Diagnosing Noise in Bridgeport Series 1 J-Head in High Gear

[Xyphota]

I was finally able to get around to wiring up a plug and run my mill for the first time, but there is a pretty good rattling coming out of the head when in high gear. The noise goes away in low gear. I took a short video to show the noise in action.

My first guess as to the origin of the noise is the dog gears are rattling around and hitting each other when in high gear, but it is not clear to me what adjustment can be made to fix this. I am to believe that the dog gears are disengaged in High gear and engaged in low gear? I screen grabbed a picture from the H&W Machine Repair channel to show which part I'm talking about. I wanted to hear some opinions before I start disassembling the head.

 

[Susquatch]

I was finally able to get around to wiring up a plug and run my mill for the first time, but there is a pretty good rattling coming out of the head when in high gear. The noise goes away in low gear. I took a short video to show the noise in action.

My first guess as to the origin of the noise is the dog gears are rattling around and hitting each other when in high gear, but it is not clear to me what adjustment can be made to fix this. I am to believe that the dog gears are disengaged in High gear and engaged in low gear? I screen grabbed a picture from the H&W Machine Repair channel to show which part I'm talking about. I wanted to hear some opinions before I start disassembling the head.


View attachment 25070

I had the exact same problem on my Hartford Clone of the J-Head. EXACTLY.

I think the teeth are engaged opposite to what you assumed. I believe they are engaged in high speed and disengaged in low speed. Engaging them results in direct drive of the spindle from the top pulley. Separating them allows the top and bottom to turn at different speeds from each other through the reduction gear set. I wish it were as you described.......

I found references to this problem on other forums that suggested the cam that raises and lowers the dog teeth was sticking. To test for this, lower the cam and then rap on the top ring of the cam with a dead-blow hammer to see if the noise goes away. If so, you might be able to adjust and/or lubricate the cam.

In my case, it turned out that the dog teeth section was rubbing on the housing cover a bit when lowered to engage the dogs.

I did three things that dramatically reduced the noise.

1. Removed the internal cover for the bull gear, re-centered it on the bottom dog clutch, drilled new locating dowel pin holes, relieved the ID of the dog clutch hole in the cover, reinstalled the cover, and used red & sticky grease to lubricate the dogs.

2. Adjusted and lubricated the cam that raises and lowers the clutch.

3. Adjusted the belt tension of the pullies. Sometimes it still makes a bit of noise at certain speeds. (I have a variable speed VFD on it). I can usually make that go away by slightly raising the cam a bit.

Hopefully your clutch teeth are not so badly worn that they need replacement - it's expensive.

It is also possible that the bearing in the top spindle pulley has some play in it and might need to be replaced. You only need to take the top cover off to do that. The pulley is attached to the cover through the bearing.

If the time comes when I have to replace the dogs, I'll prolly just stop using hi speed and use the VFD to get me whatever speed it can deliver instead. It would be easier if the problem happened in low speed because my motor and VFD combo can run at zero.

 

[Xyphota]

Thanks for the detailed response! You are right about the direction the dogs are engaged in high vs low gear. They are engaged in high gear. I will try to do some disassembly to see what the internals look like. For the item number 1 in your list, is there a video or forum post with pictures you referenced?

Unrelated, can anyone take a guess as to why the previous owner of the mill would have added this stop to limit the total rotation of the cam?

 

[Susquatch]

Thanks for the detailed response! You are right about the direction the dogs are engaged in high vs low gear. They are engaged in high gear. I will try to do some disassembly to see what the internals look like. For the item number 1 in your list, is there a video or forum post with pictures you referenced?

Unrelated, can anyone take a guess as to why the previous owner of the mill would have added this stop to limit the total rotation of the cam?
View attachment 25091

Here is a link to the thread I made when I dealt with this issue.

Post in thread 'New to me Hartford Mill' https://canadianhobbymetalworkers.com/threads/new-to-me-hartford-mill.3490/post-52426

The page I linked to has a graphic that @Brent H provided that shows the cover and pins. The cover is item 50 and the pins are 67 or 68. I believe there are 2 or 3 cover alignment pins. Mine were loose so I added more.

