Trouble cutting bearing pockets

Tony Wells said:
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.
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Good point! OK then, I would bore it out all the way through to bearing OD size. Then make an internal bushing/spacer that would go between the bearings. This bushing/spacer could be a press fit or whatever. No flipping required. And no OD worries. Guaranteed perfect alignment…Dave
 
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Wow, thanks for all the replies. This is very helpful for someone of my experience.

First of all, the 2" is extruded 6061 and are all short pieces from the salvage yard. After reading the replies, I'm thinking boring all the way through would be the best approach for me. I was trying to avoid turning the outside diameter, it fits nicely in a 2" hole cut in oak using a fastener bit. Will try to get a photo of the project.
 
RHayes said:
Wow, thanks for all the replies. This is very helpful for someone of my experience.

First of all, the 2" is extruded 6061 and are all short pieces from the salvage yard. After reading the replies, I'm thinking boring all the way through would be the best approach for me. I was trying to avoid turning the outside diameter, it fits nicely in a 2" hole cut in oak using a fastener bit. Will try to get a photo of the project.
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if you bore all the way through the bearings will align to the accuracy of your lathe, so more than good enough. If you bore all the way through turning the OD would be up to you. If the ID is concentric enough to the OD for your purposes no need to turn it true.
 
Thanks Dan, thats what i'm thinking.
Here is a photo. A friction drive for a compact spinning wheel.

In the photo is an empty hub with a 5/8 o.d. bearing installed in the outside diameter. This leads me to another question that should probably another thread. I plunged a 5/8", 4-flute milling cutter and the bearing fits loose. What I need to know is if I can lightly grind the 5/8" to reduce its outside diameter? friction drive.jpg friction drive.jpg
 
Trying to get an accurate hole by plunging with an end mill is problematic at best, when plunging with an endmill they tend to wobble around. It is possible to drill a pilot hole that is just undersize and then plunge with the end mill but this still may not make an on size pocket. A 2 flute would be better than a 4 flute for this operation. Reaming or boring would be a much better option.
 
You could, but it's not really reasonable to expect to hold bearing fit tolerances with an end mill. That's an application for a reamer. In aluminum, a reamer would last nearly forever, especially if you spring for one that is carbide tipped.
Lightly stoning an end mill will reduce the clearance on the flutes, inducing the probability of dragging. Not good for finish or fit. I find that many, if not most carbide end mills are ~0.002 under nominal anyway, so with that and a little runout from your collet, you might get close enough, but that really isn't good practice for machine work.
 
Boring through the blank seemed like an awful lot of material removal, vs using say a thick wall tubing and the appropriate size bearings. However it sounds like RH is getting drops from the scrap yard so that is the starting point.

I certainly agree boring thru would be the most accurate.

David
 
If nothing else, this thread illustrates that in machining there are many ways to skin a cat.
 
I don't know what the speed and loads are, but just thinking out loud. This seems like it could be an ideal application for oil impregnated sintered bronze bushings. Perhaps a pair of OD 5/8", I.D 1/2" x 1/2" long. That would only require one straight through bore for a slight interference fit. Could heat the slug in the oven and slip them in from both ends.

Also with that bearing in the side, I wonder if we are running out of wall thickness if we do a straight through 1.125 " bore?

Boring the side pocket for the smaller bearing seems like and ideal application for a small boring head...or perhaps fixture to the lathe face plate and bore it that way?

David
 
RHays, did you find a workable solution?

I'm in the planning stages of a DIY 2x42 belt grinder, and I would like to turn my own rollers. Since I'm working on a mini-lathe I'm very limited in terms of tooling and work space. Your issue is the same one I will face, and I'd love to know how I'm going to work around it before I start!

Thanks!
 
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