[SScnc]

I just added the Steele belt drive and love not hearing those stinkin gears !

I did as the instructions stated and snugged the spindle jam nut then backed it off and made sure the spindle rotated freely, which it seemed to do. I just ran a program for about twenty minutes and the spindle was hot and the head was warm too.

I let it cool and then loosened the jam nut then only finger tightened it and ran it about 10 minutes and it was heating up again. I never had this before this belt kit was added. I am running it highest speed as I'm using a .125" EM.

The spindle spins fairly freely, no noticeable binding or anything. What could be causing this ? Suggestions/ideas please.

Thank you,

Steve

[Crevice Reamer]

If you are adjusting the belt too tight, it could cause this. Also, you may be running the spindle too fast for the Chinese grease.

CR.

[hoss2006]

Luck of the draw.
Happens to some people that install the belt conversion.
Some stock bearings can handle the increased speed, some can't.
Keep in mind you can pick up some new replacement bearings from Littlemachineshop.com or some real good ones from Applied.com.
Hoss

[SScnc]

Thanks guys, I had the belt only tight enough to not "flap". I switched the belt to the low speed setting and turned the pot all the way up and let 'er run for a while and no heat problems.

So, you both are right then about the bearings and speed. This is one reason I bought from Grizzly as I thought that would greatly lessen the chances of problems. It's still under warranty, would it be worth getting bearings from them or more "luck of the draw" with them too ?

I've ordered allot of bearings from VXB, I'll try to find out what the numbers are for the spindle bearings and see what they have too.

What a drag !

Thanks very much, I appreciate the help,

Steve

[Crevice Reamer]

Spindle disassembly instructions:

http://www.littlemachineshop.com/Ins...ndle%20Kit.pdf

There is a difference between R8 and MT-3 spindle bearings You have the MT-3.

BOTH upper and lower are Type 8026 or SKF TYPE 62062Z.
ID= 30MM OD= 62MM WIDTH= 16MM

All are sealed deep groove ball bearings.

SKFs are rated to 11,000 RPM. You may be able to find these bearings at a local bearing company. Check your Yellow Pages.

CR.

[SScnc]

Thank you very much for that CR ! I was Google-ing "44991 replace spindle bearings" this morning but didn't find that. That link is a tremendous help.

It looks like the MT-3 requires two 6206 brngs. I have a Fastenal near me with the ones in the link below in stock and specs of 13,000 RPM. But they are only ~ $5.00 ea. Are these a waste of time ?

Fastenal Bearings

I contacted Grizzly and they said they can send new bearings but I don't think it's worth the trouble of changing them with the exact same thing though.

Thanks again,

Steve

[Crevice Reamer]

I don't think the original bearings were rated 13K RPM, so they should not be a waste of time.

A couple of things: While you have it apart, sand the spindle slightly. The bearings should fit snugly but should not need excessive force to install. Make sure you only apply force to the inside race, not the outside.

There is often a roughness on the spindle that jams it in place when adjustment nut is tightened. This needs to be found and corrected or you will end up with the same problem: You tightened the nut too tight, the spindle jammed and overheats and now loosening the nut doesn't help because spindle is jammed in too tight position.

CR.

[SScnc]

Okay, good, I'll get the ones from Fastenal and give them a try. I'll do as you say regarding sanding the spindle, I expect I'll see what you mean when I have it all apart.

I've changed bearings on different machines and vehicles over the years and know that it needs to be done right, but what about when I'm changing tooling and I have to wack the draw bar with my brass hammer, I've always felt that would be causing harm to the bearings ?

I've made some TTS style tool holders (thanks to Hoss) but I still have to wack the draw bar until I add a power unit to it.

[Crevice Reamer]

You are right. Whacking the drawbar too hard can dent the bearing race. It's always best to support the spindle when whacking it.

Even if you DON'T have the power draw bar, add the Belleville washers anyway. This facilitates the manual tool change quite a bit.

CR.

