Juddering Fobco star quill after rebuild

[skippy75]

Hi, there seems to be a few people that have tackled the restoration of Fobco star drills here so I’m hoping someone can help.

I’ve been restoring my Star on and off for a couple of years due to ill health making things slow. I finally “finished” my drill last week, including a conversion with a Fobco Universal spindle and quill. The drill was completely broken down and rebuilt with new bearings. The spindle was new old stock and had never been used.

If I raise and lower the quill with the motor off everything is smooth although the quill is a little tight. Even without the quill return spring installed the quill doesn’t drop by itself.

If I turn the motor on and move the quill up and down I get a horribly notchy bumpy feeling and sound. It’s bad enough that you feel it through the handle like a severe juddering.

I’m completely stumped as to what’s causing this and how to rectify it. Does anyone have any ideas?

 

[Gregb23]

On my fobco 7/8 I get a vibration everytime the belt does a full rotation. I assumed it was because I never took the tension off when not in use and the belt has deformed slightly. Could it be the drive belt type?

 

[skippy75]

On my fobco 7/8 I get a vibration everytime the belt does a full rotation. I assumed it was because I never took the tension off when not in use and the belt has deformed slightly. Could it be the drive belt type?

I’d hope that wouldn’t be a problem with a link belt but maybe I can see if there’s a certain point that does it.

I did initially think it was pulley alignment but after spending a while getting them straight there was no difference

 

[frank horton]

whats it like if u rotate it by hand....bearings smooth.....new belt old belt.....
if nothing helps just run it for a few mins to c if it gets hot.....if not run it some more, say 5-10 mins then reaccess......

 

[Rrobson]

Sounds like damage between the driver tube and the driven chuck spindle (for lack of better descriptive words…), or the slidey bits that allow the quill to extend. There may be damage along its length.

I don’t think the segmented belt would cause issues, but I have to ask why you’ve chosen that over a conventional imperial ver belt? I think they’re just a standard A section belt

 

[Erie Fred]

Does it go away or stay when loaded ?

 

[Brad93]

Splines / keyway either not a good fit or your bearings are shot

 

[skippy75]

Thank you for the replies. I had an incident with the quill spring and my hand which sent me to A&E (no lasting damage) and also caught Covid so I won’t be doing a huge amount for a little while.

I did pop the quill and the top pulley bearings out though. Putting them together outside of the machine you can feel roughness, especially if the parts are twisted together so I’m guessing this is at least part of the issue.

I can’t see any damage to the splines or the keyways but there must be something. Is a good quality fine file the best way to smooth the parts? I know I have to be careful about removing too much material.

 

[Shiny Steve]

Try a small India stone first

 

[skippy75]

it seems as though the issue is fixed. I had to remove a tiny amount of metal on the side on one keyway so that the spindle slides smoothly. It’s all back in the drill and it’s much better. I’m just missing the quill spring as the final piece.

 

[skippy75]

Just wanted to say thank you for all the help and advice. I really appreciate it.

 

[skippy75]

I spoke too soon. The juddering is less severe and mainly happens when the quill is near the top but it’s still not smooth. Interestingly it’s much worse with a standard v belt compared to the link belt.

Link to video

The sound louder in real life than on the video

Measuring the front pulley as shown in the photo there’s about 0.5mm of wobble which comes from the upper bearing sleeve rather than the pulley itself being wonky. You can actually wiggle it back and forth. Perhaps this is normal though?



Edited to add video link

 

[RichardM]

If you are measuring the core of the V the belt should never touch there.

 

[skippy75]

If you are measuring the core of the V the belt should never touch there.

I didn’t realise that so it’s good to know. I’m measuring a wobble from side to side when I wiggle the pulley though rather than just checking it when it rotates.

It does also wobble when I rotated it but I will try indicating on the sides.

 

[Seadog]

If there's any wiggle it'll present as vibration. I have a similar problem on my Progress 2.