Homebrew PCBs

Stefan Trethan wrote:
> @adam on more question to tapered roller bearings:
> 
> are they "encased" by the bearing shells like thrust bearings?
> so that they are ready to use?
> i saw some on the web but they had the case rings like standard ball 
> bearings.
> so it is difficult to mount them by plates at the side.
> the angle of the rollers was only a few degrees off parallel to the axle.
> which one do you have?
> maybe i'm looking for the wrong type - are your bearings similar to thrust 
> bearings?


> which angle has the center of the rollers?
> are they more parallel to the axle or more in a right angle to it?

Yes, more parallel to the axial.

here are some links that might help.

http://www.efunda.com/DesignStandards/bearings/bearings_tapered_roller.cfm

here is a list of standard sizes, the bearings I used have part # 
  LM11749/10
http://www.zxz-bearings.com/taper.htm

There are two difficulties, with the tapered bearings. One is the 
outer case needs to fit inside a bored out hole, because the 
inner case sticks out a few mm. Alternatively you could make a 
mount using a flat plate and cut out a hole so there is some 
clearance for the inner bearing case. The opposite side of these 
bearings have the inner case facing out, so that may be able to 
clamp with friction to a flat surface. The second difficulty is 
trying to seal the bearings from dust and drill swarf, because 
tapered bearings are exposed. I haven't sealed the bearings on my 
machine yet.

It may be easier for you to use clutch thrust bearings, if you 
don't have the right tools. I'm sure if these are separated a 
greater distance than on my first drill machine, then you won't 
have a problem with side movement. My first machine used a 600 mm 
long arm and the bearings were separated 50 mm. This is a very 
large leverage, and probably why I needed two extra bearing 
guides in the middle of the arm.