You should probably read that whole thread. There is a lot of info there that would almost all apply to your mill.

I don't know for sure about that stop. My best guess is that the motor pulley wasn't correctly installed on the motor shaft so the belt was coming off when the front pulley was raised too much. So they put a limiter on it to stop it from being lifted too much. I'd get rid of that and adjust the motor pulley position to be halfway between ideal for top and bottom front pulley position. But that isn't your noise cuz that is the top (disengaged - for low speed) position.

 

[Xyphota]

I was out of town for a bit but I had time to spend a few hours working on this last night. I dissembled everything down to removing the cover for the reduction gear set. The dog clutch teeth had a bit of grit in them so I was hoping that I could clean those out and then they would engage properly but no dice.

It looks like the entire range of motion that the cam moves the dog clutch up and down is too high, which explains why a previous owner added that limit/stop to the cam. The cam could raise the assembly so high the reduction pulley timing belt would be forced into the pulley timing pulley flanges. Additionally this means that at the lowest setting, the dog clutch is still too high and is rattling around. Is it possible to lower the dog clutch relative to the cam?

EDIT: wrong terminology

 

[Susquatch]

I was out of town for a bit but I had time to spend a few hours working on this last night. I dissembled everything down to removing the cover for the reduction gear set. The dog clutch teeth had a bit of grit in them so I was hoping that I could clean those out and then they would engage properly but no dice.

It looks like the entire range of motion that the cam moves the dog clutch up and down is too high, which explains why a previous owner added that limit/stop to the cam. The cam could raise the assembly so high the reduction pulley belt would be forced into the pulley flanges. Additionally this means that at the lowest setting, the dog clutch is still too high and is rattling around. Is it possible to lower the dog clutch relative to the cam?

I'd be moving the motor pulley position first. It should be set so that it is equally off center for both top and bottom position of the front pulley. It will never be perfect, but it works fine like that on mine.

If I accept what you say about the cam, then I have to conclude that somebody messed with it. It's range of authority on mine is pretty good.

Even if I assume that your dog teeth are worn down, I still can't imagine that it could lift too high unless the motor pulley was too low. All that would happen is that you would have a lot of clearance on the dogs.

I think your motor pulley is too low. If it is too low it also increases the chance of contact with the top of the bull gear cover.

I have grandkids here today, but If I get a chance, I'll take a photo of my pullies with the front one fully up and fully down.

 

[Xyphota]

Sorry I was using the incorrect terminology. I meant the timing belt was reaching extremes.

Additionally, raising the cam the slightest amount made the sound significantly worse, so I feel if I could lower it a bit more the sound would improve. Applying a load to the spindle just with my hand also made the sound slightly louder.

 

[Susquatch]

Sorry I was using the incorrect terminology. I meant the timing belt was reaching extremes.

Additionally, raising the cam the slightest amount made the sound significantly worse, so I feel if I could lower it a bit more the sound would improve. Applying a load to the spindle just with my hand also made the sound slightly louder.

I see. Well the timing belt is gunna reach an extreme - no way around that. On mine, it is as low as it can go. It is only held on by the flange on the timing belt gear itself.

Yes, adding a hand load makes the drive belt flap around which increases the noise. You can, actually watch it happen.

But the best way to reduce that noise is to optimize the motor belt position in the two pulleys. Since yours is like mine and is quiet in low speed mode (back gear engaged, dog teeth disengaged) you prolly need to raise the motor pulley a bit. In any event, take a look at the two pullies fully up and fully down and see if it's offset too much one way or the other.

I'm still hoping to get out to the shop shortly. I'll take photos then.

In the meantime, with some fiddling under your belt, it might be a good idea to go back and review the list of possible causes that I gave you earlier.

 

[Susquatch]

Well, with that prodding, I went out and got it done.

This fully down.



This is fully up.



If you zoom in on the two photos above you can clearly see that the belt is not centered in the grooves.

This is half way with the cam set at the halfway point. You can even see the button set half way up the ramp.



As you can see, there is indeed a happy medium. This adjustment is strictly done by moving the motor pulley. If you don't have enough pulley movement going toward the motor, you will have to shim the motor up a bit.

