Craftex Mill/Drill Spindle Bearings Replacements
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
Re: Craftex Mill/Drill Spindle Bearings Replacements
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
Re: Craftex Mill/Drill Spindle Bearings Replacements
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
Re: Craftex Mill/Drill Spindle Bearings Replacements
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
Re: Craftex Mill/Drill Spindle Bearings Replacements
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.
Re: Craftex Mill/Drill Spindle Bearings Replacements
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
Re: Craftex Mill/Drill Spindle Bearings Replacements
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)
Re: Craftex Mill/Drill Spindle Bearings Replacements
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
Re: Craftex Mill/Drill Spindle Bearings Replacements
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
Re: Craftex Mill/Drill Spindle Bearings Replacements
Glad you got it done and hope you have many years of enjoyment making "stuff" :})