Chris G0704 Build

Since I upgraded the spindle motor the Achilles Heel on my machine has been the spindle bearings. No matter which bearings I've tried AC or tapered its always had mediocre TIR (.0015" - .003"). Now that I've installed the bigger motor they haven't been lasting very long either. The VXB AC bearings only lasted a month or so. I tried Timken tapered bearings and they were a little better but only lasted a few months. The last set I bought was bad right out of the box. I decided to try NSK HR32005XJ and HR32007XJP5 bearings from eBay. These bearings are much smoother than even the best set of Timkens I've bought. I broke them in for a couple hours yesterday and they were only 30F over ambient. The spindle is much quieter than it's ever been before too. I measured it at 76dB at 6750 rpm. The TIR at the bottom of the spindle taper is .0007".

Right after I purchased these bearings someone pointed me to a thread on CNCZone about better bearings for the G0704. SKF's XQ series bearings have tighter tolerances and higher rated rpms on grease than any of the others I've looked at. Next time I need a set I'll be purchasing these.

SKF 32005XQ Reference speed 11000 rpm, Limiting speed 14000 rpm
SKF 32007XQ Reference speed 8000 rpm, Limiting speed 10000 rpm

Here's a link the thread. It contains a lot of good information:
CNCZone - G0704 Tapered Bearing Upgrade
 
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That is the one upgrade that I have been avoiding for years now and mostly because of that same thread you linked.
I've stripped out the gears and converted to belt drive and amazingly enough, I'm still on my original bearings....knock on wood!

I work on mostly acetal, UHMW and PVC though so my loads are very small. I know if I start doing more heavy work that a bearing upgrade will be inevitable.
 
I think the stock bearings are fine if you're running stock speeds. I'm running my spindle at 3X stock (6750 rpm). That's what kills the cheap bearings. The loads we're putting on the spindle still aren't that high. These bearings are used as wheel bearings so they have to be able to handle loads a lot higher than we'll ever put on them.
 
I'm pricing out the SKF bearings today. I found both on Amazon for around $60. That seems pretty reasonable.
I have a call in to our SKF rep as well to see if our pricing is any better.
 
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If you find them on Amazon please post a link. I’ve searched and found them through Google but couldn’t find them on Amazon’s search engine.

I also tried to order them from a bearing shop. They told me that it wasn’t stocked by SKF but if I wanted 25 they would make them for me.
 
Amazon and eBay are known for selling knock-off bearings so I avoid them for anything critical like this or on my vehicle but here are the links.

SKF 32007 X/Q Tapered Roller Bearings 35x62x18mm Same Day Shipping !!!: Amazon.com: Industrial & Scientific

SKF 32007 X/Q Tapered Roller Bearings 35x62x18mm Same Day Shipping !!!: Amazon.com: Industrial & Scientific
www.amazon.com

SKF 32005XQ TAPERED ROLLER BEARING: Amazon.com: Industrial & Scientific

SKF 32005XQ TAPERED ROLLER BEARING: Amazon.com: Industrial & Scientific
www.amazon.com

I have a set coming direct from SKF. I don't know the price as we spend so much money with them a year that he just said not to worry about the cost.
 
Hmmm, that's interesting. When I looked for those bearings the 32007 was double the price of the 32005. When I placed my order they called me and said that the 32007XQ wasn't available but they could provide a 32007X at the same price. The X version is lower quality and higher runout. needless to say that I declined.
 
If you look at the pics of the 32007, the label on the box only shows an X not an X/Q which may explain the lower price, (and support my apprehension of ordering through Amazon sellers).
 
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