Quieted a noisy Bridgeport (clone)

[Winegrower]

I watched this video, and realized that my mill sounded exactly like his, before the fix. He explained that the gears are kept slightly apart, or some such, and if you only do this thing, it will fix it. I don't completely understand what is going on precisely - maybe someday I'll have to take that part of the mill down and then check it out.

But for now, watch this video:

I took the high/low speed ring off as he described, turned it down 0.005" in the lathe, and it really did reduce the rattling sound.
Not to zero, but at least 3dB quieter.

So this is a technically valid approach and I'm just passing on that as a fact.

 

[Ulma Doctor]

nice tip! thanks for posting

 

[plumberbutt]

To clarify for those that have never taken the top off your head to actually see what’s going on this may help. When you move lever A it raises the spindle pulley hub assembly ( associated parts attached to number 61 ) to put it in a free wheel state so the back gear can be engaged. When lowered for direct drive high speed that assembly meshes with number 28. That’s why you always rotate the spindle to make sure it drops down and engages.
When you get the grinding the assembly’s aren’t mating properly so you really need to find the cause in my opinion before making more heart ache.
I had this issue on a barely used almost pristine Bridgeport made in the early 60’s. I found all these suggestions and couldn’t accept worn gears. The issue was the original timing belt became too stiff and probably shrank over time putting too much tension on the spindle hub assembly preventing it from dropping down properly. I just checked my current Acra mill and had to lightly tap the top assembly with my finger to get it to drop as I haven’t used it for some time. Here’s the parts diagram and pics of my Bridgeport when I took it apart. Hope this helps. Z

 

[Winegrower]

Thanks, Plumberbutt. I called H&W (I really admire this company...their deep knowledge of mills and their customer support is amazing) at one point thinking I should replace the spindle bearings, because of the rattle that went away under load. I talked with the boss, who in diagnosing my complaint, asked if the rattle happened in back gear...I realized that it didn’t and he said the bearings are not the problem, it’s part 28. I suppose engaged but unloaded the short splines have some slop and can make some noise. Since a) there does not seem to be any performance issue with this and b) he said it was the second most expensive replacement part in the mill ($350 of so) I decided to ignore the noise for awhile.

So I pass his analysis on as an easy diagnostic step.

 

[plumberbutt]

I actually disassembled and reassembled the top several times to figure out the belt was the problem. Everything was clean and in great shape as expected. After assembling without the belt it worked perfectly. You can see the light scuff marks on the hubs from not engaging. One reason you may not get good engagement could be to dirt accumulating in the pockets and preventing a good seat. My belt was so tight that even using a rubber mallet and gently persuading the hub assembly to drop didn’t budge it. My opinion is to figure out the cause of the problem before you start modifying components for the quick cure.

 

[Winegrower]

I actually disassembled and reassembled the top several times to figure out the belt was the problem.

So loosening belt tension would fix the grinding sound? That’s an easy test too. I will try that.
I would call what I hear in my mill a rattle, not grinding. Maybe different issues?

 

[plumberbutt]

So loosening belt tension would fix the grinding sound? That’s an easy test too. I will try that.
I would call what I hear in my mill a rattle, not grinding. Maybe different issues?

My particular problem was that the timing belt was old and stiff. This is not the speed changing motor belt part number 60 but number 59. There is no way to loosen it. There are probably multiple reasons for the spindle hub assembly to not engage disengage properly. The angled slot in the collar #51 could be worn along with the screw pins #50 as described in the video. Although turning do down the screws just introduces more slop in the slot interface. If the “rattle” has been severe the teeth could have a burr preventing the hub to drop all the way. When you rotate lever A watch the spindle hub pulley assembly raise and lower and try to determine why it doesn’t engage disengage fully. That’s why you rotate the spindle by hand to insure engagement before powering it up. There are also four compression springs #72 that aid in engagement that could be weak. Someone that really knows these things could probably come up with many more reasons for the problem. The only thing I didn’t try was taking a closet auger to it. That’s a toilet snake. Sure it’s a pain to pull the motor and then the upper housing if things aren’t evident but getting to the root of the problem is the better solution. Unfortunately I don’t come to this site often but when I watched the video I thought it important enough to add my two cents worth on the subject.

 

[Gaffer]

I'm reviving this thread hoping one of you can help me. I have a Bridgeport Series 1 clone. I have a replacement spindle pulley bear sleeve, but I can't get the old one off (see part 70 in the diagram in post #3 by plumberbutt. I looks like it should unscrew without taking off the rest of the parts above it in the diagram. I've hit it with PB Blaster and some heat, but it doesn't want to budge, and I don't want to get to aggressive with it since I'm guessing how it comes off. I made a pin spanner wrench to hold the bearing assembly still and am using a strap wrench on the sleeve. And yes, I removed the set screws in the sleeve. I haven't touched the bearing or their bearing sleeve lockout. Thanks.

 

[Winegrower]

Sorry, Gaffer...I have not gotten that far yet. Hope I don’t have to, either.