VN How To Proceed With #12 Head Cleaning?

... I added a few more pictures of the front and back of the spindle for you to look at, and I have a few questions...

Are there any gaskets at the front of the spindle, or is the grease and labyrinth rings supposed to hold the oil in? ...
You have the 1944 version of the cutter-head. There's a seal behind the front bearing to keep oil from getting into the bearing while the head is vertical. The labyrinth seal holds grease in, but if too much grease is pumped into the bearing it will sling it out the front. There's no rear seals. Apparently the shape of the casting is sufficient to keep oil from getting into to the rear bearing and vise versa. Again, excess grease will escape around the spindle.

Here's the parts diagram that goes with your cutter-head.
12Prts13 (RLT 11-7-44).jpg

Part 12-754 is held on by a set screw. Remove it so that you can flush the bearings out. Stand the head on end and pour kerosene into the bearing, rotating the spindle until your satisfied that the old grease is gone. Make sure you remove the Zerk fitting and flush that passage as well.

You should not have taken the spindle pre-load nut (9731) off. You need to set the bearing preload before you put it back into service. I think I have a post somewhere about how to do that.

I noticed in other photos of the #12 head that the clamping bolts holding the bevel gear in place had safety wire running through the bolt heads which is absent on my unit. My bolts are drilled for such a wire. I think it would be prudent for me to check the torque on these bolts and add a wire through them. Do you agree?
I don't know about checking torque, as such, but it can't hurt to make sure the bolts are snug and then install a new stainless steel safety wire.

Since the wire has been removed, someone may have messed with the ring gear since it left the factory. It might be a good idea to put high-spot compound on the pinion gear and see if its making correct contact with the ring gear before you wire it up. While I'm familiar with to concept, the details of exactly how to evaluate the marks on the ring gear and adjust it are beyond my expertise.

And finally... how much grease should I pump into the bearings. After a fair amount of reading, I decided on Mobile Polyrex EM. I was hoping to push out any remaining old grease with the new grease and then wipe away the excess before putting the cover back on and filling the midsection. I've already used Mobile DTE Heavy Medium in the ram gearbox and it seems to run pretty quietly. Any advice would be appreciated.

Jeff
I use Mobilith SHC 100 grease; I don't know about the Polyrex, but it sounds like it's intended for permanently sealed bearings.

With the end caps off, Pump grease in via the Zerk fitting while turning the spindle. The bearing shouldn't be tightly packed; I think 60% fill is what's usually called for. Keep adding grease until you're getting new, clean grease out everywhere. When the bearings look well lubricated, wipe off any excess that's coming out the ends of the rollers and button her up; any excess grease will have space to escape into the cap. With modern grease there's no need to constantly grease the bearings. Once a year or so, take the end caps off, add grease, wipe off the excess, etc, and you're good for another year.

Cal
 
Cal:

Thanks again for your time and expertise... just what I needed.

I think I'm OK with the preload nut. When I removed it the "stiffness" of rotating the spindle did not change at all, so I'm assuming that the upper bearing is frozen to the spindle... at least enough to hold it together on the bench. After thoroughly cleaning the bearing I put the nut back on and snugged it back to its original position. I had marked the tab on the lockwasher and the slot on the nut when I took it apart so I was able to return it to its original position. After re-installing there was again no change in the "feel" of the spindle and the nut was as tight as when I removed it.

After adding the new grease the spindle did feel smoother and a little easier to spin.

One last question for now.... The collet key in the nose of my spindle (part number E-37 1/2 on your drawing) is worn down and somewhat damaged and I'd like to fabricate a new one. Does this part press out by pushing on the round pin from the outside of the spindle? And do you know where I can find dimensions of a clean part? I can run with what I have, but it would be nice to fix this last little item.

...Jeff
 
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If your bearings were noticeably stiff they are probably shot. The spindle, when the cutter-head is off the ram, should turn very easily.

Simply returning the spindle nut to the original position IS NOT sufficient to make sure the preload is correct. A new set of Class 3 bearings will run you about $500, so don't mess around taking shortcuts with the spindle preload! First of all, the last guy to tighten it may not have done it right. Second, tapered roller bearings must have some end play. The endplay should be between 0.0005 and 0.0008" for best bearing life. I suppose that it's possible that the bearing preload was set too tight and that rear cone's cage has siezed up on the spindle so that releasing the nut did not allow the bearing to relax. In any case, you need to check the endplay.

Ring and pinion backlash should be 0.004-006".

Yes, use a punch against the pin to remove the key. You can buy the E-37½ key from Repair Parts International; they were $30 a piece the last time I checked. You can make one out of a #608 Woodruff key or a 3/16"-thick chunk of 1/2" diameter stock. If you go the Woodruff key route, you need to mill off about 0.225". This drawing shows the collet and key. The key is in red. The outline of a #608 Woodruff key is in magneta:

VN C collet key - rev1.png

Use a transfer punch to mark the location of the tit (which is what the pin sticking out of a key is called) or use your existing key to locate it. Most people don't bother with the tit.

