10 years ago
I enjoyed it greatly, but I did not understand what you did.i
He removed a tool changer/toolpost turret from a very large CNC lathe, took it to a shop to repair a cracked casting properly and then reassembled it. 9" spindle bore, probably threading oil well drill string pipe fittings or something. Probably 100HP spindle. Big MF.
jon_banquer fired this volley in news:665d3f6e- firstname.lastname@example.org:
Jon,it was abundantly clear if you read the notes on the Picasa page:
"So they had me pull the turret and take it to one of the best machine repair guys I know, Jim at Quality Machining, Chino California...to reweld the assembly. "
OK, I got it, thanks. I usually think that if it cracked once, it will crack again. But it was a fun project.i
If the weld is done properly the repair will be as strong or stronger than the original material. The trick is knowing what the material actually is and which weld procedure to use. In this case it sounds like it was cast iron, and that the repair was to grind it out and weld it plus add pins across the weld to withstand the higher stress.
Cast is fun stuff, especially in areas where it lives in lubricants or oils.
I pulled down the lathe, removed the turret, took it to another shop, stripped it empty, then a guy put it up on one of his big horizontal mills, drilled and tapped the side of the casting (base) and put in stripper bolts, which drew the busted pieces together, then welded it all up with bronze. Then he put it back on the horizontal mill, remilled and put everything back to factory specs visa vis flatness and alighnment.
I then reassembled everything, adjusted clearences by experience (no manual available) and reinstalled it on the lathe. I then aligned the turret to within .001 of alignment with lathe axis and then rewired and made operational.
I had about 20 hrs in it. Jim had about 10 hrs in it. Plus taking it on a 70 mile round trip on my trailer.
The original morons had put in (2) .5" dowel pins..but had only set less than .375 in the far side of the crack..and had never pulled the crack back together and when they welded it..they never got the body of the casting hot..so they managed to simply put bronze on the small side and it had NO bond with the body of the turret. When we ground out the original braze..a big "chunk" of bronze popped out..the crack never was bonded..it was just "puttied" and that chunk of bronze was supposed to be bonded to the turret body. It wasnt. That chunk of bronze was oily..and you can see in the photo..the crack was pretty good sized.
In fact..its visible in the photo with the crack, to the right side laying loose on the body of the turret.
Now we expect it to be as strong as the original cast iron as a unit.
If not stronger.
The original guys had put on a plate of steel..just to keep the dowel pins from falling out. Pissed us both off when we pulled that plate off and the dowels were not even bonded with the bronze...yet they had been welded in. Piss poor welding...zero skills with cast iron or machinery. Unfortunately..it had been done 10 yrs ago..so we couldnt go back after them. The machine came from another shop recently..my clients bought their entire machine shop, and we moved it to their building and we set it up for operation. They do plastic and steel pipe threading and slotting etc etc for the oil and environmental industry, along with chemicals etc etc
If its fixed properly..and it was..it wont crack again. At least not in that location.
Maybe Jons keeper missed that part?
We are still not sure if it was cast iron..or cast steel.
then ground all the crap out of it and got it ready to weld
OK, thanks, now I got iti
You should have "got it" without having to be spoon fed..... AGAIN!
It is an ART to repair a casting that won't crack again! A big part of that is in the pre-heat and cool-down phases of the weld. I've had mostly good luck but a bit of bad luck. A lot depends on the metal and the phase of Venus.
Indeed it is an art. When the welding equipment companies, or other researchers, do a metallographic analysis of cast iron welds, the results will leave you wondering how it ever works at all. The weld and heat-affected zone typically is like a layer cake of weirdness.
Anyone who can get good results *consistently* is worth his pay.
BTW, the guy who allegedly was the highest-paid c.i. welder in the world, an Italian who did nothing else, was hired and shipped in many years ago by Bill Harrah to weld a crack in the block of his priceless Bugatti Royale. He did it with O/A and c.i. rod. It worked, even though it doubtless had oil in the (then) 60-year-old cast iron.
I don't know how he did the pre-heat or stress relief.
Amazing--he put it back together without getting his tongue stuck to the freezer door.
Yeah the haz in a cast weld gets interesting. Areas of carbon migration, grain structure changes and lot's more.
Gas works real good for thin wall iron. You have to watch your flame real close and only fill enough to ensure a good bond. Then watch it real close for contraction while it cools. Add enough filler and you get a good bond and repair, go under and it will crack again due to the tension stress at the site. If you go over it will probably crack in a different area due to the stress the extra material adds as it act's like a wedge.
That sounds like things I've read, but I've never attempted it. I have enough to keep me busy with mild steel.
It must require a combination of experience, knowledge, and a highly-developed feel for the materials and the work. And I'll bet that several senses are working at the same time -- touch, vision, hearing, and even smell.
As they say, it's quite an art.
Thanks for an interesting montage & backstory.
I'm no artist or expert, but I've had good luck on some repairs on older cast iron by using a million stitches with a MIG welder. Tedious but effective.
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