G3103 spindle bearings

boostin53

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I'd like to do some maintenance or just flat out replace the spindle bearings on my mill. I looked in the manual, but didn't see anything about maintaining them. I tried doing a few Google searches but no luck.

What I'm looking for is some type of guide, or any information as far as removing the spindle and bearings. I'm sure I could learn as I go, but I like to be able to look/read something for the first time. I'm also wanting to remove the R8 alignment pin in the spindle. How do I do this?
 
I am in process of doing a Rockwell mill. It is similar to yours, although not exactly the same:
https://www.hobby-machinist.com/threads/rockwell-21-100-spindle-rebuild.67913/

Diagram for your mill:
https://www.grizzly.com/products/g3103/parts

Spindle bearings are generally greased on assembly, and need to disassemble to regrease or replace.
Need to pull quill out of spindle, typically have to remove the feed mechanism and stop assembly first and it will drop out the bottom.
Once the retainer nut at base of quill (7) is removed the spindle with bearings should slide out the bottom (may also be a retaining clip on the top side that you need to pull).
You might be able to spray clean out the old grease and replace with new.
If bearings are pressed on you will generally need to replace as force to remove will damage them.

Ideally you want angular contact bearings at the bottom of spindle, with correct "back to back" orientation. they are typically purchased as a matched set. On my mill they used ball bearings here, custom ground for preload. I upgraded to angular bearings and added a grease seal since these bearings typically have none.

There are another set of bearings that support the drive pulley, these may be ball bearings. On my mill the originals were custom ground for preloading, but I am replacing with standard bearings and using a shim to preload. I'll be posting more on that in the Rockwell thread.

skf_db_back_to_back_bearing_mounting.png
 
I am in process of doing a Rockwell mill. It is similar to yours, although not exactly the same:
https://www.hobby-machinist.com/threads/rockwell-21-100-spindle-rebuild.67913/

Diagram for your mill:
https://www.grizzly.com/products/g3103/parts

Spindle bearings are generally greased on assembly, and need to disassemble to regrease or replace.
Need to pull quill out of spindle, typically have to remove the feed mechanism and stop assembly first and it will drop out the bottom.
Once the retainer nut at base of quill (7) is removed the spindle with bearings should slide out the bottom (may also be a retaining clip on the top side that you need to pull).
You might be able to spray clean out the old grease and replace with new.
If bearings are pressed on you will generally need to replace as force to remove will damage them.

Ideally you want angular contact bearings at the bottom of spindle, with correct "back to back" orientation. they are typically purchased as a matched set. On my mill they used ball bearings here, custom ground for preload. I upgraded to angular bearings and added a grease seal since these bearings typically have none.

There are another set of bearings that support the drive pulley, these may be ball bearings. On my mill the originals were custom ground for preloading, but I am replacing with standard bearings and using a shim to preload. I'll be posting more on that in the Rockwell thread.

And I'm guessing I can't get the collet alignment pin out without removing the spindle? If I can freshen up the bearings without removing the spindle, and they're still in great shape, I still would like to remove that pesky pin.
 
Not sure about the pin, as they did not put one on the Rockwell. You could try sticking an appropriately sized (tapered?) piece of round bar to try to push it flush with the inside of the spindle.

If you don't want to disassemble it, people have been known to remove the depth stop and inject some oil or grease into the hole, which will work its way into the lower bearings. Ideally you would want something compatible with the original grease...
 
I guess I should price out a set of new spindle bearings before I attempt to remove it. If they're a pretty penny, I'll just plan on cleaning and reapplying grease for the time being.
 
In looking at the parts diagram, it appears that there is a single angular contact bearing (43) at the bottom of the spindle. The one above it (44) is a ball bearing but having somewhat smaller OD. That means you cannot use matched bearings, unless you were do some machine work on the quill.

Below are prices I saw on ebay for name brand bearings. You should consider changing ZZ (shielded) to 2RS (rubber seal) style. Otherwise I would stick with the current configuration. I wouldn't buy anything until its opened it up and sizes and condition verified. Anything thats pressed together probably will need replacement. If bearings aren't noisy and everything comes apart easily you could consider regreasing, although metal shields are pretty much impossible to remove intact. The more expensive angular contact bearing is likely to be open style, so could potentially be regreased.

Lower spindle:
43 36207 Angular (now called 7207C) 35x72x17 ($100-$150)
44 6007ZZ 35x62x14 ($10)

Upper Spindle
45 6206ZZ 30x62x16 ($10)

Drive pulley
48 6009ZZ 45x75x16 ($15)
4 6009ZZ
 
I was going to wait until I pulled the spindle to being my bearing hunt, but you may have already did that for me!

I will take your advice and not order anything until I pull it and verify what's in there. I should be able to simply remove the alignment pin when I pull the spindle as well. Thank you machPete99!
 
Here's another thought...
If you have a decent lathe with a 4 jaw and steady rest, bore out the smaller bearing pocket to 72mm to match the larger one, and go another 3mm deep (make sure you have room and won't hit anything).
Then install matched 6007 bearings, for about $150 a pair:
https://www.ebay.com/itm/NSK-7207CT...ndle-Bearings-Matched-Set-of-Two/182903121251
You need to also make sure there is enough thread on the spindle to get the retaining nut on. If not might need to face it off behind the nose.
 
Well I took the leap and started to take apart the spindle, which is a first for me. I got the spindle cartridge? out. The sleeve thing that stay stationary in the mill with the actual spinning spindle inside it.

The bearings seem a tab bit rough to me. I will try giving them a thorough cleaning and fresh grease to see if they seem better. Now I have a question(s).

How do I get the splined spindle out of this sleeve, a long with the bearings? Which I assume would allow me to remove the R8 collet pin, correct?20180416_173518.jpg20180416_173509.jpg
 
On my Rockwell there was a snap ring above the top bearing that had to be removed. Then you tap the top of the spindle and it should drop out the bottom of the quill, with lower bearings attached. Do not use a steel hammer directly or you will deform things. Use either lead or copper hammer or put a block of wood in between. Depending on the fit this may cause some further harm to the current bearings. You can also potentially use threaded rod and bushings/pipe/spacers (maybe PVC drain pipe?) to accomplish this, or use a hydraulic press. Try not to be too rough and see how willing it is to come apart.

If the bearings feel rough you really need to consider replacements. Fresh grease will not fix them.
 
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