IH - RF45 bearings

[skray775]

Hi guys,
While working with my machine today the lower spindle bearing started to heat up pretty good. I was on borrowed time with the belt conversion running 6500 rpm and stock tapered roller bearings.

My question is about angular contact bearings for the spindle. It is my understanding that in a perfect world one would have a double set of AC bearings at the bottom of the spindle with a single regular bearing at the top. This eliminate the thermal expansion messing with the pre load I guess.

So on our less then perfect machines (RF-45 types) do you simply replace the tapered roller bearings with AC bearing (one on top and one on bottom) and get the pre load as close as you can? Or have you guys been machining out the lower spindle for a double set of bearings at the bottom?

I am looking at:

7207BMU Nachi Angular Contact Bearing 35x72x17 Brass Cage C3 Japan Ball Bearings... $40.00 each.

Or

7207 Nachi Angular Contact Bearing Steel Cage C3 Japan 35x72x17 Ball Bearings... $23.00 each.

Thank you for your help.

Similar Threads:

• RF45 Spindle Bearings giving up the ghost
• skate bearings versus linear bearings
• Double Bearings Or Quad Bearings?

[arizonavideo]

I think the preload is stabilized a bit by the fact that the spindle shaft is so long that it stretches a bit under high preload!

Both of the new bearings are slightly shorter than stock TRB's but the spindle nut will thread on further and almost needs a shim to set preload but should work with no mods.

I did mine and it was no problem and I found a brass cage USA bearing for $22 that gave .0002" runout.

I often end up milling deep profiles with larger cutters in steel like a 5/8" x 4" carbide cutter and I don't see the single bearing being a problem, machine flex and tool pullout yes, but not the bearing so far.

My preload ended up a bit high so I still have a fair amount of heat but no problems so far. Its making about half the heat of the TRB.

There is two small drilled holes in the lower spindle housing to help you drive out the lower race, they are not real easy to see if you don't look for them. The fit is tighter than really needs to be so clean the seat well or the new race wont seat. The upper race can be driven out by a long screw driver with a bent tip or just a shaft with a bend at the end.

If you don't go over 6500 RPM much the top bearing could be left in. It is smaller and will do better at high speed than much larger TRB at the big end.

I bought a spare 7207 Nachi to have sitting around just in case I need to do a quick replacement.

I think with some luck you could change out the lower bearing in around two hours.

I don't think there is enough metal in the housing for two bearings and considering how long a single should last and the replacement cost of a spare bearing, keeping a spare around might be just as well.

I did spend some time looking for a good low cost spindle grease as I have 4 that need re packing. I went with Mobil SHC100 NLGI 2 lithium synthetic.

It has a similar melt point and thickness as the Kubar NBU 15 and cost about $13 a 13oz tube. McMasters has it.

"The official grease of NASCAR."

So far so good on the IH A/C spindle bearings.

[skray775]

Great info AV !

Did you have different size bearings in the spindle? I see 7207 on both the top and bottom of mine. The spindle is out but not the bearings.

EDIT...
Never mind, the top and bottom bearings are different size. I will order the AC bearings today.

[ninefinger]

Hi Kelly,

Mind sharing what the top bearing size is? I might just buy some bearings in prep for a belt drive mod...

Mike

[skray775]

Hi Kelly,

Mind sharing what the top bearing size is? I might just buy some bearings in prep for a belt drive mod...

Mike

Sure Mike,

Ordered them today from VXB Bearings.

Code Product Quantity Price/Ea Total
Kit10017 7207 Nachi Angular Contact Bearing Steel Cage C3 Japan 35x72x17 Ball Bearings 1 $22.88 $22.88
Kit10016 7206 Nachi Angular Contact Bearing 30x62x16 Steel Cage C3 Japan Ball Bearings 1 $17.88 $17.88

[arizonavideo]

If you have not driven in a lot of bearing races the big problem is having the race tilt sideways and skim a thin sliver of metal in front of the race which will stop the race from seating flatly. They fit really tight and others has said the same. If your race does caulk sideways it is good idea do drive it out and look for a burr.

I made a plug from aluminum to drive it in but I also made a 6" shaft that fit the plug so I could hold it straight while driving the race in.

