The following, about overhauling the main (spindle) bearing, is from Sander Mommers on the Lenco Lovers forum at
http://www.lenco-lovers.com/forum/
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Main bearings.. here's how I do it.
First, see if the existing bushings can be re-used or not, this depends on how much play they have.
Put your fingers on top of the plateau, one hand on each side.
Push down gently alternately left and right, and see how much the plateau moves. If you can hear "clunk clunk" when you do this, the existing bushings are worn, and need replacing.
In my experience, it is very rare that the original bearing bushings are still good, as a matter of fact, I have replaced the bushings in all the bearings so far.
New bushings
Get some Oilite bronze bearing bushings from your local bearing shop. The size you need is 9 x 12, 14 mm long, and you need two of those. They should cost around $5. each. Soak the bushings in the oil you are going to use for a couple of days. (more on oil later)
Remove the screw on the side of the bearing, pull out the shaft. If the ball came with it, take it off and put it in a safe place. If not, turn the bearing upside down and tap on the table to dislodge it. Now, remove the circlip from the bottom with special circlip pliers. If you don't have those, small needle nose pliers will work too. If necessary, file or grind the tips down so that they fit inside the small holes in the circlip. Two small screwdrivers works too, but that is definitely more awkward.
Anyway.. get the blessed thing out somehow, by squeezing the ends of the circlip towards each other. Preferentially, don't do too much damage to the brass housing and the groove it sits in.
Remove the bottom plates, and measure how far "in" the bottom bearing sleeve sits with respect to the end of the brass housing. This should be 7 mm. You can now remove the old bushings. Find a suitable tool to push them out with. I use a long M6 Bolt. The head is just under 12 mm, and thus it fits inside the 12 mm bearing housing. Start by inserting the head of the bolt into the bottom of the housing. Holding the housing in your hand, gently tap on the bolt with a small hammer. The sleeve will start to move inwards. Keep going until it hits the other sleeve. Things will get a bit harder, because now you have to move two bushings, but they will come out this way. In hard cases, put the housing upside-down in an opened vise and hammer downward until both sleeves have fallen out..
Now, thoroughly clean the housing. I use a solvent (hexane, acetone) and an ultrasonic bath, or soak a kleenex in solvent and pull it through a few times. Make sure the housing is clean, and has no lint or other stuff in it.
Push in the new sleeves from each end, until they are flush with the housing. It is very important not to damage the sleeves in any way when you do this. If you are going to use a small hammer, put a small piece of wood between the hammer and the sleeve. Now, the bottom sleeve has to be tapped in some more. Put the thick bottom plate of the bearing on top of the sleeve, and push/hammer down. That was 2 mm. Now, find an M6 nut of 5 mm thick, put that on top and push/hammer until flush.
The sleeve is now exactly 7 mm down into the housing.
Polishing the spindle.
Put the spindle with the narrow end in a drill. apply jeweler's rouge to the rest, and squeeze the spindle in a cloth (old jeans are great) Now run the drill for a few seconds and voila. Repeat until the shaft is perfectly shiny, with no sign of scratches or anything. Clean the spindle with solvent (alcohol) to get rid of every last bit of jeweler's rouge.
Put a bit of oil on the haft, and verify that it slides and rotates freely in the bushings, without "binding" anywhere.
What kind of oil.....
There are many kinds of oil. For a spindle bearing you want something that is not too thin. I have used synthetic 5w40 motor oil. Some people say that synthetic is better, because it does not "cake" over time. Thin oil will feel like less friction if you hold the bearing in your hand, but that can be deceptive. You want a QUIET bearing, and that is not necessarily the same as frictionless. The idea is that there is always a layer of oil between the metals, to avoid "grinding" metal to metal. The idea of the Lenco bearing is that the weight is taken by the ball, and that there is very little sideways force on the bearing. This is only true when the plateau is LEVEL and perfectly balanced. You want an oil that is thick enough to keep a film between the metals even in a case where there is SOME sideways force on the bearing. I go for quiet, as tested with a stethoscope on the frame next to the plateau while spinning the plateau.
The silent oil wins.... I have used synthetic 5W40 motor oil, and some oils I had around at work: Edwards vacuum pump oil, Leybold and Balzers turbo-molecular pump oil. Van Den Hul sells an interesting oil for spindle bearings, with 1 micron little balls in it. I have ordered some, but I have not received it yet. It has become evident that each bearing has it's favorite.. One liked Balzers TL011, and another one was happier with the slightly thicker Leybold HE500. I'm guessing it depends on the clearance between shaft and bushings...
New bottom plate ?
Most people replace the old grey bottom plate with a hard steel disc of 12 mm diameter. The original plastic plate usually has a big dimple in it, caused by the ball. If you replace it with a metal plate, aim for something of the same thickness as the original, 0.6 mm. Others just turn the original plate upside down to get a "new" surface for the ball.
Putting it together...
New pressure plate or not, put the two bottom plates and the snap ring back in. I put a snug fitting plastic cap (without a hole, like the lenco ones have..) over the bottom of the bearing, to catch any oil spills. To dispense the oil, I use a 5 cc syringe with a thick needle (1.25 mm, I forgot to look at the Gage number) The point has been cut from the needle with a dremel tool and all burrs removed, because I don't want to scratch anything. I squirt about 2cc's of oil in the bottom of the bearing, drop the ball in, and push the spindle in. Some oil will ooze out of the bottom, and push the cap down somewhat. Now, I inject oil through the screw hole in the side, until that cavity is full of oil, and put the screw in. While holding down the spindle, I push the cap back up. Some oil will escape from the cap, wipe it off. We now have a permanently lubricated bearing with two oil reservoirs, one below each sleeve.
Time for the noise test.....
Not dead silent?? no panic. try a different oil or perhaps a tiny bit of dirt got in somehow.
For one particularly obnoxious bearing I had to resort to "wearing it in" by spinning the shaft in a drill at full speed for a minute or two, followed by a re-polishing of the shaft to get it silent.
At the end of all this you have a 100% silent bearing without any play. Better than new, I would say.
If it sounds like a lot of work.. it is, but it is well worth it.
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Sander Mommers
(Have Lenco - will travel)
