Setting up a boring head

[specv]

We use a presetter. that is the easiest way, bars are usually set .001 to .002 undersize. Cut once, then measure, adjust, cut again, good bore we have pretty much every head on the market: Devlieg, Criterion(w/tenth set), Komet, EPB, Ramsey, and my personal favorite Romicron(clicker) .00008 adjustment.

 

Pete

[MetalMarvels]

Millman, the part is 2.6 inches deep, 2.6 wide and 3.55 long and is buried in hardjaws with only about .5 inches above the jaws. When cut to full width, the 2.000 dia hole, 2.000 deep leaves 0.3 walls on the sides (and about 1 inch on one end). I have a Circle boring bar in and even (sigh) cut it down for minimum overhang. Tried the rubberband thing with enough that it would just clear the walls. Tried a flat-top and a chip-breaker insert and even tried the regrind trick. I got it to better than a 125 um finish, but not good enough. Interestingly, the middle section (about a 3/4 inch band) was worse than above or below.....

 

Gcode, the only thing I couldn't change was that the head is on a 3/4 dia straight shank in an e-mill holder. I don't (yet) own a direct screw-on Cat40 holder for the head. Just wish the central spigot wasn't in there - could have used the "solid" Ramsey boring head.

 

I broke down and ordered a long 4-flute finishing mill to sneak up on it using circle interpolation (at least it is only a 2.000 dia +0 / -.002), that much I can do by interpolation. I just didn't have a 3/8 dia emill that long..... At least I can get it within +/- .0005 with an adequate finish (I hope....).

[MetalMarvels]

Sort of the same subject... How does everyone define there boring head setup in Mastercam. The Ramsey type was easy since it is "solid". For example there can't be any central features sticking up inside the hole, since the tool can't clear them (rather like the heads in the upper left of Keith's photo). However, defining an inserted boring bar type of head (like the Criterion) seems to require a "custom" drawing to define it.

[Harryman]

Yo Marvels, I've had pretty good luck with Criterion.

 

Thoughts: look for clearance between the clamping element of the dovetail and the slider on the z axis end of the clamp. Contact there could make the head scream. Also check the fit of the arbor shoulder to the head, if the threads between arbor and head are bottoming B4 shoulder contact that would be fixable too.

[crazy^millman]

Wel Metal you do come across those like that. It seems just no matter what you do it just doesn't come out right. I have also put the center line of the cutter a little part past or a little before center in hope of either creating a negative style cut or an even more positive style of cut. I have also written a macro program to do what I call the up and down game on the spindle. I would do an incremental down feed .005 at 300 rpm then the next loop at 400 rpm then back to 300 rpm. It is a real pain in the but to write and get to work properly but I use to do Stainless Steel sleeves in a lathe that were .187 wall thinkness by 11" long and that always did the trick. The thoery I had behind that is if you start taking a cut and for the first 2 sec it does great why the bar, the head, the part, and the machine have not got the ring going. By breaking up the rpm you don't give it a chance to catch up to all the above. I have sat there on a machine and do this with the rpm up and down to the point I had to have the spinlde override replaced on one machine. Well as shallow of a depth that is you should be fine withthe carbide endmill. I would also do 2 to 3 deflection passes even using a carbide endmill 3/4" in Dia. I was able to hold .0002 bores all day long that way takes a while but gives one hell of a finish.

 

Well good luck

 

Crazy Millman

 

[ 10-06-2003, 03:56 PM: Message edited by: Millman^Crazy ]

[MetalMarvels]

Thanks, Harry. I will check that this evening. It is about time for me to leave my day job, put on my shop owners' cape, and start my afternoon/evening job.

[Müřlıń®]

Yo, Metal....I couldn't find where you said what material you were cutting. Is it an interrupted cut?

 

quote:

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the only thing I couldn't change was that the head is on a 3/4 dia straight shank in an e-mill holder

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This is your whole problem with chatter...you will have to use a very sharp cutter since you have no rigidity. You might as well be doing this on a Bridgeport....You might try loosing the holder and putting the head in a 3/4 collet chuck.

 

I have gotten some extremely good finishes with HSS with 6% cobolt boaring. You can grind the tool with very sharp positive rake and have about a 15 degree neg lead angle so the cut will have enough pressure on it to dampen the chatter.

 

Of course if you have thousands of parts to do, this method will not be fast enough...

 

 

Murlin

 

[ 10-07-2003, 12:03 AM: Message edited by: Murlin ]

[Harryman]

quote:

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very sharp positive rake and have about a 15 degree neg lead angle

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Yup Murlin, I think I know that one too. Used it a bunch with the 45 deg broached Bridgeport bar. It's a very not chattery grind. If you ever learn to write well enough to explain how to grind that in text... Richard Marcinko will be calling you SIR.

[MetalMarvels]

Thanks, Murlin. I suspect that it is indeed the holding arrangement. When I can afford it, I will try to get a short CAT40 to head adapter to get the setup as rigid as possible. I need to have one anyways, since I have a couple of other heads that fit the same thread. Perhaps after I get paid (if I get paid) for the last three jobs. The time between buying material and getting paid for the job is a killer.....

 

The material is 6061-T651. I can get a smooth, beautiful cut if I take at least .005 DOC - except thru the middle 3/4-inch where it sings no matter what I do... Unfortunately the hole is tapered afterwards (about 0.0015 top to bottom). Any sort of skim cut or spring cut, even with a dead-sharp tool results in singing.

 

I am going to circle interpolate the bore with the long 4-flute tool that should arrive this afternoon so that I can get this part out the door. I will come back to this problem when I have some spare time because I am certain that it will come up again.

 

[ 10-07-2003, 10:14 AM: Message edited by: MetalMarvels ]

[Müřlıń®]

quote:

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If you ever learn to write well enough

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LOL....Ya, I come up a little short in the that department

 

Literature was not my best subject

 

quote:

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The time between buying material and getting paid for the job is a killer.....

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You're telling me......sometimes it takes me 90 days to get paid on a job I had 2 months in already.......

 

Glad I could have some input Metal, good luck.

 

Murlin

[Harryman]

quote:

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If you ever learn to write well enough

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No slam here Murlin. If any of us ever can discribe that tool in text...