Noise in Bridgeport 2J head (audio file included)
I finally got my Bridgeport mill wired up this weekend. The head makes a very loud noise, and I was hoping someone here might recognize the sound and have a good idea of specifically what part needs to be replaced/repaired. There is a short sound clip at the end of this thread you can download to hear the sound. It is actually quite a bit louder, but my microphone is not great.
Mill specifics: 2J vari-speed head, 2 HP motor, early 1980's production, appears to be in very good condition otherwise.
Some observations I have made: The noise is about the same in high and in low gear. It is definitely not a noise coming from the spindle like a bearing, because when in low speed and gear (60 rpm), the frequency of the noise is MUCH higher than the spindle speed. The noise does get slightly louder when changing the vari-speed drive to a higher speed (within the same speed range).
I believe this is a common problem. When I bought the mill, I had the guy power up several mills so I could swap this head for a better one, and they all made about the same noise.
I have bought and read the maintenance manual for this machine. The only reference about noise it mentions is something about an adjustment of a small part that controls the clutch and is by the high/low/neutral lever. It looks like I have to take the head partially apart to get to this.
I have seen some kits on ebay that replace the plastic bushing (part 59 in link below) for the reeve's drive pulleys (the cone shaped pulleys). They claim this could be a cause for noise and vibration. I don't know if this is the problem my machine has or not.
I figure I will have to take the head apart, but I was hoping someone here might have a good idea of what area to look at.
Here is a link to an exploded view of the head. If you think you know where the problem could be, please refer to the drawing numbers they use so we can communicate effectively. You have to click on "Bridgeport Replacement Parts" then "Variable Speed Top Housing Assembly"
The most common reason for noise in the head is that the moving vari drive disc bushings wear out. Usually the motor one wears out first. In 1980 these were thin black plastic that were epoxied into the vari drive disc. The newere verion are a thick green insert but it is not replaceable. If you let it go too long, it will tear up the motor shaft. I do not recommend replacing the bushings. I rebuild these heads in my garage and in the field. I cannot guarantee that you can glue these in and still have the varidisc run dead nuts true. You may wind up with a vibration and be doing this all over agian in a few mounths. I typically do a "top end kit" which include the 3 bearings, motor adjustable vari disc, driven adjustable vari disc, and a vari drive belt. In a production enviroment, you should be good for 6 years or so before doing this again. If your motor shaft is torn up, that can be purchased as a balanced rotor and shaft assembly. I work for Bridgeport dealer. My parts man is Alan at 1-800-245-2598. He can quote all of this for you. Yes, horsepower matters.
Wow, I didn't think I would ever get a response. Thanks.
I actually just completeed putting the mill back togetehr this week. I bought the kit that has all 4 of the thin black bushings and replaced them all. While I had the mill apart, I decided to take it even further apart for cleaning. I took it all the way down to the casting that holds the quill. That turned out to be a waste of time as even the grease in that area was clean. However, I did learn how the machine works, which is always a good thing.
Anyway, the machine still makes the noise, but it doesn't seem as bad.
I don't think its the bearings. When I spun them, they didn't feel gritty. One bearing did feel gritty, so I took it apart, cleaned and greased it, and it felt much better afterwards. That was the bearing on the aluminum bracket that moves the top spindle-side pulley.
I had measured the spindle pulley shaft and the motor shaft that the plastic bushings ride on. The spindle was well within a tenth its whole length. The motor shaft was slightly dished for about 1 inch. The change in diameter from the lowest part of the dish to the original diameter of the shaft was .001. I don't know if that is enough to be concerned about.
All that said, I think it is the belt. I will order one and I might also order the top bearing, or at least take a closer look at it and clean it.
I also have a question abut how much grease to use in various parts of the head. I'll post that in this thread tomorrow.
Thanks for the help.
I see your point about the possible out of round that may result when replacing the plastic bushings. I was thinking about that when I was installing them. But then how do you make the repair? Do you replace the ENTIRE moving pulleys (both) with the new design that has the thick green bushing? If so, that seems like a very expensive way to go.
A belt will typically make noise if someone stalled the machine and the motor varidrive kept turning causing a low spot.
Also I have often seen that the bearing that is in the front stationary vari disc goes bad and starts to eat through the vari disc.
Remember the "clutch" teeth you saw? When new, they actually engage each other about half way down. As they wear, they go deeper untill they bottom out. Eventually they will have slop (play) and can be a source of noise. Try raising the back gear handle a bit further up to engage the clutch teeth a bit more and see what happens.
My customers are typically commercial machine shops. It is cost effective to just replace the discs. It gives them a machine that will not need me a lot longer and my office charges $120.00 per hour for me. That makes a difference also.