Damaged chuck - a forensic investigation

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Demoman357
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Damaged chuck - a forensic investigation

Post by Demoman357 » Sun May 26, 2019 12:10 pm

I inherited a Goodway 16x60 engine lathe from my father. My sibling used the lathe just before my father died. My father said that he thought that my sibling had damaged something badly when he used it. My sibling will not confess to any such sin, but...
This are pictures of a Bison 3245 scroll chuck. The chuck was a complete rust ball so I disassembled it to clean it. Then I discovered the evidence of bad things. My question is really two-part: what could have happened to cause this damage and, more importantly, what damage should I be looking for on the lathe itself?
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John Evans
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Re: Damaged chuck - a forensic investigation

Post by John Evans » Sun May 26, 2019 12:39 pm

CRASH ! That chuck had the jaw run into something like the tool holder or compound I would guess. Look for visual damage to tool post ,compound, cross slide etc. Run the lathe and listen for odd noises ,check all the power feeds for correct operation. Odd possibility the chuck was dropped and that jaw hit the floor first,looks to be a side impact caused that rather rotational .
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John Hasler
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Re: Damaged chuck - a forensic investigation

Post by John Hasler » Sun May 26, 2019 1:08 pm

Two slots are damaged.

Another guess: the jaws were backed way out, something was clamped only with the tips of the jaws, and then the chuck was tightened with a monkey wrench on the key.

In any case, I'd follow John's advice. Check the spindle, too.

armscor 1
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Re: Damaged chuck - a forensic investigation

Post by armscor 1 » Sun May 26, 2019 4:54 pm

My Sibling, 3 year old daughter was playing with my DSG 13x42 lathe levers, switched off of course.
Did not notice the next day she had engaged the half nuts and I have a habit of running the carriage all the way to the tailstock end.Started motor and engaged clutch, horrible crunching sound as carriage tried to push off lead screw, feed shaft support bearing block.
$500 later for 2 new gears and many hours of work the lathe was back in service, and yes the shear pin had been substituted for a hardened steel roll pin by previous owner.
Relaced the shear pin with correct pin.
Just buy a new chuck and go forward.

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SteveHGraham
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Re: Damaged chuck - a forensic investigation

Post by SteveHGraham » Sun May 26, 2019 5:56 pm

I'm going with "dropped on its face," which is something your brother definitely remembers.
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pete
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Re: Damaged chuck - a forensic investigation

Post by pete » Sun May 26, 2019 8:22 pm

Ouch, :-( It obviously takes a serious hit to do damage that sever. And any 16 x 60 lathe is going to have ample power to do so. Dropped on say a chuck jaw extended out from the body is possible, but even hardened jaws are going to show evidence of it on both the non gripping end of the chuck jaw and probably at least one secondary minor dent on the chuck body itself. At best that chuck might do well enough for welding work. It's now both unsafe and pointless to try to use it for it's intended purpose.

Those with lesser experience on machine tools have all probably had one or more crashes to learn from. Probably we've all done or will do so. Usually there not as bad as what that one seems to have been. I'm betting on a crash being the most logical. Check all the surfaces on the left side of the carriage, cross, top slide and tool post for chuck rash plus cracked castings. If it really was a crash the evidence will be there and unmistakable if you know what to look for. Also check the bed surfaces to see if something got dropped on or left there to cause an interference between the bed and an extended chuck jaw. That lathe may have shear pins or a clutch on the lead and feed rods. A clutch might not show any problems, but if the shear pins on either didn't break as there supposed to one will be bent enough to make removal a serious issue. As John mentioned I'd also pull the chuck and start indicating the spindle nose for excessive run out both radially and axially. If it was a crash it's more than possible to bend the spindle and/or damage the spindle bearings. It takes a whole lot less to do even minor damage to spindle bearings than most think. So if you do start finding that evidence of a serious crash I'd then pull the head stocks top cover and spin everything over by hand and visually start checking the shafts and gear teeth. I've no idea how involved it is to gain access, but the same needs to be done for the gear box as well. If your really lucky it was just a dropped chuck. If not there's not a hope any crash bad enough to do that hasn't caused some serious and expensive further problems. And with any actual crash it also depends on what axis was engaged when it happened. So damaged power cross feed parts aren't impossible.

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GlennW
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Re: Damaged chuck - a forensic investigation

Post by GlennW » Sun May 26, 2019 8:33 pm

I'd say dropped and landed primarily face down on the two jaws since all four ways are broken in the same direction.
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Glenn Brooks
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Re: Damaged chuck - a forensic investigation

Post by Glenn Brooks » Sun May 26, 2019 10:36 pm

I also have an old chuck with similar damage. Cracked on two of the three jaws. I never did find any sign of headstock misalignment -even though the crossslide was clearly whacked any number of times in the past - permanently sheared off at the edges from 30 or 40 years of machining by the Canadian Navy. mine was a old big iron Standard Modern 12 x 48 1950 model. Wonderful machine that lasted far longer than the damaged chuck.

Now as you describe the chuck was a ball of rust, perhaps also consider the possibility the damage was inflicted at some earlier time. The only way to really pinpoint a date for the damage is to cross cut or break off the cracked edges and look at how much corrosion and aging has taken place along the various crack lines. It’s possible to see two or three different eras of cracking- but it does require some destructive testing and examination to confirm.

May or may not be worth the effort...

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whateg0
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Re: Damaged chuck - a forensic investigation

Post by whateg0 » Tue May 28, 2019 7:37 pm

armscor 1 wrote:
Sun May 26, 2019 4:54 pm
My Sibling, 3 year old daughter was playing with my DSG 13x42 lathe levers, switched off of course.
Did not notice the next day she had engaged the half nuts and I have a habit of running the carriage all the way to the tailstock end.Started motor and engaged clutch, horrible crunching sound as carriage tried to push off lead screw, feed shaft support bearing block.
$500 later for 2 new gears and many hours of work the lathe was back in service, and yes the shear pin had been substituted for a hardened steel roll pin by previous owner.
Relaced the shear pin with correct pin.
Just buy a new chuck and go forward.
That's one of the things I like about my 10ee. The halfnuts can't be engaged unless the feed is disengaged. That would be a sick feeling.

I too am going with dropped on its face. Did the jaws have any kind of marks on the corners?

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BadDog
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Re: Damaged chuck - a forensic investigation

Post by BadDog » Tue May 28, 2019 7:40 pm

If I read that correctly, it's not a matter of half nut + feed, it's that the half nuts were engaged sending it rapidly to the end of travel.
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Harold_V
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Re: Damaged chuck - a forensic investigation

Post by Harold_V » Wed May 29, 2019 1:16 am

BadDog wrote:
Tue May 28, 2019 7:40 pm
If I read that correctly, it's not a matter of half nut + feed, it's that the half nuts were engaged sending it rapidly to the end of travel.
Yeah, that's the way I read it, too.
Fact is, most quality machines have interlocks to prevent feed and half nuts from being engaged at the same time.

An accident like that can be minimized by keeping the banjo just snugged up--so if it gets overloaded it will move and disengage. Not suggesting a lathe should be so operated, but it is a solution to a problem.
H
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pete
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Re: Damaged chuck - a forensic investigation

Post by pete » Wed May 29, 2019 4:45 pm

A great tip about just snugging the banjo up Harold, I'll have to borrow that one.

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