Cast Iron Chucks

[Dieselman 63]

Looking through a brochure for the Colchester Master 2500 lathe, I noticed a plaque fixed to the lathe which reads ‘do not use cast iron chucks’. Why would you not use a cast iron chuck? The spindle takes a d1-6 camlock I think.

I don’t have one, I’m just curious, since the Bantam has no such warning sign and a similar speed range - 36-2000 on the Bantam, 30-2500 on the master.

 

[Hood]

Speed, cast iron chucks can disintegrate at speed.
The Bantam will use a smaller chuck so the rated speed of a cast Iron chuck for it will likely be within their safe range. The Master will likely use a bigger chuck and that will fall outwith the safe speed range of the chuck. The bigger the chuck the slower max speed it can handle.

 

[Hood]

Here is an example I have just grabbed from some random site.
I boxed the sizes and speeds to show it clearer.

 

[Dieselman 63]

Speed, cast iron chucks can disintegrate at speed.
The Bantam will use a smaller chuck so the rated speed of a cast Iron chuck for it will likely be within their safe range. The Master will likely use a bigger chuck and that will fall outwith the safe speed range of the chuck. The bigger the chuck the slower max speed it can handle.

Wow! I had no idea that could happen... I’ll add that to the list of workshop fears, along with a grinding stone wheel explosion!

 

[Hood]

Most chucks whether cast or steel will have a max rpm stamped on them.

 

[Pete.]

Modern cast iron chucks can cope with a lot more rpm than the older ones. My 8" chuck can spin to 2800 I think.
If you don't know the rating of the chuck then use it conservatively. If you need 3000rpm then your part must be small diameter so use a collet chuck or a small diameter one.

 

[Maker]

My 8" four jaw is stamped with a maximum speed, 1600 RPM I believe.

 

[Tinbasherdan]

Wow! I had no idea that could happen... I’ll add that to the list of workshop fears, along with a grinding stone wheel explosion!

It’s why most motorsports ban the use of cast flywheels on cars, seen one explode and it didn’t leave much of the front end behind

 

[Morrisman]

Modern cast iron chucks can cope with a lot more rpm than the older ones. My 8" chuck can spin to 2800 I think.
If you don't know the rating of the chuck then use it conservatively. If you need 3000rpm then your part must be small diameter so use a collet chuck or a small diameter one.

Odd how cast iron engine crank shafts can be wound up to 8000+ rpm without disintegrating.

30 years ago I operated a 2000rpm Colchester lathe with a 16” cast iron chuck on it.

 

[mtt.tr]

Odd how cast iron engine crank shafts can be wound up to 8000+ rpm without disintegrating.

30 years ago I operated a 2000rpm Colchester lathe with a 16” cast iron chuck on it.

Quality of casting, techniques, shape

 

[ronan]

It’s why most motorsports ban the use of cast flywheels on cars, seen one explode and it didn’t leave much of the front end behind

Correct Dan, the old Norton Commando's had cast iron flywheels and they were known to detonate if the revs climbed too high. I believe it was an experience once undergone, you'd never want to repeat.

 

[Dieselman 63]

Ouch! Reminds me of the time I blew up a ride on engine, hot oil spilling everywhere!

 

[mtt.tr]

Correct Dan, the old Norton Commando's had cast iron flywheels and they were known to detonate if the revs climbed too high. I believe it was an experience once undergone, you'd never want to repeat.

Still see them in amateur racing, saw one go in a nova bloody mess it made. Amazingly i welded the bell housing put a new box in it and it was racing up until last year (3 years on) then it got a bigger engine

 

[Seadog]

Whoops

 

[Seadog]

the old Norton Commando's had cast iron flywheels and they were known to detonate if the revs climbed too high

The problem with the Commando crank was identified by a friend a few years back. The sludge trap, aka the large hole inside each journal was drilled. Nothing fancy, just a drill. Now we all know a drilled blind hole has a conical bottom which transitions to the straight sides at a sgarp corner. This corner coincided exactly with the inside face of the web. A classic stress raiser. No one at the factory every seemed to realise this

 

[ronan]

"Bring some JB weld, and a clean pair of thunderpants"

 

[Seadog]

Yup, that's it. I did forget to say that it was the most heavily stressed side, i.e. the drive side, where this wonder of British Engineering skill was to be found

 

[Munkul]

Odd how cast iron engine crank shafts can be wound up to 8000+ rpm without disintegrating.

Nearly always cast steel, not cast iron.
Of course, you still get cast iron rods, which is also why sometimes they break and put holes in blocks after someone has been tinkering with them...

 

[ronan]

I did hear of a mill engine explosion in Bolton, maybe Tinbasherdan knows of it. The Governor on the steam engine stuck allowing the engine to rev much faster than was prudent, the rope race wheel it was driving, 70 tons of cast iron was spinning much too fast and finally exploded, demolishing half the engine house and surrounds.

 

[graffian]

It’s why most motorsports ban the use of cast flywheels on cars, seen one explode and it didn’t leave much of the front end behind

I think if you look up hoop strength you will find about it. When the force is > the tensile strength of the iron it comes apart.