GearHeads Forum

If you think the end mill is flexing then instead of running a single pass run it a second time. If it is bore is bigger after the second pass  then you have flex.
Dan Mauch

marklazarz wrote: Since I use a CNC to cut holes for my bearings, I can make them any size so I decided to investigate press fits.  I found that with a bearing OD of 0.875", a press fit in plywood was -0.005" and in Oak -0.009".  Kind of surprising but I figured it had something to do with cutter flex using a 0.125 end mill.  I'm sure that machine calibration is critical when dealing with these small differences.  I would be interested in hearing what others have found if they did any experimentation.

Since I use a CNC to cut holes for my bearings, I can make them any size so I decided to investigate press fits.  I found that with a bearing OD of 0.875", a press fit in plywood was -0.005" and in Oak -0.009".  Kind of surprising but I figured it had something to do with cutter flex using a 0.125 end mill.  I'm sure that machine calibration is critical when dealing with these small differences.  I would be interested in hearing what others have found if they did any experimentation.

I happened upon a video of bearing manufacture, a serious kinetic marvel in itself...

https://www.youtube.com/watch?v=7E7n3OtrauU


Eric

Another unusual source of  bearings are those used in modern high performance yo-yos. They are small but might be good for small scale clocks ot toys made with plexiglass gears.

Yomega yo-yos are the ones I'm fmailiar with.  They would spin for a long time.

Bill

Mark,
  Great idea for a dedicated thread. I'm curious, does anyone else feel that modern skateboard bearings have far more friction than those from the past? I remember spinning my skateboard wheels as a kid, they used to spin quite freely. These modern bearings give one or two revolutions. I don't remember the bearings being shielded or caged either.

Anyone agree?


Eric

Thanks for the info Mark..


Cheers
Bob

There seems to be a lot of interest in bearings and their importance in kinetic sculptures, clocks, etc. so I thought a new discussion thread with the topic might be useful.  Although it is probably obvious to anyone using bearings, one hint is to make sure nothing touches the sides of the outer race of your bearings.  I am fortunate to have a lathe so I can machine washers to an appropriate OD by holding them in a jig designed for the purpose.  The washer is held on a mandrel with a lip slightly less than the thickness of the washer, the lip is machined to the ID of the washer and the washer is held in place by a screw when turning.  Tube spacers are also useful for keeping things properly positioned and allow all components on a shaft to be tightened securely without compromising the reduced friction afforded by the bearing.

Mark