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Re: Damaged chuck - a forensic investigation

Posted: Wed May 29, 2019 9:14 pm
by SteveHGraham
armscor 1 wrote:
Sun May 26, 2019 4:54 pm
$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.
Reminds me of the horror stories a friend tells about his brother. He moved into my friend's house, didn't pay rent, and then sublet to his son, whom he charged. He took my friend's snowblower out and broke the shear pin. Replaced it with a hard bolt. You know the rest of the story.

Finally got him out of the house, before he destroyed it. He did lots of amusing things. He used to heat the bathroom to tropical temperatures when he showered. Melted the snow on the roof above it, over and over. Ended up with a big, heavy bathroom-shaped block of ice on his roof. When it melted, the water had to find a way out.

Good times.

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 6:37 am
by RSG
It's ok Steve, he's family.....LMAO

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 12:35 pm
by Demoman357
More pictures of the evidence:

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 12:37 pm
by Demoman357
Even more pictures of a ruined chuck:

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 12:40 pm
by Demoman357
I am liking the “dropped chuck” theory. The lathe has no visible damage to the bed, carriage, tool holder, or cross slide so I am hoping for the best. I have hand-rotated everything I can without hearing any horrendous noises or feeling any strange resistance. I will start now to indicate the spindle and go from there.

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 1:28 pm
by spro
These pics have helped the investigation. I thought it looked to be dropped face first. It looks differently now. Pics 4,6,8,9,10,11,12 are the same master jaw but now we can see how the top jaw was fitted ( tall to center). So a drop didn't cause the outer slides to crush. Pics 4 ,12 show how a Major crash, which hit the inner tall jaw, fractured the jaws scroll threads and started tearing the jaw in half. It had fractured in a V shape and acted as a wedge against the outer ways.
Pic 1 shows a damaged lock pin and I believe he had a time getting it to release. That also shows it was a crash.

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 1:52 pm
by GlennW
spro wrote:
Thu May 30, 2019 1:28 pm
These pics have helped the investigation. I thought it looked to be dropped face first. It looks differently now.
It's now broken in two different directions. :?

Had a crash, then took it off and dropped it...

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 3:16 pm
by John Hasler
Had a crash, then damaged further pounding on it to get it to release?

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 3:23 pm
by spro
Oh yes. Right guys.
I think it fair to say this chuck is toast. The previous replies about checking the spindle run out, is also right.

Re: Damaged chuck - a forensic investigation

Posted: Thu May 30, 2019 3:52 pm
by spro
Expecting that this isn't the end of the conversation, I can say more. These aren't older Skinner chucks with thick jaw ways around their scroll threads. It doesn't make sense that they would be the same. They would be too heavy and project far from the main bearing. If we look closely at the jaw"s scroll teeth, we can see it was ground hardened nice to fit the scroll. In ordinary use, these wouldn't wear too much but sudden impact breaks it. It becomes a cascade of destruction within a second.

Re: Damaged chuck - a forensic investigation

Posted: Fri Oct 25, 2019 5:04 pm
by Mr Ron
I would say the chuck jaws were extended to the max and hit the carriage as it was traversing from right to left. Check for marks on the carriage.