The force is high so the bench was not stiff enough so I used the floor with a piece of soft aluminum as a buffer and a good size hammer.

I have done hundreds of bearing replacements as I use to be a mechanic so the job was no big thrill but a race driver that fit well really helped.

Have fun
Dave

[skray775]

Thank you AV,
I have done a few bearings but never hurts to listen to other people experience.

So I have the bearings in hand an tell me if I am wrong on this....

In the picture the lower spindle bearing surface was sized to have the tapered roller bearing pressed onto the shaft and the bearing race pressed into the quill.

With AC bearings shouldn't the bearing be a very tight fit but still be able to slide onto the shaft with light pressure? If you have to press the bearing on the spindle and then press the bearing into the quill housing it would make it pretty difficult to set the pre-load unless the upper bearing can slide on the shaft as well.

I was thinking of lightly sanding the bearing surface until the AC bearing will start to go on with light tapping/pressure.

What are your thoughts on this?

[skray775]

All done and back together.

Its late so I will do the testing in the morning.

[arizonavideo]

A light slip fit would not be OK for the inside race, you need a fair amount of preload on all surfaces to maintain a ridged system under load.

Mine was not too bad. A press would be easier but if you set up the drivers well it is fairly easy with a hammer and a piece of pipe with a squared end.

[wizard]

All done and back together.

Its late so I will do the testing in the morning.

I'm a little late but have a few pointers for the next time.

Freeze the spindle and heat the bearing about to be pressed on. If you don't have a bearing heater a toaster oven can do the job. The bearing inner race at the spindle nose has to be a press fit at normal temperatures ( on most spindle designs), however nothing says you have to assemble at normal temperatures. Do consult with the bearing supplier for maximum temperatures for the bearing. With the right temperature differentials the bearing should slip on or at least be much easier to put on.

On spindle designs where you have adjustability for the preload the rear bearings inner race shouldn't be as tight of a press fit. That would lead to adjustability issues. However sloppy is not acceptable. The adjustment nut should be able to push the inner race forward with a spanner wrendh applying torque to the nut. if it can't with reasonable effort your chances of properly adjusting the preload is thin at best.

[skray775]

I'm a little late but have a few pointers for the next time.

Freeze the spindle and heat the bearing about to be pressed on. If you don't have a bearing heater a toaster oven can do the job. The bearing inner race at the spindle nose has to be a press fit at normal temperatures ( on most spindle designs), however nothing says you have to assemble at normal temperatures. Do consult with the bearing supplier for maximum temperatures for the bearing. With the right temperature differentials the bearing should slip on or at least be much easier to put on.

On spindle designs where you have adjustability for the preload the rear bearings inner race shouldn't be as tight of a press fit. That would lead to adjustability issues. However sloppy is not acceptable. The adjustment nut should be able to push the inner race forward with a spanner wrench applying torque to the nut. if it can't with reasonable effort your chances of properly adjusting the preload is thin at best.

I was able to get the spindle nose bearing pressed on without issue using the pipe method AV talked about below.

For the upper bearing I did sand or polish slightly the bearing surface so the inner race could move and adjust the pre load.

Same principal as the ball screw ends supported by AC bearings... something has to move so the nut can control the pre-load.

Now I did fight the pre load setting most of the day but I think I got it. I sure am tempted to cut a hole in the front of the spindle housing to get at that adjusting nut from the front panel without having to remove the spindle. Since I have a belt drive the gear box is empty anyway!

I am getting .0005 run-out on the finished edge of a Tormach TTS holder. I wonder if I should skim the spindle nose with a lathe tool again since it has new bearings.

[arizonavideo]

What runout did you have before?

[skray775]

What runout did you have before?

I looked back on my build thread and I can't find that info. I know I measured it but never poasted it and forgot... It's hell to get old!

Anyway I decided to measure again today with a tool instead of the edge of the holder.

It looks like .0002 if I turn it by hand but here is a video at 500 rpm.

[arizonavideo]

I would say that the $23.00 bearing was money well spent.

I often see people buy the high dollar bearings but most of the time a good quality standard bearing give great results.

When your down to .0002" with a tool holder you are doing quite well.

[Randdy]

I would say that the $23.00 bearing was money well spent.

I often see people buy the high dollar bearings but most of the time a good quality standard bearing give great results.

