Thread on Ball bearing

[Niels Abildgaard]

I am trying to build the simplest possible two stroke crank and crankcase held togetherwith screws.quite conventional I would say.Picture Total
It would be much nicer to use the 90mm outside of the roller bearing as locking device.
Picture Skruet
Off cource it can be ground somehow and expensive.
Can it be screwcut with carbide?

 

[n4zou]

Why not a simple press fit?

 

[MuellerNick]

Ball bearings have a hardness of about HRC 55. And you can turn that with CBN. You might try your luck with carbides, but they won't last long, especially with the sensible tip of a threading tool.
And you need a stiff lathe.


Nick

 

[Swifty]

How about shrinking a ring onto the outer dia of the bearing, then screw cutting that.

Paul.

 

[Niels Abildgaard]

Thank You n4zou and Swifty for suggesting press fitting one way and another,but that will change the running clearance of the bearing and then by the way was not invented by me.
Thank You NickMuller for threading advice.
I like to think my Boxford on Rock the most rigid of the big Southbend family in the whole world and my homemade carbide holders likewise.Hope I am rigth as such CBNs are expensive I think?

 

[mu38&Bg#]

What is the speed rating of the bearing? Are you using a 4 point contact "x" type?

 

[Niels Abildgaard]

Hello Greg
The bearing is 90 times 70 times 10 mm and tolerates at least 8500 rpm.Piston stroke is 60 mm.Probably C3 clearance due to outher ring being compressed sligthly by screw action.It is not nessecary to use preloaded four point bearings.The crank tilting torque during revolution varies but never becomes zero.It is a two stroke