If you replace the motor like I did, this will be the least of your issues. As you can tell, I lost one of the 4 pulley positions. For me, that didn't matter because the VFD more than compensated for that small loss.

 

[Susquatch]

Here is a photo of my measured speeds with the missing pulley. The original chart is also in the photo.



As you can see the original fastest speed is 2720, the new fastest speed with the missing pulley at 60Hz is 2234. But throw in the VFD at 120Hz, and the new fastest speed is 4468 rpm.

Similarly, the old slowest is 80 rpm. The new one at 60 Hz is 127. But with the VFD I can quite literally go to zero with simply amazing torque.

So ya, I don't miss the 4th pulley position at all!

In fact, I generally run it on the middle pulley which will give me zero to 3000 rpm with all the oomph anyone could dream of having!

 

[Xyphota]

So after some poking and prodding, I realized that the previous owner drilled new holes for the cam ring pins. I measured one of them to be about 0.020-0.025” lower than the original holes. This means the whole assembly lost that amount of travel on the bottom so it was impossible for the dog gears to completely mesh. Running the motor with the cam removed altogether sounded great.

This also explains why they added the limit plates as the cam would otherwise move 0.020” too high.

Thanks for your help!

 

[Susquatch]

So after some poking and prodding, I realized that the previous owner drilled new holes for the cam ring pins. I measured one of them to be about 0.020-0.025” lower than the original holes. This means the whole assembly lost that amount of travel on the bottom so it was impossible for the dog gears to completely mesh. Running the motor with the cam removed altogether sounded great.

This also explains why they added the limit plates as the cam would otherwise move 0.020” too high.

Thanks for your help!

Any idea at all why they would do this?

 

[Xyphota]

The cam ring pins thread into a thin piece of steel and the pins are cantilevered out quite a bit so they are prone to pull out the theads in the sliding assembly I guess.

Bridgeport includes a second set of drilled and tapped holes from the factory for the pins for when the first ones wear out. You just rotate the sliding assembly and use the new holes. My for mill, it looks like the previous owner wore both sets of holes out and then tried to drill and tap a third set, but didnt get them bang on.

 

[Susquatch]

The cam ring pins thread into a thin piece of steel and the pins are cantilevered out quite a bit so they are prone to pull out the theads in the sliding assembly I guess.

Bridgeport includes a second set of drilled and tapped holes from the factory for the pins for when the first ones wear out. You just rotate the sliding assembly and use the new holes. My for mill, it looks like the previous owner wore both sets of holes out and then tried to drill and tap a third set, but didnt get them bang on.

Really? ..... Huh..... As far as I know, my Hartford clone only has one set of holes.

I cannot imagine wearing out the holes. The pins maybe, but not the holes. I'd like to research that a bit to understand what that's all about. It could also be an adjustment of some kind. Or perhaps a choice to accommodate different timing belt sizes or dog clutch sizes. Your observation that the holes are worn out is compelling though..... Please let me know if you learn anything more.

I did add some grease to my cam surfaces which would both reduce any wear as well as making the camming process a bit easier on everything including the cam pins, threaded holes, and cam surfaces.

 

[Xyphota]

Perhaps “wearing” out is not the correct terminology. The sliding assembly is lifted solely through those pins so presumably the sliding fit seized up with some grit or something and then the pins just pulled the threads out of the holes when the assembly pulled up. So in my case there are two sets of holes with no threads left in them, and a third set that are slightly too low.

 

[Susquatch]

Perhaps “wearing” out is not the correct terminology. The sliding assembly is lifted solely through those pins so presumably the sliding fit seized up with some grit or something and then the pins just pulled the threads out of the holes when the assembly pulled up. So in my case there are two sets of holes with no threads left in them, and a third set that are slightly too low.

That makes a lot more sense. My lift ring is a nice loose fit. I don't think it will ever seize up. But with your clarification, at least now I can see how it could happen.

The most important thing is that you are all set now and your noise is gone.

I love how quiet and smooth my machine is. I don't think a vari-drive could ever be as nice. And of course, with a VFD on a pulley machine - the appeal of a vari-drive is just not there.

I hope you love yours as much as I love mine.