When your down to .0002" with a tool holder you are doing quite well.

I am totally agreed with you and i only focus on good quality rather than spending money.

[rwskinner]

AV, so did you use AC bearings for top and bottom or an AC for the bottom and TRB for the top? I don't have a clear picture of what your stating.

Richard

I think the preload is stabilized a bit by the fact that the spindle shaft is so long that it stretches a bit under high preload!

Both of the new bearings are slightly shorter than stock TRB's but the spindle nut will thread on further and almost needs a shim to set preload but should work with no mods.

I did mine and it was no problem and I found a brass cage USA bearing for $22 that gave .0002" runout.

I often end up milling deep profiles with larger cutters in steel like a 5/8" x 4" carbide cutter and I don't see the single bearing being a problem, machine flex and tool pullout yes, but not the bearing so far.

My preload ended up a bit high so I still have a fair amount of heat but no problems so far. Its making about half the heat of the TRB.

There is two small drilled holes in the lower spindle housing to help you drive out the lower race, they are not real easy to see if you don't look for them. The fit is tighter than really needs to be so clean the seat well or the new race wont seat. The upper race can be driven out by a long screw driver with a bent tip or just a shaft with a bend at the end.

If you don't go over 6500 RPM much the top bearing could be left in. It is smaller and will do better at high speed than much larger TRB at the big end.

I bought a spare 7207 Nachi to have sitting around just in case I need to do a quick replacement.

I think with some luck you could change out the lower bearing in around two hours.

I don't think there is enough metal in the housing for two bearings and considering how long a single should last and the replacement cost of a spare bearing, keeping a spare around might be just as well.

I did spend some time looking for a good low cost spindle grease as I have 4 that need re packing. I went with Mobil SHC100 NLGI 2 lithium synthetic.

It has a similar melt point and thickness as the Kubar NBU 15 and cost about $13 a 13oz tube. McMasters has it.

"The official grease of NASCAR."

So far so good on the IH A/C spindle bearings.

[arizonavideo]

I changed both to A/C but the top bearing could be left a TRB because it is much smaller and can go 8000 RPM just fine and they are stronger than a A/C bearing. It is a bit thicker too so you might not need to add a shim under the nut to have things fit. The A/C bearings are shorter/ thinner.

I only changed my top bearing because I knew I would be doing some high speed testing of the belt drive units and I didn't want to run into bearings problems. I don't think its a good idea to run the spindles much over 6500 RPM anyhow.

[circlecn]

Hi, lots of good information in this thread. I am replacing these two spindle bearings on my IH-RF45 which I acquired 7 years ago. The TRB on this IH are only 14mm and 15mm thick. The replacement A/C bearings are 2mm thicker (16mm and 17mm). My question is do I need to machine both ends to accept these thicker bearings. I am a novice as you might gather from my question. Thanks for any help.

kent

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[Uguessedit]

Old post but I am curious if anyone has doubled them up too. Also the very top two of the four deep groove seem to be standard abec 1 quality on all my mills and wondering if anyone upgrades those? Especially given a belt drive conversion it seems abec 3 is the way to go since nothing better is available out there right now in a standard deep groove. Obviously ac bearings won’t work where they can’t be preloaded. I blew a seal on one of my mills so I figured I’d change all the seals and bearings. I might even make my own belt drive if time allows.

Hi guys,
While working with my machine today the lower spindle bearing started to heat up pretty good. I was on borrowed time with the belt conversion running 6500 rpm and stock tapered roller bearings.

My question is about angular contact bearings for the spindle. It is my understanding that in a perfect world one would have a double set of AC bearings at the bottom of the spindle with a single regular bearing at the top. This eliminate the thermal expansion messing with the pre load I guess.

So on our less then perfect machines (RF-45 types) do you simply replace the tapered roller bearings with AC bearing (one on top and one on bottom) and get the pre load as close as you can? Or have you guys been machining out the lower spindle for a double set of bearings at the bottom?

I am looking at:

7207BMU Nachi Angular Contact Bearing 35x72x17 Brass Cage C3 Japan Ball Bearings... $40.00 each.

Or

7207 Nachi Angular Contact Bearing Steel Cage C3 Japan 35x72x17 Ball Bearings... $23.00 each.

Thank you for your help.