303 stainless cracked after boring

[dogdoctor]

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?
Regards
David

[+ or - Zero]

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.

[winchman]

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.

[Asquith]

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!

[Toolguy]

Crack

That sounds like a bad piece of material to me. 303 is soft enough it shouldn't crack like that.

[Black_Moons]

'snug fit' Do you mean it sliped on with hand force, or was it a press fit you hammered/pressed on?

[goose]

Defective material.

[dogdoctor]

and the winners are

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
regards
david

[Asquith]

Thanks for the feedback.

[dogdoctor]

bigger picture , I hope

[boslab]

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!
regards
mark