[grinderdust]

Hello, I am looking for a little help in adjusting the spindle bearings on my mill. I am hoping to improve the surface finish I get when cutting with the side of the end mill. I have had this machine for a few years now and it has been a good one but it always leaves a poor finish on the vertical surfaces. Has anyone else had this problem? It does a little better when I climb the finish cut but it is not comparable to the finishes I used to get at work on the old bridgeports. I am really not expecting any miracles here and I realize you get what you pay for. I am just looking for a little insight as to what is causing this. Is it the runout on the spindle itself? Or is it the bearings they used? I am sure they don't use the same ones as the big boys. Will the ballscrews help when I get them on? It also could be worth mentioning that my belt drive could use some smoothing out. could this affect the finish? Has anyone tried those belts you put together in links? Alot of questions I know but thanks for taking the time to read my post.

[ViperTX]

Why don't you stick an indicator on it...check for total spindle runout....also check the head tram....and yes the bearing on the Bridgeport were most likely Class 7 and the RongFu...probably has Class 3 bearings...

[grinderdust]

The head tram has always been pretty acceptable to me. I now see however the runout is very high at .0006 or 7. It seems to coincide with the slack/tight action of the belt which is also due for upgrade. Can I try tightening/upgrading the spinde bearings to get rid of some of this? What can you do about the head tram on a machine like this anyways?

[ViperTX]

That is the round column mill....it has 4 bolts that hold the round column....you would loosen those and place shims...

Check the tram......see how that and the runout affect accuracy...

[grinderdust]

It looks like the column on mine is bolted to the base and then welded in place. The overall accuracy of the machine is not that bad for cast on cast ways and cheap screws. The surface finish is what is bothering me. On the horizintal sufaces the finish looks good. The vertical sufaces are a little choppy. I believe it is either the runout or the bearings are loose. My machine manual is not too legible so I guess I am looking for a guide to adjusting/upgrading the spindle and bearings. I have been preparing to cnc this machine and have most of what I need but if I cant improve the finish on the parts it's going to slow things down in production. Those old bridgeports on ebay are looking cheap when you consider the nice finish you'll get!

[philbur]

Is the bad finish with the quill retracted and locked.

Regards
Phil

Hello, I am looking for a little help in adjusting the spindle bearings on my mill. I am hoping to improve the surface finish I get when cutting with the side of the end mill. I have had this machine for a few years now and it has been a good one but it always leaves a poor finish on the vertical surfaces. Has anyone else had this problem? It does a little better when I climb the finish cut but it is not comparable to the finishes I used to get at work on the old bridgeports. I am really not expecting any miracles here and I realize you get what you pay for. I am just looking for a little insight as to what is causing this. Is it the runout on the spindle itself? Or is it the bearings they used? I am sure they don't use the same ones as the big boys. Will the ballscrews help when I get them on? It also could be worth mentioning that my belt drive could use some smoothing out. could this affect the finish? Has anyone tried those belts you put together in links? Alot of questions I know but thanks for taking the time to read my post.

[grinderdust]

It doesn't seem to matter what position the quill is in. I will measure the deflection of the quill but honestly I can flex the whole head about .001 if I just push on it. It is definately not as ridgid as it could be. I don't think that is the problem though. I am experiencing this problem even with the lightest of cuts. Is there anything that can be done with the runout? Are the class 7 bearings available for this mill? Has anyone tried those link belts? I am starting to think those wonky belts are having something to do with the finish. It causes vibration and if the bearings arent tight then that could cause deflection.

[philbur]

Everything deflects when you push on it, 0.001" is good for say a 15 to 25LB push. My point was that the quill is very often a loose fit in the head. With regard to bearing adjustment it should be possible. I have an RF40 clone so I dont know the procedure for yours. Check out the mill-drill group on Yahoo.

