...and I forgot to mention that I have NO plans to ever clean/regrease these bearings unless the machine starts telling me to do so. I don't think it is worth the extra time, hassle, and cost of that liquid gold Kluber grease.
Yes, by design because that way you don't need to use any force to press the bearing down most of the length of the spindle shaft. It only seats at the bottom.
People knock these G0704s for being POSs, but the design is pretty good. There are definitely some parts and fits/finishes that they go too cheap on IMHO. However, I also realize that they are trying to meet a price point and there is certainly an asymptote in the $ per unit of machining accuracy curve. I'm pretty happy to have a machine for less than $1,500 that can regularly cut parts to within a few thousandths or less. In order to squeak out those last couple thousandths costs a lot more money. So far, none of my garage creations has required such machining precision, and if it does I could probably manually machine/measure/machine those parts to get that tolerance.
...and I forgot to mention that I have NO plans to ever clean/regrease these bearings unless the machine starts telling me to do so. I don't think it is worth the extra time, hassle, and cost of that liquid gold Kluber grease.
Hi JJ
I understand the logic all right, but does the mfr make that claim? I am curious.
Cheers
Roger
I don't know, but if I had to make these spindles I sure would do the same thing. It makes good sense. I just didn't even notice it at first because it was such a small step up in diameter and it wouldn't have even been an issue for me if my tube I.D. didn't happen to almost perfectly match the spindle shaft O.D. by pure chance.
JJ
Why would the manufacturer make the claim? You expecting a Grizzly technician to come out and spec the spindle? The thing costs $700.
I’ve had two spindles and they were damn near identical. They match the description here.
Fair enough. It may be so.
Cheers
Roger
Just an update on this project for anyone who cares. I have been running the machine since the post 4ish years ago at least twice a week for runs that are between 6-9 hours. I have had no issues and have not had to disassemble the spindle for any reason. Most of my work is with small cutters but I do use a 1/2" 3 glute rougher at 6000rpm, .5" doc and .05" woc.
This bearing upgrade and the AC spindle motor have been the most reliable parts on my G0704. I wish I could say the same for the rest of the mill.
Worth knowing about, thank you.
Cheers
Roger
May have cursed myself but today the bearings finally gave up. Felt a scorching hot tool when I went to change it and let the spindle cool down to see how bad the damage was. Once it cooled it almost wouldn't move and when it did it made a ton of noise and the spindle load was around 25%. Ordered new bearings, 5 years wasn't too bad considering the amount of use and lack of maintenance I did on it. When I got it disassembled there was almost no grease left on the bearings. The housing design is not a great design for grease retention. Especially the bottom bearing. Grease just seems to melt down and lay well below the bearing.
In the future I will just plan to disassemble the spindle and relube it once a year.
248 and 251 are the only spindle bearings. Bearings 205 and 207 carry the drive train. The quill function. Yes, they turn with the spindle, but the only carry the load of the drive. With the gear drive, they have to be large because of the forces involved. That also means they are terrible at high speed.
Personally, I think you should bail on the quill if you are cnc. Just get rid of all the quil junk and run a belt direct to the spindle.
I concur, but that appears easier said than done.
I have a Minipro belt drive kit that is going on. It replaces 206 with a straight shaft with a longer top extension. The pulley mounts to the OD of this shaft. The inside of the shaft is broached to fit the quill spines. OEM-sized bearings (205 and 207) are pressed on to this shaft, and it looks like the Naichis I bought (6209ZZE Nachi Bearing Shielded C3 Japan 45x85x19, 6007ZZE Nachi Bearing Shielded C3 Japan 35x62x14) are indeed for this outer shaft.
They are also permanently greased from the factory (?)
But as I look deeper into this, the collet is 246 and the only way to drive it is though the quill spines engaging with the interior splines on 206 - unless 206 is replaced with a solid assembly with solid "pucks" that take the place of 205 and 207, 246 is redone with a round shaft (instead of splined) and at least one more bearing is installed at the top of the now-round 246 shaft between it and 206, to support the top of the shaft against pulley loads (as the pulley now connects to 246 instead of 206).
That's a lot of work... and I think that the existing design already does a good job of isolating driveline loads from machining loads.
The fact that the only thing keeping the 249 spindle assembly from falling out is the 236-237 quill lock is hokey, but I don't see any other way to secure it.
So that returns to this: which are the aftermarket bearings to replace 248 and 248-1? (not 251 - that's the preload nut - my bad)
The quality of the 248 bearings sets the accuracy of the machine. Buy good ones.
Maybe not super-precision ones, but 'good' ones.
Cheers
Roger
Good ones: I suggest bearings with known western brands. They may or may not have been made in China, but the western brand companies will provide the QA. Avoid cheap bearings with unknown brands (also usually from China0. The latter might be OK, but you just don't know.
Mount carefully, with either EP grease or lithium grease. Useful if you can arrange for some way of adding grease or oil later on.
The lower bearing is the critical one: it is nearest to the cutter. The upper one matters too, but its function is to support the drive end. This is smoother than the cutter end.
Take your time with the replacement, use clean rags for wiping and clean new (butchers) paper underneath everything. Keep it all clean!
Cheers
Roger
Those bearings worked perfectly for our build..should do the same for you. We were judicious in the use of Kluber on the spindle bearings, took our time to run them in, fine adjust them and watch the temps while adjusting.
Stuart
"THE GRIZZ" photo album - https://goo.gl/photos/yLLp61jooprtYzFK7
Youtube - https://www.youtube.com/channel/UCT2lq9obzEnlEu-M56ZzT_A
When you remove the current bearings, you should find their model numbers engraved on the outer bearing ring.
You need to do a web search using those numbers.
Cheers
Roger