you have to finish to center the bottom of the bore but it is cheaper than buying a custom bar with the right angles for your job.


The basic choices are steel, heavy metal, carbide, tuned in that order. Also that is generally the pricing order.
Don't buy more than you need.

If it was easy or simple one size fits all rules it would not be fun. :)
Bob
 
To CarbideBob's point, a customer purchased a Carbide/de-vibe bar from Dorian several weeks ago. Their literature recommends running the bar above center, by a drastic amount, that follows a formula based on stickout.
 
Yeah, I know about setting them a bit higher for deflection. Some stuff I do need to be able to face right to the center though.
I'll stick to carbide for now, if I really need to go to a tuned bar for some application I'll spend the $ then I guess.
I've done a few things to try to tune bars a bit before with copper shims and such that change the frequency a but when torqued, but it doesn't usually solve it entirely.

I've used pretty much only CCMT to bore for years, but I think some DCMT might be worth looking at now for less chance of chips rubbing. I hate it when a chip gets wedged between the bar, I'll try to have through coolant on all of them though.
 
Solid carbide bars are stiff, and much more resistant to deflection than steel. They don't have any inherent antivibration qualities beyond that they don't bounce so much. They'll still chatter and squeal if you have too much overhang.

Antivibration bars flex much more than carbide, but kill chatter before it starts and can reach far greater LxD than solid carbide.

Different tools for different purposes.

I don't recommend C shape inserts for boring, except for short overhang and heavy roughing. Positive or negative, D works better for most things.
 
While talking boring bars, do you guys have any easy tricks to set them to be sure they're dead on center at the insert tip since it looks like most rounds shanks can just spin right round?

If you buy a Sandvik SILENT bar, they come with a scribed line on the bar, and you use their boring bar holder that has a ball detent to locate the bar correctly.
Dampened bars aren't cheap,but man they are worth every penny.
 
i have used anti vibration boring bars. i believe they are internally slit to vibrate out of phase to help cancel normal vibration. they are not just a different metal type
.
my experience using same program and part and boring same hole. with anti vibration boring bar, easily quite obvious massive improvement in surface finish and ability to hold a tight tolerance and quite normal to be able to increase feeds and speeds and still get a better finish than a regular boring bar
 
If you buy a Sandvik SILENT bar, they come with a scribed line on the bar, and you use their boring bar holder that has a ball detent to locate the bar correctly.
Dampened bars aren't cheap,but man they are worth every penny.

The SL heads also have a flat on the top of the connection that you can indicate parallel with the X axis.

On the same subject all the non-SL Sandvik bars I have the rear clearance edge (behind the insert) parallel to the Y axis, so they can also be indicated in that way. I don't know if that applies to all or any others, or even all Sandvik bars, but it's useful.

I have lots of sandvik devibe and solid full round bars, but none of the ball detent holders.
 








 
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