soft O-1, best wheel to grind radius into it.

I have to grind a 6mm radius into a length of annealed O-1. Surface roughness of .8um

Part is 12mm wide (radius on all long edges) 20mm tall and 80 long. Hardened to 60C

How much do you think it will warp?

6mm radius, 12mm wide . . .
If ground INTO the part you are left with sharp edges sticking up, and will likely warp enough to come off the chuck with a loud noise. If on the part, you are left with a 12mm diameter, and could likely do it easier on a cylindrical grinder with very little warp.

Mebfab said:

I have to grind a 6mm radius into a length of annealed O-1. Surface roughness of .8um

Part is 12mm wide (radius on all long edges) 20mm tall and 80 long. Hardened to 60C

How much do you think it will warp?

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If I am reading this correctly, you end up with a part with two opposed parallel flats 8mm wide and two opposed parallel convex radiused surfaces with a 12mm diameter? In other words the part is symmetric if sliced in half along its central long axis? And the part is only about 4 times as long as it is wide?

And you are required to grind it first in annealed condition and THEN harden it?

Finally, if the grind/hardening order is specified as I asked, using A2 to minimize distortion is not allowed?

Denis

A CNC cylindrical grinder would do it right quick. A manual grinder could not do a 6mm radius on an 20mm piece. Cut a 45 on the corners before grinding the profile.
I'd use a cold air gun on the piece, minimize warping.

The parts are 12mm wide. The height is 15-45mm depending on which one. Think of rectangular barstock with a radius on the corners down the length. I will rough with corner rounder. Then grind or better yet leave a little over, harden then finish grind.

Mebfab said:

The parts are 12mm wide. The height is 15-45mm depending on which one. Think of rectangular barstock with a radius on the corners down the length. I will rough with corner rounder. Then grind or better yet leave a little over, harden then finish grind.

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Makes way more sense. Those short chunky parts should move very little with proper vigorous-agitation oil quenching.

Denis

I will have a real heat treat shop harden them. But how much to leave and what wheel?

Mebfab said:

I will have a real heat treat shop harden them. But how much to leave and what wheel?

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Nearly a day has gone by with no further reply to your query. I was hoping others would chime in.
My experience base is far less than a lot of folks on this sub-forum, but I will try to get the discussion going. I would expect a fair range on suggested allowances. And then there is the unknown as to whether hundreds of parts or ten or twenty (sounds more like this) are involved.

What wheels do you have? Maybe a 46 grit? O1 is so easy to grind that most likely any 46 or 32 of whatever common hardness will work. But maybe a J hardness for starters.

http://www.practicalmachinist.com/v...grinding-wheels-what-would-you-choose-252558/

Mist or flood would be a help. One wheel with the corner radius and one with a flat surface.

I would guess leaving 10 or 15 thou when sent to HT on the width and thickness should do. But that depends some on your heat treater. Having to send out makes experimenting somewhat costly in time and, depending on the treater's minimum policies, expensive in cash. What else to do than make a few parts and send them and then grind to get a feeling for how much stock it takes to get cleaned up? Then adjust accordingly.

Denis

I would think you're on the right track by rough milling and grinding after HT. I think I would use either a 38A or 32A 46H wheel first. The 38A will break down faster, but will grind cooler. An I or J wheel would work too, less wear but more heat. A 6mm radius is a good amount of contact area.

Kevin