Cal
 
Cal:

I'm sure that I do not have any end play in the spindle bearings.... even with the nut removed from the spindle and all the grease cleaned out it takes a moderate amount of force to hand-turn the spindle. So now I'm left with the dilemma of damaging the spindle bearings over time with too much preload or damaging them all in one day trying to loosen them up!

From my experience pressing out wheel bearings I know that I can't apply pressure on the upper bearing rollers and races by pushing down on the top of the spindle. That will destroy the upper bearing for sure. I just don't know how I'm going to get it loose so that I can reset the preload. I can try freezing the spindle and warming the bearing, but I've tried that trick before to separate pressed together parts without much success. I'm open to suggestions. Maybe a longer soak in a good solvent would help.

Jeff
 
Hi Jeff,

I think that you're better off heating the head up and cooling the spindle, so that it contracts. If you cool the head and heat the bearing race it's trying to expand against the mass of the casting, etc.

I guess I would try warming the cutter-head up, maybe set it out in the sun for several hours, then stand it upright and load crushed ice into the spindle. Line the spindle with a small garbage bag to protect it from the moisture. Then try a light press. Do some research to find out what the maximum axial load the bearing can tolerate and don't exceed that pressure. If that doesn't work, maybe heat the head up to 150 in an oven and try dry ice.

Might look at this re axial loading:
http://www.eng-tips.com/viewthread.cfm?qid=325338

CRC makes a product called "Freeze Off" that might be worth trying.

Cal
 
Cal:

I've got access to ovens and liquid Nitrogen at work. I've used LN2 to shrink parts and fit together by hand, what would have been an impossible interference fit at room temperature. But getting a temperature difference between the inner and outer parts is simple for assembly... not so for disassembly. When parts are already locked together with an interference fit you can't get a good temperature difference between the parts anymore and the temperature trick just doesn't work.

The bearing inner and the spindle are not an interference fit however... just a gummed-up close fit. If the gunk in between is a poor thermal conductor then cooling the spindle may help. I'll ponder this approach a bit more and try figuring out the coefficients of thermal expansion for the various parts. I have thermally cracked warm cast iron with careless uneven application of LN2, so some caution is warranted.

I will check out the load rating of the upper roller bearing, but I am very leery of loading the bearing to even a small fraction of the rated axial load. Especially while the bearing is not rolling.

And now I'm wondering.... If the preload was not set correctly, and the safety wire was missing from the bevel gear bolts... could the bevel gear have been messed with as well? I was hoping to patch up the machine, change the fluids, and use it for a few quick jobs, but now I feel like the right thing to do for the machine's sake is take the head completely apart, find an expert to teach me how to shim spiral bevel gears and properly preload the bearings, and do a complete refurbishment of the head. I'm sure I'd learn a lot and have fun doing it as well. Preserving/restoring the VN for another generation trumps getting it back on-line quickly... at least that's how I feel about it.

Jeff
 
If I were you I'd go ahead and take it apart.

If you press the bearing off, worst case is that you trash the rear cone; the cup should be fine. The rear cone is about $125 in class 3. The next class is class 2 (they have an odd class numbering system) and those go for about $12. Class 3 has a 0.0003" runout spec; class 2 is 0.0015". You might try a class 2 cone on the rear, since it's away from the spindle nose and runout would be less of a problem than it would be for the front bearing.

Try soaking the thing in a 50/50 mixture of transmission fluid and acetone; it's about as good a penetrant as anything.

Cal
 
So I've done a lot of reading about shimming bevel gears. Condensing and simplifying the info greatly.... there are four things to get right... 1) both shafts in the same plane (so they intersect) 2) Both shafts intersecting at an exact 90 degree angle, 3) axial position of the pinion (for contact patch) and 4) axial position of the gear (for backlash). Of these four important things the first two are built into the geometry of the machine and are non-adjustable. That leaves the position of the pinion gear (the small one coming out of the ram) which I assume can be shimmed from behind to set its position, and the gear in the head which is adjustable with the threaded collar and locking bolts.

As the pinion gets smaller and the gear gets larger, the pinion becomes more important for adjusting the contact patch and the gear becomes more important for adjusting backlash.

Apparently really high accuracy bevel gears are made in matched sets with witness marks on the edges of the each gear showing which teeth to mesh together, and individual mounting dimensions for each gear that provide optimum contact. I have not checked my bevel gears for any such marks and scribed dimensions but I'll try to take a look later today.

Jeff
 
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Hi Jeff,

I think that the only adjustment that you have is the axial position of the ring gear. It looks like the location of the shaft is controlled by the plate with the 4 SHCSs, behind the pinion. There may be shims behind it, but they don't show up on the parts diagram. In any case, I wouldn't mess with the gearbox shaft and pinion gear until I was convinced that it had to be adjusted.

Any luck getting the rear bearing off?

Cal
 
Hi Cal:

I spent this week moving my daughter from Massachusetts to New Jersey for her first job, so not any time to work on the VN head. I'll post here as soon as I have some news.

Jeff
 
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