Bridgeport Mill Making Knocking Or Clicking Noise

A friend of mine has a Bridgeport knee mill making a loud clicking or knock
ing sound in the head. I could not find any obvious reason. So I sorta just
said sorry man I can't find anything. Well about 2 weeks later Karma I gue
ss, I have a large Jet knee mill 3 phase started doing the exact same thing
.So I am telling myself the same thing, (sorry man can't find anything ). H
as anybody got info as to a guess what it is ? I am not a machinist just a
hobbiest. Thanks for any input you might offer.
Reply to
kujans0
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Is it a varispeed head (2J)? If so, it is likely to be the plastic bushing on the varispeed cone pulleys. I think the one on the motor can tear up the motor shaft, so you really want to get it fixed. The plastic piece is not expensive, and it dosn't take a massive amount of dissasembly.
Jon
Reply to
Jon Elson
cking sound in the head. I could not find any obvious reason. So I sorta ju st said sorry man I can't find anything. Well about 2 weeks later Karma I g uess, I have a large Jet knee mill 3 phase started doing the exact same thi ng.So I am telling myself the same thing, (sorry man can't find anything ). Has anybody got info as to a guess what it is ? I am not a machinist just a hobbiest. Thanks for any input you might offer.
It is not a Varispeed.
Reply to
kujans0
Are these pure step-belt pulleys for speed control, or variable speed pulleys? If the latter, the moving half of each pulley has a black plastic (Delrin) sleeve inside it and a key on the shaft screwed to the inside of the pulley with a Delrin cover over it to minimize play and friction in the keyway. These eventually wear out, and need to be replaced. If you don't replace them, the key starts wearing the keyway in the shaft wider and wider, with a loud "CLACK" as the motor is started or stopped.
If the step belt pulleys version -- I don't know, but perhaps the spline which couples the upper pulley to the spindle is dry and worn.
Good Luck, DoN.
Reply to
DoN. Nichols
If the bearings in the front pulley are worn, belt tension can pull the face coupling out of alignment. This will cause a knocking sound in direct drive, that will go away in back gear. Had a Millport with this problem.
Jon
Reply to
Jon Anderson
If it makes the noise in direct drive, but not in back gear, see my reply to Don's post.
Jon
Reply to
Jon Anderson
Oh, well, that BLOWS that theory! So, this is a 1J (4 step pulley)? There is a 1" belt that is the first stage of the back gear reduction. The belt is held on one of the pulleys by a flange that is bolted to the face of the pulley. That could be working loose, or the belt could be disintegrating. Take a look at that assembly, rotating by hand and looking with a flashlight.
Disengage the feed worm (little crank on right front of head). Put the direct-drive clutch in neutral (push lever on top clockwise looking down from top, it raises the driven pulley about 1/2") and spin the spindle as fast as you can. Does it still knock? If so, bad news, that sounds like main bearings.
Doesn't knock? There are a bunch of commodity bearings in the head, in the back gear assembly. First, remove motor (it's heavy). Then, remove nuts under belt housing, and you can lift that straight up and off the spindle spline. The back gear is under a metal cover with a few screws. If the bearings are blitzed, the ball retainers will have crumpled up and been spat out. That's how mine were. Also, the motor bearings could be bad. Thay are relatively easy to replace.
I can't say if your Jet is built the same way, but it probably is fairly close.
Jon
Reply to
Jon Elson
OK, two more things to think of. If the spindle spline is badly worn, it will clatter when taking short (as in along the length of the cutter) cuts. What I mean here is that the cutting flute is not continuously cutting workpiece material, like when cutting 1/8" sheet with a 1" end mill, for instance. Each cutter flute digs in and the comes free. This will rattle the spline. Easy to check, just twiddle the spindle nose and see how much it can be turned CW/CCW before it hits the other side of the driving spline. This will generally only rattle when cutting, and run totally quiet when running without cutting.
One other thing is a shot V belt. If the V belt has started to break down in one spot, it will ride lower in the pulley V groove. As the thin spot alternately rounds the driven, then the driving pulley, it will cause large speed-up/slow-down of the spindle. It can actually start the whole machine shaking! I saw this on a lathe once, it was QUITE dramatic.
Jon
Reply to
Jon Elson
I apologize for jumping in without having followed the entire thread, but has anyone suggested that it could be as simple as a cracked bearing ball?
Reply to
edhuntress2
On top is the lever arm that rotates a ring with two grooves at an angle in which there are pins attached to the part that engages the low range gears. When the lever is moved to high range these pins pull up on the engagement cogs for low range. These pins can work loose enough that the cogs are not fully disengaged in high. That's the rattle you hear, the cogs hitting each other ever so slightly. phil k.
Reply to
Phil Kangas
Oh, I think a cracked ball will go from bad to worse at a very rapid pace. Possibly a dinged ball in the backgear assembly (like when it ran over the bits of the retainer cage) could just get noisy and stay that way for a long time. That's the kind of shape my back gear bearings were in, and they generally made a loud whirring noise. But, a really cracked in half ball ought to be fairly disasterous.
Jon
Reply to
Jon Elson
I was thinking of my old drill press, which had a cracked ball (not cracked in half, but badly chipped -- last replaced in 1948) which made a "tick, tick" sound.
Reply to
edhuntress2
"Phil Kangas" wrote in message >
I posted a response because this is what happened on my Millport. Call it first hand info not speculation. If it rattles only in high range then that's it. phil k.
Reply to
Phil Kangas
I heard a report that Wieber was rushed to the ER after a freak accident. Seems he was confused about which end of his screwdriver stethoscope was which. In addition to the hearing loss, the fluid leak was lapped up by a few dogs, causing them to be "adopted out," if you know what I mean.
BTW, here's an "engineering" tip: I store my 7 to 13 screwdriver stethoscopes with the correct end out of harms way in a sort of hammock made from something I found on sale for $1.99 at HF. Not sure what it was supposed to be, but it's various bits of tubing connected together. There are also some plastic gizmos that can be repurposed as earplugs if you block the little holes in them.
Reply to
Caroline Says
That is a lie! It was only an infection caused by ear mites. Everybody gets them now and then. And there's nothing wrong with my 20 dogs either. Im not trying to brag but how many dogs do you have...Hmmm? Sucks to be you.
You think your funny, but I know all the best stethoscopes. The one your talking about isnt 2 bucks its four! And I can prove it.
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Who has that kind of money? Cash is very... very tight right now. So screw you pustilant leftist! Im submitting your name to the listkeepers again. When the People drag you out and hang you from a bit of barbed wire after kicking you off a lawn chair..Ill be very happy. In fact..I hope the doers send me a video clip of your ending. Knowing you were disposed of, along with the many thousands of your bretheren..and knowing that you will be gone into a mass grave somewhere along with the rest of the trash who have tried so hard to ruin America..will allow me to believe that America will indeed survive Get your affairs in order you mentally ill welfare queen.
Gunner, Coyote Engineering Machinery Repair Tech.
Reply to
Caroline Says

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