The Shop > Tools
The Sajo mill is here
Trion:
Been a bit lazy about taking pictures as progress goes along, but here goes.
I got the gear of the shaft, after having made these super fancy brackets ::)
Rough illustration of the assembly
After having disassembled the whole lot, I wrote up all the bearing numbers and went shopping
The spindle main bearing is a tapered roller bearing.
Though the foil is in on this picture, there is actually a notable height difference between the new and the old bearing..
Before starting the assembly I figured I should make a tightening tool for the spindle, as previous tightening attempts seem to have set its marks
Some M6 screws and flat iron became this
A bit of grinding and welding later, the finished tool has emerged :dremel:
Then I began with the assembly. I started off with the ingoing shaft of the 90 degree transmission. All parts cleaned and lined up for assembly :)
I made a relief cut in the old inner ring of the bearing and used this to punch the new bearing in place.
Afterwards I could pull the cut bearing ring of by simple hand force
I also hit in a new bearing in the housing. These bearings are angular contact ball bearings, and are positioned such that by tightening the screw on the end of the shaft, bearing play is eliminated
Then i soaked the bearings in grease
Before I assembled the whole lot
Then I fitted the washer and the key
And fitted the gear, with some more grease being applied to the new bearings
Next up was the outgoing shaft of the 90 degree gearbox
Bearings mounted in the same manner
I chose to preheat the gear to ease the installation. Heated it to a surface temperature of about 70 degrees celsius
It slid much nicer onto the shaft
But the retaining nut had some ugly marks on it
So I chucked it in the lathe to skim of the marks
I didn't bother about the marks that didn't protrude out of the surface, as I wanted to keep as much of the threads as possible
After having deburred the edges, I mounted the nut and locking ring and tightened
Finally the main spindle assembly. As you can see the main bearing is a big tapered roller bearing. It is tightened towards a flat ball bearing, while sideways movement also is supported by the top bearing which is a flat roller bearing without any locating edges to only support the sideways motion of the shaft.
What concerns me about this setup is the location of the gear (previously known as the bad gear). The axial movement of the gear is only limited by it's counterpart. So when assembling the unit, the shaft and gear coming in from the side has to be mounted, then this gear has to be pressed onto the main shaft until it contacts the gear coming in from the side. It will get clearer when I assemble the unit again.
To give you an idea, the total height of the gear and the bearing is 51,98mm. If the gear is pressed on until it reaches the edge on the shaft, the top of the bearing will be below the lowest threads, making the adjustment nut useless.
Judging by the marks, this is about the way it was mounted before I disassembled the head. Like I said, the only thing limiting the gear from traveling further down is the othe gear coming in from the side. To add to this, the gear sitting on the main shaft is fitted with such a press fit that the only way to move it along the shaft is by using a hammer! Again making the tightening nut useless :bang:
I started mounting the main bearing, but ran out of grease so stopped the assembly here
In the meanwhile, i started stripping the heads for paint
The old badge was removed and is probably not going to be refitted again
I also started sanding down the housing, but the paint is thick and requires a lot of sanding to become even. The dust also smelled quite toxic, so I will need a good mask before I make further progress.
dsquire:
Trion
Thanks for the update on the repair. You certainly should have a very fine mill when you are finished with the repair and cleanup that you have undertaken. It seems like a lot of work now but it will be worth it in the future. :D :D
Cheers :beer:
Don
Brass_Machine:
Trion...
Wow. What can I say, but this is a very good post to read. Lots of pictures! Ingenious use of shop made tools! Did I say lots of pictures? Clear ones at that. I am sure you will get the Sajo up and running again. Probably even better than it has in a long time!
Eric
djc:
I notice that you are using grease in the bearings during assembly. Is this mentioned in the manual? There is an external nipple for periodic lubrication. What are you supposed to pump in there? What happens to it when it gets inside the head? I'm not saying you are wrong, but it may be that the bearings should be _oiled_ not greased.
With respect to the mitre gears, one or the other needs to be movable to set the backlash and the depth of mesh. You might have to do a trial assembly without the mitre gear and set the bearings. Measure from the underside of the bearing to the shoulder (or the top of the shaft). Disassemble and fit the mitre gear with a spacer up to the preload nut. Set the position of the gear (using cigarette paper or something between the teeth as a spacer). You might have to make a very temporary fixture to keep the top of the spindle central, or do it all with the head inverted so it hangs from what is normally the bottom bearing. Measure its position relative to the top of the shaft.
Make sure there is no clash between top of gear and bottom of bearing, remembering that you might need to readjust the bearings after running in. If there is, you might have to grind a little off the top of the gear. Much better if there is a gap that can be shimmed as it's easy to remove a shim.
In operation, the forces will tend to push the gear nearer the bearing (loosen the mesh), hence I don't think it would harm if you lapped out the gear so that it is a tight but sliding fit on the shaft (have you checked that the gear itself WITHOUT THE KEY is too tight on the shaft as it is possible that it is binding on the key?).
Davo J:
Hi,
I have been watching this thread from the beginning, and for someone new to milling machines you sure have taken to it like a fish to water.
Good onya for getting in and fixing it up, it will be a dream to use with all it's rigidness when you have finished.
Dave
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