Isopropyl & Dry Ice Cooling Bath for Bearings

[macardoso]

I want to make sure I am understanding what this part does, I took a look at the parts manual on the Grizzly site and it looks like you are making a new part to drive the spindle spline that will be connected to the motor? If so, then yes an H6 fit would likely be proper for the application since you will have a point load from the motor torque on the housing. Since you are using a CN bearing, I would not want to have interference in the fit that would compress the outer ring after installation, and the point load should keep it from spinning in the housing.

The limiting speed you referenced in a comment above can be higher or lower than what is stated in the bearing catalog and is based on the actual load conditions. The number in the catalog is for a standardized condition and there are adjustment factors for your actual conditions. Do you have a way to install a temperature sensor in the housing so it directly measures the outer ring? The limiting speed assumes 70C outer ring temperature. The standard also assumes a load of 5% of the static rating of the bearing and an ambient temperature of 20C.

Once you get this running, I would run it in in stages to see how the temperatures go to make sure you don't seize a bearing. If the temperature runs away too quickly, it can lock the bearing and do a good bit of damage. If you find the temperature is getting too high, you might need to use C3 bearings in this application.

The Explorer bearings Beckerkumm mentioned are similar to FAG X-Life bearings that are made to P6 standards and are smoother running and can carry a higher load than standard bearings without much added cost, so if the size you are using is available in that series, it is a good idea to go with those.

Sorry for the delayed response. This will be a tad confusing because I have modified my G0704 spindle for belt drive w/o quill function. You are correct that I am replacing the upper drive tube (items 205-207 in image below). The main difference is that my spindle is driven by a pulley on the spindle itself now rather than through the spline. This new tube simply supports the long and skinny spindle for the radial loads of the belt, and minimizes radial runout of the pulley. I have the option to mount an encoder to this assembly, so there is a plastic spline disc to transmit a small amount of torque to this tube (just to prevent them slipping relative to each other) but no cutting load will be seen by this assembly. Additionally, the spindle floats axially in this new assembly so no thermal growth will add axial loading to the bearings. This new assembly was needed to downsize the bearings to reach the 10,000rpm drive speeds desired.



Since the new bearings are smaller than the stock bearings, There is an outer housing to create the needed fit between the bearings and the bores in the existing housing. The entire assembly looks like this:





Here is a colored coded assembly diagram. I've already machined the orange shaft, and I'm working on selecting the final fits for the purple housing.



I think a looser fit for the housing seems to be appropriate. H6 seems to be that fit, but I have no experience in this.

I'll price out those bearings! Thanks for the info.

 

[Ischgl99]

It looks like there is a small gap between the part with the bearings and the spindle, is the pinkish part the pulley and is it fitted to the new hollow shaft so that the pulley torque is transmitted to the bearings? If there is not any radial or axial load on these bearings, they could skid and fail quickly, especially at 10,000 rpm. Bearings have a minimum load they must be subjected to to keep this from happening. To keep the outer ring from rotating during use with an H fit, there needs to be a point load. If the pulley is fitted to the hollow shaft, then the force from the motor torque will exert an opposing force on the outer ring and keep it in place, so an H6 fit should work in that case.

 

[macardoso]

It looks like there is a small gap between the part with the bearings and the spindle, is the pinkish part the pulley and is it fitted to the new hollow shaft so that the pulley torque is transmitted to the bearings? If there is not any radial or axial load on these bearings, they could skid and fail quickly, especially at 10,000 rpm. Bearings have a minimum load they must be subjected to to keep this from happening. To keep the outer ring from rotating during use with an H fit, there needs to be a point load. If the pulley is fitted to the hollow shaft, then the force from the motor torque will exert an opposing force on the outer ring and keep it in place, so an H6 fit should work in that case.

The hot pink element is the pulley which transmits torque to the dark blue spindle. The spindle is quite long and flexible at the back end, so the radial load is supported by a transitional fit between the spindle (blue) and the upper bearing assembly tube (orange). The static belt tension is in the 25lbf range and my calcs show that the belt tension can reach 300lbf at full speed and rated torque. This passed the SKF calculator requirements for minimum radial load to avoid skidding.

