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View Full Version : When boring jobs go bad!



wierdscience
08-17-2005, 10:57 PM
Some days you can't win.It started out simple enough,chuck up and bore a 6-1/2" hole in a 22"diameter 1-1/2" thick plate.I swapped out the 3 for the 4 jaw started to chuck the plate and of course the chuck jaws wouldn't clear the back vee way,so out comes the gap.24x120 Italian lathe when you take the gap out the compound slide is no closer than 18" from the chuck,which on this job means 16" of over hang on a 2" boring bar,bad,but I have to live with it.
Next comes an Armstrong boring bar holder,2" capacity,but only has a 4" od footprint and even worse a lousy little 3" long double D shaped Tee-bolt.
I had it all setup and spinning,cored out the center with a holesaw(this part actually went really well)then proceeded to bore.It didn't even chatter even though I was only taking .050" DOC passes.Then I had to step a shoulder in 1/4" of an inch,that's when it happened.
The carrage handwheel has a fair amount of backlash in it,not from wear in the pinion/rack,but slack in the spline that allows the handwheel to be disengaged when the powerfeed or rapid traverse is used.I usually leave the handwheel disengaged,but this time I was feeding by hand because of the shoulder and the fact that the feed clutches even thou electric don't always drop out on a dime.I finished the cut and let go to grab the clutch and the handwheel went over TDC and bumped the carrage just enough for the toolbit to snag,I heard a slight thack!,then saw the boring bar holder drop into the gap,two nice big D shaped knotches busted out of the Tee slot lips http://bbs.homeshopmachinist.net//mad.gif

After the cursing stopped,I stripped the top off the slide and started setting it up in the mill.I'll post pics of the repair if anybody is interested.

Boss said,so what,just fix it and move on,kind sucks wrecking a 15 year perfect record of no crashes.

WJHartson
08-17-2005, 11:24 PM
Join the club, My last couple of days haven't been great either. Bought a Hardinge lathe and tried to get the adjusting nut off the back end of the spindle with no luck. It is tapered and keyed. So far I have only broken one puller, pulled a link in half at a bolt hole. It is a good old puller and not junk from harbor freight. My next step is dry ice in the spindle and heat on the nut. The nut is not threaded according to the manual and the tech rep I talked to.

Today I lost the engine in my cub cadet tractor. Rod knocking and it is only about 25 years old. I am going to take tomorrow off and enjoy myself.

Joe

darryl
08-18-2005, 01:05 AM
24x120 lathe, hmm. Both my lathes would get lost in the gap in that thing. Could probably get the mill in there too. http://bbs.homeshopmachinist.net//smile.gif

I know there are much larger machines out there than that. It amazes me sometimes just to think of the size of things that can be machined on. Things like a crankshaft for an ocean liner, or a rotor for a multi-megawatt alternator. I wouldn't want to be the guy making a measurement error and, say, turning a journal down too small, or having the workpiece come loose and careen around the shop for awhile.
Anyway, good luck fixing the thing.

madman
08-18-2005, 02:22 AM
Hah tonight i got to square up and grind a 798 pound block of P20é The old blanchard stinks to high heaven. I was done at quitting time and then the twenty ton crane wouldnt go in the up direction. Left a note and left. **** happens and jobs just get boring more with the passage of time it seems. I might have to start up the business with Audrey and try something differant again.

Swarf&Sparks
08-18-2005, 12:19 PM
Darryl, speaking of crankshafts....
I think it's been posted here before, but still worth a look.

http://www.bath.ac.uk/~ccsshb/12cyl/

Rgds, Lin