sticky cast iron

I just spent a couple of hours getting a cast-iron bush to fit a reamed hole, also in cast iron. I had a good finish and finally it fitted all the way in with, I thought, only gentle persuasion.

Then it stuck. I spent another half hour separating the bits and now have a ragged tear in the bush (though the bore is still fairly smooth). I doubt I'll be able to get it back in the 4-jaw sufficiently well centred to clean it up.

What did I do wrong ? Should I have lubricated it ? Or not tried for such a close fit ? I might have expected soft aluminium to grab but I thought cast-iron was hard and slippery.

-adrian

Reply to
Adrian Godwin
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Did it get cocked over? Did the leading edge of the bush have enough/any chamfer? Was either the bore or the bush tapered the odd tenth? Was there a whisker of swarf in the bore? Lubrication always helps, even if the lubrication is Loctite!

Or, as happened to me this afternoon... Was the bit of tube that was being used as a spacer when pressing the parts together about 5 thou too short, thus causing them to _almost_ go together :-(

Mark Rand RTFM

Reply to
Mark Rand

On or around Sat, 6 Jan 2007 17:00:42 +0000, Adrian Godwin enlightened us thusly:

Sods law strikes again... when cutting CI, it's a dead bad move to lubricate it...

Mind, I've had a new stainless steel nut weld itself to a new stainless steel bolt sufficiently solidly that it sheared the bolt rather than came undone. and that was just by tightening it (not all that tight) once.

Only wish it was that easy to weld things together that I want to stay put.

Reply to
Lord Austin the Ebullient of H

Don't think it was cocked, as it jammed when nearly fully inserted. There was a tiny chamfer on the tip (just deburred, really). The bore may have had a slight taper from the reamer, but since (from the location of the torn surface) it appeared to jam at the outer end i don't think that was to blame either. Can't say for sure whether there was a taper on the bush - it depends how true the lathe turns. No lubrication - I thought making an airtight seal might be a bad idea.

-adrian

Reply to
Adrian Godwin

No lubrication, either on the cut or when trying the fit.

Too right !

-adrian

Reply to
Adrian Godwin

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