[SScnc]

You are right. Whacking the drawbar too hard can dent the bearing race. It's always best to support the spindle when whacking it.

Even if you DON'T have the power draw bar, add the Belleville washers anyway. This facilitates the manual tool change quite a bit.

CR.

That brings up a couple of questions...

How to support the spindle and remove the TTS adapter at the same time ?

Using the Belleville washers helps put the correct "draw" on it ? Not sure I understand how they help in manual mode.

[Crevice Reamer]

Belleville washers add a little "shock absorber" springiness. You don't have to hit very hard, and may not even HAVE to whack--only unscrew draw bar a little and TTS drops into your hand. Just holding spindle with hand may be enough to tighten draw bar--Without a spindle lock.

Try it!

CR.

[sansbury]

I went down this rabbit hole myself about 6 months ago. Spent about a month tearing spindles apart and rebuilding before I basically gave up. There is a guy named lbakeland on eBay selling bearing upgrade kits for mini-machines, you might want to look into what he's offering.

A couple other things to keep in mind. First, it's very easy to over-tighten the spindle nut and cause excessive friction. It should spin without feeling any obvious drag. If it's too loose, it will make a loud rattling racket. Second, the critical temperature is fairly high--165 degrees IIRC is where the grease starts to break down. It tends to "feel hot" at a much lower temperature.

[SScnc]

WOW ! Thanks for that Sansbury ! I found that guy's listing HERE
I was happily suprised to see that it was for the MT-3 too. Using tapered roller bearings is the smart way to go.

I appreciate you posting this before I did the change out. Had you not, I probably would have never known about this guy, I've search for mini mill stuff on ebay allot and never seen him. I'll contact the seller today. I wonder what the RPM rating on these bearings are ? (just curious)

Best regards,

Steve

[sansbury]

Well, I'm interested in this guy's stuff myself, so I'll be looking forward to a report when you're done.

[The Blight]

The CNC lathe I made has the same bearings as the ones listed on ebay. Bought the ones I have at little machineshop. The lathe also has the same belt drive, and I have never had any heat problems.

[mchabot]

Hi,

I have done the tapper roller bearing change on my X2 (with belt).
One important thing is to be sure that the upper roller cage slide on the spindle.
If not, you cannot precharge the bearing correctly. You may also need to shorten the pulley a little bit because roller bearing are wider (1.25mm).

For easy fitting, I heat the housing to 60°C and bearing to -20°C, it really drop directly in place.

Grease lightly the bearings and be very gentle on the precharge, or you will end up with heat again...

[SScnc]

Excellent ! Now that is the way spindle bearings should be. Great pictures too.

Did you order a kit or just find the correct bearings yourself ?

Thanks for the pics and details, nice job,

Steve

[mchabot]

I have ordered the bearings myself (as I am in France).

Here I have a pair of (probably) chinese roller bearing, as I do not want to spend $$ on a rather uncommon mod.
I have a pair of timken that wait the next maintenance round (probably soon as I have a DRO to mount).
Chinese tapper roller are quite noisy, and the surface finish is well bellow timken.

I need also add some shielding, as open bearings can be easily contaminated.

I found that there is a significant drop in chatter (but not as dramatic as other column reinforcement mods). And there is no more fear of damaging bearing when MT3 is stuck (even with lead hammer it was damaging original bearings).
I will try also the belleville washer mod.

[SScnc]

A couple of questions,

Can you provide the numbers on the bearings ?

And they look dry, did you pack them with grease ?

Thanks,

Steve

[mchabot]

They are 30206 bearing (european numbering scheme), this is for MT3 spindle only, as R8 has different shoulders.
They are 30mm inside, 62mm outside, packing width 17.25mm.

When you purchase them, they are lightly greased, but it is not enough for normal use (especially after mounting them with heat and WD40).

I found very difficult to apply the correct amount of grease, too much and you get power loss and heating at high speed, too little and you can destroy the bearing quickly.
I use Rocol sapphire 2 grease and I am quite happy with it (it's a bearing GL2 grease).