Spindle bearing chatter

[befunovo]

OK, found a new one they other day. Making a countr bored hole. I had a 3/8" hole drilled through some 1/2" CRS plate. I was plunge cutting with a 3/4" end mill to counter bore it about 1/4" deep. Locking the table and head in and using the spindle to plunge with was causing it to chatter.

Locked the quill into place and cut lowering the head and it cut SMOOOTH!!!

Seems looser than it used to. anyone know how to check the bearings on the spindle and quill? Are they adjustable for preload? Anyone else with this problem. Not a ton of use on the mill, but has seen some use over the last three years.

Been to busy to tear into it right now. Probably will in January, but figured I would ask here first.

Thanks all.

Edit.
OK, found the 7045FG manual. Looks like the spindle has two taper ball bearings on it, a 7206E and 7208D. Anyone adjust these? Under trouble shooting and spindle shake it says "(1) The gap of spindle taper is too wide---Adjust the gap in proper or replace bearing with new one.

Locking the quill made it better, so not sure if it would be related to the spindle bearings. What does the quill ride in? Going to have to go look at the mill again.

Anyone adjust this?


Brian

[Cruiser]

You didn't say what machine other than 7045 fg, I have the IH mill and my stock spindle bearings went dry and destructed. I found that it took 1/2 hr to pull spindle and get it apart, washed and inspected. My bearings could have been reused but only for a short time as they were definately damaged. I went to the local McGuire bearing house and ordered up the less expensive of the "Angular contact" bearings > 7206 bgc3 & 7207 bgc3 for my spindle. I AM NOT SAYING THESE WILL FIT YOUR MACHINE ! At the same time I purchased some quality spindle grease too, this grease is less likely to melt off and sink to bottom of quil but eventually it will, I believe any grease will, so it would be recomended to drop spindle from time to time and grease it even if you only needle inject the top bearing. I also cut some leather from an old boot tongue and made a barrier that goes under between bottom bearing and on top of the threaded shield which can be seen under quil, this quite effectively prevents the grease from wicking out of bottom of quil and being lost. As for pre-load on these new bearings, info is basic and not specific to the spindle setup. I started with zero and tightened nut to first lock position, but this proved too loose, tested by running spindle and warming it then stopping spindle and grab tool and give it a shake ! if it wiggles then it is too loose ! I ended up taking two more positions on lock ring before the spindle would feel firm after warmup ! I now have been running it for a while and it remains quiet but i also give it a warm up time before going to full rpm from cold ! Starting at 1200 rpm and let it idle for a time. You will not necessarily benifit from going AC bearings, You will benifit from new bearings and keeping them greased by checking them from time to time. As easy as it is pulling quil i'd advise it, you don't really have to take spindle apart to grease it, just get access to top bearing and inject. bottom can be done by spinning off the threaded shield and injecting, but top will destruct first so get it greased. When i washed mine down for bearing change i used a clean pan and checked the fine in pan when i was done. I found lots of very fine cast iron left behind from the machining, that made it's way through factory assembly. This circulating with the grease caused enough heat to vaporize what little grease there was till it was dry then bearings howld and screamed like crazy. It was not mistakeable ! If your spindle is telling you it is in pain then fix it rite away !

[befunovo]

My mill was one of the first to come over I guess, or the first design before they changed the head attachment. 7045FG was what is on the front of the operation manual, didn't even think about that being generic. Bought it 3 years ago this month.

I will look into the bearings. Spindle seems fine, seems more like it is a quil problem. Doesn't seem to be making much noise, but I will check them.

You mention warming up the mill at 1200 rpm. I rarely spin it that fast. Generally I use the 330 or 480 range, sometimes the 910. Have only usd the 1600 a few times.

[Cruiser]

I guess i need to clarify then, My spindle runs on a pulley system and no gears in box ! I run at 1200 which is near 20 hrz on vfd which is the lower end of a start speed. Ah, If your were declaring the effect of plunging an end mill into steel then hearing the quill buck in the bore of the gear box then i'd say you will have to modify your proceedure to minimize this by drilling a hole. My quill has some play within the bore of gear box too and there is nothing short of dissassembling the quill / spindle and having the outside of quill plated but this is a lot of expense and may require grinding and refitment etc.
You may still have some slop in the spindle bearings that you are hearing and this could be taken up with the nut and since your machine is old enough to be in need of maintanance then > > > > refer to above ! At anyrate I guess I have out spouted my yap enough !

