[urbanimports02]

Ok, so I have been running my 200 for 2 years now, and have had most of the noted issues that others have had no doubt, but I have always had good results and good surface finishes. Lately I have been getting more and more chatter. I have checked and adjusted the gibs and have put a dial indicator on everything. Scary as things do move on this thing, but everything bounces right back to zero. I did notice .002 of runout measured on several different tools and holders as well as the spindle nose itself, all in the same spot relative to the spindle. That seems like a lot. How could this grow assuming it has been fine for 2 years? Also when I push on the spindle from different angles I can move it .004 with maybe 25 lbs of force, but it always goes back to zero, so clearly flex, not movement. Thats as measured at both the spindle itself, and the mill head right above it. For the first time ever, I have had to throw away parts due to severe chatter marks, and it's a part and program I have run hundreds of times. Any thoughts?

[ihavenofish]

sounds like the bearings are worn or loose. youll have to pull the whole metal cover off the spindle head to get access to tighten things up. this is something i have been meaning to do on my machine for a little while.

[urbanimports02]

i was not aware that you could tighten anything... thought the spindle used ball bearings. wouldn't I have to pull the spindle and replace the bearings? i am guessing it would be advised to go for better quality bearings while i am at it. is it normal for the spindle bearings to go out in less then 2 years? i do run the mill quite a bit, and i do run heavy cuts for this size of mill, so i guess its possible. the bearings have never made noise, and still feel smooth as of now. what would cause the runout if the bearings are bad? i understand play, but the runout is in the same spot as i turn it, and the play i measure with the dial indicator seems to be the head itself flexing, not the spindle moving relative to the bearings, so i do not measure any bearing play so to speak.

[urbanimports02]

to pull the spindle, i first pull covers, then pull motor, then top plate, belt, pulley, then the 3 bolts out of the bottom, and pull the spindle out the bottom correct? or does the motor and top plate come off together because of the belt and pulley, or just loosen belt and top plate has a large enough hole for the pulley to come through? does anyone have an exploded view diagram? maybe smithy 1240? i remember seeing this floating around somewhere.

[Frogblender]

i was not aware that you could tighten anything... thought the spindle used ball bearings. wouldn't I have to pull the spindle and replace the bearings? i am guessing it would be advised to go for better quality bearings while i am at it. is it normal for the spindle bearings to go out in less then 2 years? i do run the mill quite a bit, and i do run heavy cuts for this size of mill, so i guess its possible. the bearings have never made noise, and still feel smooth as of now. what would cause the runout if the bearings are bad? i understand play, but the runout is in the same spot as i turn it, and the play i measure with the dial indicator seems to be the head itself flexing, not the spindle moving relative to the bearings, so i do not measure any bearing play so to speak.

The bottom bearings are usually roller. At the top of your spindle will be the preload nut - this is what can become loose - and is probably the source of your problems if runout suddenly became worse. I've had two spindles, and both nuts loosened by themselves.

On the NM135 you remove the spindle assembly from the mill head, tighten the nut (there are others threads discussing how much to tighten), and re-install the spindle - NM200 is probably similar. This does not require you to disassemble the spindle itself.

If you want to make a project for yourself you can disassemble the spindle, and inspect/replace/regrease/repack the bearings.

[urbanimports02]

according to the smithy manual, the lower 2 bearings are ball bearings separated by an inner and outer sleeve, then another ball bearing above that, followed by what they call 2 radial ball bearings above that, one below the pulley, and one above the pulley. so are these adjustable by tightening preload? does anyone with direct knowledge of the nm200 have any insight? i am going to start tearing it apart right now, just not super confident this is going to fix my problem, and not sure where the runout comes from in this case. it is consistently in the same spot as you spin the spindle. i did rig up my dial indicator on the mill head to the spindle to see if i could move the spindle side to side, and i could move it .001-.002 either direction with a good bit of force, problem is i never checked this when it was good, so i have nothing to compare to.

[urbanimports02]

got it all apart, except the spindle outer sleeve is stuck in the mill head. i am headed over to a friends shop that has a large press to press it out of the head. the spindle uses a pair of angular contact ball bearings at the bottom, and a single angular contact at the top of the cartridge , and then a larger sealed ball bearing below the pulley and another above it. these feel fine, but the lower pair of angular contact bearings feel loose and have a few catchy spots. there was not much grease in these bearings, and kind of curious why not use a sealed bearing, or atleast pack the snot out of these things with grease? they used what looks like cheap white grease. any alternatives? maybe red synthetic grease? headed to the bearing shop to get new ones....

