# A Heads-UP for anybody with a mill-drill



## historicalarms (Apr 26, 2020)

Ever since my mill-drill was new, there was always a little oily film that seemed as tho it came from the quill body. I just thought it had an oil bath for the bearings that caused the weeping a bit...didn't concern me much for the years that I have owned it but did always wonder how to replenish the leakage when the time came...as anyone knows that has bought one of these Taiwanese machines, the "operators/service manuals are very sparce in usable info (cant find mine anymore anyhow).
    Anyhow, the other day I noticed that this oil film had pretty well dried up...oh-oh, time to investigate how to service the thing before bearing failure became an issue and yesterday was the day.
     Never having one apart before it was a sort of "search & destroy" mission without trying to do so. It took me about an hour-hour-and a half to get the quill completely out of the head. first was to remove the depth indicator completely, then the coil-return spring. Just remove the holding knob from the spring housing and then pry the housing out a bit from the head...don't try to hold onto it (you don't want to create any leaky spots in your fingers), just let it go "spoing" when the cover comes unhooked. There is a screw that attaches the spring to the geared adjusting shaft so it wont go anywhere uncontrolled, now pry the coil over a bit so the screw is removable. Now you can remove the socket-head screws that hold the quill adjusting shaft crank & levers to the head, the shaft will now be easily removed from the machine. The quill is now loose to be removed through the bottom of the head, no need to remove the top pulley as the splined drive on the main shaft will just drop out of it. Don't just let it drop uncontrolled, I used a stack of blocks and removed one at a time  until it was resting on the mill table.
    Two things I discovered when I got it apart...there is no "oil bath" chamber for the bearings, they are just tapered bearings that were greased when new and no thought was given for adding a shot now and then along its lifetime. The second thing that surprised me was that the top bearing is wide open to whatever shop dust or scarf that might get launched into the head area (and there was a considerable amount of crud accumulated in the head casting). The bottom bearing has a rubber dust cover to keep scarf out of it so it is a bit protected.
    One thing I will mention if anybody else tackles this job, the bearing pre-load nuts on the main tool-head shaft are left hand threads. After the pre-load nuts & tab locker are removed ,the shaft easily tapped out of the main quill body. The top bearing cone is out now and easily inspected ( mine still had a smidge of original grease in it, not much but it appears still usable & undamaged). I guess there were tree things that surprised me, the third being that the bearings are not Chinese made, they are Japanese built and they appear to be high quality.  The bottom bearing is still in the body as the rubber guard didn't get pushed out when  removing the shaft. That's as far as I got last night and am still pondering how to get the rubber guard out without damaging it beyond re-use. There is no outside visible methods of removal, appears to be a sort of "wheel-seal" type of thing that is pressed in.


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## David_R8 (Apr 26, 2020)

Thanks for this, I have a 1980 Taiwanese Long Chang mill. 
There's a zerk fitting on the lower end of the spindle but nothing for the upper bearing as far as I can tell. 
I have accuracy class P5 bearings, the equivalent of ABEC 5 replacement angular contact bearings that will replace the existing spindle bearings. These are permanently lubricated and sealed bearings from FAG.
Part numbers:
Upper: *FAG 7206-B-XL-2RS-TVP*

Lower: *FAG 7207-B-XL-2RS-TVP*

The standard bearings used on the drive sleeve of the RF-31 (and likely all clones) are 6009ZZ shielded bearings. I will replace mine with Nachi 6009-2RS bearings that are permanently lubricated sealed deep groove bearings.


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## historicalarms (Apr 27, 2020)

I finished the tear-down of the quill yesterday. Not wanting to damage the seal beyond re-usable, I drilled a small hole into the heavy flange at the bottom of the quill right beside the seal pocket, just big enough and just deep enough that I could get a small pry tool inside. It popped the seal out with just a slight dent in the outside form, was easily re-formed.
   after a total clean-up (still had original shipping cosmoline on a lot of it), now to find a suitable grease to re-pack the cones. The original grease is a very thick consistency, sticky stuff, hence why there is still some in the cages after 20 yrs of intermittent use. My first inclination was to just use the "gun grease" that we have on the farm...after all it served us good for going on 50 years...but on reflection, everything we greased with that stuff was re-greased almost daily...and I don't want to do a tear-down daily LOL.... any advise on what to use would be appreciated. Prob. ordinary wheel bearing grease would be appropriate in this case but am open to ideas.

  David, I thought about changing to sealed bearings but cant figure out how you would set tapered cone pre-load on a sealed bearing??? All sealed bearings I have ever used were round rollers, not settable and all with a certain amount of "run-out" that wouldn't be appropriate for a mill I don't think.


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## David_R8 (Apr 27, 2020)

I have yet to do either replacement but this is the article I'm going on.
https://www.hobby-machinist.com/threads/spindle-bearing-replacement-for-the-rf-31-mill-drill.49002/


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## historicalarms (Apr 28, 2020)

Thanks for the link David, lots of good stuff there...I do agree with Canuck75 on the locking tab order of use, his method ( it's the same as nine was from the factory) locks both nuts to the spline without any unnecessary tightening of the outer nut that will add pre-load to the inner nut when tightened so much.

    I wont be changing bearings for mine, I found some grease that my brother had. He used to build race cars & I think the first page on any race car manuals states in bold block letters  "do not ever use anything that isn't expensive". 
    He has two tubes of grease that he sent me a photo of, one is a tube 4" long by1" in dia that shows a price tag of $20...the other is a tube, more of a dispenser shaped like a hypodermic syringe about as big around as a pencil and only an inch long...it showed a price sticker of $40 and I would probably need 4 syringes to fully pack both bearings...I told him anything I spend $160 bucks on better come with her own "lube"....I'll use the cheap stuff!!


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## Downwindtracker2 (Apr 28, 2020)

A affordable? grease, is the moly grease they sell for FWD CV joints. . In industry it's used for couplings, Falk sells some, but Mobil 101 is the industrial standard.


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