[philbur]

If it plunge cuts fine with the quill locked then I doubt it is the spindle bearings. It was probably the quill bouncing on the rack and pinion, which can be adjusted to some extent, or the quill is loose in the head/housing, for which there is no adjustment. The only work around for a loose quill that I know of is to leave the quill lock partly set in order to take up any sloppiness.

Phil

PS: when plunging an end mill (especially a 3/4" into a predrilled hole) it trys to pull into the work so I would bet on a bouncing rack and pinion.

Originally Posted by befunovo OK, found a new one they other day. Making a countr bored hole. I had a 3/8" hole drilled through some 1/2" CRS plate. I was plunge cutting with a 3/4" end mill to counter bore it about 1/4" deep. Locking the table and head in and using the spindle to plunge with was causing it to chatter. Locked the quill into place and cut lowering the head and it cut SMOOOTH!!! Seems looser than it used to. anyone know how to check the bearings on the spindle and quill? Are they adjustable for preload? Anyone else with this problem. Not a ton of use on the mill, but has seen some use over the last three years. Been to busy to tear into it right now. Probably will in January, but figured I would ask here first. Thanks all. Edit. OK, found the 7045FG manual. Looks like the spindle has two taper ball bearings on it, a 7206E and 7208D. Anyone adjust these? Under trouble shooting and spindle shake it says "(1) The gap of spindle taper is too wide---Adjust the gap in proper or replace bearing with new one. Locking the quill made it better, so not sure if it would be related to the spindle bearings. What does the quill ride in? Going to have to go look at the mill again. Anyone adjust this? Brian

[Cruiser]

Now that ya mention it I was suffering from tunnel vision here ! This slop will be pronounced any time ya plunge an end mill as they will just plain want to grab and bite. Any play anywhere will come into view. Don't forget that the "z" gibs, feed screw,nut block etc. will also allow the whole gearbox to jump up and down with violence ! Mine did just that when i pushed too hard. Forgot all about it till reminded of it. I modified my machine so that is a non issue for the most part so i guess i just ignored the thought.
I will say that 3/4" minus 3/8" still leaves .o6 on side and if hand feeding it would be a lot. If your trying to ream the hole with the end mill then its too much of a bite anyway for the rigity your describing. Even big heavy machines will show problems with size and finish when doing this.
OH, I'll bet your running tapered roller bearings, not ball !

[BobWarfield]

Personally, I think the quill is the weakest link in the accuracy of these machines. Eliminating the need to use it is one of the big advantages of a CNC conversion of the machine. I would expect there to be advantages to finding a way to seriously lock down the quill once and for all on a CNC converted mill that doesn't need it.

This is not necessarily unique to the IH or similar mills either. Widgitmaster made some sort of interesting spacer/wedge arrangement to solidly lock his Bridgeport's quill when he needs extra precision or rigidity.

Meanwhile, I always lock my quill if I can before making a cutting pass. Obviously it is most difficult to do when plunging!

Cheers,

BW

[scudzuki]

I leave a little drag on the quill lock when using the quill to plunge with a big drill or end mill, reduces the tool "bounce". This will happen on a knee mill (bridgeport) as well, it has more to do with cutting dynamics than a deficiency in the machine. This is not to say that the spindle bearings don't need some attention...
Joe

[Cruiser]

I once tried to punch a 1" hole in mild steel with an old but freshly ground drill bit and used the quil snubber to lock in place then programed it to drill a hole, What i saw was not only the head stock bouncing up and down but the column was flexing too. The act of trying to punch a virgin hole of 1" was absurd in this machine. but ! put in a end mill and interpulate the hole and it was perfect ! what it amounts to is technique, or methodology involved with getting the job done. Another angle of attack would be to drill a pilot hole and then increase hole till i was to what i wanted to have. I've drilled holes using an Ikeda radial arm drill machine with big twist drill and it would do the same thing it would buck and jump but the chips would fly out of the hole. You can get anything you want at alice's restaurant that you can imagine exept alice ! I guess what i'm saying is that there are weeknesses and there are strengths ! Learn to use the strengths and avoid the weeknesses and you won't have neer as much to complain about. Usually when i get like this I just kill the page instead of hitting the post key ! guess what i did tonight ?

[befunovo]

Haven't done anything yet, to dang busy working!

I did plunge cut a 3/4 mill bit into a piece of cast iron that was drilled 5/8" through, it went fine using the hand crank.

I usually loosen the quill lock, change the depth and then tighten the quill lock when I am machining.

If I need to plunge cut and depth is not critical, I lock the quill and lower the gear box (same as a cnc conversion will do). That usually works well.

Brian