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Centec 2A Rebuild

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mm289:
So after taking the Richard King scraping course a few weeks back I intend to continue the refurbishment of the Centec partly to get it running nice, but also partly as practice before attempting to rebuild the Beaver VBRP I have in pieces for the last 2 years :D

Just as  bit of history, I bought the Centec locally a few years back, it was in decent condition but as I have started to learn how to use it I have found it has a lot of slop in the table especially and if you try to take this out with the gibs it binds at each end of travel.

So, as it is a sensible size it also seemed a fair contender for a "project"  :thumbup:

Below are a few pics of what it looked like when I picked it up and a couple with it in its new home.

(vtsteam edit: reduced all photos from 3000 pixels wide to 800)

mm289:
Just as a bit of history the first job I did was to replace the tapered bearings on the shaft in the vertical head. There was a fair bit of run out and, although I am still not convinced it is good as it should be, it is better than it was.

There is very little info on the web about the inner workings of these machines that I can find apart from a Yahoo Group, but navigating the Yahoo UI is soooooo painful I tend not to frequent that gathering.

So just for posterity sake, a brief overview of how to overhaul the head is as follows (from what I can remember :bugeye:)

The vertical head mounts where the horizontal mill overarm normally goes and is driven by belt of the horizontal arbour pulley. It rotates to allow milling at angles and has a MT2 taper as per pic 1 & 2 below.

The shaft sits in two taper roller bearings at the top and bottom and is driven from a bezel gear off the pulley shaft. The bottom of the head has a plate held in by 3 screws, remove this and you expose the lower bearing. Pic 3

The shaft also has a preload arrangement for the bevel gear pic 4. Having removed the head from its mounting you can loosen this off and then I used a hydraulic press to push the shaft downwards and out of the top bearing. Removing the bearings and cups was then just a case of using the press and various bearing pullers I had in the auto shop.

With everything stripped I could then look at the bearings involved.

(vtsteam edit: reduced oversize photos)

awemawson:
Looking good Paul  :thumbup:

Do you think you can possibly edit those pictures down to 800 x 600 max size to reduced storage capacity. They will still have more than enough detail

mm289:
Will try to do that Andrew, don't suppose there is a quick way other than editing every individual picture?

Back to Centec, the pic below gives the specs of the bearings that came out - useful to know as I couldn't find this info anywhere on the web.

Ordered up replacements, but I know understand there may be different "grades" of bearing with high precision bearings needed for these sort of applications ?  :bang:

Anyone able to tell from these bearings what standard they are? Couldn't see any other options when I bought the replacements.

Cheers,

Paul.

mm289:
So prior to starting to scrape stuff I looked up Connelly and a few posts on here. First job was to check the true ness of a datum point, namely the horizontal arbour, so you can then use this to set the knee flat to the shaft.

I have included the relevant pages as attachments below but basically you are checking for run out on the spindle end face, what I would call "end float" on the spindle (in/out movement) and then run out at various projections from the spindle.

The bad news was that although my spindle run out with "no load" was only about 1 thou, when any side load was applied it was up to 7 thou and the end float when applying load (pushing/pulling the pulley) was 10 thou.

This was with the bearing pre load way higher than I would like so I think the bearings are knackered  :Doh:

So before I can start scraping in the ways I need to get some new bearings ordered. Pulled the old ones out which are Timken and interestingly marked as "Precision 5" - so I guess I have answered my own question about precision bearings being used in these machines.

I now need to find a supplier of precision bearings  :doh:

The project continues (slowly) :)

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