Need Help!- Machining S355J0 Structural Steel

[wganders]

I need to machine 300 bushing from S355J0 structural steel!! It's cut from 125mm hot rolled bar stock and the OD finishes at 121mm but the ID finishes at 106mm +.0016 by 35mm long. I roughed and finished one side and when I remeasured it the next day it was .002 out-of-round. Do I need to stress relieve/normalize this material before finishing? Maybe rough out, normalize, then finish?

My boss is pissed because he knows squat about machining and doesn't understand what the problem is!!!

Any advice will probably save my job!!!

Wganders

[Geof]

I guess your boss is it little shy on knowledge as you suggest; why are you making bushings out of that material?

Rough out, normalize then finish is probably the way to go.

Then when everything is done you will discover these are just big spacers for some 4" diameter bolts.

[wganders]

Geof,

We're trying to land Siemans as a customer and they have certain criteria for their machining processes. It's a European company and we have to please them. They've been getting these parts from somewhere and we have to replicate. Basically, we're going after the laser parts but we have to provide machining service as well.

Thus my question! Do we have to anneal/normalize all the machined structural steel components before we machine them, or rough them out and then anneal/normalize???????

[Geof]

You really need to get advice from someone with more metallurgical knowledge than me. I am fairly sure that rough machining followed by normalizing then finish machining would give a stable part. Probably just getting the blanks normalized before any machining would work fine, but both of these certainly add cost and time.

There is another technique for stress relieving called 'vibratory stress relief' and this is something you can by equipment for to do in-house, just Google the words in quotes.

[crabbass]

Are you using a three jaw with excessive clamping force? Perhaps you could rough , refixture/adjust jaw pressure, then finish.

AC