CNC crash repair

tooltechtroy · Feb 9, 2021

A new operator crashed a mill and after checking the spindle for runout, my boss began tapping the spindle to “tunk” the bearding back into alignment from being off 3 micron. This spindle will max out at 10,000 rpm and we cut steel all day long. Am I being fed some bs or is this really a trick of the trade I have not yet seen?

Joe Miranda · Feb 9, 2021

I've never heard of that but how do you know it was off 3 microns? After "thunking" it did it get better? I would have just crashed it from the other side and called it a day.

Hardplates · Feb 9, 2021

No doubt it sure is a trick.

If your boss worked for me he would be unemployed

Scruffy887 · Feb 10, 2021

Joe Miranda said:
I've never heard of that but how do you know it was off 3 microns? After "thunking" it did it get better? I would have just crashed it from the other side and called it a day.

I can vouch for that method.

DDoug · Feb 10, 2021

Did the boss use a simple "bonker" ?
Or a right proper "wonker" ? ISO certified of course....

Bobw · Feb 10, 2021

digger doug said:
Did the boss use a simple "bonker" ?
Or a right proper "wonker" ? ISO certified of course....

I would have used a long bolt threaded into a 1-2-3 block.

That makes a really good precision hammer.

Hardplates · Feb 10, 2021

Bobw said:
I would have used a long bolt threaded into a 1-2-3 block.

That makes a really good precision hammer.

One of those fancy ones with the built in bottle opener?

hanermo · Feb 10, 2021

No idea.
It might even have some merit -- maybe it offsets some of the stress in the bearing balls and races ..
but I would expect that to need impacts equivalent to heavy hits.

Otoh, a sharp impact does not need a lot of mass or weight to distort metal.
Peening and brinelling are 2 good examples.

If it works .. I await more results with a very expectant eye.

Hardplates · Feb 10, 2021

The only thing I can see it working at is doubling the number of brinelled spots on the races.

I've heard some dumb shit in my time but this topic is certainly in the top 100

DDoug · Feb 10, 2021

Hardplates said:
The only thing I can see it working at is doubling the number of brinelled spots on the races.

I've heard some dumb shit in my time but this topic is certainly in the top 100

Naw....it's got "Ceramic Bearings".....

mhajicek · Feb 10, 2021

hanermo said:
Otoh, a sharp impact does not need a lot of mass or weight to distort metal.
Peening and brinelling are 2 good examples.

Low mass sharp impacts work shallow, high mass impacts work deep.

Gobo · Feb 10, 2021

A "new operator" crashed it. Okay...... We always blame it on the guy who just quit.

Scruffy887 · Feb 10, 2021

Major crash that ruined a VDI holder into a spinning sub spindle. Sub chuck had a slight wobble after that, turret was fine but fakked alignment. I re bored the jaws to get good parts again.
10 years later I hear the sound of a toolholder slowly going into the sub chuck. I'm in the office above that room. Not a sound you forget.
DANG! Tool stick ruined, but wobble gone! Re bore jaws again. That was 8 years ago. Still making good parts.

But now that I have said that........

GregSY · Feb 11, 2021

Right off the bat, we have confusion. The OP says his boss 'tunked' the spindle, then the second post says 'thunked'. There's a world of difference. duh.

Joe Miranda · Feb 11, 2021

GregSY said:
Right off the bat, we have confusion. The OP says his boss 'tunked' the spindle, then the second post says 'thunked'. There's a world of difference. duh.

Oops ... my bad!

D Dubeau · Feb 11, 2021

Scruffy887 said:
Major crash that ruined a VDI holder into a spinning sub spindle. Sub chuck had a slight wobble after that, turret was fine but fakked alignment. I re bored the jaws to get good parts again.
10 years later I hear the sound of a toolholder slowly going into the sub chuck. I'm in the office above that room. Not a sound you forget.
DANG! Tool stick ruined, but wobble gone! Re bore jaws again. That was 8 years ago. Still making good parts.

But now that I have said that........

We used to have an old Chrysler 9.9hp outboard on a 14ft tinner at the cottage. I ran the lower unit into some rocks going through the channel into the main lake when I was a young teen, and was blamed for the motor never running right after that. THe lower unit also sounded rough and "grindy". A couple years later while out fishing with Dad, he ran it into the same rock, but coming back the other way. No word of a lie, the grinding noise went away and that motor ran like swiss watch for the next 10 years until it got sold with the cottage.

To this day when something doesn't run right, and is in need of an adjustment one of us will jokingly suggest hitting it with a rock lol.

Every year we or someone on that river would put a marker on that rock, and the crusty old guy who's cottage sat in front would always cut it off as he liked the entertainment. Some people just like to watch the world burn.

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