Need help making precision rounded rod ends?

[Inflight]

I need help making rounded rod ends.:whiteflag:


My part is similar to a small connecting rod with each end curved around a pivoting shaft. The material is A36 steel, .250" thick and .375" wide and an inch in length. I am attempting to surface grind all faces ±.0001" as this project is part of tool that I'm likely to use often and I'd like to look at something nice.

Over the years, I've rounded all sorts of ends using different methods such as milling with the work firmly affixed to a rotary table, pivoted the part by hand around a pin fixture, and turned larger radii on the lathe using faceplates or similar fixtures. All of those methods worked well at the time and were appropriate for the job at hand, but this time I am striving for much higher tolerances and surface finish.

Here are some typical setups I've seen and used:


Are there any other methods that you would consider very precise and better than the above setups?


Any and All help welcome!

 

[Ray C]

Part of the problem you're facing is that A36 does not lend itself to cuts with precision in the ten-thou range. +/- half thou, maybe. 0.0001, not a chance. The stuff is like gum -warm gum on a hot sidewalk to be precise. Ten-thou work is done on precision grinders on hardened metal upward of 40 Rockwell. The deformation on softer metal is the limiting factor.


I would make the part oversized out of 1045 etc then, heat treat and precision grind to size. You'll need to rig-up some kind of a small rotary grinder instead of an endmill to pull it off.

Ray

 

[Inflight]

...A36 does not lend itself to cuts with precision in the ten-thou range...

I would make the part oversized out of 1045 etc then, heat treat and precision grind to size.
Ray

You are right about material choice. My final version will be some form of tool steel and properly heat treated prior to finish grinding.

You'll need to rig-up some kind of a small rotary grinder instead of an endmill to pull it off.

I think this is a great solution. I'll see what I can do!

 

[Inflight]

The .625" sq stock I started with has one end was stamped 1018. :whistle: That's why grinding has yielded nice results so far as I haven't had to deal with the gummy mess you describe.

I'm still trying to figure out how to build an accurate grinding jig. :thinking:

 

[astjp2]

Ball turner on a lathe then mill flat, you can do it with a tool post grinder. Tim