Spindle to hot to touch!!!

[slatronic]

Just got my manual IH in. I was breaking in the spindle and gears this morning and it got really hot. To hot to touch. I had it running for about an hour. Running it manual I probably wont run it constant for that long but if and when I CNC it, I will. My guess the preload on the bearings is to much. But how do you go about checking it and redoing it? Never done that. I'm sure I can handle if I can see a few pics and get a bit of explanation. Should I check the bearings for grease? Not sure what to do. I'm pretty sure it should get warm but not untouchable. I work with hot metal all day so I know its damn hot.

thx
slater

[arizonavideo]

Mine did that the first break in too. You should let it cool and then do it again but go through the speeds slowly.

With a new spindle you don't know for sure if the preload or bearing are correct so you need to watch it.

Were you breaking it in at low speed?

Move the gear sectors by hand to find a place where the machine will be in between gears and have no drag on the spindle. Turn the spindle by hand. It should turn 100% smooth with only the slightness drag. If you cant turn it by hand something is wrong.

It if feels OK then put the head in low gear and run it for 15 minuets or so watching the temp all the time. It should not get more than warm on low.

Do this for all the speeds.

I let mine run at 1000 RPM for a few hours after the first break in.

The first run at high speed the head will get much hotter than normal but it should break in and run cooler over time. You do need to make sure the spindle is not allowed to get over 160 deg or so for break in. If you are going by touch you should be able to touch it but not hold you hand on it for more than 5 seconds or so. Burning hot is not OK.

My head ran hot for a few weeks. The whole head and motor would get smoking hot after an hour of heavy milling. I changed out the oil in the head with Mobil 20W50 synthetic oil and the head now runs much cooler.

[slatronic]

I tried moving the gear selectors in between gears and it was difficult to turn spindle by hand. Its pretty stiff. Not smooth, kinda sticky feeling. But not impossible to turn.

I ran through all speeds for about 10 minutes each. Both forward and reverse. Started in low and ran all the way through high. After that it was super hot. Like I said I touch super hot metal all day so my hands are kinda desensitized to heat and there is no way I could hold my hand on it for 5 seconds.

thx
slater

[M250cnc]

Slater follow these links for running in bearings the amount of grease required ETC

The amount of grease required is staggering, in my case with a bearing of almost 3" diameter it requires 1/5 of a cubic centimetre. I can now run my spindle at 4000 Rpm only gets slightly warm now

http://www.skf.com/portal/skf/home/p...newlink=9_0_70

Phil

[Cruiser]

If, in neutral, it feels rough, then it needs to be dropped out and checked. Better safe than sorry ! Mine had cast iron fine in it and it vaporized the grease that didn't run out the bottom. Make sure it has a good spindle grease in it rather than plain bearing grease. the melting or running temp is differant. There are several threads with all the info you need here, just need to do a little searching. The spindle drops out so easy that there is no excuse for not doing it when in doubt.

[gda]

There are of course many reasons why a milling spindle will run at higher temperatures than it should.
Over many years I have found that the reason for most problems of this nature are poor alignment between shaft and bearings. In other words, when the spindle shaft is originally ground, diameters at either end of the shaft usually are not concentric with one another. This is generally caused by grinding the front end of the shaft to the correct dimensions for the main bearings, then breaking the set-up and taking the shaft off the centers, turning it around, fitting it back on centers and grinding the rear end of the shaft for the usually single bearing at the rear. This is of course is not a recommended practice, the correct way being to grind both ends of the shaft in the same setup, assuring concentricity.
If this is suspected, it is easy enough to prove one way or another. The shaft has to be removed anyway, in replacing bearings, so set up the shaft on centers in an accurate inspection instrument, and run a dial indicator on both ground portions of the shaft in the same set-up. If there is run-out more than the bearings are guaranteed for,(spindle bearings usually allow .0002-.0003" run-out) you would have re-course against the manufacturer of the spindle.
If the spindle checks out ok, the problem may be at the housing, or where the outer diameter of the bearing is fit to. If the housing is not accurately ground, this is where your problem may be.
Generally speaking, designing and building a precision spindle is a science unto itself, and the reason why top quality spindles sell for many thousands of dollars. Taking all of this into consideration, all the consumer can do, save being involved with litigation against the machine manufacturers, is to use good quality bearings, and the recommended lubricant for those bearings. Another thing that can be done is to make a simple antifreeze jacket to house a few inches of the front-end of the spindle, with a feed and return line, coming from a small submersible pump to constantly "liquid cool" a rather poorly designed or built spindle.
If you need to see what the Antifreeze Jacket looks like, feel free to e-mail me and I will be more than happy to send you a 3-D model, in the jpg format, of what you can easily build for your spindle.
gda

