Fobco Star Drill refurbishment - bearing question

[Dissolve]

Hello,

I'm at the stage where I'm assembling my drill, I've got everything sorted except one very annoying problem..

The spindle/quill assembly has one bearing fitted to the spindle that sits against a flat disc/washer and the other bearing sits just inside the quill itself. I have been advised that these bearings are angular contact bearings and the closest measurements I had corresponds with a modern day "7202" coded bearing. I purchased two SKF 7202BEP bearings.

I went to fit them and the bearing inside the quill went in with no trouble but it's locked in there right. The other one went onto the spindle without too much trouble and everything seemed great..

I went to insert the spindle into the quill it went in a little too easily, the spindle bearing moves quite freely in and out of the quill which was a bit worrying.. but there is retaining cap that sits above the quill and clamps with a grub screw to the spindle.. this holds the spindle tight but after inserting the quill into the head casting and setting up the return spring etc the retaining cap seems to work loose allowing some play between the spindle and the quill.

Obviously the retaining ring cannot hold the spindle tight inside the quill alone and the spindle bearing isn't as tight a fit as the previous. Can anyone suggest what to try before I order more bearings from a different manufacturer or resort to gluing bearings in!! :lol:

 

[chippy1970]

Are you tightening the grub screw tight enough ? It shouldn't work loose like that. I tightened mine while pushing down on it to lock it down tight against the bearings.

My bottom bearing is loose too, be interesting to hear ideas to fit it snug. It's causing play on mine which is annoying after all the work I put into restoring it

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[Dissolve]

Are you tightening the grub screw tight enough ? It shouldn't work loose like that. I tightened mine while pushing down on it to lock it down tight against the bearings.

My bottom bearing is loose too, be interesting to hear ideas to fit it snug. It's causing play on mine which is annoying after all the work I put into restoring it

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Hello, Yes that's the issue, but the retaining ring isn't "working Loose" as such, I've tried tightening to the absolutely maximum and it still manages to cause slight play between the spindle/quill.

The play comes from the bearings themselves, because they're angular contact, the have a loose sort of "play" in them when handling them until the inner and outer race are held perfectly in plane with one another (obviously this should be the case when installed)

I've tried pushing the retaining clip on using another set of hands and tightening it but after the small amount of handling it takes to get the rest of the drill together it's worked loose. I tried using solvents to De-grease the clip/grub screw/spindle shaft.. but it still ends up slipping that tiny amount to cause problems.

Are you saying your lower spindle bearing is like mine.. A tight fit on the spindle and a loose fit between the outer race/quill?

 

[tnoy66]

I know you jokingly mentioned glueing the bearings in, but you can get bearing grade loctite to do exactly that.

 

[chippy1970]

Yeah the outside diameter of my lower bearing isnt a tight fit in the quill tube. You can move the quill slightly side to side in the tube. I was thinking of using some type of packing or filler around the bearing to take up the play.

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[tnoy66]

If there's that much movement then the loctite probably won't work.
It's really just to hold the bearing in place if you can push them in and out by hand pressure.

Next idea, a feeler gauge wrapped around the bearing may take the play out, should be easy to trim to fit

 

[chippy1970]

Yeah that sounds a good idea. Its not a lot but enough to make drill bits wobble

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[Spindle]

Hi

It sounds like you both have the wrong sized bearings or worn quill and spindles. When you sourced the bearings did you accurately measure the diameters of the bearing seats on the quill and spindle?

Bearings designed to be a sliding fit can be retained with adhesive - see below for specific properties, you could 'get away' with 0.5mm gap filling, (Loctite 660), but I don't think I'd go there unless I couldn't get a closer matched set of bearings.

http://www.loctite.co.uk/loctite-4087.h ... 000028Z%7c

Finally - angular contact bearings need to be used in the correct orientation - probably teaching you to suck eggs here though.

Regards Mick

 

[chippy1970]

They're the right bearings its a worn tube I reckon. Funny thing is if you look at my fobco thread posted here a year or so ago. You will see when I took the quill out it was upside down. Someone in the past must have took the spindle out and then put it back in the wrong way round. I wonder if they did that to lose the play as the bearing seat on the top of the tube is tighter.

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[Dissolve]

Hi

It sounds like you both have the wrong sized bearings or worn quill and spindles. When you sourced the bearings did you accurately measure the diameters of the bearing seats on the quill and spindle?

Bearings designed to be a sliding fit can be retained with adhesive - see below for specific properties, you could 'get away' with 0.5mm gap filling, (Loctite 660), but I don't think I'd go there unless I couldn't get a closer matched set of bearings.

http://www.loctite.co.uk/loctite-4087.h ... 000028Z%7c

Finally - angular contact bearings need to be used in the correct orientation - probably teaching you to suck eggs here though.

Regards Mick

Don't be daft! I'm taking all the help I can get with this! The lower bearing on my spindle doesn't have enough gap to cause serious side to side play, but because it's loose enough to in and out of the quill tube it allows the bearings to utilize some their "diagonal" play which I noticed before installing them. As I mentioned previously, When the retaining ring is pushed on tight, before anything gets moved around the bearings are snug and there is no play in then.

I'm thinking the loctite would suffice in this issue, so I might just gibe that a go!

When you say they need to be the correct orientation, I took two pieces of advice, I made sure two were installed different ways round messing one facing up and one facing down.. I then matched the orientation to the way the original bearings went in.

Does anyone have a bit of advice on how to double check the orientation these should be before I decide to loctite?

Thanks guys!

 

[Spindle]

Hi

I don't have any documentation specific to this drill however the basis for angular contact is as follows:

Figure 1. shows the bearings assembled 'back to back' - this orientation accommodates loads in both axial directions, (load paths are indicated by the arrows).

Figure 2. shows the bearings arranged 'back to face' - this orientation accommodates axial load in only one direction.

As a drill spindle can experience loads axially in both directions I would expect the bearings to be orientated 'back to back' as per figure 1.

The above is a very basic explanation of angular contact and may not be fully representative for your drills, please confirm before you assemble.

Regards Mick

 

[chippy1970]

I've always suspected that my spindle isn't dead straight so that doesn't help.

Yeah Mick mine are back to back as they should be

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