[Jim Anderson]

The bearings in my spindle of this CRAFTEX mill/drill are getting tired. Has anyone ever replaced or upgraded the bearings in a spindle even similar to this? This machine has an R8 collet and is 2 hp.

I would prefer to have a solid plan in place before tearing into it.

Thanks,
Jim
Anderson Prototypes

[dertsap]

its basically an x2 mill with a different paint job so there is some info out there for the x2 .
little machineshop should have you bearings , but double check the measurements , last night I installed my new belt drive that i bought from little machinshop and had to do some mods to made it work , not sure if it was because mine is an mt3

this should be of some help http://www.littlemachineshop.com/Ins...ndle%20Kit.pdf



.

[pete from TN]

IS that a round column machine? Looks like an RF31 when i did a search for it... Not sure how many craftex mills there are tho...He said it is 2hp, I thought the mini mills were less than that.. peace


Pete

[Jim Anderson]

Hey guys,

The machine is not currently on BusyBees site. It is quite a robust table top mill with a round column. I'm not saying its the greatest in the world , and it will be replaced with a knee mill soon enough, but for today, I need to get new spindle bearings.

This is its little brother..
MILLING DRILLING M/C 1 1/2 HP 220V - Busy Bee Tools

Thanks for the help...
Jim
Anderson Prototypes

[pete from TN]

Yeah that is what I figured... It is basically a clone of the RF31 like I used to have here. Great little mill and smooth and quiet. I would start by searching on RF31 and you will probably find more information about that mill here. There have been a lot of threads about converting them and other mods. My pal Art aka COuntrybubba has one as well as a lot of others. I never replaced the spindle bearings on my machine so I cannot comment on that. I am sure that there are some nice angular contacts that you could buy for a reasonable price that would fit. If It were me I would just remove the spindle, measure the bearings and go find what I was looking for in that regard. How old is the machine, I know they have been importing these little mills for some time now but you are actually the first I have heard of that wore out the original bearings. Mine was used when I bought it, well used when I sold it, and still had the chinese bearings in it. Kinda wish I still had it now... Good luck with your search and peace

Pete

[Bubba]

HI,
If we can "assume" this is a variant on the RF31, I recently had to replace the bearings in my spindle.
My bearings came out as noted below and the numbers to the left are the reference numbers on the exploded pictorial view in the manual and the ones on the right are the bearing dimensions in mm :

3-18 30207J Bearing lower spindle 35x72x18.25
3-15 30206J Bearing upper spindle 30x62x17.25

To replace them:
1. remove the spring for the spindle return on the left side of the head after locking the quill.
2. remove or at least disengage the down feed pinion by removing the two screws holding the fine down feed on the right side of the head.
3. raise/rotate the head so you have clearance to remove the quill assembly.
4. while holding the quill, release the quill lock and it will drop out.
5. Remove the locknut/lockwasher assembly from the top of the quill. (I used a punch and hammer to loosen the nut)
6. Turn the assembly bottom side up and the plastic "shield" on the bottom unscrews. NOTE: This is a LEFT HAND THREAD!
7. I then used some persuasion to knock the spindle out the bottom of the quill.
8. I then removed the outer races just like I used to on a car as there is a couple of cutouts in there so you can get a bar in to drift the races out. Do this for both the top and bottom.
9. Clean everything up.

Reassembly:
1. drive the outer races into the quill and make sure they are properly seated.
2. Grease your bearings. NOTE: for a high speed application like this, you use a light grease and only fill to about 30-50%. I used Grease use is "SuperLube" by SyncoChem Company Bohemia, NY Grease | Oil | Synthetic Lubricants LA101-6 or 8 and it has been working very well.
3. Press the lower bearing on the spindle, and insert the assembly back into the quill.
4. Put the top bearing on and now you need to tighten the lock nut down to try and get the proper pre-load.
DISSERTATION: At this point, I did NOT lock the nut with a tab on the washer, you can now start the break in procedure and I placed the assembly in my lathe so I could have good access to the lock nut in case it needed adjustment.

Break in procedure, I found this surfing the net:
Typical run in for spindles is a starting point of about 400 rpm,
up to max in 500 rpm increments, in steps of 30 - 45 minutes.
Check housings for excessive heat as you go.
Then reverse and do it over!
Watch temperature. If it gets hot, stop let cool and do over.

The Fafnir Superprecision Machine Tool Bearing catalog suggests that with optimal design, bearings running synthetic low friction grease ought to be able to run about 20 degrees C over ambient or about 40 degrees F. In fact, they suggest a proper break-in procedure temperature of 130 degrees F involves running the spindle until it reaches 150 degrees F, turning it off to cool, and repeating the cycle until the spindle stabilizes at 130 degrees F or lower operating temp.
The ideal equilibrium operating temperature is 95 to 115 degrees F. Maximum temperatures should not exceed 170 degrees F. Timken's published specs for tapered roller bearings, including bearing life specs, assume an operating temperature of 130 degrees F.

I followed these procedures using a spread sheet to record values, and a non-contact thermometer to check temps. When I ran out of rpm on my lathe (2700 max)and I was satisfied the pre-load appeared satisfactory, I reinstalled the quill in the mill and then continued the break-in procedure up to max rpm of my machine. Also note, it was done in both forward and reverse directions.

So far, bearing temps are reasonable and the mill is working fine with prolonged runs up to 4000 rpm.

HTH

[dertsap]

oops sorry scratch my post
thought you meant the smaller mill

[dsage]

Art:

I'm reading your post on changing the spindle bearings with great interest as I'm about to do the same thing.
I haven't started yet but I think what you're saying makes some sense.
Question:
Aren't there some bearings up farther under the pulley for the top end of the spindle as well?

