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well i've got an older bench top mill. when i try to mill aluminum it seems like the cutter pushes out of its path and doesn't track. if i go really slowly then it seems to work but i shouldn't have to. also when i use an end mill to drill (yes its centercutting) it seems like the end mill wanders on the peice. it doesn't make a much bigger circle but enough to be worried about. i've had the column appart and i've replaced the bearings it just seems like i can't get it tight enough.
is the top bearing supposed to be an interference fit with the spindle? is there an easy way to hold the spindle while tightening the top nut?
thanks
and you've trammed the head and your end mills are sharp and you'v measured the run out and it's okay? If all that checks out you could chuck up some thick drill rod....and with the motor off measure the side play....I suspect you'll see quite a bit....which most likely indicates that on new bearings you have too much play...either because you can't preload them enough or the bearings are just not very good.
Or the quill has warbled out the race it slides in. If thats the case you prettymuch have to live with it. You should be able to tighten up the bearings quite a bit, unless something has worn out of tolerences or the bearings are wrong or bad. I have a brand new never used replacement spindle with bearing set and locknuts. I had not intended to sell it but if your desperate and you think that it would help, i might consider. It sounds like it is either the bearing races in the quill or the quill housing though. I assume you didnt detect a bunch of play in the bearings when you put them on the spindle shaft, right? Good luck.
Halfnutz
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
yes the quill is trammed in and i used brand new endmills. i think there is problem of getting enough preload on the bearings. i've read that the area where the bearing resides is supposed to be hot to the touch. mine barely gets warm. when i put the drill rod into the collet thats mounted in the quill it doesn't seem like there is any play. i really can't explain it. i can't seem to generate the problem without running the mill. which leads me back to bearings and them not being tight enough. on my spindle the top bearing has an interference fit and for this type of assembly i don't think that its supposed to. also i can't hold the spindle tight enough while trying to tighten the lock nut to preload the bearings. i can get it so far and then it starts to slip. i think i've found a way to stop the spindle from turning and i will try it tonight. i will let you know how it turns out.
Stick a t-bar in a collet or drill chuck to keep the spindle from turning while you tighten it up. Just remove it before you power up....
i did but then the t bar starts turning in the collet. at least thats what happened the last time. i need some kind of positive stop so i can tighten the bearings. i think i will disassemble it again and sand down the collar where the top bearing sits. once this fit is loosened up i should be able to tighten everything up.
is there some kind of reference other than "so tight" to snug the nuts? any kind of torque spec for preload on these bearings?
Im not aware of any spec for the pre-load. My mill had lots of slop when i bought it and I called HF and ordered a replacement spindle and set of bearings (at no charge) anticipating the worst. I spoke at length with the CS department at Grizzley also and dont rcall hearing about a preload torque spec. from them either. What I ended up doing was tightening untill I felt some friction and then backed them off a quarter. This did not help, so I retightened and put some small amount of preload on them(tightening only the top set of nuts). That immediately showed a great improvement. The mill stoped vibrating and the finish became very nice. After several hours of use I re-checked the free motion feel of them (removed belts) for any tight or rough spots, and while using for the first several hours I checked for overheating (yes they do run warm, especially at 2500 RPM), but everything seemed fine and I have had no problems since, that's how I ended up with the new spindle. The guys at grizzley are great help, tell them you have a 1006 or a 3358 you bought used, and they will answer any questions better than I can. i wish I could help you more, but thats about all I know. good luck.
Halfnutz
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
ok, after looking at it some more, there were two set screws on either side of the spindle that when tightened down didn't allow the spindle to turn. i tightened these down and tried adjusting the preload. i couldn't turn the nut. i will be disassembling the spindle one more time and i'm going to add a washer up top and also polish the shaft so there is a slight interference fit not a near press fit. there might also be a burr up there i don't know. any other suggestions before i tear this down?
Nothing other than go for it. The whole quill, everything just drops right out and is very easy to tear down and re-assemble. Just release the coil spring on the side slowly and have your head up high enough to drop out the quill. Its very simple and can be R&R'd in 20 minutes or so. Pull the lift mecanism out of the right side - after you pull off the pulley up top. Put a towell over your table so the quill doesnt slam down on bare metal. As you pull the right side of the lift/fine feed/ worm screw assembly off, the quill will drop right out.
Halfnutz
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
i've had the spindle out before. its really doesn't come out like you described but thats fine. i have found out that it is an RF-20 clone. in any case i will try and fix it but if it doesn't work, then i'm buying an enw mill and moving on with my cnc conversion.
well, heres what happened. after disassembling the spindle again, the top bearing wouldn't seat on the spindle itself and was never allowing any preload onto the lower bearing. so i took the bearings off. chucked up the spindle in my lathe and polished the section where the bearing sits. this removed all burrs and smoothed the surface. after i was done i was just able to install the bearing with no play. maybe .001 interference. this was what i needed. i proceeded to reinstall the spindle and snug the preload nut. then i ran it for a while and let it get warm. made a few cuts and it was a little loose. tightened up the preload nut a little more and ran it again. made some more cuts and they were straight. problem solved.
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