[slatronic]

I did some research this weekend on the forum and I think I have it mostly figured out. I tried to drop the spindle out this morning. Its not dropping out though. I removed the retainer from the bottom of the quill and I can see the bottom bearing. It has some grease on it. I also removed the two set screws from the left side of the head. I have two pics showing, one showing the retainers I removed and one showing where I removed the set screws from next to the quill lock. I read a post by Cruiser that said I just need to remove the two set screws on the left and it should fall right out. It didn't. Do I need to tap the top of the spindle with a rubber mallet? Just don't want to mess anything up. It's scary tearing apart my brand new machine but if its gonna make it better and last longer its worth it.

I figure while I'm at it I might as well replace the bearings with some AC bearings. What I figured out reading was that I need 7206B and 7207B bearings. I want to get the spindle out and measure before I order though. I was also thinking about using Kluber nbu15 spindle grease. Seems like the stuff to go with. Any suggestions would be greatly appreciated.

Thanks for all the help so far and any help in the future.

slater

[Cruiser]

The feed worm has to come off too ! first take off the return spring housing (in pic) then pull the worm out the other side, insure that the pinch lock is loosened, then drop spindle.

Also, take a piece of boot toung leather and make a shield the same size as the bottom threaded shield, make it to fit snug to spindle and to the thread and when putting it all together put it in then run the shield nut up to it snug. This will keep any grease from being lost from bottom bearing and from coolant or swarf from getting inside. You still need to look at the top bearing once in a while and insure it is keeping its grease visable. This can be done by chisleing off the boss on top of box and bearing is visable and grease can be put on top to make up for any losses. It may not be kosher but it works.

[gda]

Slater,
With regards to how your particular spindle and quill drop from the housing, I would need to see a print before I could answer. It is in your best interest to have a print on hand.
Generally speaking, the draw bar threaded into the back of a collet will hold everything together,in the vertical plane; just remove the collet and the drawbar should slide out from the top. If the drawbar is holding a collet-holder, rather than a collet, then of course you would have to remove the collet, then tap the top of the draw-bar, until the seal between the taper in the spindle and the taper of the collet holder breaks, and you should be clear of that problem, anyway.
Another thing that could be holding the spindle in is the connection between the feed worm and crank handle. This of course would have to be dissasembled in order for your quill to slide free in the housing.
With regards to lubrication, you are better off following the recommendations of the bearing manufacturer.
On a personal level, for a milling spindle, I much prefer to use 60-90 weight non detergent oil. If there are no oil-holes in the side of the quill, I would put the appropriate ones in and hand-crank the spindle down every 4 or 5 days until the holes are revealed, and put a few drops in. The top bearing, because it would be difficult to access to oil, I would lubricate well with 90 weight way-lube, then pack in a fine grade of grease.
I hope this helps.
gda

[Cruiser]

gda, Draw bar don't hold nuthin but the tool holder and spindle will drop out with it, altho a bit too long with it in.
Oil in this spindle is a nogo ! it will run out just as fast as you pour it in !
The lube recommended is a good spindle grease, not automotive ! A grease that will hold while in the vertical plane is needed, hence, higher melt point and more vehicle to hold its body.
When ya don't have a clue it is best to not prove it !

[slatronic]

Cruiser,

thanks man, that did it.

So i have the quill and spindle dropped out. Now I need to remove the spindle from quill housing. Do I just remove spanner nut at top and pull spindle down from quill? (PIC 1).

I also have a few other pics included. Doesnt look like there is much grease actually in bearings. There's some splattered on edges but doesnt look like there is much in the bearings. Never really done this so not sure what looks right. I also included a pic of the worm feed gear with a patch of grease that has some paint on it. If this is any indication of the rest of the machine I sure it's gonna be worth my time to completely tear it down and clean it.



thx

slater

if anybody wants me to take pics while I have it torn down let me know. I like taking pics cause I love looking at others pics myself. Im a very visual person. I will be gone this weekend. Going to the MASTERS!!!!!!

[slatronic]

Now that I have it out, I tried to spin the spindle while it was still in the quill housing still and its stiff. It doesnt spin how I would imagine bearings should spin. Sticky to stiff, not free to turn. I assume it shouldn't be loose and jiggly but this feels to tight.