These bearings should experience the full radial loading from the belt, but no axial loads. At least that’s the plan

 

[Ischgl99]

The hot pink element is the pulley which transmits torque to the dark blue spindle. The spindle is quite long and flexible at the back end, so the radial load is supported by a transitional fit between the spindle (blue) and the upper bearing assembly tube (orange). The static belt tension is in the 25lbf range and my calcs show that the belt tension can reach 300lbf at full speed and rated torque. This passed the SKF calculator requirements for minimum radial load to avoid skidding.

These bearings should experience the full radial loading from the belt, but no axial loads. At least that’s the plan

That’s good, I wanted to make sure I was understanding it correctly. I would go with the H6 fit.

 

[Inferno]

FWIW, most places who supply liquid nitrogen will "loan" a dewar if a customer only needs the liquid nitrogen once or twice. They might ask for a deposit.
I'm lucky enough to own a pair of 30 liter dewars . Someday I want to have a reason to use one or both.

 

[macardoso]

The Explorer bearings Beckerkumm mentioned are similar to FAG X-Life bearings that are made to P6 standards and are smoother running and can carry a higher load than standard bearings without much added cost, so if the size you are using is available in that series, it is a good idea to go with those.

So I looked and you cannot buy the X-life bearing in deep groove radial, but you can buy FAG's "Generation C" line of bearings. Ended up being $35 for the pair and dang these are nice. You can hear the see the differences in quality between these and the unbranded VXB bearings I previously bought. The metal shields have nearly zero clearance to the inner race which is really impressive.

I don't want to remove the bearing I already installed so I'll keep the 6206 from FAG as a spare, but install the FAG 6205 on the bottom of the shaft.

 

[Ischgl99]

So I looked and you cannot buy the X-life bearing in deep groove radial, but you can buy FAG's "Generation C" line of bearings. Ended up being $35 for the pair and dang these are nice. You can hear the see the differences in quality between these and the unbranded VXB bearings I previously bought. The metal shields have nearly zero clearance to the inner race which is really impressive.

I don't want to remove the bearing I already installed so I'll keep the 6206 from FAG as a spare, but install the FAG 6205 on the bottom of the shaft.

Sorry, I forgot the DGBB are not available in x-life. I haven’t kept up with the latest news since I have been out of industry, so I took a look into the generation c bearings, it sounds like they have the same benefits as x-life. That would explain why the DGBB are not available in x-life.

The top tier bearings are a noticeable improvement over the bargain brands, I’m glad you got to see that first hand. I have seen some of the internal test results between the top tier bearings and overseas counterparts, I won’t even consider those no name brands after that.

I’m looking forward to seeing your machine up and running!

 

[woodchucker]

I hope you realize that the Name Brands Timken for example make a lot of their bearings in China now. I bought Timkens, spent way more than others available to me, and got Made in China on the boxes. I was very upset.

 

[Ischgl99]

I hope you realize that the Name Brands Timken for example make a lot of their bearings in China now. I bought Timkens, spent way more than others available to me, and got Made in China on the boxes. I was very upset.

Yes, Timken has been doing that for a while. I don’t believe FAG or SKF import from China, but they do have manufacturing plants all over the world, so you might not get a German or Swedish bearing if buying one of those.

 

[pontiac428]

Yes, Timken has been doing that for a while. I don’t believe FAG or SKF import from China, but they do have manufacturing plants all over the world, so you might not get a German or Swedish bearing if buying one of those.

I don't know about FAG, but SKF has lines in China. Unlike Timken, they have the good sense to put different brand names on their economy lines so the buyer knows the difference.

The Chinesium Timkens I've bought for my equipment are holding up just like... new bearings. They seem good. They're Amazon priced. I'm guessing they have to meet some kind of quality standards to wear the name, so given the choice between them and regular generic China bearings I've been hedging on the Timkens. Of course, I could just be another sucker paying for tap water in a bottle with a french sounding name and a picture of a mountain on the label.