Regards
Phil

It doesn't seem to matter what position the quill is in. I will measure the deflection of the quill but honestly I can flex the whole head about .001 if I just push on it. It is definately not as ridgid as it could be. I don't think that is the problem though. I am experiencing this problem even with the lightest of cuts. Is there anything that can be done with the runout? Are the class 7 bearings available for this mill? Has anyone tried those link belts? I am starting to think those wonky belts are having something to do with the finish. It causes vibration and if the bearings arent tight then that could cause deflection.

[grinderdust]

I checked the quill for looseness in the head by putting an indicator on it and lowering all the way. gave it a shove locked and not locked. It didn't seem to make much difference and it seemed pretty tight and ridgid. I did however notice something. The runout all but disappeared when the quill is all the way up. How could the runout be .0006 with the quill extended and .0001 when retracted? The finish is about the same with the quill retracted and locked though. I am going to check out the yahoo group now that I know about it. Thanks for all the helpful replies and please keep them coming.

[philbur]

Have you got your numbers correct. That's 6 tenths and 1 tenth of a thou. If those number are correct then every thing is resonably good. Or did you mean 0.006 and 0.001. If you have preload on your spindle bearings then the position of the quill should make no difference to the run-out. Unless your method of measuring run-out is incorrect. If your procedure is good then it can only be random reading due to lack of preload. What procedure are you using. The dial indicator should be fixed to the table, or better still to the head, and the tip or finger of the indicator on the taper, inside the quill.

If you are using the table as you base for measurements you can assess head deflection by putting the indicator on the head, close to the quill, and applying a similar force as applied to the quill. You can do this both horizontally and vertically.

Regards
Phil

I checked the quill for looseness in the head by putting an indicator on it and lowering all the way. gave it a shove locked and not locked. It didn't seem to make much difference and it seemed pretty tight and ridgid. I did however notice something. The runout all but disappeared when the quill is all the way up. How could the runout be .0006 with the quill extended and .0001 when retracted? The finish is about the same with the quill retracted and locked though. I am going to check out the yahoo group now that I know about it. Thanks for all the helpful replies and please keep them coming.

[grinderdust]

Yes, .0006 is what I measured with the quill out about 3/4 of the way. It was less than .001 for sure. I was confounded by the difference in the readings as well. I agree It shouldn't make a difference what position the quill is in for runout. I will double check everything tonight. Are you sure that .0006 is acceptable runout? It seems to me that that much wobble in the spindle would have a profound effect on the finish. I did some reading on the yahoo group and found that smoothing out the drive train and or tightening the preload might help the finish. It looks like I will have to make 2 spanner wrenches and possibly remove the quill to adjust the bearings. I think i will try some new belts first. Happy Thanksgiving everyone! Thanks for all your Help.

[philbur]

The run-out should be better than 0.0006”. However, for example, a standard ER20 collet has an acceptable run-out of almost 0.0008” measured 3/8” from the end. Allowable run-out for a standard endmill holder is even greater. So I don’t think it is run-out as such that is causing a bad finish, loose bearing might though. The variation in run-out that you see can, to my mind, only be possible with loose bearings. The variation could be caused by the driving spline applying a small radial force to the splined shaft due to a small misalignment. This force would vary depending on the degree of extention of the shaft and therfore could effect the indicated run-out if the bearings are loose. If the bearings have preload it would not be possible to deflect the spindle in its bearings. So to save a lot of effort I would eliminate the doubt about bearing preload before chasing all manner of other possibilities. Its neasy to do on an RF40 clone, I’m not sure about an RF30.

Let us know how you get on.

Regards
Phil



QUOTE=grinderdust;221198]Yes, .0006 is what I measured with the quill out about 3/4 of the way. It was less than .001 for sure. I was confounded by the difference in the readings as well. I agree It shouldn't make a difference what position the quill is in for runout. I will double check everything tonight. Are you sure that .0006 is acceptable runout? It seems to me that that much wobble in the spindle would have a profound effect on the finish. I did some reading on the yahoo group and found that smoothing out the drive train and or tightening the preload might help the finish. It looks like I will have to make 2 spanner wrenches and possibly remove the quill to adjust the bearings. I think i will try some new belts first. Happy Thanksgiving everyone! Thanks for all your Help.[/QUOTE]