My secondary purpose for going through this is I have a problem with a bit of rotational slop when you hold the spindle and rotate the pulley at the top back and forth. Something like what a sloppy keyway might sound like.
I assume there must be something like a keyway that transfers the drive from the pulleys to the spindle shaft?. It makes a lot of clacking noise while milling

Any insight before I get started would be helpful.

Sage

[Bubba]

Sage,
Yes there are bearings for the spindle pulley, but they are completely separate from the spindle itself. The top of the spindle is "splined" and fits into an internal spline in the center of the drive pulley and IIRC, these are sealed bearings. If you want to take the pulley off, the big nut on top is LEFT HAND THREADED and the pulley is tapered. As I remember, there is no key between the stub shaft and the pulley. Going strictly on a weak memory here as that was about 15 years ago when I had to tighten the nut as the pulley was rotating on the stub shaft. This happened right after I bought the machine and got it set up.

Yes, what you describe sounds like a rather loose fit in the splines. I add a little grease to the spline every once in a while. With the quill in the full up position, you can see the top of the splined shaft and if you get up on a ladder or something, you will be able to see the looseness in the splines. The aforementioned grease will diminish the clacking sound for a while.

HTH

[dsage]

Hi Art:

Thanks for the quick response. I think we're still talking about the same machines here so I'll ask another couple of questions. The big nut on mine is a standard right hand thread. I've had it off. But I didn't go any farther because I have no idea how I'm going to release the taper on the pulley. But if that is how it's on there - and that's what is suggested in the exploded view - then I guess I can make a big bolt driven puller of some sort. If I'm going to take it apart I think I'll change all the bearings and have a look at the splines. I think I beat it up too much with intermittent cuts over the years.
So another question:
You say the spindle will come right out after you remove the return spring and get the fine feed rack and pinion out of the way but perhaps I'm mis-understanding where it comes apart. Wouldn't you also have to remove the big collar at the bottom of the quill - the one with the vertical bolt with the depth gauge on it - that only appears to be there to keep the spindle from rotating??

Thanks

Sage

[Bubba]

Sage,
OK first off, you don't need to remove the pulley.

An old trick that we used to use on pre 50 ford cars that had their brake drums held on with a taper was to loosen the nut a couple of turns and then drive it on a bumpy road for a bit. By the time we got back to the shop (or my case the back yard), the taper was broken loose. Take the nut off and pull the drum. The principle here would be the same, loosen the nut a bit and purposely do an interrupted cut and pretty soon the taper will break loose. You will know it as the spindle will stop and the the pulley will turn. Thats how I found mine was loose to begin with.
Next, yes you need to remove the big collar at the bottom as it is for the depth gage. On the left side of the head above the return spring is a slotted screw with a lock nut on it. This rides in a key slot in the quill. It needs to be pulled out. This is what controls the rotation of the quill.

Lock the quill in place with the quill lock before you pull the pinion gear etc. Then loosen the lock and the whole quill cartridge will come out the bottom. You will have to swing the head on a round column to get it all out. The pulley etc will stay in place.

sorry I didn't mention the depth stop previously. Oh by the way, when I took mine apart, the top quill bearing was a bit tight on the shaft and I had to turn the quill upside down and thump the spindle shaft on a block of wood to get the bearing to release. The top bearing should be able to move with little pressure as it need to be able to move a bit to setup the preload on the bearings.

HTH and let me know if you need more detail.

[dsage]

Thanks Art:

I like your method of breaking the taper loose.
I'll have a go at all of this over the next while. My machine is complicated by my conversion to CNC and the pulley's etc on the Z axis rack and pinion. Plus I've added a precision vertical bar alongside the column so I can adjust the head height without rotation. (works well) So I'll have to remove all of that stuff first.
There's no way it will come out even with the head cranked all the way up ?? R&R of the bar modification is very time consuming.

BTW - what is HTH?

Thanks

Sage

[Bubba]

Sage,
I don't remember if I had to rotate the head to get it out. That was a couple three years ago and I just don't remember. I did what was necessary is all I remember:}) It might have, but I don't want to swear by it one way or the other! Know what you mean about the conversion to cnc as I had this problem also.

HTH (Hope This Helps)

[dsage]

I guess it should be somewhat apparent by measuring how much space is below the head with it all the way up vs the length of what's inside.
Not a problem.
I was also going to make a direct way of driving the Z-axis with the CNC. There's too much backlash driving the old handles with two racks and pinions in the train now. Something I should have done 5 years ago.
I'll need to use the machine to make that first. SO it will be a while.
I'll report back.

And yes, TWH (that was helpful)

Sage

[dsage]

Ok. I got the bearings changed without too much trouble. There was plenty of room to pull the spindle out with the head cranked to the top. My bearings were a bit smaller than yours presumably because I have the smaller version of the two Rong FU mills commonly available. I followed your idea of mounting the spindle in the lathe which makes it very easy to measure the end-play in the bearing assembly. I found the best way to set the preload was to adjust the nut only until the end play was eliminated (spinning for a minute or two in steps to be sure the grease is distributed) and then add a barely perceptible bit more turn on the lock nut. The bearing seemed to stabilize at about 140deg F at full speed no load and I think they might be getting a bit cooler after a bit of use.
I had tried a few degrees of nut tightening as preload but the bearings were getting too hot. I presume because as they heat up they get tighter anyway. So setting them to just eliminate the endplay seemed better. I'll keep an eye on them for end play.

Thanks for your help

Sage

[Bubba]

Glad you got it done and hope you have many years of enjoyment making "stuff" :})