Trouble cutting bearing pockets

R

RHayes

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I want to install bearings (R8 2RS) in both ends of a 1.5" piece of aluminum round bar that is 2.00" diameter.

In a 3-jaw, I face it, bore 3/4" through, then cut the first recess. Remove from chuck, reverse, cut second recess. Then install the bearings, with a light press fit,

Any tips on improving the accuracy? The .5" shafting never fits as well as the individual bearings do on the shaft. I have a Grizzly 4003G with 3-jaw and try to reverse the piece as best I can but feel this isn't the proper way to do this operation. Ultimately, the 2" round "hub" gets installed in a woodworking project not requiring high tolerance or subject to high load, but I still want to do the bearing installation as best I can, and ultimately would like to make 50 or more of these.

Thanks in advance for any suggestions.
 
The problem comes when you turn it around, and is likely mostly due to the inherent inaccuracy of the three jaw chuck. If you use a four jaw chuck and dial it in carefully for each end, you should have better results. Your piece is not very long, but you still also need to check and correct for runout from one end of the part to the other while it is chucked as well.

Edit: Another thing you can do is to accurately finish the through hole bore while doing the first side, and then turn it around and indicate the hole on the second side to get it lined up better. Still need to watch for runout from end to end while mounting in the chuck...
 
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Once you move the work it indeed will move.


Suggest drill slightly smaller then bore through so you have a good reference.

Flip part and 4 jaw should be used but you could test centering with dial indicator in bored hole and maybe shift in chuck until it runs true.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
Normally, to get the best out of flipping work like that you have to at least skim cut the OD of the stock to get a round surface. If they are already cut to length you have to go another route. You also have to avoid chucking too tightly on an aluminum piece with ~7/16" wall. If you were going to make 50 and sawed them, you could forego the OD turn if you face/bore through/counterbore as a first operation, then make up a expanding stub mandrel for the other end. Then you would face to finish OAL and counterbore for the other bearing.
 
like what Greg said about boring all the way through--or start with a thick walled 2" OD tube if you want to make many, and use a spacer lightly pressed between the bearings---spacer can be pinned to housing after bearings are pressed in if desired.----Dave
 
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Spacer could even float a little if the bearings were tight enough. Just make sure if you go that way to make the spacer ID large enough to pass the shaft easily.
 
I would not flip the round bar in the chuck. I would use a steady rest set-up when machining BOTH ends of the round bar. Taking a skim cut on the OD ends before you start would be a good idea as well...Dave
 
The way I read it, the OAL is 1.5", so steady rest is not much help. Turned OD and bored soft jaws would be the best way for me to do it.
 
My first question would be did you turn the bar OD to 2.0" or is this raw bar stock? If it's just plain extruded aluminum, you can not trust that it is round.

Unless you have a really dialed in 3 jaw, the bores won't be coaxial, and that will cause binding.

The best way to hold something like this, is in a collect (unlikely at that diameter). Next would be a 4 jaw if you only have one or 2 to do. Finally would be custom soft jaws like Tony said.
 
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