[DareBee]

Couple of things.

1) Your run-out sounds like it is a worn out spindle taper. Grind or replace the spindle.
2) Spindle bearings (usually) are carefully selected to do their job. Packing the snot out of them will fry them extremely fast, as will using the wrong type/grade of grease.

[urbanimports02]

ya, i remembered that basic bearing theory after i posted that. i once had a conversation with a bearing expert when discussing race car wheel bearings and how a good quality bearing with a light dose of quality grease was way better then a low quality bearing heavily packed. these bearings have a half a$$ed p5 stamped on the outside of the outer race, when they should be stamped on the edge of the race, and its more of an ink type etching that looks like an after thought. the true stamping numbers match up to what all of my research shows to be low quality c3/abec3 bearings. so best case they were p5/abec5. the lower bearings were certainly worn out and loose and catchy. the balls feel flat spotted. i ordered a high quality matched set of lower bearings in abec7/9 (p4/p2) quality ($pendy buggers) and a single abec7 upper. i will put it all back together and recheck runout, and will keep the worn spindle in mind. i have heard of doing the spindle regrind on machine, what is the procedure for that? back on grease, what should i use? they had what looks like white lithium grease, and it was all slung out and balls looked dry.

[urbanimports02]

i am also considering upping the spindle speed while i am in there by going to a 1.5:1 pulley ratio. right now it uses 2 25 tooth pulleys, so going to a 30 on the motor and 20 on the spindle should do the trick. any idea where to get the new pulleys? all my searching last night found lots of different sources, but none that speced out the same as the motor pulley. most went up to 1" wide belt and stopped. also 25 tooth appears to be mostly metric pulleys, all of the 3/8" pitch pulleys i found go from 22-24-26 tooth. the belt is stamped 187L which is the markings of a 50 tooth 3/8" pitch belt, and both the belt and the pulleys measure 3/8", but the width of the belt is odd as well. actually looks like they took a 1.5" or 2" belt and cut it down. anyway, on the new pulleys, would i be best off specing out custom pulleys? if so, any sources for doing so? i thought this would be more cut and dry....

[ihavenofish]

ya, i remembered that basic bearing theory after i posted that. i once had a conversation with a bearing expert when discussing race car wheel bearings and how a good quality bearing with a light dose of quality grease was way better then a low quality bearing heavily packed. these bearings have a half a$$ed p5 stamped on the outside of the outer race, when they should be stamped on the edge of the race, and its more of an ink type etching that looks like an after thought. the true stamping numbers match up to what all of my research shows to be low quality c3/abec3 bearings. so best case they were p5/abec5. the lower bearings were certainly worn out and loose and catchy. the balls feel flat spotted. i ordered a high quality matched set of lower bearings in abec7/9 (p4/p2) quality ($pendy buggers) and a single abec7 upper. i will put it all back together and recheck runout, and will keep the worn spindle in mind. i have heard of doing the spindle regrind on machine, what is the procedure for that? back on grease, what should i use? they had what looks like white lithium grease, and it was all slung out and balls looked dry.

c3 is a clearance rating. p5 is the precision. p5 is MORE than good enough for a low speed milling spindle.

brand name p4 bearings for this machine will cost $400+ and its difficult to say if they are worthwhile, because the inherent runout in the spindle shaft and spindle taper and especially the collet would negate any gains.

basically, your first exercise should not be changing anything, only tightening and checking that nothing is loose or broken.

[urbanimports02]

i already ordered the bearings, and i feel much better spending a little more for better quality, as i really do not think these bearings were even p5, and they failed pretty early in my opinion. i will re-address runout once it is all re-assembled, but these bearings were shot, and there is no adjustment for these bearings. they are ball bearings separated by an inner and outer spacer and then a nut tightens down on them followed by a jam nut (tightens, not adjusts tensions/preload). you can adjust tension on the upper bearing, but that would not have solved my problem as there was in fact slop in the lower bearings along with what looks and feels like flat spots on the balls themselves. on top of that, there was tiny metal shavings in the bearings which is not a good sign. i will reassemble with new bearings, checking and adjusting preload as necessary, and re-test once assembled. i will then look into regrinding the spindle if necessary. by using higher quality bearings i am killing a few birds with one stone, 1)no excuses for slop/run out 2)new bearings 3)increased ability/comfort increasing rpm 4)longevity 5)resale value. when i sell this mill, someone will be getting a novakon with upgrades, and headaches already addressed.