Steve- yep thats me.
I'm forever looking for ways to manufacture same(or better) quality faster to bring my end prices down.
I found full specs on those bearings and they are only rated up to 28krpm. Other bearings with higher speed rating are getting a little too far out of my range... typically 3x the price. I couldnt imagine having to build a spindle for a "real" machine.
To get around the thermal expansion, I could "back-to-back" these two bearings on the nose end of the spindle (image here:
http://www.micro-tools.com/Merchant2...ode=SHER-40230) and then a regular bearing on the top, as I believe someone mentioned. Any suggestions for use for a bearing on the top? 20mm ID, 42mm OD and 30k rpm rated. somewhere in the $80-$90 range..
OR
Go ahead with the one on top and one on bottom configuration as mentioned by c-c-cncboy with the spring washer(s) there ready to take up the thermal expansion. How much "preload" do these usually have on them? In otherwords, how many LB of spring pressure should I plan to place on the top bearing to complete the "sandwich"?
I really like this method more.. for a few reasons-
- "drop in" modification in the Sherline spindle assembly (bearing "sandwich").
- cheaper since its only 2 instead of 3 bearings.
- according to the bearing data sheet for these (
http://www.nachi-fujikoshi.co.jp/eng...df/183-198.pdf part #7004CDB), when used in the duplex is when they are limited to 28krpm.. when in single they are rated to 35krpm!! I assume this is due to cumalative heat when they are next to each other??
So a cooling mechanism is called for as well... hmm. Will something as simple as pressurizing the housing between the bearings so that air escapes through them provide enough cooling? (this is the cooling method of the Kavo spindle). Or how about air blowing over cooling fins in the head/housing?
thanks so far all!
Colin