View Full Version : 303 stainless cracked after boring
03-10-2012, 04:19 AM
Just spent $100 on 2metres by 1 inch of 303 stainless bar. Cut off 50mm with my ancient power hacksaw, put it in the 3 jaw and drilled and bored out to 15.85mm to fit a shaft. I was just admiring the snug fit(still a novelty for me) when I noticed a crack extending along the whole length which extended through the wall of the bored part. It was up to 0.5mm wide in places
Did I do something wrong or is the metal dodgy?
+ or - Zero
03-10-2012, 05:24 AM
At a guess, I'd suspect that unless you were using flood cooling the heat stress on a wall that thin in a three jaw was the root cause. 303 builds heat at the cutter tip so where that thin wall is gripped by a jaw it can create quite a heat stress line down the work bore.
I could easily be way off on this guess, I just know that 303 likes flood cooling when being worked.
03-10-2012, 05:54 AM
You might get better results by cutting a longer piece so 2" sticks out of the chuck. Turn the OD to the final size, drill/bore the ID, and part off.
03-10-2012, 06:06 AM
Possibly a stringer (slag inclusion).
Have a look elsewhere on the bar, using a magnifying glass.
The stringer (if that's what it is) shouldn't be very long, so make the next sleeve from the other end of the bar!
03-10-2012, 12:12 PM
That sounds like a bad piece of material to me. 303 is soft enough it shouldn't crack like that.
03-10-2012, 02:47 PM
'snug fit' Do you mean it sliped on with hand force, or was it a press fit you hammered/pressed on?
03-10-2012, 02:54 PM
03-12-2012, 06:00 AM
all the people who voted for a defect in the metal. Went to the supplier today who sugested ( as several people here did) to check the bar i cut the 50mm bit off. Sure enough there was an identicla crack extending about 300mm up the bar. They are going to replace the bar and threw a huge bit of leaded free machining rod for nothing.
If you send a self addressed envelope you will receive a hand engraved Steinlager bottle top as a prize
The marks in the mill table were done by the previous owner
03-12-2012, 06:25 AM
Thanks for the feedback.
03-12-2012, 06:34 AM
bigger picture , I hope
03-12-2012, 06:35 AM
In sheet its called a lamination, probably the same in bar, the crap in the crack is normally slag/al203/mould powder from the billet caster, it arrives due in part to mis alligned rolls in the caster, could be a segment out or a support bearing failed, the solidification requires a 'head' of ferrostatic pressure to feed the solidification point, if the billet gets to hit a bump the head of pressure gets cut off and a centre line lamination occurs.
Glad they fessed up and dropped you a bit of bar!