View Full Version : milling machine problem
10-23-2001, 12:09 AM
I got this here mill ya see. It seems to be a goodern except when it comes time to bore me a hole. Durn thang chatters a bit at most any speed or feed. Lookin' in the hole, ya see chatter marks only just in one spot. Allus the same spot too. 'Bout the 7 o'clock position give or take a coffee break. Any advice and I'd shore appreciate it.
Steve Bob from down south(Illinois)
This is with a boring head and single-point tool? What's the shank on the boring head? Are you holding a straight shank in a collet? My experience is that doing so is significantly not as rigid at using a taper shank (R8, Morse 2, or whatever) on the boring head.
Sort of hard to diagnose from a distance. Offhand, I can't think of anything that would make me say, "Chatter at 7 o'clock? Oh sure! Your woozzleframitz is too tight," or anything like that.
Have you tried locking the X-Y slides, to eliminate as much possible motion as you can? If it's a hole of any size, you'll want a SLOW rpm. And experiment with the way you're sharpening the toolbit and it's orientation in the boring head.
10-23-2001, 06:36 PM
Well, I guess just a tad more information might be waranted here. OK, first off it's an Index vertical mill. One of those Chinese Bridgeport clones with variable speed.
Bore head is about 3 inch dia. with an R-8 shank. Mostly I use bars for carbide inserts and flats on the shank for indexing so everything should be OK there. Slides are always cinched tight when boring of course.
The chatter shows up consistently on any size hole, any depth of cut, any speed, any feed, any material. And I suppose I should clarify by saying the chatter is CENTERED at 7:00 or thereabouts. Typically runs to about 25% of the circumference.
Good try but the woozzleframitz was rebuilt and set three months ago. :-)
10-23-2001, 08:31 PM
Since lack of rigidity is one of the chief causes of chatter I would check with an indicator to see if there is an unusual amount of play in the spindle in the direction of the chatter. There may be something going inside that you cannot see.
That is a problem!
Does the chatter show up when you use the knee feed crank with every thing else locked down? or only with the power quill feed? or hand-wheel quill feed? or,lever quill feed? Is the knee locked? Have you filled and used the oiler with the correct oil *( Vactra#2)? Are you using the recommended oil in the cups on the head? Break the problem into separate things, sometimes that will answer the question.
keep us posted
* you may also use chainsaw bar oil according to a tool setter and rebuilder I've met. Or, you could take a new 3# can of coffee and a gallon gas/kerosine can to your local machine shop and see if they would share with you the Vactra #2 also offer to pay for it! The coffee is theirs either way. You build a good relationship with them and it pays later!
10-23-2001, 11:38 PM
This sounds real bad. You could have hatched spindle bearings. They might just be drier than an ant fart in the Sahara. Check for lube in the spindle, if it does not have any that is probably the problem.
Does your spindle feel tight or rough in spots when you take the belt off and rotate it by hand? (Not THAT one, the one on the machine - doh!) Is it does, this is bad - see your Doctor right away ;-)
Sympathetic vibrations can set up from inadequate lube on the ways. Is there a work clamp in the 7 o'clock pos? Are all the clamps tight? Are there any unusual projections on the work piece that may be vibrating freely?
10-24-2001, 02:03 AM
First of all, thanks to all who responded to my problem and second, thanks for overlooking my sad attempt at being humorous. :-) (I get weak sometimes.)
Definitely there's something going on that I can't see. I've never used the knee feed to bore, but I've seen it done. Seemed really weird to me. Yep, this is with the power quill feed. Knee is locked. Does it with everything I've tried to bore really. Some clamped down, some in a vise. If I finish up real slow with a couple of .001 passes, I can live with it on most stuff.
Everything gets straight 30 wt. motor oil here. Seems to work OK on everything else. The spindle is free turning by hand, no noticeable rough spots. I suppose the spindle bearings are the likely culprit, but I really did not want to hear that. sigh
Sounds like a 1 to 1 gear problem between the spindle gear and a gear in the power quill feed. Probably a piece of swarf ( goober) in between the gear teeth, spindle to power down-feed. Only way to find out is to bore a hole with the knee or handwheel on the head. No chatter =power down feed. You would rather have bad spindle bearings!
Luck to you
09-26-2005, 11:25 AM
Can a picture can be taken and loaded it might generate more Idea's
09-26-2005, 12:09 PM
How long is that bar with carbide inserts?
If that's a lathe boring bar with flats and an insert, you may have waaay tooo much overhang.
Inserts generally don't cut freely and need a heavy cut to perform.
That is impossible with a stock lathe bar made to be chucked up in the lathe holder.
Most people typically purchase the longest boring bar in the catalog.
For Bridgeport/Bridgeport knockoff type boring, you need a very small radius on the tool.
I re-gring worn, and chipped end mills to make boring bars.
Some machines do chatter in a certain quadrant, or other, for some reason when milling, and boring.
Some cnc's even do it when milling a circle.
I wasn't aware that Index was a Chineese knock off.
I think you may have a tooling problem.
09-26-2005, 01:58 PM
The fact that this thread is four years old should temper the replies.
09-28-2005, 08:38 PM
<font face="Verdana, Arial" size="2">Originally posted by JCHannum:
The fact that this thread is four years old should temper the replies. </font>
That’s funny, mills fixed and snorman has probably learned English by now
[This message has been edited by Mcgyver (edited 09-28-2005).]