spindle binding (I think) on BP mill

diamond

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I recently got a BP Series 1 1.5hp vary-speed. This is my first mill and I'm a newbe. Previous owner had started a head rebuild. I finished the rebuild with a full bearing & belt replacement. (head rebuild kit from H&W). New sealed spindle bearings, new bushing and all that. The motor and vary-disk shafts were in good tolerances. Took a big risk buying a machine torn down. It looked good, the ways and table and all visibly looked in really good condition. To my uneducated eye it looked lightly used. Not so sure now.

The problem I've run into is the spindle up/down movement seems to have a very distinct spot in rotation where it binds or rubs. Can feel this by trying to lower the quill while the mill is turning. It is a distinct "catch" or "pulsing" (depending on how fast the mill is running) as you lower the quill. I can also turn the spindle by hand and find a spot where raising and lowering the quill is distinctly feels harder like it's rubbing where elsewhere in the rotation it is more free. At higher speeds it's like a strong vibration as you raise and lower the quill. Also quite a loud noise.

I'm wondering if the spindle shaft is actually bent and rubbing somehow in the bull gear shaft. My next step is to pull the spindle and see if I can tell if it is bent somehow. Maybe chuck it up in my lathe between centers and see if I can measure any bend with an indicator.

Is this binding like this a common thing and could it be caused by anything else? I can't really think of anything else that could cause this other than a bent spindle. Obviously that's going to be a pretty expensive fix if it is so I thought I'd ask if there were any other thoughts.
 
I have only worked on two J vari-speed heads; a 1-1/2hp and a 2hp. They are basically the same inside. From what I am understanding, from what you are describing, it does sound to me like something might be bent and/or not running true.

There are YouTube videos on pulling the spindle on a Bridgeport. Sounds like a good plan to check yours for run out.

If the spindle is all the way up does the top part of the spline (where the draw bar seats) look like it's running out? Can you get an indicator on it and check it while in the head rotating it by hand? This might help show something...

Ted
 
When reassembling the head it is possible to misalign the top and bottom housings and this will cause the quill shaft to bind in the bull gear spline. There are no aligning surfaces or pins. I think there actually is a procedure to do the alignment, but I have always done it by feel.

The pic shows the split where the misalignment can occur.

1545410713104.png
 
You are on the right track, check the spindle between centers- If you have access to a hydraulic press you may be able to carefully straighten it.
mark
 
Before I pull the spindle I think I will try that adjusting the alignment of the bull gear housing. Super hopeful that's the issue and save me a lot of money on a new spindle! When assembling it I did notice the bull gear housing can rotate on that joint to any position. I tried to get it back to as close to where it was previously by looking at marks on the flange but could have easily been off. I don't know how sensitive this alignment is. I was even thinking, why is this adjustable? Didn't quite make sense to me at the time.

Anyone have more thoughts on that alignment, how to do it? Jim when you say by feel, do you mean just loosen and move it until I no longer feel any binding when rotating by hand? Guessing so but if there's a more procedural way would like to know.

Thanks guys!!! I so much appreciate the support on this site!

-dave
 
You are on the right track, check the spindle between centers- If you have access to a hydraulic press you may be able to carefully straighten it.
mark

You're close, check the runout with the quill shaft running in it's own bearings. :) Remove the quill assembly and lay it on the mill table on the center T-slot so it doesn't roll around. Don't remove the quill shaft from the ram. Now you can rotate the shaft and check the runout on the spline end. The likelihood of the quill being bent below the top bearing is very small. If anything is wrong I would expect a twist in the splines caused by a major jam rather than a bend.
 
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Jim when you say by feel, do you mean just loosen and move it until I no longer feel any binding when rotating by hand?

Yup, loosen it a bit and move it around with a dead blow hammer.
 
Ah makes sense about any bend being above the bearings. The spindle is much thicker below the splines.

This is great, I have some easy things to try this weekend that don't involve tearing down the entire head. There is hope. LOL I'll update y'all with what I find.

-dave
 
Pulled the spindle measured runout following Jim's suggestion to just lay it on the bearings. Measured ~.001 runout on the spindle just above the top bearing. Move 6" up the splines, towards the top of the spindle, and it's ~.007 runout. So there is definitely some bend in the spindle above the bearings. I don't know what the tolerances are for the spindle spline fit in the bull gear splines but I assume it's pretty tight. Having any backlash in the fit would be a bad thing I'm guessing. So unfortunately it is looking like a bent spindle is one of my issues. I'm guessing this is binding and the cause of the "pulsing" feeling as it rotates and I raise & lower the quill.

I think I have a second issue in the drive but I'm not sure yet what it is. After I pulled the spindle I ran it to see if the noise went a way. It is reasonably quiet in neutral however when high range is engaged that loud "growl" is still very much there and a fair amount of vibration. I know vary speed heads are noisy but this still doesn't seem right. The rebuild has all new bearings & bushings but I did not replace the bull gear shaft or the vary disk shaft. The clutch cogs looked ok to me and they mesh up without any play but maybe I missed something in there.

So I pulled the motor and upper belt housing and I did discover the new grease I put in the bull gear housing is getting forced up through the hole in the cover and into the belt housing. I think I over filled it. H&W kit said to use two tubes of grease, so I did. I may have to tear it down further and remove some of that grease. It's getting on the timing belt and that's probably not a good thing. Might be causing other issues. I'm almost wondering if it could even be pushing up the aluminum cover causing it to rub on something.

Oh well, I'm getting pretty good at tearing down a BP Series 1 head. lol
 
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